Published

4 weeks ago

May 16, 2025

Alice Rush

Even passing 1.5C of global warming temporarily would trigger a “significant” risk of Amazon forest “dieback”, says a new study.

Dieback would see large numbers of trees die, shifting the lush rainforest into a dry savannah.

The research, published in Nature Climate Change, assesses the impact of “overshooting” the aspirational goal of the Paris Agreement on the Amazon and Siberian forests.

Overshoot would see warming surpass 1.5C above pre-industrial levels in the coming decades, before being brought back down before 2100 through large-scale carbon dioxide removal.

Using hundreds of climate-model simulations, the authors assess the influence of the “sensitivity” of the climate – a measure of the planet’s temperature response to a given increase in atmospheric CO2.

Across all simulations where global warming in 2100 surpasses 1.5C, 37% show “some amount of dieback”, the study says.

However, the risk increases further in the long term, with “55% of simulations exhibiting dieback by 2300”.

One author tells Carbon Brief that the study highlights that overshooting 1.5C leaves forest ecosystems “exposed to more risk than [they] need to be”.

The findings show that “we can’t afford complacency”, he warns.

Warming pathways

As the planet warms, there is an increasing risk that parts of the Earth system will cross “tipping points” – critical thresholds that, if exceeded, could push a system into an entirely new state.

For example, a seminal 2022 study warned that five tipping elements – including the collapse of the West Antarctic ice sheet and abrupt permafrost thaw – are already within reach, while others are becoming increasingly more likely as temperatures rise.

One way to limit warming to 1.5C by the end of the century involves initially overshooting the threshold. However, research published last year warns that the longer the 1.5C threshold is breached – and the higher the peak temperature – the greater the risk of crossing tipping points.

The new study uses modelling to investigate the risks of overshoot for the Amazon and Siberian forests.

The paper considers three illustrative mitigation pathways taken from the Intergovernmental Panel on Climate Change’s (IPCC) mitigation report from its sixth assessment cycle, which was published in 2022.

Gregory Munday is an applied scientist at the UK Met Office Hadley Centre and lead author on the study. He tells Carbon brief that the authors selected “optimistic” pathways that “each have different relationships to the Paris Agreement goals”.

For each scenario, the authors assess a range of different climate sensitivities – a measure of the planet’s temperature response to a given increase in atmospheric CO2. The average outcome of each pathway is:

The “renewables” scenario shows a future with reduced emissions and a heavy reliance on renewable energy, which keeps warming below 1.5C by 2100.
The “negative emissions” pathway shows a world in which warming initially overshoots the 1.5C threshold, but extensive use of carbon removal sees warming drop back below 1.5C before 2100.
The “gradual strengthening” pathway illustrates a strengthening of climate policies implemented in 2020, with rapid reductions mid-century and a reliance on net-negative emissions by the end of this century. This pathway sees global average temperatures reach 1.8C by 2100.

The authors run the emissions pathways through a simple climate “emulator” model, which calculates the global temperatures associated with each emission pathway.

The charts below show cumulative CO2 emissions (left), atmospheric CO2 concentration (middle) and changes in global average surface temperature compared to the pre-industrial level (right), for the renewables (green), negative emissions (purple) and gradual strengthening (yellow) pathways until the year 2300.

The panels show cumulative CO2 emissions (left), atmospheric CO2 concentration (middle) and changes in global average surface temperature compared to the pre-industrial level (right), for the C1:IMP-Ren renewables scenario (green), C2:IMP-Neg negative emissions (purple) and C3:IMP-GS gradual strengthening (yellow) pathways until the year 2300. Source: Munday et al. (2025)

The authors then use a different modelling framework to project the impacts of each emissions scenario.

Study author Dr Chris Jones leads the UK Met Office Hadley Centre’s research into vegetation and carbon cycle modelling and their interactions with climate. He tells Carbon Brief that the new study is the first application of this modelling framework, which he describes as a “rapid response tool”.

He says the tool was developed to “rapidly look at a range of climate outcomes, both global and local, for new scenarios”, adding that it provides a “pretty good approximation” of what traditional global climate models would do.

Munday adds that the framework is able to produce results within days or weeks, rather than taking “months and months”.

Finally, the authors use land surface model JULES to assess forest health under the different scenarios. Overall, the authors produce 918 simulations each of Amazon and Siberian forest health.

Forest health

The authors assess forest health using two metrics. The first is the forest growth metric “net primary productivity”, a measure of the rate that energy is stored as biomass by plants, which can indicate forest productivity. The second metric, forest cover, is a way of measuring the forest’s long-term response.

The models show that rising CO2 levels causes net primary productivity to increase, due to the CO2 fertilisation effect, driving more rapid forest growth. Conversely, many of the impacts of climate change, such as increased heat and changes to rainfall patterns, can be detrimental to forests, damaging or killing trees.

To identify the impacts of overshooting 1.5C on the Amazon and Siberian forests, the authors compare the “renewables” and “negative emissions” pathways. Both of these scenarios reach a similar global average temperature by the year 2100, but the former does so without overshoot, while the latter overshoots 1.5C before temperatures come back down.

The maps below show the difference in net primary productivity in the Amazon (left) and Siberian forests (right) between the two scenarios in the year 2100. Brown shading indicates that net primary productivity was higher in the non-overshoot scenario, while blue indicates that it was higher in the overshoot scenario.

The difference in net primary productivity in the Amazon (left) and Siberian forests (right) between the two scenarios. Brown indicates that net primary productivity was higher in the renewables (non-overshoot) scenario, while blue indicates that it was higher in the negative emissions (overshoot) scenario. Source: Munday et al. (2025)

The maps show that “large areas of both Amazonian and Siberian forest show reduced net primary productivity” by 2100 due to overshoot, compared to a scenario with no overshoot, the paper says.

‘High-risk zones’

From the three pathways, the authors generate 918 simulations of future climate and corresponding Amazon forest health.

The authors use these results to identify which future temperature and rainfall conditions result in net forest “dieback”. This is when large numbers of trees die, shifting the rainforest into a dry savannah.

The plots below show which simulations result in Amazon dieback by the year 2100 (left) and 2300 (right), for different amounts of rainfall and temperature levels in the year 2100. Each graph is divided into four sections – hot and wet (top right), hot and dry (bottom right), cold and wet (top right) and cold and dry (bottom right). These sections are based on average regional temperature and rainfall in the year 2100.

Coloured dots indicate scenarios that see forest dieback. These are coloured by pathway, for renewables (green), negative emissions (purple) and gradual strengthening (yellow). Grey dots indicate scenarios without Amazon dieback. The red lines indicate “high-risk climatic zones”, above which there is “a significant risk of dieback”.

Amazon dieback in the year 2100 (left) and 2300 (right), for different amounts of rainfall and temperature levels in the year 2100. Coloured dots indicate scenarios that see forest dieback. These are coloured by pathway, for renewables (green), negative emissions (purple) and gradual strengthening (yellow). Grey dots indicate scenarios without Amazon dieback. Source: Munday et al. (2025)

The study finds that most Amazon dieback scenarios happen in hot, dry conditions, the authors note.

Across all simulations where warming in 2100 is above 1.5C, 37% show “some amount of dieback” the study says. However, in these model runs, the risk increases further in the long term, the study notes, with “55% of simulations exhibiting dieback by 2300”.

Prof Nico Wunderling is a professor of computational Earth system science at the Potsdam Institute for Climate Impact Research and was not involved in the new research. He tells Carbon Brief it is significant that, according to this study, the Amazon will face impacts from climate change below the tipping point threshold of 2-6C, as assessed in the landmark 2022 tipping points paper.

The authors also carry out this analysis for Siberian forests. Instead of a drop in tree cover, they find a change in the composition of trees. Munday tells Carbon Brief that the vegetation shifts “from grassy surface types to lots more trees and shrubs” in a process called “woody encroachment”.

Woody encroachment can have significant negative impacts on terrestrial carbon sequestration, the hydrological cycle and local biodiversity.

“The Siberian forest is probably committed to a long-term, and possibly substantial, expansion of tree cover,” the authors write.

High-risk scenarios

The greatest uncertainty in this study comes from the spread of climate sensitivities, Munday tells Carbon Brief.

He elaborates:

“This means that although we simulate the impacts from extremely optimistic mitigation scenarios, there is a chance that the Earth’s climate sensitivity is much higher than we expect, and so, small but significant risks of short- and long-term forest ecosystem impacts exist in spite of the choice of these strong-mitigation scenarios.”

In other words, if climate sensitivity is higher than expected, forests could face harmful impacts even under low emissions scenarios.

Dr David McKay – a lecturer in geography, climate change and society at the University of Sussex – is the lead author of the 2022 study. He tells Carbon Brief that the new paper “shows the value in focusing not just on model averages, but also exploring a wide range of possible futures to capture potential ‘low probability, high impact’ outcomes”. He adds:

“[The study shows] how negative emissions to reduce warming might help restabilise these forests in future if we do overshoot 1.5C, but as such large-scale CO2 removal remains hypothetical, we shouldn’t assume we can rely on this in practice.”

However, McKay also notes some uncertainties in the models used. Mckay tells Carbon Brief that the vegetation model used in this study doesn’t include fire and “has some limitations around soil moisture stress and vegetation in the tundra”. These are “likely important for resolving potential tipping points in these biomes”.

Therefore, he adds, the study “doesn’t show how regional tipping points could potentially further amplify and lock-in these future forest shifts, even with negative emissions”.

Dr David Lapola is researcher at the University of Campinas in Brazil and was not involved in the study. He also warns that vegetation models provide a “poor representation of how CO2 may affect these forests directly”. Lapola argues that scientists must “collect field data to make any new advancement with models”.

Nevertheless, Lapola tells Carbon Brief that studies such as this will be “extremely useful” for the IPCC’s upcoming seventh assessment cycle, which will include a dedicated chapter on tipping points and other “low-likelihood high impact events” for the first time.

Study author Jones tells Carbon Brief that overshooting 1.5C leaves forest ecosystems “exposed to more risk than [they] need to be”. The findings show that “we can’t afford complacency”, he warns.

The post ‘Significant’ risk of Amazon forest dieback if global warming overshoots 1.5C appeared first on Carbon Brief.

‘Significant’ risk of Amazon forest dieback if global warming overshoots 1.5C

Greenhouse Gases

DeBriefed 13 June 2025: Trump’s ‘biggest’ climate rollback; UK goes nuclear; How Carbon Brief visualises research

Published

6 hours ago

June 13, 2025

Alice Rush

Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.

This week

Trump’s latest climate rollback

RULES REPEALED: The US Environmental Protection Agency (EPA) has begun dismantling Biden-era regulations limiting pollution from power plants, including carbon dioxide emissions, reported the Financial Times. Announcing the repeal, climate-sceptic EPA administrator Lee Zeldin labelled efforts to fight climate change a “cult”, according to the New York Times. Politico said that these actions are the “most important EPA regulatory actions of Donald Trump’s second term to date”.

WEBSITE SHUTDOWN: The Guardian reported that the National Oceanic and Atmospheric Administration (NOAA)’s Climate.gov website “will imminently no longer publish new content” after all production staff were fired. Former employees of the agency interviewed by the Guardian believe the cuts were “specifically aimed at restricting public-facing climate information”.

EVS TARGETED: The Los Angeles Times reported that Trump signed legislation on Thursday “seeking to rescind California’s ambitious auto emission standards, including a landmark rule that eventually would have barred sales of new gas-only cars in California by 2035”.

UK goes nuclear

NEW NUCLEAR: In her first spending review, UK chancellor Rachel Reeves announced £14.2bn for the Sizewell C new nuclear power plant in Suffolk, England – the first new state-backed nuclear power station for decades and the first ever under a Labour government, BBC News reported. The government also announced funding for three small nuclear reactors to be built by Rolls-Royce, said the Times. Carbon Brief has just published a chart showing the “rise, fall and rise” of UK nuclear.

MILIBAND REWARDED: The Times described energy secretary Ed Miliband as one of the “biggest winners” from the review. In spite of relentless negative reporting around him from right-leaning publications, his Department of Energy Security and Net Zero (DESNZ) received the largest relative increase in capital spending. Carbon Brief’s summary has more on all the key climate and energy takeaways from the spending review.

Around the world

UN OCEAN SUMMIT: In France, a “surge in support” brought the number of countries ratifying the High Seas Treaty to just 10 short of the 60 needed for the agreement to become international law, according to Sky News.
CALLING TRUMP: Brazil’s president Luiz Inácio Lula da Silva said he would “call” Trump to “persuade him” to attend COP30, according to Agence France-Presse. Meanwhile, the Associated Press reported that the country’s environmental agency has fast tracked oil and highway projects that threaten the Amazon.
GERMAN FOSSIL SURGE: Due to “low” wind levels, electricity generation from renewables in Germany fell by 17% in the first quarter of this year, while generation from fossil-fuel sources increased significantly, according to the Frankfurter Allgemeine Zeitung.
BATTERY BOOST: The power ministry in India announced 54bn rupees ($631m) in funding to build 30 gigawatt-hours of new battery energy storage systems to “ensure round-the-clock renewable energy capacities”, reported Money Control.

-19.3C

The temperature that one-in-10 London winters could reach in a scenario where a key Atlantic ocean current system “collapses” and global warming continues under “intermediate” emissions, according to new research covered by Carbon Brief.

Latest climate research

A study in Science Advances found that damage to coral reefs due to climate change will “outpace” reef expansion. It said “severe declines” will take place within 40-80 years, while “large-scale coral reef expansion requires centuries”.
Climatic Change published research which identified “displacement and violence, caregiving burdens, early marriages of girls, human trafficking and food insecurity” as the main “mental health” stressors exacerbated by climate change for women in lower and middle-income countries.
The weakening of a major ocean current system has partially offset the drying of the southern Amazon rainforest, research published in Environmental Research has found, demonstrating that climate tipping elements have the potential to moderate each other.

(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)

Captured

Aerosols have masked a substantial portion of historical warming. Chart for DeBriefed.

Aerosols – tiny light‑scattering particles produced mainly by burning fossil fuels – absorb or reflect incoming sunlight and influence the formation and brightness of clouds. In this way they have historically “acted as an invisible brake on global warming”. New Carbon Brief analysis by Dr Zeke Hausfather illustrated the extent to which a reduction in aerosol emissions in recent decades, while bringing widespread public health benefits through avoided deaths, has “unmasked” the warming caused by CO2 and other greenhouse gases. The chart above shows the estimated cooling effect of aerosols from the start of the industrial era until 2020.

Spotlight

How Carbon Brief turns complex research into visuals

This week, Carbon Brief’s interactive developer Tom Pearson explains how and why his team creates visuals from research papers.

Carbon Brief’s journalists will often write stories based on new scientific research or policy reports.

These documents will usually contain charts or graphics highlighting something interesting about the story. Sometimes, Carbon Brief’s visuals team will choose to recreate these graphics.

There are many reasons why we choose to spend time and effort doing this, but most often it can be boiled down to some combination of the following things.

Maintaining editorial and visual consistency

We want to, where possible, maintain editorial and visual consistency while matching our graphical and editorial style guides.

In doing this, we are trying to ease our audience’s reading experience. We hope that, by presenting a chart in a way that is consistent with Carbon Brief’s house style, readers will be able to concentrate on the story or the explanation we are trying to communicate and not the way that a chart might have been put together.

Highlighting relevant information

We want to highlight the part of a chart that is most relevant to the story.

Graphics in research papers, especially if they have been designed for a print context, often strive to illustrate many different points with a single figure.

We tend to use charts to answer a single question or provide evidence for a single point.

Paring charts back to their core “message”, removing extraneous elements and framing the chart with a clear editorial title helps with this, as the example below shows.

This before (above) and after (below) comparison shows how adding a title, removing extraneous detail and refining the colour palette can make a chart easier to parse.

Ensuring audience understanding

We want to ensure our audience understands the “message” of the chart.

Graphics published in specialist publications, such as scientific journals, might have different expectations regarding a reader’s familiarity with the subject matter and the time they might be expected to spend reading an article.

If we can redraw a chart so that it meets the expectations of a more general audience, we will.

Supporting multiple contexts

We want our graphics to make sense in different contexts.

While we publish our graphics primarily in articles on our website, the nature of the internet means that we cannot guarantee that this is how people will encounter them.

Charts are often shared on social media or copy-pasted into presentations. We want to support these practices by including as much context relevant to understanding within the chart image as possible.

Below illustrates how adding a title and key information can make a chart easier to understand without supporting information.

This before (left) and after (right) comparison shows how including key information within the body of the graphic can help it to function outside the context of its original research paper.

When we do not recreate charts

When will we not redraw a chart? Most of the time! We are a small team and recreating data graphics requires time, effort, accessible data and often specialist software.

But, despite these constraints, when the conditions are right, the process of redrawing maps and charts allows us to communicate more clearly with our readers, transforming complex research into accessible visual stories.

Watch, read, listen

SPENDING $1BN ON CLIMATE: New Scientist interviewed Greg de Temmerman, former nuclear physicist turned chief science officer at Quadrature Climate Foundation, about the practicalities and ethics of philanthropic climate-science funding.

GENDER HURDLES: Research director Tracy Kajumba has written for Climate Home News about the barriers that women still face in attending and participating in COPs.

OCEAN HEATWAVES: The New York Times presented a richly illustrated look at how marine heatwaves are spreading across the globe and how they affect life in the oceans.

Coming up

16-26 June: Bonn climate talks, Bonn, Germany
16 June: 79th meeting of the World Meteorological Organization executive council, Geneva, Switzerland
17 June: International Energy Agency (IEA) Oil 2025 report launch

Pick of the jobs

Inside Climate News, California environmental reporter | Salary: Unknown. Location: Southern California
Natural Resources Wales, lead marine and energy policy advisor | Salary: £45,367-£50,877. Location: Wales
Children’s Investment Fund Foundation, senior manager, climate | Salary: £82,000. Location: London/hybrid
Green Party,social media and digital content officer | Salary: £33,211. Location: London/remote

DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.

This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.

The post DeBriefed 13 June 2025: Trump’s ‘biggest’ climate rollback; UK goes nuclear; How Carbon Brief visualises research appeared first on Carbon Brief.

DeBriefed 13 June 2025: Trump’s ‘biggest’ climate rollback; UK goes nuclear; How Carbon Brief visualises research

Greenhouse Gases

Chart: The rise, fall and rise of UK nuclear power over eight decades

Published

8 hours ago

June 13, 2025

Alice Rush

The UK’s chancellor Rachel Reeves gave the green light this week to the Sizewell C new nuclear plant in Suffolk, along with funding for “small modular reactors” (SMRs) and nuclear fusion.

In her spending review of government funding across the rest of this parliament, Reeves pledged £14.2bn for Sizewell C, £2.5bn for Rolls-Royce SMRs and £2.5bn for fusion research.

The UK was a pioneer in civilian nuclear power – opening the world’s first commercial reactor at Calder Hall in Cumbria in 1956 – which, ultimately, helped to squeeze out coal generation.

Over the decades that followed, the UK’s nuclear capacity climbed to a peak of 12.2 gigawatts (GW) in 1995, while electricity output from the fleet of reactors peaked in 1998.

The chart below shows the contribution of each of the UK’s nuclear plants to the country’s overall capacity, according to when they started and stopped operating.

The reactors are dotted around the UK’s coastline, where they can take advantage of cooling seawater, and many sites include multiple units coded with numbers or letters.

UK nuclear capacity, 1955-2100, gigawatts. Individual plants are shown separately. Source: World Nuclear Association and Carbon Brief analysis.

Since Sizewell B was completed in 1995, however, no new nuclear plants have been built – and, as the chart above shows, capacity has ebbed away as older reactors have gone out of service.

After a lengthy hiatus, the Hinkley C new nuclear plant in Somerset was signed off in 2016. It is now under construction and expected to start operating by 2030 at the earliest.

(Efforts to secure further new nuclear schemes at Moorside in Cumbria failed in 2017, while projects led by Hitachi at Wylfa on Anglesey and Oldbury in Gloucestershire collapsed in 2019.)

The additional schemes just given the go-ahead in Reeves’s spending review would – if successful – somewhat revive the UK’s nuclear capacity, after decades of decline.

However, with the closure of all but one of the UK’s existing reactors due by 2030, nuclear-power capacity would remain below its 1995 peak, unless further projects are built.

Moreover, with the UK’s electricity demand set to double over the next few decades, as transport, heat and industry are increasingly electrified, nuclear power is unlikely to match the 29% share of generation that it reached during the late 1990s.

There is an aspirational goal – set under former Conservative prime minister Boris Johnson – for nuclear to supply “up to” a quarter of the UK’s electricity in 2050, with “up to” 24GW of capacity.

Assuming Sizewell B continues to operate until 2055 and that Hinkley C, Sizewell C and at least three Rolls-Royce SMRs are all built, this would take UK capacity back up to 9.0GW.

Methodology

The chart is based on data from the World Nuclear Association, with known start dates for operating and retired reactors, as well as planned closure dates announced by operator EDF.

The timeline for new reactors to start operating – and assumed 60-year lifetime – is illustrative, based on published information from EDF, Rolls-Royce, the UK government and media reports.

The post Chart: The rise, fall and rise of UK nuclear power over eight decades appeared first on Carbon Brief.

Chart: The rise, fall and rise of UK nuclear power over eight decades

Greenhouse Gases

Guest post: How climate change is fuelling record-breaking extreme weather

Published

9 hours ago

June 13, 2025

Alice Rush

Recent years have seen a rapid succession of climate-related records broken.

To name just a few, the world has witnessed record warmth in the Atlantic, unprecedented glacier melt, all-time low Antarctic sea ice extent, the Amazon’s worst drought since observations began and UK temperatures soaring past 40C for the first time.

In a review article, published in Nature Reviews Earth & Environment, my coauthors and I look at how the frequency of weather records is changing as the planet warms.

We find that the number of hot temperature records observed around the world since 1950 far exceed what would be expected in a million years in a world without human-caused climate change.

Specifically, we show that “all-time” daily hot records on land were more than four times higher in 2016-24 than they would have been in a world without climate change.

Meanwhile, daily maximum rainfall records were up 40% over the same time period and record cold events were twice as rare.

A key finding of our research is that it is the pace of global warming that controls the occurrence of records.

We show that, if the pace of warming were to slow down, the frequency of record-breaking hot events would start to decline – even if global temperatures continue to rise.

Counting records

By definition, records are supposed to be rare events, at least in a system that is not changing.

Statistics of record occurrence are remarkably simple. They are expected to become rarer the longer a measurement series gets.

The chance of observing a new record after 20 years of measurement is one in 20, or 5%. And after 100 years of observations, the chances of a new record drops to 1%.

For example, this is why it becomes increasingly difficult to break records in athletics as time goes by, unless training methods or sports equipment improve.

Record-breaking weather events – for example, the highest windspeed, most intense rainfall or hot and cold temperatures – also face these odds in a climate that is “stationary”.

However, today’s climate is not stationary, but warming at a very high pace. This has significant implications for the record count.

The plot below shows how the frequency of all-time hot records (dashed red line) and record cold events (dashed blue line) has changed since the 1960s. This is compared to the probability that would be expected under a stationary climate (black line).

(The plot uses ERA5, a reanalysis dataset, which combines observations and models from the European Centre for Medium-Range Weather Forecasts (ECMWF).)

It illustrates how the frequency of hot events declined more slowly than would be expected in a stationary climate since 1950, before increasing in the last 15 years. Meanwhile, the frequency of record cold events is declining more quickly than expected.

The frequency of all-time hot records (dashed red line) and cold records (dashed blue line) over global land regions shown as a nine-year running average over 1950-2024, as represented by the Copernicus/ECMWF ERA5 surface temperature reanalysis. This is contrasted with the theoretical probability of new records expected in a stationary climate as the temperature measurement series expands (black line). Credit: Amended from Fischer et al (2025).

The record ratio

Tracking the ratio between the measured number of records and the one theoretically expected in a stationary climate – the “record ratio” – reveals the fingerprint of climate change.

Analysis of ERA5 data and Berkeley Earth surface temperature observations finds that the record ratio over the last decade for hot records over global land regions is more than four. For cold records, it is between 0.2 and 0.5, showing that record-breaking cold has declined

In other words, there were more than four times as many hot record events and less than half as many cold record events than would be expected without global warming.

In 2023 and 2024, the record ratio for hot events reached 5.5 and 6.2, respectively.

Record ratios tend to be higher over global oceans than on land. They are also higher for monthly or seasonal record temperatures than all-time daily records.

This is because natural variability in the climate tends to be smaller over oceans and for longer averaging periods, such as months and seasons.

Record counts directly relate to the relationship between rates of warming and natural fluctuations in the climate. This is sometimes referred to as the “signal-to-noise ratio”. (The “signal” being the long-term trend of climate change and “noise” referring to short-term fluctuations of natural variability.)

As a result, event types and regions with a higher signal-to-noise ratio tend to see a greater number of records.

Another way of illustrating the signal of climate change is by counting the total number of records in a measurement series.

In a stationary climate, there should be about five records in 100 years of temperature measurements, 7.5 in 1,000 years and less than 10 in 10,000 years.

However, our analysis of records in two measurement series shows how the number of record-breaking events has become significantly higher as the climate has changed.

For example, as the figure on the left below illustrates, a new annual record for average global temperature has been set 25 times over the past 175 years.

Meanwhile, the figure on the right shows how, in the Pacific north-west, a new five-day average heat record has been set 14 times within the last 75 years. The spike in temperature in 2021 reflects the brutal heatwave that killed hundreds of people and brought devastating wildfires that almost entirely destroyed the Canadian village of Lytton.

(In both figures, the warm records are marked by pink circles.)

According to fundamental laws of statistics, 14 new records would not be expected in more than a million years in a climate that is not warming.

Left: Global annual average temperature anomalies between 1850-2025, relative to 1850-1900, based on Berkeley Earth Surface Temperatures (BEST) data. Twenty-five warm records are marked by pink circles. Right: Annual five-day maxima of average temperature in the Pacific north-west, based on ERA5 reanalysis, along with 14 heat records marked by pink circles. Credit: Erich Fischer.

It is worth noting that some climate variables, including ocean heat content, sea level rise and minimum glacier or ice sheet volumes, are changing so relentlessly that new record levels are currently set every year.

Record-shattering events

Record-shattering events are a subset of record-breaking events whose magnitude exceeds the previous event by a large margin.

In our research, we define this as more than one standard deviation, which is a measure of how spread out data is from the average.

(The exact value of standard deviation varies for different parts of the world. For example, when it comes to year-to-year average temperatures, one standard deviation is typically 2-3C in the Arctic, but less than 0.5C over the ocean).

These events of unprecedented intensity are often very impactful as they strongly exceed the conditions that society or ecosystems have experienced in the past.

The 2021 heatwave in the Pacific north-west, mentioned above, is a forbidding example.

Our research finds that the large number of record-shattering events in the past three decades is the consequence of a very high warming rate.

Using a simple timeseries model, we illustrate why the pace of warming is the key factor explaining the occurrence of record-shattering events.

In the left-hand figure, we assume a 150-year period of no warming followed by some linear warming at three different rates, which is a very simplistic approximation of historical and future warming pathways.

The right-hand figure illustrates what happens to the probability of record-shattering events in the Pacific north-west region under these three simplified pathways. It shows that the probability of record-shattering events at first rapidly increases and then stabilises. And the level at which the probability stabilises is greater the higher the rate of warming.

Left: Three illustrative warming pathways with +/- 20% differing warming rates from a timeseries model. Right: Annual probability of record-shattering events (at or beyond one standard deviation) for different warming rates. Residual variability is used from Community Earth System Model 2 simulations for annual five-day maxima over the Pacific north-west. Credit: Amended from Fischer et al (2025).

We therefore conclude that the high frequency of record-shattering hot extremes in recent years is controlled by the very high rate of warming caused by human-caused greenhouse gas emissions.

This tight coupling of record counts to the rate or speed of warming implies that there will be early benefits of slowing down global warming.

In our research, we look at how the probability of hot and cold records changes under different emissions reduction scenarios. To do this, we analysed the occurrence of record hot and cold events in climate model projections in the CMIP6 archive.

The figure below shows how stabilising temperatures by achieving net-zero carbon emissions (SSP1-1.9 and SSP1-2.6) will lead to a rapid decline of records, even if temperatures remain higher than in the historical period.

(It is worth noting that, while the number of records will decline under this lower-emissions scenario, the number of heatwaves would remain higher than today.)

Under intermediate (SSP2-4.5), high (SSP3-7.0) and very high emission (SSP5-8.5) scenarios, the number of records would continue to increase to levels much higher than today.

Projected changes in record hot and cold records under different Shared Socioeconomic Pathways (SSP), including SSP1-1.19 (light blue), SSP1-2.6 (dark blue), SSP2-4.5 (yellow), SSP3-7.0 (orange) and SSP5-8.5 (dark red). The record ratio is calculated as the probability of all-time record daily hot or cold temperatures across global land regions, relative to the theoretically expected occurrence in a stationary climate. The black line represents the historical record. Credit: Fischer et al. (2025)

Rainfall records

We would also expect rainfall records to become progressively rarer in a stationary climate.

However, we find that record-breaking heavy precipitation occurred about 40% more often in 2015-24 than would be expected in a stationary climate. Many record-shattering heavy rainfall extremes occurred in the mid-latitudes and led to flooding which had large impacts.

(Calculating the frequency of records is more challenging for rainfall than for temperature, given small-scale variations and uncertainties in rainfall observations.)

The greater number of record-breaking rainfall events is due to an increase in precipitation intensity over most land regions as the atmosphere warms, as well as larger variations of rainfall intensity on a day-to-day, season-to-season and year-to-year basis .

We also find that the margin by which previous rainfall records are broken tends to become larger and larger in time. This is due to the “non-symmetric” distribution of rainfall – where there are many days with little precipitation, less with heavy precipitation and very few with very extreme precipitation.

It is therefore not surprising to see record-shattering precipitation events exceeding previous records by 20-50% in intensity, even if overall precipitation intensity increases by roughly 7% per degree of warming.

Preparing for the future

Efforts to adapt to climate change are typically informed by the worst events observed in recent generations.

This means that society is often underprepared for record-shattering events – which by their very definition are of unprecedented intensity.

Qualitative and quantitative storyline methods can offer insight into the many record-breaking events to come into the future – and, thus, help society prepare for escalating climate impacts.

These methods combine information from historical and paleoarchives, long measurement series, targeted climate model experiments, statistical and machine learning methods and weather forecasting systems.

Ultimately, these methods can improve society’s preparedness to climate change, so that the next record-shattering extreme does not come as a surprise.