We handpick and explain the most important stories at the intersection of climate, land, food and nature over the past fortnight.
This is an online version of Carbon Brief’s fortnightly Cropped email newsletter. Subscribe for free here.
Key developments
‘Tricks’ and ‘cover-ups’
LIVESTOCK EMISSIONS: Climate scientists speaking to the Financial Times accused the governments of New Zealand and Ireland of using an “accounting trick” to “cover up” methane emissions from their livestock sectors. An open letter from 26 climate scientists and covered by the newspaper said that New Zealand’s “proposed new methane targets risk setting a dangerous precedent”. The title added that scientists have separately raised concerns about Ireland’s approach.
POTENTIAL PROBLEMS: The controversy hinges on a way for measuring the impact of methane emissions on climate change, called “global warming potential star” (GWP*), the FT said. This method “estimates [methane’s] contribution to warming based on how emissions are changing relative to a baseline”. By contrast, the “long-established approach” used by most countries “compares the total warming impact of a given mass of methane to the same mass of [carbon dioxide] over a 100-year period”, the newspaper said.
‘MISAPPLICATION’: The scientists told the FT that some governments are “misapplying” GWP* to justify setting “no additional warming” targets, which allow methane emissions to remain flat rather than decline. The governments of Ireland and New Zealand did not respond to the newspaper’s requests for comment. But the newspaper added that “proponents” of the GWP* typically argue that it “better reflects methane’s short-lived nature in the atmosphere compared to the long-lasting effects of CO2”. One of the scientists behind the letter explained more of his thoughts in a LinkedIn post. A scientist not involved in the letter also posted a response.
SOMETHING FISHY: Elsewhere, an investigation by DeSmog and the Guardian has alleged that several UK supermarkets have sold seabass linked to “devastating overfishing” in Senegal. The two publications said that the retailers are accused of selling fish from Turkish farms that import large quantities of “fishmeal” – ground up fish used as feed – sourced from the African nation. Overfishing for fishmeal in Senegal is linked to “unemployment” and “food insecurity”, according to the Guardian. Responding to the claims, several of the supermarkets said they do not currently source from the implicated farms, but declined to say whether they had in the past.
Wild weather worldwide
EARLY MONSOON MAYHEM: An “unprecedented” early monsoon caught India’s farmers off guard, with “massive crop losses in states such as Tamil Nadu, Maharashtra, Telangana and Gujarat”, IndiaSpend reported. Climate scientists attributed the pre-monsoon thunderstorms to “unusual sea surface temperature patterns in the Pacific since 2023” and a higher frequency of “western disturbances” – extratropical storms originating over the Mediterranean. In the past week, north-eastern India has been battered by flash floods and landslides, with “at least 32 people killed and tens of thousands displaced”, the Independent reported. The newspaper noted that “studies show the monsoon in south Asia is getting worse due to the climate crisis”.
DELUGE AND DROUGHT: BBC News reported that more than 700 people are believed to be dead after “devastating” floods hit Nigeria, with the farming region of Mokwa witnessing “the worst [floods] in the area for 60 years”. Separately, Reuters reported that China’s south-western Yunnan province was hit by “flash floods and mudslides”, triggered by heavy rainfall. In unconnected reporting, Bloomberg said that China had stepped up cloud seeding to “bolster rainfall across parched wheat-growing areas” in the north, adding that the country had ramped up “weather modification” investments as “climate change heightens food security risks.”
CANADA BURNS: Canada’s prairie provinces continued to reel from “record-breaking” early-season wildfires, the Guardian reported. It pointed out that in Manitoba alone, wildfires have burned “about 200,000 hectares already this year” – three times “the recent full-year average”. Manitoba premier Wab Kinew said that simultaneous fires “in every region” were a “sign of a changing climate that we are going to have to adapt to”. The Guardian added that First Nations peoples in Saskatchewan – one of three recognised Indigenous peoples in Canada – “have been particularly affected, with some entire communities evacuated”.
Spotlight
UK’s former lead negotiator on UN nature talks
In this Spotlight, Carbon Brief speaks to the UK’s former lead UN negotiator about the successes and challenges of international nature talks.
Will Lockhart OBE represented the UK in UN nature negotiations from 2021 until the end of COP16 talks in Rome in February of this year.
In 2022, he helped to negotiate the Kunming-Montreal Global Biodiversity Framework (GBF), a landmark deal which has a headline “mission” to “halt and reverse” nature loss by 2030.
Following his departure from government, he spoke to Carbon Brief about his highs and lows, whether the world is making progress towards meeting its biodiversity goals and the role of UN summits – called COPs – in tackling environmental issues.
Carbon Brief: When you look back at your time heading up biodiversity negotiations, what are your highlights?
Will Lockhart: It’s all still emotionally raw. From a global perspective, the agreement of the GBF was a huge personal highlight. That was a really, really complicated negotiation. The notion that you could have frontpage news that was about an international agreement on nature, that was immensely exciting.
CB: In your view, is it possible to achieve the GBF’s mission to halt and reverse biodiversity loss by 2030?
WL: The trajectory right now would suggest, no, it’s looking incredibly hard to achieve. But, even then, with exactly the right interventions at exactly the right scale, it might still be possible. A fair question might be was it ever possible?…There has always been a contested evidence base about whether it could ever have been achieved.
The important thing is that people spent a lot of time thinking about why we were setting certain kinds of targets…We wanted them to be specific, measurable and achieveable. What does achievable mean? What does ambitious mean? What message are we trying to send? This is politics, this isn’t necessarily science.
If the answer is that it was never possible in the first place, then the question is: ‘Why did the world agree to it?’ And the answer to that is: ‘Because it matters that we try.’
CB: Could there be a better way for countries to address biodiversity loss than the current system?
WL: It’s a very complicated question. A question that everyone has to bear in mind is: ‘What [is the] value [of] the COPs?’ You pour a huge amount of time and resource into a global dialogue, which results in a very, very carefully negotiated outcome. It’s extremely important, in my view, that you have a space where the whole world can come together in a room and agree that it wants to do something. The question is, where does the world locate that process?
I worry that the world is simultaneously asking too much and too little of COPs. It’s asking too much in the sense that there’s so much coverage and intense scrutiny of ‘this person’s arrived’, ‘this comma has moved’…There’s an extraordinary media circus. [There is] extreme expectation on each individual meeting.
And, at the same time, it’s simultaneously asking too little of them. It’s like: ‘Great, this word was in so it was a good COP’ or ‘this word was out so it was a bad COP’. And of course COPs are just one tiny part of this huge global process that needs to happen if we’re going to tackle these problems. I rather worry – and I know that colleagues feel the same – they’re just viewed as ends in themselves.
This interview has been edited for clarity and length. A longer article has been published on Carbon Brief’s website.
News and views
RECORD FOREST LOSS: Tropical forest loss hit its highest level in a two-decade record in 2024 – double the level of 2023 – according to satellite data from Global Forest Watch covered by New Scientist. The report authors “attributed the surge in forest loss to the El Niño weather phenomenon and the warming global climate, which made the rainforest a tinderbox”, the magazine said. Climate Home News added that the rate of forest loss was the equivalent of losing 18 football pitches every minute.
RATIFY THIS: The EU ratified the UN “High Seas Treaty” last Wednesday, “joining a global effort to protect the ocean, curb environmental damage, tackle climate change and preserve biodiversity”, Jurist News reported. The EU’s ratification of the landmark treaty was joined by six of its member states: Cyprus, Finland, Hungary, Latvia, Portugal and Slovenia. The EU also pledged €40m as part of a Global Ocean Programme to support African, Caribbean and Pacific countries, according to an EU Commission press release.
THOUSAND CUTS: A “cornerstone” ecological research programme could potentially be culled by the Trump administration, the New York Times reported. Abolishing the Ecosystems Mission Area (EMA) “was an explicit goal of Project 2025, the blueprint for shrinking the federal government”, the story added. However, the budget cut “still needs to be approved by Congress”, with scientists rallying to save the EMA, the paper wrote. On Monday, the Trump administration announced plans to “eliminate federal protections across millions of acres of Alaskan wilderness” that could open the region to drilling and mining, according to another New York Times story.
NET NATURE LOSS?: In the UK, the Guardian reported that the “nature-friendly farming budget is set to be slashed” for “all but a few farms” in an upcoming spending review. Meanwhile, legal analysis of the Labour government’s new planning and infrastructure bill showed that “more than 5,000 of England’s most sensitive, rare and protected natural habitats are at high risk of being destroyed by development”, per another Guardian story. A key concern for green groups, it added, is a “cash for trash” clause that allows developers to “inflict adverse effects on the integrity of a protected site” if they pay into a fund to restore nature elsewhere.
MIRAGE CITY: Reuters reported on Egypt’s plans to build a new desert city, 42km west of Cairo, that could reroute “about 7% of [its] annual Nile River quota” from fertile delta land. According to the story, an estimated 10m cubic metres of Nile water will flow daily to Jirian city to “pass by upscale glass-fronted housing units and eventually” irrigate a 2.28m acre “New Delta” agricultural project. Jirian city will include luxury housing, a free economic zone and even a “yacht marina”, the newswire added, noting that the country is facing “mounting water shortages, power constraints and deepening economic crisis”.
FOREST-FRIENDLY BATTERIES: Electric car batteries made using iron and phosphorus “that pose less of a threat to forests” are “rapidly replacing batteries reliant on cobalt and nickel”, according to an International Energy Agency (IEA) report covered by Climate Home News. From 2020 to 2024, the market share of lithium nickel manganese cobalt batteries has risen from one-tenth to almost half, according to the IEA data. Both cobalt and nickel are “mainly mined in rainforest countries”, such as the Democratic Republic of the Congo and Indonesia, the publication added.
Watch, read, listen
REFORESTED SCHOOLS: Mongabay explored how “urban forests” in schools in Niger are helping to build “climate resilience and education”.
SO LONG, SALGADO: The New Yorker examined the visual legacy of photojournalist Sebastião Salgado, who died last week. Salgado’s Genesis series is celebrated as a “paean to natural landscapes and Indigenous ways of living”.
SECOND ACT: In an Atlantic long-read, writer Emma Marris looked at the debate calling for a law to protect ecosystems along with endangered species in the US.
PROUD, NATURALLY: CBC News reviewed Animal Pride, a new documentary about queer animal behaviour that filmmaker Connel Bradwell described as “nature’s coming-out story”.
New science
- Greater fish biodiversity can help improve nutrition and make fisheries more resilient, according to new research published in Nature Sustainability. The study found that fishing waters with complementary species could provide more than 60% in additional nutrients than a similar-sized catch of the most nutrient-rich species.
- A new study in Nature Climate Change found that “natural climate solutions” in croplands offer only “modest” mitigation benefits if reductions in crop yields are to be avoided. According to the authors, this indicates that “cropland soil will constitute a fraction of food system decarbonisation”.
- New research in Communications Earth and Environment found that global agricultural labour productivity could decrease by 18% by 2100 under a scenario of high heat-stress and labour sensitivity.
In the diary
- 2-6 June: 69th Meeting of the Global Environment Facility Council | Washington DC
- 5 June: World Environment Day
- 7 June: Ocean Rise and Coastal Resilience Summit | Nice, France
- 9-13 June: 2025 UN Ocean Conference | Nice, France
- 16-26 June: UN Framework Convention on Climate Change intersessional meetings | Bonn, Germany
Cropped is researched and written by Dr Giuliana Viglione, Aruna Chandrasekhar, Daisy Dunne, Orla Dwyer and Yanine Quiroz. Please send tips and feedback to cropped@carbonbrief.org
The post Cropped 4 June 2025: ‘Tricks’ and ‘cover-ups’; Wild weather; Former UN nature negotiator interviewed appeared first on Carbon Brief.
Cropped 4 June 2025: ‘Tricks’ and ‘cover-ups’; Wild weather; Former UN nature negotiator interviewed
Greenhouse Gases
DeBriefed 13 June 2025: Trump’s ‘biggest’ climate rollback; UK goes nuclear; How Carbon Brief visualises research
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 – 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.
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.
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.
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.
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
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 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.
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.
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.
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.
The post Guest post: How climate change is fuelling record-breaking extreme weather appeared first on Carbon Brief.
Guest post: How climate change is fuelling record-breaking extreme weather
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