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Secretary-general calls latest ipcc climate report ‘code red for humanity’, stressing ‘irrefutable’ evidence of human influence.

Following is UN Secretary-General António Guterres’ statement on the Intergovernmental Panel on Climate Change (IPCC) Working Group 1 report on the physical science basis of the sixth assessment, today:

Today’s IPCC Working Group 1 report is a code red for humanity.  The alarm bells are deafening, and the evidence is irrefutable:  greenhouse‑gas emissions from fossil-fuel burning and deforestation are choking our planet and putting billions of people at immediate risk.  Global heating is affecting every region on Earth, with many of the changes becoming irreversible.

The internationally agreed threshold of 1.5°C is perilously close.  We are at imminent risk of hitting 1.5°C in the near term.  The only way to prevent exceeding this threshold is by urgently stepping up our efforts and pursuing the most ambitious path.

We must act decisively now to keep 1.5°C alive.  We are already at 1.2°C and rising.  Warming has accelerated in recent decades.  Every fraction of a degree counts.  Greenhouse‑gas concentrations are at record levels.  Extreme weather and climate disasters are increasing in frequency and intensity.  That is why this year’s United Nations climate conference in Glasgow is so important.

The viability of our societies depends on leaders from government, business and civil society uniting behind policies, actions and investments that will limit temperature rise to 1.5°C.  We owe this to the entire human family, especially the poorest and most vulnerable communities and nations that are the hardest hit despite being least responsible for today’s climate emergency.

The solutions are clear.  Inclusive and green economies, prosperity, cleaner air and better health are possible for all if we respond to this crisis with solidarity and courage.  All nations, especially the G20 and other major emitters, need to join the net-zero emissions coalition and reinforce their commitments with credible, concrete and enhanced nationally determined contributions and policies before COP26 in Glasgow.

We need immediate action on energy.  Without deep carbon pollution cuts now, the 1.5°C goal will fall quickly out of reach.  This report must sound a death knell for coal and fossil fuels, before they destroy our planet.  There must be no new coal plants built after 2021.  OECD [Organisation for Economic Co-operation and Development] countries must phase out existing coal by 2030, with all others following suit by 2040.  Countries should also end all new fossil fuel exploration and production, and shift fossil-fuel subsidies into renewable energy.  By 2030, solar and wind capacity should quadruple and renewable energy investments should triple to maintain a net-zero trajectory by mid-century.

Climate impacts will undoubtedly worsen.  There is a clear moral and economic imperative to protect the lives and livelihoods of those on the front lines of the climate crisis.  Adaptation and resilience finance must cease being the neglected half of the climate equation.  Only 21 per cent of climate support is directed towards adaptation.  I again call on donors and the multilateral development banks to allocate at least 50 per cent of all public climate finance to protecting people, especially women and vulnerable groups.  COVID-19 recovery spending must be aligned with the goals of the Paris Agreement.  And the decade‑old promise to mobilize $100 billion annually to support mitigation and adaptation in developing countries must be met.

The climate crisis poses enormous financial risk to investment managers, asset owners and businesses.  These risks should be measured, disclosed and mitigated.  I am asking corporate leaders to support a minimum international carbon price and align their portfolios with the Paris Agreement.  The public and private sector must work together to ensure a just and rapid transformation to a net-zero global economy.

If we combine forces now, we can avert climate catastrophe.  But, as today’s report makes clear, there is no time for delay and no room for excuses.  I count on Government leaders and all stakeholders to ensure COP26 is a success.

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The IPCC Report: Key Findings and Radical Implications

By Brian Tokar , originally published by Climate and Capitalism

August 24, 2021

IPCC weather map

Beyond the headlines: what climate science now shows about Earth’s future. Can we act in time?

The UN-sponsored Intergovernmental Panel on Climate Change (IPCC) recently released its latest comprehensive report on the state of the earth’s climate. The much-anticipated report dominated the headlines for a few days in early August, then quickly disappeared amidst the latest news from Afghanistan, the fourth wave of Covid-19 infections in the US, and all the latest political rumblings. The report is vast and comprehensive in its scope, and is worthy of more focused attention outside of specialist scientific circles than it has received thus far.

The report affirms much of what we already knew about the state of the global climate, but does so with considerably more clarity and precision than earlier reports. It removes several elements of uncertainty from the climate picture, including some that have wrongly served to reassure powerful interests and the wider public that things may not be as bad as we thought. The IPCC’s latest conclusions reinforce and significantly strengthen all the most urgent warnings that have emerged from the past 30 to 40 years of climate science. It deserves to be understood much more fully than most media outlets have let on, both for what it says, and also what it doesn’t say about the future of the climate and its prospects for the integrity of all life on earth.

ipcc report pdf 2021

Click image to download report. (PDF, 248MB)

First some background. Since 1990, the IPCC has released a series of comprehensive assessments of the state of the earth’s climate, typically every 5–6 years. The reports have hundreds of authors, run for many hundreds of pages (this one has over 3000), and represent the international scientific consensus that has emerged from the period since the prior report. Instead of releasing a comprehensive report in 2019, as originally scheduled, the IPCC followed a mandate from the UN to issue three special reports: on the implications of warming above 1.5 degrees (all temperatures here are in Celsius except where otherwise noted), and on the particular implications of climate change for the earth’s lands and oceans. Thus the sixth comprehensive Assessment Report (dubbed AR6) is being released during 2021–22 instead of two years prior.

Also the report released last week only presents the work of the first IPCC working group (WGI), focused on the physical science of climate change. The other two reports, on climate impacts (including implications for health, agriculture, forests, biodiversity, etc.) and on climate mitigation — including proposed policy measures — are scheduled for release next February and March, respectively. While the basic science report typically receives far more press coverage, the second report on climate impacts and vulnerabilities is often the most revealing, describing in detail how both ecosystems and human communities will experience the impacts of climate changes.

In many respects, the new document represents a qualitative improvement over the previous Assessment Reports, both in terms of the precision and reliability of the data and also the clarity of its presentation. There are countless detailed charts and infographics, each illuminating the latest findings on a particular aspect of current climate science in impressive detail. There is also a new Interactive Atlas (freely available at  interactive-atlas.ipcc.ch ), which allows any viewer to produce their own maps and charts of various climate phenomena, based on a vast array of data sources and climate models.

If there is a key take-home message, it is that climate science has vastly improved over the past decade in terms of its precision and the degree of confidence in its predictions. Many uncertainties that underlay past reports appear to have been successfully addressed, for example how a once-limited understanding of the behavior and dynamics of clouds were a major source of uncertainty in global climate models. Not only have the mathematical models improved, but we now have more than thirty years of detailed measurements of every aspect of the global climate that enable scientists to test the accuracy of their models, and also to substitute direct observations for several aspects that once relied heavily upon modeling studies. So we have access to better models, and are also less fully reliant upon them.

Second, scientists’ understanding of historic and prehistoric climate trends have also vastly improved. While the IPCC’s third report in 2001 made headlines for featuring the now-famous “hockey stick” graph, showing how average temperatures had been relatively stable for a thousand years before starting to spike rapidly in the past few decades, the current report highlights the relative stability of the climate system over many thousands of years. Decades of detailed studies of the carbon contents of polar ice cores, lake and ocean sediments and other geologically stable features have raised scientists’ confidence in the stark contrast between current climate extremes and a couple of million years of relative climate stability.

The long-term cycle of ice ages, for example, reflects shifts of about 50 to 100 parts per million (ppm) in atmospheric carbon dioxide concentrations, compared to a current concentration (approximately 410 ppm) that is well over 150 ppm higher than the million-year average. We need to look back to the last interglacial era (125,000 years ago) to find an extended period of high average temperatures comparable to what we are experiencing now, and current carbon dioxide concentrations in the atmosphere are believed to be higher than any time in at least two million years.

With these overarching issues in mind, it is time to summarize some of the report’s most distinctive findings and then reflect upon their implications.

First, the question of “climate sensitivity” has been one of the more contentious ones in climate science. It is a measure of how much warming would result from a doubling of atmospheric CO2 from preindustrial levels, i.e. from 280 ppm to 560 ppm. Early estimates were all over the map, giving policymakers the wiggle room to suggest it is reasonable to reduce emissions more slowly or wait for newer technologies — from better batteries to carbon capture and even nuclear fusion — to come along. This report greatly narrows the scope of that debate, with a “best estimate” that doubling CO2 will produce approximately 3 degrees of warming — far too high to avoid extremely dire consequences for all of life on earth.

Climate sensitivity is very likely (more than 90% confidence) between 2.0–4.5 degrees and likely (2/3 confidence) between 2.5 and 4 degrees. Of the five main future scenarios explored in the report, only those where global greenhouse gas emissions reach their peak before 2050 will avoid that disastrous milestone. If emissions continue increasing at rates comparable to the past few decades, we’ll reach doubled CO2 by 2100; if emissions accelerate, it could happen in just a few decades, vastly compounding the climate disruptions the world is already experiencing.

A second key question is, how fast do temperatures rise with increasing emissions? Is it a direct, linear relationship, or might temperature rises begin to level off any time in the foreseeable future? The report demonstrates that the effect remains linear, at least up to the level of 2 degrees warming, and quantifies the effect with high confidence. Of course there are important deviations from this number (1.65 degrees per thousand gigatons of carbon): the poles heat up substantially more quickly than other regions, the air over continental land masses heats up faster than over the oceans, and temperatures are warming almost twice as fast during cold seasons than warm seasons, accelerating the loss of arctic ice and other problems.

Of course more extreme events remain far less predictable, except that their frequency will continue to increase with rising temperatures. For example the triple digit (Fahrenheit) temperatures that swept the Pacific Northwest of the US and southwestern Canada this summer have been described as a once in 50,000 years event in “normal” times and no one excludes the possibility that they will happen again in the near future. So-called “compound” events, for example the combination of high temperatures and dry, windy conditions that favor the spread of wildfires, are the least predictable events of all.

The central conclusion from the overall linear increase in temperatures relative to emissions is that nothing short of a  complete cessation  of CO2 and other greenhouse gas emissions will significantly stabilize the climate, and there is also a time delay of at least several decades after emissions cease before the climate can begin to stabilize.

Third, estimates of likely sea level rise, in both the near- and longer-terms, are far more reliable than they were a few years ago. Global sea levels rose an average of 20 centimeters during the 20th century, and will continue to rise throughout this century under all possible climate scenarios — about a foot higher than today if emissions begin to fall rapidly, nearly 2 feet if emissions continue rising at present rates, and 2.5 feet if emissions rise faster. These, of course, are the most cautious scientific estimates. By 2150 the estimated range is 2–4.5 feet, and more extreme scenarios where sea levels rise from 6 to 15 feet “cannot be ruled out due to deep uncertainty in ice sheet processes.”

With glacial melting expected to continue for decades or centuries under all scenarios, sea levels will “remain elevated for thousands of years,” potentially reaching a height of between 8 and 60 feet above present levels. The last time global temperatures were comparable to today’s for several centuries (125,000 years ago), sea levels were probably 15 to 30 feet higher than they are today. When they were last 2.5 to 4 degrees higher than preindustrial temperatures — roughly 3 million years ago — sea levels may have been up to 60 feet higher than today. Again these are all cautious estimates, based on the available data and subject to stringent statistical validation. For residents of vulnerable coastal regions around the world, and especially Pacific Island dwellers who are already forced to abandon their drinking water wells due to high infiltrations of sea water, it is far from just a theoretical problem.

Also, for the first time, the new report contains detailed projections for the unfolding of various climate-related phenomena in every region of the world. There is an entire chapter devoted to regionally-specific effects, and much attention to the ways in which climate disruptions play out differently in different locations. “Current climate in all regions is already distinct from the climate of the early or mid-20th century,” the report states, and many regional differences are expected to become more pronounced over time. While every place on earth is getting hotter, there are charts showing how different regions will become consistently wetter or dryer, or various combinations of both, with many regions, including eastern North America, anticipated to experience increasingly extreme precipitation events.

There are also more specific discussions of potential changes in monsoon patterns, as well as particular impacts on biodiversity hotspots, cities, deserts, tropical forests, and other places with distinctive characteristics in common. Various drought-related phenomena are addressed in more specific terms, with separate projections for meteorological drought (lack of rainfall), hydrological drought (declining water tables) and agricultural/ecological drought (loss of soil moisture). It can be expected that all these impacts will be discussed in greater detail in the upcoming report on climate impacts that is due in February.

There are numerous other important observations, many of which directly counter past attempts to minimize the consequences of future climate impacts. For those who want to see the world focus more fully on emissions unrelated to fossil fuel use, the report points out that between 64 and 86 percent of carbon emissions are directly related to fossil fuel combustion, with estimates approaching 100 percent lying well within the statistical margin of error. Thus there is no way to begin to reverse climate disruptions without an end to burning fossil fuels. There are also more detailed projections of the impacts of shorter-lived climate forcers, such as methane (highly potent, but short-lived compared to CO2), sulfur dioxide (which counteracts climate warming) and black carbon (now seen as a substantially less significant factor than before).

To those who assume the vast majority of emissions will continue to be absorbed by the world’s land masses and oceans, buffering the effects on the future atmosphere, the report explains how with rising emissions, a steadily higher proportion of the CO2 remains in the atmosphere, rising from only 30 to 35 percent under low emissions scenarios, up to 56 percent with emissions continuing to increase at present rates and doubling to 62 percent if emissions begin to rise more rapidly. So we will likely see a declining capacity for the land and oceans to absorb a large share of excess carbon dioxide.

The report is also more skeptical than in the past toward geoengineering schemes based on various proposed technological interventions to absorb more solar radiation. The report anticipates a high likelihood of “substantial residual or overcompensating climate change at the regional scales and seasonal time scales” resulting from any interventions designed to shield us from climate warming without reducing emissions, as well as the certainty that ocean acidification and other non-climate consequences of excess carbon dioxide would inevitably continue. There will likely be substantially more discussion of these scenarios in the third report of this IPCC cycle, which is due in March.

In advance of the upcoming international climate conference in Glasgow, Scotland this November, several countries have pledged to increase their voluntary climate commitments under the 2015 Paris Agreement, with some countries now aiming to achieve a peak in climate-altering emissions by mid-century. However this only approaches the middle range of the IPCC’s latest projections. The scenario based on a 2050 emissions peak is right in the middle of the report’s range of predictions, and shows the world surpassing the important threshold of 1.5 degrees of average warming in the early 2030s, exceeding 2 degrees by mid-century, and reaching an average temperature increase between 2.1 and 3.5 degrees (approximately 4–6 degrees Fahrenheit) between 2080 and 2100, nearly two and a half times the current global average temperature rise of 1.1 degrees since preindustrial times.

We will learn much more about the impacts of this scenario in the upcoming February report, but the dire consequences of future warming have been described in numerous published reports in recent years, including an especially disturbing very recent paper reporting signs that the Atlantic circulation (AMOC), which is the main source of warm air for all of northern Europe, is already showing signs of collapse. If carbon emissions continue to increase at current rates, we are looking at a best estimate of a 3.6 degree rise before the end of this century, with a likely range reaching well above 4 degrees — often viewed as a rough threshold for a complete collapse of the climate system.

There are two lower-emissions scenarios in the report, the lowest of which keeps the temperature rise by the century’s end under 1.5 degrees (after exceeding it briefly), but a quick analysis from MIT’s  Technology Review  points out that this scenario relies mainly on highly speculative “negative emissions” technologies, especially carbon capture and storage, and a shift toward the massive-scale use of biomass (i.e. crops and trees) for energy. We know that a more widespread use of “energy crops” would consume vast areas of the earth’s landmass, and that the regrowing of trees that are cut down to burn for energy would take many decades to absorb the initial carbon release– a scenario the earth clearly cannot afford.

The lower-emissions scenarios also accept the prevailing rhetoric of “net-zero,” assuming that more widespread carbon-sequestering methods like protecting forests can serve to compensate for still-rising emissions. We know that many if not most carbon offset schemes to date have been an absolute failure, with Indigenous peoples often driven from their traditional lands in the name of “forest protection,” only to see rates of commercial logging increase rapidly in immediately surrounding areas.

It is increasingly doubtful that genuine long-term climate solutions can be found without a thorough transformation of social and economic systems. It is true that the cost of renewable energy has fallen dramatically in the past decade, which is a good thing, and that leading auto manufacturers are aiming to switch to electric vehicle production over the coming decade. But commercial investments in renewable energy have leveled off over the same time period, especially in the richer countries, and continue to favor only the largest-scale projects that begin to meet capitalist standards of profitability. Fossil fuel production has, of course, led to exaggerated standards of profitability in the energy sector over more than 150 years, and most renewable projects fall far short.

We will likely see more solar and wind power, a faster tightening of fuel efficiency standards for the auto industry and subsidies for electric charging stations in the US, but nothing like the massive reinvestment in community-scaled renewables and public transportation that is needed. Not even the landmark Biden-Sanders budget reconciliation plan that is under consideration in in the US Congress, with all its necessary and helpful climate measures, addresses the full magnitude of changes that are needed to halt emissions by midcentury. While some obstructionists in Congress appear to be stepping back from the overt climate denial that has increasingly driven Republican politics in recent years, they have not backed away from claims that it is economically unacceptable to end climate-altering pollution.

Internationally, the current debate over reducing carbon pollution (so called “climate mitigation”) also falls far short of addressing the full magnitude of the problem, and generally evades the question of who is mainly responsible. While the US and other wealthy countries have produced an overwhelming share of historic carbon pollution since the dawn of the industrial era, there is an added dimension to the problem that is most often overlooked, and which I reviewed in some detail in my Introduction to a recent book (co-edited with Tamar Gilbertson),  Climate Justice and Community Renewal  (Routledge 2020). A 2015 study from Thomas Piketty’s research group in Paris revealed that inequalities  within  countries have risen to account for half of the global distribution of greenhouse gas emissions, and several other studies confirm this.

Researchers at Oxfam have been studying this issue for some years, and their most recent report concluded that the wealthiest ten percent of the global population are responsible for 49 percent of individual emissions. The richest one percent emits 175 times more carbon per person on average than the poorest ten percent. Another pair of independent research groups have released periodic Carbon Majors Reports and interactive graphics profiling around a hundred global companies that are specifically responsible for almost two-thirds of all greenhouse gases since the mid-19th century, including just fifty companies — both private and state-owned ones — that are responsible for half of all today’s industrial emissions (See  climateaccountability.org ). So while the world’s most vulnerable peoples are disproportionately impacted by droughts, floods, violent storms and rising sea levels, the responsibility falls squarely upon the world’s wealthiest.

When the current IPCC report was first released, the UN Secretary General described it as a “code red for humanity,” and called for decisive action. Greta Thunberg described it as a “wake-up call,” and urged listeners to hold the people in power accountable. Whether that can happen quickly enough to stave off some of the worst consequences will be a function of the strength of our social movements, and also our willingness to address the full scope of social transformations that are now essential for humanity and all of life on earth to continue to thrive.

Brian Tokar

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IPCC report: ‘Code red’ for human driven global heating, warns UN chief

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Climate change is widespread, rapid, and intensifying, and some trends are now irreversible, at least during the present time frame, according to the latest much-anticipated Intergovernmental Panel on Climate Change (IPCC) report, released on Monday.

Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Scientists are also observing changes across the whole of Earth’s climate system; in the atmosphere, in the oceans, ice floes, and on land.

The evidence is irrefutable: greenhouse gas emissions are choking our planet & placing billions of people in danger.Global heating is affecting every region on Earth, with many of the changes becoming irreversible.We must act decisively now to avert a climate catastrophe. https://t.co/TQlgp1D9AV António Guterres, UN Secretary-General antonioguterres

Many of these changes are unprecedented, and some of the shifts are in motion now, while some - such as continued sea level rise – are already ‘irreversible’ for centuries to millennia, ahead , the report warns.

But there is still time to limit climate change, IPCC experts say. Strong and sustained reductions in emissions of carbon dioxide (CO2) and other greenhouse gases, could quickly make air quality better, and in 20 to 30 years global temperatures could stabilize.

‘Code red for humanity’

The UN Secretary-General António Guterres said the Working Group's report was nothing less than " a code red for humanity . The alarm bells are deafening, and the evidence is irrefutable".

He noted that the internationally-agreed threshold of 1.5 degrees above pre-industrial levels of global heating was "perilously close. We are at imminent risk of hitting 1.5 degrees in the near term. The only way to prevent exceeding this threshold, is by urgently stepping up our efforts, and persuing the most ambitious path.

" We must act decisively now, to keep 1.5 alive ."

The UN chief in a detailed reaction to the report, said that solutions were clear. " Inclusive and green economies, prosperity, cleaner air and better health are possible for all, if we respond to this crisis with solidarity and courage ", he said.

He added that ahead of the crucial COP26 climate conference in Glasgow in November, all nations - especiall the advanced G20 economies - needed to join the net zero emissions coaltion, and reinforce their promises on slowing down and reversing global heating, "with credible, concrete, and enhanced Nationally Determined Contributions (NDCs)" that lay out detailed steps.

Human handiwork

The report , prepared by 234 scientists from 66 countries, highlights that human influence has warmed the climate at a rate that is unprecedented in at least the last 2,000 years.

In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years , and concentrations of methane and nitrous oxide were higher than at any time in the last 800,000 years.

Global surface temperature has increased faster since 1970 than in any other 50-year period over a least the last 2,000 years . For example, temperatures during the most recent decade (2011–2020) exceed those of the most recent multi-century warm period, around 6,500 years ago , the report indicates.

Meanwhile, global mean sea level has risen faster since 1900, than over any preceding century in at least the last 3,000 years.

The document shows that emissions of greenhouse gases from human activities are responsible for approximately 1.1°C of warming between 1850-1900, and finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5°C of heating.

Ice sheets in Jökulsárlón, Iceland.

Time is running out

The IPCC scientists warn global warming of 2°C will be exceeded during the 21st century. Unless rapid and deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades, achieving the goals of the 2015 Paris Agreement “will be beyond reach”.

The assessment is based on improved data on historical warming, as well as progress in scientific understanding of the response of the climate system to human-caused emissions.

“It has been clear for decades that the Earth’s climate is changing, and the role of human influence on the climate system is undisputed,” said IPCC Working Group I Co-Chair, Valérie Masson-Delmotte. “Yet the new report also reflects major advances in the science of attribution – understanding the role of climate change in intensifying specific weather and climate events”.

Extreme changes

The experts reveal that human activities affect all major climate system components, with some responding over decades and others over centuries.

Scientists also point out that evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and their attribution to human influence, has strengthened.

They add that many changes in the climate system become larger in direct relation to increasing global warming.

This includes increases in the frequency and intensity of heat extremes, marine heatwaves, and heavy precipitation; agricultural and ecological droughts in some regions; the proportion of intense tropical cyclones; as well as reductions in Arctic sea ice, snow cover and permafrost.

The report makes clear that while natural drivers will modulate human-caused changes, especially at regional levels and in the near term, they will have little effect on long-term global warming.

Air pollution from power plants contributes to global warming.

A century of change, everywhere

The IPCC experts project that in the coming decades climate changes will increase in all regions. For 1.5°C of global warming, there will be increasing heat waves, longer warm seasons and shorter cold seasons.

The #IPCC released its latest #ClimateReport today, #ClimateChange 2021: the Physical Science Basis.“The role of human influence on the climate system is undisputed.” – Working Group I Co-Chair @valmasdel Report ➡️ https://t.co/uU8bb4inBBWatch the video, 🎥 ⬇️ pic.twitter.com/hZOSU1xWQR IPCC IPCC_CH

At 2°C of global warming, heat extremes are more likely to reach critical tolerance thresholds for agriculture and health.

But it won’t be just about temperature. For example, climate change is intensifying the natural production of water – the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.

It is also affecting rainfall patterns. In high latitudes, precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon rain patterns are expected, which will vary by region, the report warns.

Moreover, coastal areas will see continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion.

Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.

The report also indicates that further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice.

Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels, affect both ocean ecosystems and the people that rely on them, and they will continue throughout at least the rest of this century.

Magnified in cities

Experts warn that for cities, some aspects of climate change may be magnified, including heat, flooding from heavy precipitation events and sea level rise in coastal cities.

Furthermore, IPCC scientists caution that low-likelihood outcomes, such as ice sheet collapse or abrupt ocean circulation changes, cannot be ruled out.

Limiting climate change

“Stabilizing the climate will require strong, rapid, and sustained reductions in greenhouse gas emissions, and reaching net zero CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have benefits both for health and the climate,” highlights IPCC Working Group I Co-Chair Panmao Zhai.

The report explains that from a physical science perspective, limiting human-induced global warming to a specific level requires limiting cumulative carbon dioxide emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions.

“Strong, rapid and sustained reductions in methane emissions would also limit the warming effect resulting from declining aerosol pollution”, IPCC scientists underscore.

A 16-year-old child swims in the flooded area of Aberao village in Kiribati. The Pacific island is one of the countries worst affected by sea-level rise.

About the IPCC

The Intergovernmental Panel on Climate Change (IPCC) is the UN body for assessing the science related to climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization ( WMO ) in 1988 to provide political leaders with periodic scientific assessments concerning climate change, its implications and risks, as well as to put forward adaptation and mitigation strategies.

In the same year the UN General Assembly endorsed the action by the WMO and UNEP in jointly establishing the IPCC. It has 195 member states.

Thousands of people from all over the world contribute to the work of the IPCC. For the assessment reports, IPCC scientists volunteer their time to assess the thousands of scientific papers published each year to provide a comprehensive summary of what is known about the drivers of climate change, its impacts and future risks, and how adaptation and mitigation can reduce those risks.

'Before our very eyes'

Multiple, recent climate disasters including devastating flooding in central China and western Europe have focused public attention as never before, suggested Inger Andersen, Executive Director of the UN Environment Programme (UNEP).

“As citizens and as businesses and as governments, we are well aware of the drama,” she said “The drama exists, we have seen it and we heard about it in every news bulletin. And that’s what we need to understand, that the expression of what the science says is exhibited before our very eyes , and of course what this excellent report does is, it projects those scenarios outward, and tells us, if we do not take action, what could be the potential outcomes, or if we do take action, what will be a very good outcome.”

Climate adaption critical

Apart from the urgent need for climate mitigation, "it is essential to pay attention to climate adaptation", said the WMO chief, Peteri Taalas, "since the negative trend in climate will continue for decades and in some cases for thousands of years.

"One powerful way to adapt is to invest in early warning, climate and water services ", he said."Only half of the 193 members of WMO have such services in place, which means more human and economic losses. We have also severe gaps in weather and hydrological observing networks in Africa, some parts of Latin America and in Pacific and Caribbean island states, which has a major negative impact on the accuracy of weather forecasts in those areas, but also worldwide.

"The message of the IPCC report is crystal clear: we have to raise the ambition level of mitigation."

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The Latest IPCC Report: What is it and why does it matter?

The UN released a new climate report—here's what it says, and what we can do about it

Last updated April 04, 2022

This article was updated on March 20, 2023, to include findings from the most recent IPCC report.

The IPCC has released a new climate report, updating and synthesizing the findings from a series of previous reports. But what exactly is the IPCC? What do all these reports mean? Is our situation as grim as some of the news headlines make it sound?

We’ve prepared this guide to help you understand what these climate reports are, what their findings mean for our world and what we can do.

What is the IPCC and what do they do?

IPCC stands for Intergovernmental Panel on Climate Change . The IPCC is the scientific group assembled by the United Nations to monitor and assess all global science related to climate change. Every IPCC report focuses on different aspects of climate change.

This latest report is the IPCC’s 6 th Synthesis report. It updates and compiles in one report findings from all the reports in the IPCC’s sixth assessment cycle, which covered the latest climate science, the threats we’re already facing today from climate change, and what we can do to limit further temperature rises and the dangers that poses for the whole planet.

What should I know about the latest IPCC report?

There is some good news in this synthesis report. There have been promising developments in low-carbon technologies. Countries are making more ambitious national commitments to reduce their emissions and doing more to help communities adapt to the effects of climate change. And we’re seeing more funding committed for all of this work.

The problem is it’s still not enough. Even if every country in the world delivers on its current climate pledges, that’s probably not enough to keep global warming to 1.5°C above pre-industrial levels—a threshold scientists believe is necessary to avoid the worst impacts of climate change.

Current adaptation efforts, too, are scattered and leave behind some of the most vulnerable communities. And if the planet gets much warmer, we may see irreversible changes to some ecosystems around the world, which would be catastrophic for the people and wildlife that depend on them.

Want to go deeper on the findings? TNC Chief Scientist Katharine Hayhoe breaks them down in this Twitter thread .

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Is there any hope then?

Yes. Climate change is here today, reshaping our world in ways big and small—but that doesn’t mean our future is predetermined. Every fraction of a degree of warming makes a big difference in how powerful the effects of climate change will be, including the frequency and intensity of heatwaves, storms, floods and droughts. That means every action we take to limit further warming makes a big difference, especially for vulnerable communities around the world.

We need bolder global climate commitments, and we need them fast so we can transition to clean energy and reach “net zero” emissions as soon possible . And as the IPCC's reports shows, we’ll not only need to cut out emissions—we’ll have to remove some of the carbon that’s already in the atmosphere. Fortunately, nature created a powerful technology that does just that: photosynthesis . Plants naturally absorb carbon from the air and store it in their roots and in the soil.

In addition to phasing out fossil fuels, we also need to protect the natural habitats around the world that store billions of tons of this “living carbon.” We can also help by changing the way we manage working lands like farms and timber forests so they retain more carbon, and restore natural habitats on lands that have been cleared or degraded.  

What can we do to stop climate change?

A global challenge like climate change requires global solutions. It will require movement-building and on-the-ground action, as well as new national policies and economic transformations. Here’s a few things that communities, governments, and business can do.  


  • When it comes to working with nature to fight climate change, we cannot achieve effective action without the leadership of Indigenous Peoples and local communities (IPLCs).
  • These communities are some of the most important protectors of the world’s living carbon, as lands owned or managed by IPLCs often have much lower deforestation rates than government protected areas. In fact, Indigenous-managed lands support about 80 percent of the world’s remaining biodiversity and 17 percent of the planet’s forest carbon.
  • To help Indigenous groups keep playing this crucial role, governments must formally recognize their land and resource rights, and funding for climate action should include support for their communities.

Related reading: Protecting nature through authentic partnerships.  


  • All countries—especially the wealthy countries that generate the most emissions— must create more ambitious climate action plans to eliminate emissions and pull more carbon from their atmosphere—and they need to follow through on them.
  • In addition to cutting fossil fuel use, this can be done investing more in nature . The IPCC estimates it would cost about $400 billion to make the changes to agriculture, forestry and other land uses required to limit emissions. That sounds like a lot—but it’s less than the government subsidies these sectors are already receiving .
  • The best part? Many of these natural climate solutions benefit society in other ways , like improving air and water quality, producing more food and protecting the variety of natural life we all depend on.

Related reading: Canada's new climate plan includes working with nature to reduce emissions.

  • Like national governments, businesses must first and foremost commit to reaching net-zero emissions in their operations—they have to stop putting more carbon into the air.
  • The most direct way to do this is to switch to clean energy sources . Transitioning to renewable energy provides a low-cost, low-carbon, low-conflict pathway to meet global energy needs without harming nature and communities.
  • Those sectors that will have a hard time reducing their emissions today—like airlines, for example—should find ways to offset their impact.
  • Carbon markets offer one way to achieve this. Carbon markets allow businesses and other polluters to purchase “offsets” for their unavoidable emissions, which pay to protect natural lands that would have otherwise been cleared without that funding or restore those that would not recover. 

Related reading: An illustrated guide to carbon offsets.

What can I do as an individual?

  • Learn how to talk about climate change: We can all help by engaging and educating others. Our guide will help you feel comfortable raising these topics at the dinner table with your friends and family. Download our guide to talk about climate change.
  • Share your thoughts: Share this page on your social channels so others know what they can do, too. Here are some hashtags to join the conversation: #IPCC #ClimateAction #NatureNow
  • Join collective action : By speaking collectively, we can influence climate action at the national and global levels. You can add your name to stand with The Nature Conservancy in calling for real solutions now.
  • Keep learning : Educate yourself and share the knowledge—you can start with some of these articles, videos, and other resources .

Videos: Climate Issues Explained

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Climate Action Resources

Natural Climate Solutions Handbook

October 2021

A technical guide for assessing nature-based mitigation opportunities in countries More information on Natural Climate Solutions

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Playbook for Climate Action

This playbook showcases five innovative pathways for reducing emissions and climate impacts. A comprehensive suite of science-based solutions, the playbook presents actions governments and companies can deploy—and scale—today. Visit the Digital Version

Further Reading

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COP28: Your Guide to the 2023 UN Climate Change Conference in UAE

COP28 takes place November 30-December 12, 2023 in United Arab Emirates. This guide will tell you what to expect at COP28, why TNC will be there, and what it all means for you.

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  • Published: 16 November 2023

Controversies of carbon dioxide removal

  • Kevin Anderson 1 , 2 , 3 ,
  • Holly Jean Buck 4 ,
  • Lili Fuhr 5 ,
  • Oliver Geden   ORCID: orcid.org/0000-0001-9456-4218 6 ,
  • Glen P. Peters   ORCID: orcid.org/0000-0001-7889-8568 7 &
  • Eve Tamme   ORCID: orcid.org/0000-0002-1549-5689 8  

Nature Reviews Earth & Environment ( 2023 ) Cite this article

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  • Climate-change mitigation
  • Climate-change policy
  • Environmental impact

Various methods of carbon dioxide removal (CDR) are being pursued in response to the climate crisis, but they are mostly not proven at scale. Climate experts are divided over whether CDR is a necessary requirement or a dangerous distraction from limiting emissions. In this Viewpoint, six experts offer their views on the CDR debate.

You have full access to this article via your institution.

Carbon dioxide removal (CDR) encompasses various deliberate human approaches that can remove CO 2 from the atmosphere and store it in oceanic, terrestrial or geological reservoirs over climate-relevant timescales of decades to millennia. These approaches include schemes such as reforestation, afforestation, iron fertilisation, ocean alkalinity enhancement, enhanced rock weathering, bioenergy with carbon capture and storage (BECCS) and direct air capture and storage (DACCS). CDR is distinct from methods aimed at preventing new emissions at point sources, such as carbon capture and storage (CCS) at fossil power plants or cement works, as these prevention methods are classed as emission reduction strategies.

Why are climate scientists divided about CDR?

Eve Tamme: The Intergovernmental Panel on Climate Change (IPCC) 1 has established CDR as an essential and unavoidable tool to achieve net-zero greenhouse gas (GHG) emissions. However, scientists’ views differ regarding the expectations for the required annual volumes of CDR by 2050, with the lower end around 1.5–3 billion tonnes (ref. 2 ) and the higher estimates stretching from 4.7 to 10 billion tonnes per year 3 . Ultimately, the amount of CDR needed depends on how swiftly global emissions can be reduced, the level of residual emissions and how these residual emissions will be restricted over time.

Economists and physical scientists tend to focus on different aspects regarding CDR. Economists are looking at it as a climate change mitigation solution that offers certain volumes and price ranges, especially in the context of carbon pricing mechanisms. Physical scientists focus more intensely on the actual climate impact, the questions around the durability of different CDR methods and how to bring these aspects together. Transferring the expertise from the physical scientists to the realm of economists will help design policy tools, including carbon markets, that deliver real climate benefits.

Glen Peters: There are two broad areas of disagreement on CDR, revolving around the technical feasibility at scale and how CDR is used in mitigation discourse.

CDR started appearing in mainstream emission scenarios in the late 2000s (ref.  4 ) and has become a dominant element of most mitigation scenarios consistent with the Paris Agreement’s temperature goals. Initially, CDR was dependent on the assumed success of CCS applied to bioenergy (termed BECCS). Although there was much promise for CCS in the 2000s, including an IPCC Special Report in 2005, the technology has not yet lived up to its hope, despite lofty policy ambitions 5 . CCS and most CDR methods are a complex set of technologies that have proved difficult to deploy at scale in real-world contexts. The repeated failure of CCS and CDR to deliver as promised has led many to question their feasibility, particularly at scale.

In addition, CDR has long been identified as a potential ‘dangerous distraction’ 6 owing to its widespread deployment in emission scenarios but not in reality. Given that the entire mitigation agenda is predicated on CDR working at scale, and if CDR does not work at the scale intended, then the world will go more rapidly into carbon debt and be locked into a higher-temperature pathway 7 . A more risk-averse approach that uses only a modest scale of CDR would require greater near-term emission reductions that avoid going into carbon debt 7 . If real-world rate and scale constraints keep CDR marginal, it can never compensate for a failure to sufficiently reduce emissions. Hence, the best antidote to a risky temperature overshoot is to reduce emissions, even if CDR shows promise.

Oliver Geden: There are good reasons to be cautious about the promise of large-scale future CDR deployment. This caution can revolve around negative side effects when implementing methods like BECCS and afforestation, for example, when it comes to competition with land suitable for food production, especially in the Global South. Additionally, there is a problem when enormous volumes of CDR are built into implausible mitigation scenarios for the second half of the century, generating a false sense of optimism that we can still meet ambitious temperature goals, even though global emissions are still not declining. I got into the CDR debate prior to the Paris Agreement in late 2015, by criticizing the use of CDR in scenarios for effectively masking insufficient political action while not making policymakers aware about the important role that future CDR deployment already played in IPCC Annual Report 5 (ref. 8 ).

With the advent of the global 1.5 °C goal and net-zero emission targets, and with more and more scientists arguing that CDR is needed to achieve these targets, the debate slowly started to shift towards a serious discussion around which CDR methods should be deployed by whom, by when, at which volumes and in which ways — and recognizing that we are already doing CDR, mostly in the form of conventional land-based practices like afforestation and reforestation 9 .

Holly Jean Buck: CDR has some role in responding to climate change and reaching net-zero emission targets. However, there is a range of opinions about what approaches deserve further research and what amount of CDR is realistically possible versus what is desirable.

Viewpoints on the desirability, type and amount of CDR depend on one’s assumptions about how fast technological development and social change can happen. For example, if you are from a social group that believes a rapid global phase-out of fossil fuels is possible, and are optimistic about the possibility of the development of renewables, green hydrogen and other mitigation technologies but not optimistic about carbon management technologies, you might not see a need for much CDR. If the political belief of your social group is that it is possible and desirable to dramatically reduce the demand for fossil energy in the global North, then you might not see a need for much CDR. If your belief is that it will take more time to develop mitigation strategies for the hardest-to-abate sectors, you might think society should invest in CDR. Climate scientists are going to be divided on their beliefs and views about how the world works, just like any other social group.

Science can bound the numbers of what is technically feasible with regard to CDR versus emission reductions, and can tell us some important things about trade-offs in terms of land, water or energy between different options — but science cannot be the sole authority on what pathway society should take towards net-zero emissions.

Kevin Anderson: I see the division regarding CDR arising primarily from the pressured working lives of academics, a failure to take the time to carefully consider each other’s respective arguments and an increasing societal preference for polarized positions. When having conversations privately over a coffee or a pint or via an open-ended virtual discussion, many of the disagreements between climate scientists rapidly resolve into issues of scale and timeline rather than the science of CDR itself.

These more nuanced positions then escalate into apparent disagreements when Integrated Assessment Models (IAMs) are used to develop mitigation scenarios to deliver on the Paris Agreement’s 1.5–2 °C commitments. The main (IAM) modelling groups might work quite objectively, but they do so within deeply subjective political boundaries 7 . Their low carbon futures are locked into tech-dominated versions of the present with no changes to core political elements or values of society in relation to fairness, or distribution of resources or power. Such tight political criteria, combined with very small carbon budgets, force all mitigation scenarios assessed by the IPCC to include increasingly extreme levels of CDR.

As such, although typically there is private agreement between climate researchers that the levels of CDR required are extreme, to express such concern in public raises challenging political questions, an area where most scientists simply fear to tread. Ultimately, CDR in the models both sidesteps overt political choices and locks in today’s political norms. In relation to energy emissions aligned with the Paris Agreement, CDR is much more an expedient political football than a serious technical consideration.

Lili Fuhr: Amongst scientists and activists, there is a consensus that we need to go beyond reducing emissions and that the most effective strategy is to phase out all fossil fuels as fast as possible 10 . That also means that any measures taken to mitigate climate change must not slow down or divert political attention and funding away from that main strategy. When it comes to CDR, the terminology can be confusing as it combines two very different methods: restoring natural carbon sinks, such as forests, soils or oceans, and investing in unproven technologies, like BECCS, DACCS or enhanced weathering. We absolutely need to protect and restore natural carbon sinks to enhance their capacity for biological carbon sequestration. Restoration of natural carbon sinks should certainly not be used to justify any additional industrial or fossil fuel emissions 11 . Speculative and largely unavailable CDR technologies are very different because they would require setting up entirely new industrial infrastructures at a large scale. As such, the majority of groups in the global climate movement see them as false solutions and dangerous distractions 12 .

How essential are CDR approaches to meeting climate targets and combatting climate change?

GP: The IPCC essentially outlines three potential and distinct phases of CDR in the mitigation portfolio.

In the first phase, before net-zero emissions are reached, CDR helps reduce net emissions, but its role is marginal in comparison to the role of emission reductions. Gross CO 2 emissions (excluding removals) decline in excess of 80% from today until net-zero CO 2 emissions in the average scenario, with CDR scaling from close to zero today to fill the remaining 20% gap.

In the second phase, CDR is necessary at the point of net-zero emissions (CO 2 or GHG) to counterbalance the so-called hard-to-abate residual emissions. These are the emissions that remain after all emission reduction options are exhausted, including political or social barriers. However, the definition of ‘hard-to-abate’ is obviously a slippery slope.

In the third phase, CDR is used to achieve net negative CO 2 emissions by removing more CO 2 from the atmosphere than is emitted. These net negative emissions are expected to lower the global average temperature, after exceeding a temperature target (‘overshoot’). In this CDR scenario, a climate target is knowingly, perhaps deliberately, exceeded on the assumption that the climate problem can be cleaned up by future generations with a costly technology with limited evidence that it will work at scale 7 .

OG: Essentially, stopping global temperature rise requires some level of CDR because stabilization can only be achieved with net-zero CO 2 emissions, in which the ‘net ’ indicates the assumption that there will be residual CO 2 emissions left at the time of net zero, to be counterbalanced by CDR 13 . And because the IPCC AR6 Synthesis Report made it clear that the warming level of 1.5 °C will be reached and probably crossed in the 2030s, the world would even need to go one step further and try to achieve net-negative CO 2 emissions globally in order to attempt to bring temperature down to 1.5 °C again 13 .

There could have been times when mitigating less in the near-term and making up for it with net-negative CO 2 emissions in the far-away future was mainly a result of macroeconomic optimization in scenarios 8 , but with a rapidly depleting carbon budget for 1.5 °C, there is no credible pathway left without going net-negative emissions. However, this net-negative scenario could be unfeasible, and to make it more likely to be feasible, the cumulative CDR volumes need to be kept in check, which again is an argument for prioritizing emission reductions 3 .

HJB: The IPCC states that “CDR is a necessary element to achieve net zero CO 2 and GHG emissions both globally and nationally, counterbalancing residual emissions from hard-to-transition sectors. It is a key element in scenarios that limit warming to 2 °C (>67%) or lower by 2100 ( robust evidence , high agreement ).” 9 . Even low energy demand scenarios still require some amount of CDR 14 , although they can bring this number lower by ramping up things like energy efficiency or making assumptions about what amounts of living space or meat consumption can be allocated per person. Clearly, some CDR capacity is essential for reaching net-zero emission targets. There is already about 2 billion tonnes of CDR occurring on land 3 , but there is the question of how much that can be maintained and enhanced under climate change.

LF: Climate targets are set by governments, not scientists. But the science presented by the IPCC has left no doubt that irreversible impacts would come from overshooting 1.5 °C, that there are huge physical uncertainties of doing large-scale carbon removal, that reliance on future CDR is delaying deep emission cuts now 15 and that CDR technologies like BECCS and DACCS come with potential risks and harms for ecosystems and communities.

As the fossil economy is threatened by the economic viability and competitiveness of renewable energies, big polluters and fossil fuel companies are promoting technological CDR as a cover-up for expanding their business. This cover-up is clearly not aligned with IPCC findings. The IPCC’s Working Group III report 1 highlights the dangers of overreliance of governments on these unproven technologies. Unfortunately, these warnings are downplayed in the heavily negotiated IPCC Summary for Policymakers. They are buried under an array of models and pathways that rely on precisely such technologies, that project continued use of fossil fuels for decades and that overwhelmingly assume that the world will go beyond 1.5 °C for decades or longer — with surprisingly little attention paid to the human and environmental consequences such assumptions entail.

KA: The ubiquitous assumption of planetary-scale CDR has been a key factor in derailing the 2015 Paris Agreement 1.5 and 2 °C commitments as well as the obligation to “avoid dangerous anthropogenic interference with climate system” enshrined in the original United Nations Framework Convention on Climate Change in 1992. Absolutely central here is the distinction between CDR itself and the ubiquitous assumption of planetary-scale CDR in the IAM models. In so many respects, the major IAM modelling groups have inadvertently done the bidding of both Big Oil and those deeply wedded to the obscene asymmetry in responsibility for emissions 16 . Since the early 2000s, these models have increasingly normalized many hundreds of billions of tonnes of CDR as a means of maintaining the political status quo and seriously delaying the need to phase out fossil fuels.

It is now October 2023, and even the most optimistic reading of the science suggests we have around 8 years of current emissions before we exceed the carbon budget for a 50% chance of not exceeding 1.5 °C, having squandered almost 0.3 trillion tonnes of CO 2 since the Paris Agreement in 2015. In an emergent process of appeasement, an alliance has arisen between failed (and failing) political leadership and complicit IAM modelling of the community’s escalating dependence on CDR to reconcile the irreconcilable of delivering on the Paris Agreement 1.5 °C to 2 °C commitments without rocking the political boat. As such, from an energy-only perspective, I have long viewed CDR as a dangerous distraction from timely zero-fossil-fuel narratives.

ET: The Paris Agreement requires “balancing emissions by sources and removals by sinks in the second half of the century”. First and foremost, getting to that stage requires very steep emission cuts in the next couple of decades. The more successful the world is in rapid decarbonisation, the less CDR will be needed during the net-zero point, and for net-negative emissions thereafter.

When putting this reality in the context of the question at hand — how essential is CDR — the clear answer is that reducing emissions is the most urgent task today. There is a role for CDR deployment next to it, but it is not the main priority when looking at the big picture.

Zooming in on CDR in its complementary role next to emission reductions opens up a vast ecosystem of CDR methods. Given that all these methods have limitations, a growing portfolio of CDR approaches needs to be developed and deployed simultaneously to have the best chance of removing the required volumes of CO 2 by mid-century and beyond.

Which CDR methods do you think could be promising?

LF: Promising for whom? Delaying deep emission cuts into the far-away future is a convenient way for big polluters to distract from the urgency to start phasing out fossil fuels today and to drastically reduce emissions in the critical decade ahead. The oceans, forests and soils are the best allies we have in removing excess carbon from the atmosphere. But as the climate is heating up, extreme weather events are becoming more frequent and we are approaching various tipping points; we risk losing the sink capacity of various ecosystems. The fossil fuel industry is also polluting them with microplastics and toxic chemicals, which further threatens their survival and carbon storage capacity.

The way in which we produce food and manage land can have a key role in storing carbon in soils. Indigenous peoples have acted as stewards of these ecosystems for hundreds of years. Protecting their rights is in the interest of everyone. Industrial-scale ‘carbon farming’ to produce carbon credits is a false and dangerous promise.

GP: If we look at solar, wind, electric cars or batteries, we have direct evidence of what looks promising, through operation and deployment. It is not possible to say which CDR methods are most promising because, so far, all have failed to deploy at any meaningful scale. It is possible to postulate theoretical pros and cons of each CDR method, but without sufficient deployment, they remain theoretical. Even afforestation and reforestation have limits, not only in terms of land competition but also in resilience to a changing climate and verifying how much carbon dioxide is removed over extended periods.

KA: For the purposes of this conversation, I will focus on two forms of technology-based CDR, BECCS and DACCS, and one so-called nature-based solution.

As an engineer with a background in design and construction in the petrochemical industry, I feel a streak of professional shame when, in 2023, the pinnacle of engineering prowess is burning plants and burying the carbon (termed BECCS). There are many reasons for this shame, but key amongst these is the very low energy density of plants. Add this to the inefficiencies in thermal electricity generation and nation-sized areas of land needed to be put aside to deliver the volumes of BECCS assumed in the IAM models. Yet, with very few exceptions, it is such an unsustainable and yesteryear approach to current problems that the IAM modelling groups evoke on a huge planetary scale. So, for me, and on so many levels, BECCS is a blunder of monumental proportions and illustrates just how low we are prepared to stoop to get the carbon molecules to add up in models.

DACCS is a much more elegant engineering option than BECCS. DACCS typically relies on renewable energy to flow air over a catalyst, where the CO 2 is captured before being stripped from the catalyst and subsequently stored. Despite its engineering appeal, it is still a fledgling technology and with very little scope to deliver real carbon reductions within the tight 1.5 °C–2 °C timelines . Moreover, as it stands today, in almost all nations, electricity, the key power source for DACCS, is under 20% of ‘final energy consumption’, and only a relatively small fraction of that is from low carbon generation. A triage approach to how we use what low-carbon energy supply we have would very likely see DACCS a long way down the priority order.

In terms of nature-based solutions, planting trees is the most widely discussed approach. However, the carbon budgets provided by the IPCC already rely on a massive shift away from deforestation and a programme of forestry management, reforestation and some afforestation. So caution needs to be applied to ensure these options are not double counted. Moreover, as we are increasingly witnessing, trees are not a secure carbon sink, as situations such as fire, land use practices, fuel shortages or pest movements can release the carbon back into the atmosphere. Finally, whilst there is immediate popular appeal to planting trees as a store of carbon, in practice, trees need to be considered as part of a rich ecosystem, including their impact on soil carbon cycling.

In my view, BECCS has little to no worthwhile potential, for multiple reasons. DACCS and some carefully applied nature-based solutions could have a useful role in GHG mitigation but should in no way be assumed to compensate for any fossil fuel emissions.

OG: The most promising CDR methods will strongly depend on regional geographical and climatic conditions and how political preferences or social acceptance evolve in different countries. Although there should be specific attention to potential co-benefits and synergies with other societal goals like socioeconomic development or biodiversity, it is important to keep a strong focus on CDR methods with characteristic timescales of storage beyond 100 years, like biochar, enhanced mineral weathering or DACCS.

ET: CDR methods range widely regarding their climate mitigation potential, technology readiness level (TRL) and expected price range. Conventional CDR methods like afforestation, reforestation, soil carbon sequestration and peatland restoration have the highest TRL levels but do not offer long-term durability for CO 2 storage. DACCS, BECCS and biochar are much more novel methods that offer strong mitigation potential and high durability and are not too far behind in terms of TRL. It is essential to support the scale-up of technologies that are ready to be commercialized, whilst helping newer promising CDR methods to continue innovating and moving to higher technological readiness levels.

HJB: Biomass carbon removal and storage involves using biomass (such as algae, municipal waste, agricultural or forest residues) to remove CO 2 from the atmosphere and store it underground or in products. It looks promising in many areas but is very context-dependent. There are a number of methods that deserve more research, including ocean alkalinity enhancement, enhanced rock weathering and agrigenomic ideas such as engineering plants for enhanced carbon sequestration or microbe-based carbon capture soil amendments. It is early to assess the scalability of all these approaches, and much of the scalability depends on culture and policy. The IPCC assesses that moderate-to-large future mitigation potentials are estimated for direct air carbon capture and sequestration, enhanced weathering and ocean-based CDR methods, with medium evidence and medium agreement 9 .

In your view, what are the main socioeconomic problems with CDR?

HJB: The main socioeconomic problem with CDR is that only a tiny fraction of the population is aware of carbon removal, which limits meaningful engagement and just deployment. This lack of awareness is set within the wider problem that many in society do not realize the scope of transformation needed for decarbonization, in terms of deploying clean energy at a massive scale, building electrification, redesigning transport, retrofitting factories, reforming agricultural practices and more. Without that knowledge base, publics are not well-equipped to debate the nuances of CDR approaches within the wider climate response. So if you ask someone whether they want a CDR facility near them, the answer is probably no because it is an unfamiliar industrial project. This is similar to challenges with battery manufacturing plants, transmission lines or other industrial underpinnings of this transition. If you ask people whether they think there should be CDR facilities to compensate for emissions from aviation, or alternatively whether they think there should be limitations on flying, or whether we should use biomass-derived aviation fuels (even if they bring land use and food price impacts) or whether we should carry on as we are despite climate change, who knows what the answer would be. But we are very far from a society-wide deliberation on these trade-offs because the basic contours of the challenge are not fully appreciated.

OG: The main problem is that international policymakers are implicitly relying on remarkably high volumes of CDR to help fix trajectories that already indicate a 1.5 °C overshoot, without necessarily knowing much about CDR or taking responsibility for the expected overshoot. Incorporating CDR in global scenarios is not slowing down emission reduction efforts, but it is hiding the impact of increasing global emissions 17 and sparing climate policymakers the embarrassment of admitting that always staying under 1.5 °C is no longer achievable. But with the advent of national net-zero emission targets, the level of political scrutiny becomes higher, and it is easier to keep expectations about future national CDR levels in check — at least in countries that take their net-zero emission targets seriously 13 . Once governments start splitting their net-zero emission targets into emission reductions and carbon removal components, we can expect healthy national debates on the assumed trajectories, not only regarding CDR but also regarding the types and volumes of residual emissions.

ET: Scaling up CDR could delay reducing emissions. Policymakers can address this risk by establishing separate climate targets for emission reductions and CDR. Given how deep the emission reductions need to be, separate targets help prioritize reductions over removals in the coming decades while also incentivizing CDR to scale it up to the required levels by the right time. A notable example is the design of the European Union’s 2030 climate target of a 55% reduction in net greenhouse gas emissions by 2030 compared with those during 1990, complemented by a separate net CDR target of 310 million tonnes by 2030 from the land use, land use change and forestry sector. The contribution of the CDR target towards the 55% emission reduction target is limited to 225 million tonnes. However, the construction of these EU targets and the scope of CDR could be further improved — something the upcoming 2040 climate target proposal is well-placed to address.

CDR must be deployed in an inclusive and considerate way from local to global level. Project developers should meaningfully include local communities in the decision-making process. Environmental justice also has a global aspect, for example, the geopolitical considerations on who is responsible for cleaning up CO 2 from the atmosphere. Developing countries should benefit from the technology transfer of novel CDR methods and have the capacity to decide what is in their best interest and fair contribution when scaling up CDR globally.

GP: Although many advocate CDR for the right reasons, it is important to acknowledge that CDR deters emission reduction efforts 18 . The level of deterrence is difficult to define and quantify. The mitigation levels reported by the IPCC, and used by countries to support their emission pledges, assume that large-scale CDR will be deployed. If the IPCC reduced the reliance on CDR in emission scenarios, the IPCC would report greater short-term net emission reductions, and mitigation policy would have to be recalibrated to a different mix of mitigation measures. The mere existence of CDR in scenarios effectively delays emission reductions, a characteristic not existing for technologies that reduce emissions (such as solar power).

Through time, it is possible to connect various statements and actions of politicians, companies or individuals who claim to be striving toward ‘net zero’, while continuing or expanding emitting activities and either implicitly or explicitly relying on CDR. This contrasts with emission scenarios, in which all emitting activities rapidly decline and CDR counterbalances small remaining residual emissions.

LF: Both land-based and engineered CDR directly and indirectly threaten human rights, for example those of communities living in or dependent on the land or forests in the areas where a CDR-related activity is taking place 19 . They also indirectly impact human rights by diverting resources from proven mitigation measures and delaying the necessary fossil fuel phaseout. Human rights experts and bodies such as the Advisory Committee to the Human Rights Council, the Special Rapporteur on Toxics and the UN Committee on the Rights of the Child have warned against reliance on unproven, speculative technologies and declared geoengineering — including CDR, marine and solar geoengineering — incompatible with human rights.

KA: My headline view on CDR (and one I have held and made repeatedly over many years) is that we should fund research and development into CDR and deploy such approaches provided they meet stringent social and ecological sustainability criteria. However, we should cut emissions from our energy system assuming CDR will not work at scale. Even if CDR turns out to be as successful as some suggest, it will be required to compensate for the warming from those GHGs that are impossible to eliminate from agriculture, such as methane and nitrous oxide 20 .

What are the main technical limitations of CDR?

OG: The technical limitations of CDR depend strongly on the characteristics of CDR methods and respective implementation options, which vary widely in terms of their maturity, removal process, timescale of storage, storage medium, mitigation potential, costs, and co-benefits and risks, and governance requirements 9 . For novel, currently not widely deployed CDR methods like enhanced mineral weathering, biochar or DACCS, the technical challenges widely differ, whereas the sociotechnical challenge is a similar one — passing through a formative phase in which dedicated resources are scarce, risk of failure for individual implementation options is high and adoption is limited to small niche markets. Substantially scaling these novel CDR technologies will require dedicated innovation policies 3 .

ET: All CDR methods have distinct limitations. These differ from one method to another and include competition for land or water, reversal of CDR via wildfires, high energy requirements and many other constraints. Access to sustainable biomass, renewables, land and suitable geological formations, among other aspects, define where specific CDR methods are feasible to deploy.

Establishing the exact climate impact of some CDR methods — monitoring, reporting and verifying how many tonnes of CO 2 are removed — has high uncertainty levels, and bringing those down will take time and effort.

Another challenge relates to the durability of different CDR methods, ranging from a few decades to thousands of years. From a climate impact standpoint, it is crucial to guarantee that any residual emissions of fossil carbon are balanced by storage on the same millennial timescale 3 . Shorter durability would only partially balance such emissions. Translating this ‘like for like’ approach into policy tools is widely discussed in the discourse of incorporating removals into carbon markets 21 .

Setting up biochar production is relatively fast, hence, the reason biochar carbon removal has become the leading novel CDR method to deliver tonnes of carbon removed today. Building DACCS and BECCS plants is a longer and more complex undertaking that takes several years. Therefore, very different policy mixes and sequences must emerge to scale the vast ecosystem of CDR methods.

HJB: For direct air capture, low-carbon energy and cost are the main limitations. For biomass with carbon removal and storage, biomass and land are limitations. Other techniques face limitations in terms of land or in terms of robust schemes for monitoring and verification. The most relevant limitations will probably be social rather than technological, given the limited awareness of CDR, the poor conditions of our media ecosystem and the erosion of democracy in many parts of the world.

KA: Firstly, the timeline of staying within carbon budgets aligned with the Paris Agreement’s 1.5–2 °C commitments; these are a far cry from the dangerously misleading and highly inequitable net-zero framing that has come to dominate the mitigation agenda. Secondly, there is the naive assumption that a few pilot schemes with chequered technical histories can unproblematically be rolled out at a planetary scale; such adolescent and ubiquitous modelling is far removed from real-world engineering.

LF: Beyond the fact that these technologies are largely speculative and must be weighed against the fundamental uncertainties of removing large amounts of carbon from the atmosphere, I want to highlight one specific limitation: many CDR approaches rely on carbon capture and storage as an enabling technology. The IPCC AR6 Synthesis Report highlights that the implementation of CCS faces technological, economic, institutional, ecological-environmental and sociocultural barriers. It also points out that global rates of CCS deployment are far below those in modelled pathways. These findings are confirmed by real-world evidence: most existing CCS projects in the world are enhanced oil recovery projects. That means that the captured carbon is used to produce more oil, not to reduce emissions. CCS has a decades-long history of overpromising and under-delivering. Despite having been around for decades, CCS facilities currently capture less than 0.1 % of global emissions. CDR technologies are not going to be available at scale in the critical decade ahead. A rapid fossil fuel phaseout and rollout of renewable energies alongside energy efficiency and demand-side measures remain the clearest and most certain path to avoid overshoot.

GP: Although CDR works fine theoretically, various technical barriers limit its deployment. I would argue that it is the technical barriers that lead to the standard response that CDR needs greater policy and financial support. CCS is a good analogy. CCS has been around for decades in various configurations, but it has never taken off as a technology. There is debate over whether this is because of lack of policy support or because the technology is not delivering as promised.

CCS and CDR have renewed policy and financial interest; although some full-scale CCS facilities exist, most CDR applications are small-scale pilots or demonstrations. It might be that the CCS and CDR industries have finally overcome the limitations and they will start to scale in the next few years. Time will tell. However, the point remains that almost all emission reduction options are easier and cheaper than CDR, and it is unlikely a company serious about mitigation would rationally opt for CDR over emission reductions. The cost of CDR is also a motivation for engineers to discover cheaper ways to reduce emissions, rather than continuing to emit carbon dioxide only to remove it later with great difficultly and high cost.

What do you recommend is the best way to move forward in the debate and combat climate change?

KA: With specific reference to the role of academics and wider ‘independent’ experts, and without intending to come across as flippant, I suggest we need integrity, cogency, courage, openness, humility and system-level consistency — all aligned with our United Nations Framework Convention on Climate Change commitment to avoid ‘dangerous’ levels of climate change or, in modern parlance, not exceeding 1.5 °C of warming (or as near as is possible). Accompanying this, I suggest that it is important that we have complete disinterest in the sensibilities of  paymasters, such as the media. In other words, we need to do our work carefully and diligently and communicate our conclusions widely and without fear or favour.

LF: The most ambitious mitigation pathways put out by the IPCC set the floor, not the ceiling, for necessary climate action. Deep, immediate and sustained emission reductions through a rapid and equitable fossil fuel phaseout is the surest path to limiting global warming to 1.5 °C. CDR technologies only serve the interests of big polluters and are a dangerous distraction from what needs to happen.

HJB: Mitigation hinges on having actual climate policy that puts a price on carbon and restricts carbon pollution. Carbon capture and storage has experienced delays for many reasons, but a main one is economic: pollution has had no cost to date, so many big emitters ask themselves what the point is in them installing expensive CCS to reduce their emissions. If we successfully create the conditions for rapid mitigation, we also create the conditions for some amount of CCS and CDR. Until then, the main focus should be on supporting innovation so that when serious climate policy arises, the technology will be ready to deploy. Spending a few billion dollars on the science does not present a serious risk to mitigation. The main mitigation deterrence risk is not from CDR, which few policymakers even know about, but from the fact that fossil fuels are entwined with governments and their stability across the globe. That should be our focus. If we do not get serious climate policy soon, we have bigger problems than debating how to best deal with the last 10% of emissions.

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G.P.P. acknowledges support from the European Union’s Horizon Europe Research and Innovation Programme under grant agreement number 101056306 (IAM COMPACT). O.G. receives support from the Federal Ministry of Education and Research (grant numbers 03F0898E and 01LS2101A). L.F. acknowledges funding from a number of foundations and individual donations that support The Center for International Environmental Law (CIEL; see https://cielannualreport.org/supporters/ ). K.A. acknowledges the following colleagues for their long-term engagement on CDR issues: A. Larkin, D. Calverley and I. Stoddard.

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Kevin Anderson

Centre for Climate and Energy Transformation (CET), University of Bergen, Bergen, Norway

The Centre for Environment and Development Studies (CEMUS), Uppsala University, Uppsala, Sweden

Department of Environment and Sustainability, University at Buffalo, Buffalo, NY, USA

Holly Jean Buck

Fossil Economy Program, Center for International Environmental Law (CIEL), Berlin, Germany

Research Cluster Climate Policy and Politics, German Institute for International and Security Affairs (SWP), Berlin, Germany

Oliver Geden

CICERO Center for International Climate Research, Oslo, Norway

Glen P. Peters

Climate Principles, Tallinn, Estonia

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Kevin Anderson is a professor of Energy and Climate Change. Previously he held the Zennström professorship (Uppsala, Sweden) and was director of the Tyndall Centre (Manchester, UK). Kevin engages with governments, industry and civil society, has a decade of experience in the petrochemical industry, is a chartered engineer and is a fellow of the Institution of Mechanical Engineers.

Holly Jean Buck is an Assistant Professor of Environment and Sustainability at the University at Buffalo, and her research focuses on public engagement with emerging climate technologies. She is the author of the books After Geoengineering and Ending Fossil Fuels: Why Net Zero Is Not Enough .

Lili Fuhr directs the Fossil Economy Program at the Center for International Environmental Law . She has followed the IPCC’s 6 th Assessment Cycle as an expert reviewer for the Special Report on Global Warming of 1.5 °C and participated as an observer in the Synthesis Report approval plenary. Lili sits on the Steering Committee for the Fossil Fuel Non-Proliferation Treaty Initiative .

Oliver Geden is senior fellow and head of the Research Cluster Climate Policy and Politics at the German Institute for International and Security Affairs (SWP). He is co-editor of the annual State of Carbon Dioxide Removal report, acted as lead author for IPCC Sixth Assessment Report (AR) Working Group III and the Synthesis Report, and is currently vice-chair of IPCC Working Group III.

Glen P. Peters is a senior researcher at CICERO Center for International Climate Research who explores trends in global carbon dioxide emissions and how they link to future emission pathways and global climate objectives. He is on the executive team of the Global Carbon Budget and was a lead author for the IPCC Sixth Assessment Report on emission scenarios.

Eve Tamme leads Climate Principles, a climate policy advisory. She has worked on climate policy since 2004 in public and private sectors, specializing in European and international policy developments. Her work focuses on carbon removal, carbon markets, carbon capture and climate governance.

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Correspondence to Kevin Anderson , Holly Jean Buck , Lili Fuhr , Oliver Geden , Glen P. Peters or Eve Tamme .

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IPCC Special Report on 1.5 °C Warming: https://www.ipcc.ch/sr15/

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ipcc report pdf 2021

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IPCC Report 2022 AR6: Summary Part 1

What does the IPCC Sixth Assessment Report say, why is it so alarming and can we stop the consequences of man-made climate change now? Here are the key messages of the IPCC 2022. We’ll start with Working Group 1 , first part of the report.

The Intergovernmental Panel on Climate Change (IPCC) – often referred to as the “Intergovernmental Panel on Climate Change” – is an institution of the United Nations. On its behalf, experts around the world are compiling the current state of knowledge on climate change. It was founded in 1988 and in 2007 it even received a Nobel Peace Prize. Since then, everyone looks forward to the annual IPCC report . The Sixth IPCC Assessment Report (AR6) has just been published. This consists of three parts, which in turn consist of several more parts. Don’t worry, we will summarize the core messages of all three parts for you – in three blog articles .

Important : We have translated and summarized central messages from English. The complete scientific report, including references and additional graphics, can be found on the IPCC website .

The cover of the IPCC report shows a heatmap of the earth with purple areas.

Here are the most important key messages of the IPCC 2022 I

It is undeniable that human influence on the climate has warmed our atmosphere – water and land. far-reaching and rapid consequences for the atmosphere, oceans, cryosphere and biosphere have arisen..

  • Each of the last four decades has been successively warmer than any previous decade since 1850.
  • In 2019, atmospheric CO 2 concentrations were higher than ever before in at least the last 2 million years. Concentrations of CH4 and N2O were higher than at any other point in time in at least 800,000 years.
  • It is almost certain that man-made CO 2 emissions are the main cause of the current global acidification of the open ocean at the surface.
  • Human influence is most likely the main cause of the global retreat of glaciers since the 1990s and the retreat of thesurface of the Arctic sea ice between 1979–1988 and 2010–2019. The decrease was 40% in September and 10% in March.
  • It has been practically proven that the upper ocean (0–700 m) has warmed since the 1970s. It is very likely that human influence is the main cause.
  • The global glacier retreat since the 1950s, with almost all of the world’s glaciers retreating at the same time, is unprecedented in the last 2000 years.

Human-made climate change is already having an impact on many weather and climate extremes in all regions across the globe. Evidence of observed changes in extremes such as heat waves, heavy precipitation, droughts and tropical cyclones has increased.

  • It is virtually certain that heat extremes have become more frequent and intense in most rural regions since the 1950s, while cold extremes have occurred less frequently and less severely. It is highly probable that man-made climate change is the main cause of these changes.
  • It is likely that the global share of severe tropical cyclones (category 3 to 5) has increased over the past four decades.
  • It is very likely that heavy precipitation events will increase and become more frequent in most regions with further global warming. On a global scale, it is projected that extreme daily precipitation events will increase by about 7% per 1°C of global warming.
  • Many changes in the climate system are becoming greater in direct connection with increasing global warming. These include the increase in the frequency and intensity of extreme heat waves, marine heat waves, heavy precipitation and, in some regions, agricultural and ecological droughts; an increase in the proportion of intense tropical cyclones and a decline in Arctic sea ice, snow cover and permafrost.

Under all emission scenarios considered, the global surface temperature will continue to rise until at least the middle of the century. Global warming of 1.5°C and 2°C will be exceeded over the course of the 21st century unless CO 2 and other greenhouse gas emissions are greatly reduced in the coming decades.

  • Compared to 1850–1900, the global surface temperature is very likely to rise by 1.0°C to 1.8°C on average over the years 2081–2100 in a scenario with very low greenhouse gas emissions. With medium greenhouse gas emissions, the temperature will rise by 2.1°C to 3.5°C. In the scenario of very high greenhouse gas emissions, the increase will increase by around 3.3°C to 5.7°C. The last time the global surface temperature was 2.5°C or more above the 1850–1900 level was over 3 million years ago.

From a scientific point of view, limiting man-made global warming to a certain level requires a limit of cumulative CO 2 emissions. At the minimum a net zero value for CO 2 emissions must be achieved, together with a strong reduction in other greenhouse gas emissions.

  • Achieving global net-zero CO 2 emissions, where anthropogenic CO 2 emissions are offset by anthropogenic co2 degradation, is a prerequisite for stabilizing the CO 2 -related increase in global surface temperature.
  • If negative net CO 2 emissions are achieved and maintained worldwide, the global CO 2 -related increase in surface temperature would gradually be reversed. But other climate changes will continue in their current direction for decades to millennia. For example, it would take several centuries to millennia for the rise of the global mean sea level to reverse, even with large negative net CO 2 emissions.

Many changes due to past and future greenhouse gas emissions are irreversible over centuries to millennia – especially changes in the oceans, ice sheets and global sea levels.

  • In the next 2000 years, the global mean sea level will rise by about 2 to 3 m if warming is limited to 1.5°C. It will rise by 2 to 6 m if it is limited to 2°C and by 19 to 22 m if heated to 5°C.
  • In the period from 2011–2020, the Arctic sea ice area reached its lowest annual average level since at least 1850. In late summer, the Arctic sea ice surface was smaller than it had been for at least 1000 years.
  • It is almost certain that mean global sea levels will continue to rise in the 21st century. Compared to 1995–2014, the likely rise in global mean sea level by 2100 is 0.28–0.55 m in the very low greenhouse gas emission scenario. In the scenario with average greenhouse gas emissions 0.44–0.76 m and 0.63–1.01 m according to the scenario with very high greenhouse gas emissions.
  • In the longer term, due to the continued warming of the deep sea and the melting of ice sheets, sea levels will rise for centuries to millennia and will remain elevated for thousands of years.


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