Analysis: The climate papers most featured in the media in 2025

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Original article republished from Carbon Brief under a CC license

The year 2025 saw the return to power of Donald Trump, a jewellery heist at the Louvre museum in Paris and an engagement that “broke the internet”.

Amid the biggest stories of the year, climate change research continued to feature prominently in news and social media feeds.

Using data from Altmetric, which scores research papers according to the attention they receive online, Carbon Brief has compiled its annual list of the 25 most talked-about climate-related studies of the past year. 

The top 10 – shown in the infographic above and list below – include research into declining butterflies, heat-related deaths, sugar intake and the massive loss of ice from the world’s glaciers:

  1. Indicators of Global Climate Change 2024: annual update of key indicators of the state of the climate system and human influence
  2. Rapid butterfly declines across the US during the 21st century
  3. Global warming has accelerated: Are the UN and the public well informed?
  4. Community estimate of global glacier mass changes from 2000 to 2023 
  5. The EAT-Lancet Commission on healthy, sustainable and just food systems 
  6. Carbon majors and the scientific case for climate liability 
  7. Estimating future heat-related and cold-related mortality under climate change, demographic and adaptation scenarios in 854 European cities 
  8. Systematic attribution of heatwaves to the emissions of carbon majors 
  9. Ambient outdoor heat and accelerated epigenetic aging among older adults in the US 
  10. Rising temperatures increase added sugar intake disproportionately in disadvantaged groups in the US

Later in this article, Carbon Brief looks at the rest of the top 25 and provides analysis of the most featured journals, as well as the gender diversity and country of origin of authors.

New for this year is the inclusion of Altmetric’s new “sentiment analysis”, which scores how positive or negative a paper’s social media attention has been.

(For Carbon Brief’s previous Altmetric articles, see the links for 202420232022202120202019201820172016 and 2015.) 

Global indicators

The top-scoring climate paper of 2025, ranking 24th of any research paper on any topic, is the annual update of the “Indicators of Global Climate Change” (IGCC) report.

The report was established in 2023 to help fill the gap in climate information between assessments of the Intergovernmental Panel on Climate Change (IPCC), which can take up to seven years to complete. It includes the latest data on global temperatures, the remaining carbon budget, greenhouse gas emissions and – for the first time – sea level rise. 

Ragout: Indicators of Global Climate Change 2024: annual update of key indicators of the state of the climate system and human influence

The paper, published in Earth System Science Data, has an Altmetric score of 4,099. This makes it the lowest top-scoring climate paper in Carbon Brief’s list since 2017.

(An Altmetric score combines the mentions that published peer-reviewed research has received from online news articles, blogs, Wikipedia and on social media platforms such as Facebook, Reddit, Twitter and Bluesky. See an earlier Carbon Brief article for more on how Altmetric’s scoring system works.)

Previous editions of the IGCC have also appeared in Carbon Brief’s list – the 2024 and 2023 iterations ranked 17th and 18th, respectively.

This year’s paper was mentioned 556 times in online news stories, including in the Associated PressGuardianIndependentHill and BBC News

Many outlets led their coverage with the study’s findings on the global “carbon budget”. This warned that the remaining carbon budget to limit warming to 1.5C will be exhausted in just three years if global emissions continue at their current rate.

Headline_Montage

In a Carbon Brief guest post about the study, authors Prof Piers Forster and Dr Debbie Rosen from the University of Leeds wrote:

“It is also now inevitable that global temperatures will reach 1.5C of long-term warming in the next few years unless society takes drastic, transformative action…Every year of delay brings reaching 1.5C – or even higher temperatures – closer.”

Forster, who was awarded a CBE in the 2026 new year honours list, tells Carbon Brief that media coverage of the study was “great” at “putting recent extreme weather in the context of rapid long-term rates of global warming”. 

However, he adds:

“Climate stories are not getting the coverage they deserve or need at the moment so the community needs to get all the help we can for getting clear consistent messages out there.”

The paper was tweeted more than 300 times and posted on Bluesky more than 950 times. It also appeared in 22 blogs. 

Using AI, Altmetric now analyses the “sentiment” of this social media attention. As the summary figure below shows, the posts about this paper were largely positive, with an approximate 3:1 split of positive and negative attention.

Altmetric’s AI-generated summary of the sentiment of social media posts regarding the Forster et al.
Altmetric’s AI-generated summary of the sentiment of social media posts regarding the Forster et al. (2025) paper. Totals may add up to more than 100% because of rounding. Source: Altmetric

Butterfly decline

With an Altmetric score of 3,828, the second-highest scoring climate paper warns of “widespread” declines in butterfly numbers across the US since the turn of the century.

The paper, titled “Rapid butterfly declines across the US during the 21st century” and published in Science, identifies a 22% fall in butterfly numbers across more than 500 species between 2000 and 2020.

(There is a higher-scoring paper, “The 2025 state of the climate report: a planet on the brink”, in the journal BioScience, but it is a “special report” and was not formally peer reviewed.)

Ragout: Rapid butterfly declines across the United States during the 21st
century

The scale of the decline suggests “multiple and broadly acting threats, including habitat loss, climate change and pesticide use”, the paper says. The authors find that “species generally had stronger declines in more southerly parts of their ranges”, with some of the most negative trends in the driest and “most rapidly warming” US states.

The research was covered in 560 news articles, including the New York TimesGuardianAssociated PressNPREl País and BBC News. Much of the news coverage led with the 22% decline figure.

The paper was also mentioned in 13 blogs, more than 750 Bluesky posts and more than 600 tweets.

The sentiment analysis reveals that social media posts about the paper were largely negative. However, closer inspection reveals that this negativity is predominantly towards the findings of the paper, not the research itself. 

For example, a Bluesky post on the “distressing” findings by one of the study’s authors is designated as “neutral negative” by Altmetric’s AI analysis.

In a response to a query from Carbon Brief, Altmetric explains that the “goal is to measure how people feel about the research paper itself, not the topic it discusses”. However, in some cases the line can be “blurred” as the AI “sometimes struggles to separate the subject matter from the critique”. The organisation adds that it is “continuously working on improving our models to better distinguish between the post’s content and the research output”. 

Altmetric’s AI-generated summary of the sentiment of social media posts regarding the Forster et al.
Altmetric’s AI-generated summary of the sentiment of social media posts regarding the Forster et al. (2025) paper. Totals may add up to more than 100% because of rounding. Source: Altmetric

On the attention that the paper received, lead author Dr Collin Edwards of the Washington Department of Fish & Wildlife says that “first and foremost, people care about butterflies and our results are broad-reaching, unequivocal and, unfortunately, very concerning”. 

Edwards tells Carbon Brief he hopes the clarity of the writing made the paper accessible to readers, noting that he and his co-authors “sweat[ed] over every word”. 

The resulting news coverage “accurately captured the science”, Edwards says: 

“Much as I wish our results were less consistently grim, the consistency and simplicity of our findings mean that even if a news story only provides the highest level summary, it isn’t misleading readers by skipping some key caveat or nuance that changes the interpretation.”

Warming ‘acceleration’

In third place in Carbon Brief’s list for 2025 is the latest scientific paper from veteran climatologist Dr James Hansen, former director of the NASA Goddard Institute for Space Studies and now adjunct professor at Columbia University’s Earth Institute.

The paper, titled “Global warming has accelerated: Are the UN and the public well-informed?” was published in the journal Environment: Science and Policy for Sustainable Development. It generated an Altmetric score of 3,474.

Ragout: Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed

The study estimates that the record-high global temperatures in the last few years were caused by a combination of El Niño and a reduction in air pollution from international shipping

The findings suggest that the cooling effect of aerosols – tiny, light‑scattering particles produced mainly by burning fossil fuels – has masked more of the warming driven by greenhouse gases than previously estimated by the IPCC.

As efforts to tackle air pollution continue to reduce aerosol emissions, warming will accelerate further – reaching 2C by 2045, according to the research.

The paper was covered by almost 400 news stories – driven, in part, by Hansen’s comments in a press briefing that the Paris Agreement’s 2C warming limit was already “dead”. 

Hansen’s analysis received a sceptical response from some scientists. For example, Dr Valerie Masson-Delmotte, an IPCC co-chair for its most recent assessment report on climate science, told Agence France-Presse the research “is not published in a climate science journal and it formulates a certain number of hypotheses that are not consistent with all the available observations”.

In addition, other estimates, including by Carbon Brief, suggest new shipping regulations have made a smaller contribution to warming than estimated by Hansen.

Hansen tells Carbon Brief that the paper “did ok” in terms of media coverage, although notes “it’s on [scientists] to do a better job of making clear what the core issues are in the physics of climate change”.

With more than 1,000 tweets, the paper scored highest in the top 25 for posts on Twitter. It was also mentioned in more than 800 Bluesky posts and on 27 blogs. 

The sentiment analysis suggests that these posts were largely positive, with just a small percentage of negative comments.

Altmetric’s AI-generated summary of the sentiment of social media posts regarding the Hansen et al.
Altmetric’s AI-generated summary of the sentiment of social media posts regarding the Hansen et al. (2025) paper. Totals may add up to more than 100% because of rounding. Source: Altmetric

Making the top 10

Ranking fourth in Carbon Brief’s analysis is a Nature paper calculating changes in global glacier mass over 2000-23. The study finds glaciers worldwide lost 273bn tonnes of ice annually over that time – with losses increasing by 36% between 2000-11 and 2012-23.

The study has an Altmetric score of 3,199. It received more news coverage than any other paper in this year’s top 25, amassing 1,187 mentions. with outlets including the GuardianAssociated Press and Economic Times

At number five, with an Altmetric score of 2,860, is the EAT-Lancet Commission on healthy, sustainable and just food systems.

Carbon Brief’s coverage of the report highlights that “a global shift towards ‘healthier’ diets could cut non-CO2 greenhouse gas emissions, such as methane, from agriculture by 15% by 2050”. It adds:

“The findings build on the widely cited 2019 report from the EAT-Lancet Commission – a group of leading experts in nutrition, climate, economics, health, social sciences and agriculture from around the world.”

Also making the top 10 – ranking sixth and eighth – are a pair of papers published in Nature, which both link extreme heat to the emissions of specific “carbon majors” – large producers of fossil fuels, such as ExxonMobil, Shell and Saudi Aramco,.

The first is a perspective, titled “Carbon majors and the scientific case for climate liability”, published in April. It begins:

“Will it ever be possible to sue anyone for damaging the climate? Twenty years after this question was first posed, we argue that the scientific case for climate liability is closed. Here we detail the scientific and legal implications of an ‘end-to-end’ attribution that links fossil fuel producers to specific damages from warming.”

The authors find “trillions (of US$) in economic losses attributable to the extreme heat caused by emissions from individual companies”.

The paper was mentioned 1,329 times on Bluesky – the highest in this year’s top 25. It was also mentioned in around 270 news stories.

Published four months later, the second paper uses extreme event attribution to assess the impact of climate change on more than 200 heatwaves recorded since the year 2000.

The authors find one-quarter of the heatwaves would have been “virtually impossible” without human-caused global warming. They add that the heatwaves were, on average, 1.7C hotter due to climate change, with half of this increase due to emissions stemming from the operations and production of carbon majors. 

This study was mentioned in almost 300 news stories – including by Carbon Brief – as well as 222 tweets and 823 posts on Bluesky.

In seventh place is a Nature Medicine study, which quantifies how heat-related and cold-related deaths will change over the coming century as the climate warms. 

A related research briefing explains the main findings of the paper:

“Heat-related deaths are estimated to increase more rapidly than cold-related deaths are estimated to decrease under future climate change scenarios across European cities. An unrealistic degree of adaptation to heat would be required to revert this trend, indicating the need for strong policies to reduce greenhouse gases emissions.”

The paper was mentioned 345 times in the news, including in the Financial TimesNew ScientistGuardian and Bloomberg.

The paper in ninth place also analyses the health impacts of extreme heat. The study, published in Science Advances, finds that extreme heat can speed up biological ageing in older people. 

Rounding out the top 10 is a Nature Climate Change study, titled “Rising temperatures increase added sugar intake disproportionately in disadvantaged groups in the US”. 

The study finds that at higher temperatures, people in the US consume more sugar – mainly due to “higher consumption of sugar-sweetened beverages and frozen desserts”. The authors project that warming of 5C would drive additional sugar consumption of around 3 grams per day, “with vulnerable groups at an even higher risk”.

Elsewhere in the top 25

The rest of the top 25 includes a wide range of research, from “glacier extinction” and wildfires to Amazon drought and penguin guano.

In 13th place is a Nature Climate Change study that finds the wealthiest 10% of people – defined as those who earn at least €42,980 (£36,605) per year – contributed seven times more to the rise in monthly heat extremes around the world than the global average.

The authors also explore country-level emissions, finding that the wealthiest 10% in the US produced the emissions that caused a doubling in heat extremes across “vulnerable regions” globally. 

(See Carbon Brief’s coverage of the paper for more details.)

In 15th place is the annual Lancet Countdown on health and climate change – a lengthy report with more than 120 authors.

The study warns that “climate change is increasingly destabilising the planetary systems and environmental conditions on which human life depends”.

This annual analysis from the Lancet often features in Carbon Brief’s top 25 analysis. After three years in the Carbon Brief’s top 10 over 2020-23, the report landed in 20th place in 2023 and missed out on a spot in the top 25 altogether in 2024. 

In 16th place is a Science Advances study, titled “Increasing rat numbers in cities are linked to climate warming, urbanisation and human population”. The study uses public complaint and inspection data from 16 cities around the world to estimate changes in rat populations.

It finds that “warming temperatures and more people living in cities may be expanding the seasonal activity periods and food availability for urban rats”.

The study received 320 new mentions, including in the Washington PostNew Scientist and National Geographic.

In 21st place is a Nature Climate Change paper, titled “Peak glacier extinction in the mid-21st century”. The study authors “project a sharp rise in the number of glaciers disappearing worldwide, peaking between 2041 and 2055 with up to ~4,000 glaciers vanishing annually”.

Completing the top 25 is a Nature study on the “prudent planetary limit for geological carbon storage” – where captured CO2 is injected deep underground, where it can stay trapped for thousands of years. 

In a Carbon Brief guest post, study authors Dr Matthew Gidden and Prof Joeri Rogelj explain that carbon dioxide removal will only be effective at limiting global temperature rise if captured CO2 is injected “deep underground, where it can stay trapped for thousands of years”. 

The guest post warns that “geological carbon storage is not limitless”. It states that “if all available safe carbon storage capacity were used for CO2 removal, this would contribute to only a 0.7C reduction in global warming”. 

Top journals

The journal Nature dominates Carbon Brief’s top 25, with seven papers featured.

Many other journals in the Springer Nature stable also feature, including Nature Climate Change (three), Communications Earth & Environment (two), as well as Nature Ecology & Evolution, Nature Medicine and Nature Reviews Earth & Environment (one each).

Also appearing more than once in the top 25 are Science Advances (three), Science (two) and the Lancet (two). 

This is shown in the graphic below.

Graphic: Journals most frequently appearing in the top 25 climate papers in 2025

All the final scores for 2025 can be found in this spreadsheet.

Diversity in the top 25

The top 25 climate papers of 2025 cover a huge range of topics and scope. However, analysis of their authors reveals a distinct lack of diversity.

In total, the top 25 includes more than 650 authors – the highest number since Carbon Brief began this analysis in 2022.

This is largely due to a few publications with an exceptionally high number of authors. For example, the 2025 report of the Lancet Countdown on health and climate change has almost 130 authors alone, accounting for almost one-fifth of authors in this analysis. 

Carbon Brief recorded the gender and country of affiliation for each of these authors. (The methodology used was developed by Carbon Brief for analysis presented in a special 2021 series on climate justice.)

The analysis reveals that 88% of the authors of the climate papers most featured in the media in 2025 are from institutions in the global north. 

Global South: The “global south” is a term used to broadly describe lower-income countries in regions such as Africa, Asia and Latin America. It is often used to denote nations that are either in… Read More

Carbon Brief defines the global north as North America, Europe, Japan, Australia and New Zealand. It defines the global south as Asia (excluding Japan), Africa, Oceania (excluding Australia and New Zealand), Latin America and the Caribbean.

The analysis shows that 53% of authors are from European institutions, while only 1% of authors are from institutions in Africa.

Further data analysis shows that there are also inequalities within continents. The map below shows the percentage of authors from each country, where dark blue indicates a higher percentage. Countries that are not represented by any authors in the analysis are shown in grey.

The number of all authors from the climate papers most featured in the media in 2025.
The number of all authors from the climate papers most featured in the media in 2025. The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Carbon Brief concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Map by Carbon Brief using Datawrapper.

The top-ranking countries on this map are the US and the UK, which account for 26% and 16% of the authors, respectively.

Carbon Brief also analysed the gender of the authors. 

Only one-third of authors from the top 25 climate papers of 2025 are women and only five of the 25 papers list a woman as lead author.

The plot below shows the number of authors from each continent, separated into men (dark blue) and women (light blue).

The number of men (dark blue) and women (light blue) listed as authors in the climate papers most featured in the media in 2025, shown by continent.
The number of men (dark blue) and women (light blue) listed as authors in the climate papers most featured in the media in 2025, shown by continent. Chart by Carbon Brief using Datawrapper.

The full spreadsheet showing the results of this data analysis can be found here. For more on the biases in climate publishing, see Carbon Brief’s article on the lack of diversity in climate-science research.

Elon Musk urges you to be a Fascist like him, says that you can ignore facts and reality then.
Elon Musk urges you to be a Fascist like him, says that you can ignore facts and reality then.
Donald Trump urges you to be a Climate Science denier like him. He says that he makes millions and millions for destroying the planet, Burn, Baby, Burn and Flood, Baby, Flood.
Donald Trump urges you to be a Climate Science denier like him. He says that he makes millions and millions for destroying the planet, Burn, Baby, Burn and Flood, Baby, Flood.
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Orcas discuss Donald Trump and the killer apes’ concept of democracy. Front Orca warns that Trump is crashing his country’s economy and that everything he does he does for the fantastically wealthy.

Original article republished from Carbon Brief under a CC license

Continue ReadingAnalysis: The climate papers most featured in the media in 2025

Climate investment is only growth opportunity of 21st century, says leading economist

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https://www.theguardian.com/environment/2025/oct/13/climate-investment-is-biggest-growth-opportunity-of-21st-century-says-economist-nicholas-stern

Nicholas Stern, pictured, led a review that concluded climate action would cost less than the damage caused by inaction. Photograph: David Levenson/Getty Images

Lord Stern says fossil-fuelled growth is futile as the damage it causes ends in economic self-destruction

Investment in climate action is the economic growth story of the 21st century, while growth fuelled by fossil fuels is futile because the damage it causes ends in self-destruction, the economist Nicholas Stern has said.

The plummeting costs of clean technologies, from renewable energy to electric cars, plus the healthier and more productive societies they enable, meant investments could simultaneously tackle the climate crisis and faltering economic growth, and bring millions of people out of poverty, he said.

This requires big changes in policies and levels of investment and Stern, at the London School of Economics, acknowledged that the geopolitical environment was currently difficult but he said making the rational argument was vital. The US president, Donald Trump, recently called climate change a “con job” and is backing fossil fuel companies to “drill, baby, drill”.

“I’d say to Trump: ‘You’ve got children and grandchildren – think about the science, think about the risks,’ and I’d give examples about the wildfires in California,” said Stern. “I’d point out to him that his place in Florida is going to be extremely vulnerable to more intense hurricanes, sea level rise and storm surges. The people and places he loves are under severe risk.

https://www.theguardian.com/environment/2025/oct/13/climate-investment-is-biggest-growth-opportunity-of-21st-century-says-economist-nicholas-stern

Neo-Fascist Climate Science Denier Donald Trump says Burn, Baby, Burn.
Neo-Fascist Climate Science Denier Donald Trump says Burn, Baby, Burn.
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Orcas comment on killer apes destroying the planet by continuing to burn fossil fuels.
Nigel Farage urges you to ignore facts and reality and be a climate science denier like him and his Deputy Richard Tice. He says that Reform UK has received £Millions and £Millions from the fossil fuel industry to promote climate denial and destroy the planet.
Nigel Farage urges you to ignore facts and reality and be a climate science denier like him and his Deputy Richard Tice. He says that Reform UK has received £Millions and £Millions from the fossil fuel industry to promote climate denial and destroy the planet.
Continue ReadingClimate investment is only growth opportunity of 21st century, says leading economist

Guest post: What 1.5C overshoot would mean for climate impacts and adaptation

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Original article by multiple authors republished from Carbon Brief under a CC license

With average global temperatures set to see another record high this year, the chances of holding warming to no more than 1.5C continue to dwindle.

Keeping warming below 1.5C by the end of the century – in line with the long-term goal of the Paris Agreement – now likely involves “overshooting” 1.5C and then bringing temperatures back down later by removing carbon dioxide (CO2) from the atmosphere. 

(What this means for “net-negative” emissions is covered in a previous guest post.)

This raises a number of unknowns in terms of what overshoot means for the impacts of climate change on the planet, people and ecosystems. 

For example, even if global temperatures can be brought back down again by the end of the century, will the impacts of climate change also reduce? Will coral reefs be able to recover or will glaciers reform? What will it mean for the world’s coastlines, food production and endangered species?

For the past three years, we have been working on a Horizon Europe-funded project called PROVIDE to dive deeper into what overshoot really looks like for countries, regions and cities. 

This data is available on the Climate Risk Dashboard – a tool to help people see how climate change will affect them and how it depends on the actions taken today.

Until carbon emissions are reduced to net-zero, the world will not stop warming. Delay will result in ever more intense climate impacts – and increase the risk of crossing irreversible thresholds. 

Urban heat stress under overshoot

One of the clearest and most acute impacts of climate change is on extreme heatwaves. Our findings suggest that, were global average temperatures to decline, extreme heat events in most locations will also decrease, on average. 

But achieving a new balance in local climates would be a slow process, influenced by ongoing climate system adjustments for decades – if not centuries – to come.

Reversing climate change would most probably take several decades, even if overshoot is limited to a few tenths of a degree. This implies that the climate risks that generations alive today will be exposed to are largely determined by collective actions today. 

We can illustrate these differences for the risks of extreme heat stress for the Indian city of Chennai, one of 140 cities for which we modelled urban heat stress risks at 100-metre spatial resolution.  

The chart below shows the projected annual number of days of extreme heat stress in Chennai – defined as days where wet-bulb globe temperature (WBGT) goes over 31C. (WBGT is a metric that combines air temperature, humidity and exposure to direct sunlight.)

This level of heat stress approaches the limits of human survivability (without adaptation) – for example, physical outdoor labour is almost impossible under these conditions.

Under current 2020 climate policies, leading to a best estimate of about 3C of warming in 2100, extreme heat days increase pretty much unchecked. By the end of the century, around half of the days (180) per year would experience extreme heat stress conditions (or even higher). 

In contrast, in a 1.5C low-overshoot scenario (the IPCC Shifting Pathway), the number of extreme heat stress days would peak mid-century at around 120 days , before declining again to around 110 days by 2100 as global average temperature decreases from just above 1.5C to around 1.3C. This is a modest decline in extreme heat risk, yet a profound difference from a 3C world. 

Projected days a year with extreme heat stress in Chennai from 2020 to 2100
Projected days a year with extreme heat stress in Chennai from 2020 to 2100 under the climate policies of 2020 (blue) and 1.5C low-overshoot scenario called “IPCC Shifting Pathway” (green). Source: PROVIDE Dashboard

Irreversible consequences from overshoot

There are many other impacts of climate change that will be irreversible – for centuries to millennia – at peak temperatures, let alone if society is able to bring warming back down.

Coral reef lossglacier losssea level rise and the loss of many species and ecosystems all fall into this category.

Yet, a lot of these losses can still be avoided by stringent mitigation. For example, our multi-scenario framework allows us to explore glacier futures showing unavoidable, or “locked-in”, risks even under the lowest emission scenario we have explored, and compare them with the avoidable risks through stringent mitigation. 

Below, we provide an example for glacier volume projections for Peru, where glaciers serve as an essential freshwater resource during the extremely dry season of June to September. Due to past warming, glacier loss will continue over the coming decades. Under a current policy scenario (blue dots), 50% of the glacier volume might be lost as early as 2050.

Yet this does not need to happen. In fact, stringent mitigation pathways (green dots) are still possible that give a four-in-five chance of preserving 50% of today’s glacier ice in Peru, avoiding the worst and helping to maintain some of their vital uses.

Chart illustrating risks of losing 50% of 2020 glacier volume for Peru today and in 2030, 2050 and 2100
Chart illustrating risks of losing 50% of 2020 glacier volume for Peru today and in 2030, 2050 and 2100, under the climate policies of 2020 (blue) and 1.5C low-overshoot scenario called “IPCC Shifting Pathway” (green). Shading highlights the avoidable risk. Source: PROVIDE Dashboard.

Overshoot risks for the biosphere

Climate change represents a major threat to biodiversity globally. We modelled species at risk from local extinction for about 135,000 terrestrial fungi, plants, invertebrates and vertebrates based on the Wallace Initiative

Under the assumption that the 1950-2000 reference climate was suitable for the species at question, we model the proportion of species for which the local climate becomes unsuitable under ongoing climate change. 

In the chart below, we illustrate the risks to species in one of the countries with the world’s richest terrestrial biodiversity, Brazil. Under the current policy scenario (blue dots), the likelihood of 50% of species being at risk of local extinction rises to 74% by 2100. Yet, our analysis shows that this likelihood can still be avoided almost entirely by stringent mitigation (green dots). 

Chart showing the likelihood of 50% of Brazilian species being at risk of local extinction today and in 2030, 2050 and 2100
Chart showing the likelihood of 50% of Brazilian species being at risk of local extinction today and in 2030, 2050 and 2100, under the climate policies of 2020 (blue) and 1.5C low-overshoot scenario called “IPCC Shifting Pathway” (green). Shading highlights the avoidable risk. Source: PROVIDE Dashboard.

It is important to highlight that species loss does depend on a range of factors – of which climate suitability is only one. Yet there is a range of other human-caused stressors to biodiversity loss and a complex interdependencies of species and food webs in particular in the most biodiverse ecosystems implies the risk of knock-on effects and ecosystem tipping points

We also note that our results do not necessarily imply global species extinction and do not allow us to quantify if and how species survival under different overshoot trajectories would emerge. 

Overshoot will stress adaptation planning

Overshoot outcomes matter for climate risk assessments. Yet, in contrast with the prominence of overshoot pathways in the climate mitigation literature, their implications for adaptation planning have not been widely explored.

Overshoot would increase the threat of climate change that society needs to adapt to – and make that adaptation more difficult. Some options may become unavailable due to limits of adaptation

Also, timescales matter. Reversing an overshoot will take decades. Even assuming reversibility of climate hazards in the future as temperatures come down, this might only matter for adaptation decisions that involve a planning horizon of 50 years or more.

This is illustrated in the chart below, from our recent Nature study. This shows a stylised trajectory of warming (top chart) with overshoot (red bars) and how it compares to planning horizons for some example adaptation options (green bars), the lifetime of those measures (blue bars) and the intergenerational equity they involve (bottom chart).

The possibility of reversing long-term impacts in the future does not reduce the urgent need to act now on closing the wide gap in current adaptation efforts.

Figure showing stylised temporal evolution of a reversible climate impact driver
Figure showing: a) stylised temporal evolution of a reversible climate impact driver under a peak and decline scenario. Dashed lines indicate a low and high overshoot outcome with median timescales of global temperature reversibility typically in line with those from the IPCC AR6 database; and b) stylised illustration of adaptation-relevant timescales starting in 2030, including different planning horizons for adaptation planning (green bars) and lifetimes of individual adaptation measures (blue), and the effect of applying discounting (reflecting societal preferences towards intergenerational equity) to future damages and adaptation benefits. Source: Schleussner et al. (2024)

Limit peak warming and aim for long-term decline

While our results clearly underscore the importance of limiting peak warming to as low as possible, there are also very good arguments for aiming for a long-term global temperature decline, irrespective of the peak warming level. 

For a wide range of time-lagged climate impacts, such as ice sheet, peatland and permafrost loss, as well as large-scale irreversible tipping points, achieving temperature decline well below 1.5C is key to limiting long-term risks from global warming. 

Overshoot is clearly not an alternative way to achieve a similar climate outcome. Effectively limiting climate risks requires restricting peak warming as low and as close to 1.5C as possible – and then aim for long-term decline to reduce the climate impact legacy of human-caused emissions.

This guest post is by:

Dr Carl-Friedrich Schleussner leads the integrated climate impact group at the International Institute for Applied Systems Analysis (IIASA) and is a scientific advisor at Climate Analytics, Berlin.

Prof Rachel Warren, professor of global change and environmental biology at the University of East Anglia.

Dr Fabien Maussion, associate professor in glaciology at the School of Geographical Sciences, University of Bristol, UK.

Dr Niels Souverijns, urban climatologist at VITO Belgium and guest professor at KU Leuven.

Dr Quentin Lejeune, a climate scientist who has led the development of the PROVIDE Climate Risk Dashboard at Climate Analytics.

Original article by multiple authors republished from Carbon Brief under a CC license

Continue ReadingGuest post: What 1.5C overshoot would mean for climate impacts and adaptation