Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Record floods across the globe
IVORY COAST: Floods and landslides killed at least 24 people in Ivory Coast’s largest city of Abidjan after a week of heavy rains that was “four times the usual volume in some cases”, the Associated Press reported. The newswire added that the city’s disadvantaged communities are “particularly vulnerable” because of poor storm drainage in informal settlements.
CHINA ‘SWAMPED’: Landslides killed eight people in their homes in southern China’s Hunan province, said the South China Morning Post, with Taoyuan county receiving 39.5cm of rain in a day. Record rains “swamped” Hunan’s capital of Changsha, “turning roads into rivers and submerging subway tunnels”, Reuters wrote. By Monday, 33 rivers had “exceeded warning levels”, Xinhua reported. Associated Press also reported that flooding killed two people in the “deluged” US midwest.
BANGLADESH INUNDATED: Widespread flooding has stranded nearly two million people in north-east Bangladesh, CNN reported. It added that “large swathes” of Sylhet and Sunamganj provinces were underwater after a second wave of flooding hit the region in less than a month, with 772,000 children “in urgent need of assistance”. Camps in Cox’s Bazaar that accommodate “almost [one million] documented [Rohingya] refugees have been overrun by the incoming floodwaters”, Down to Earth reported, with at least 10 Rohingya fatalities out of the total 31 deaths in the Bangladesh floods this year.
Heat deaths: tolls apart
PAKISTAN’S FATAL HEAT: Doctors in Karachi “treated thousands of victims of heatstroke at various hospitals” after a “days-long heatwave” scorched southern Pakistan, the Associated Press reported. While local media reported that the heatwave “killed more than two dozen people” in Karachi alone, AP added that “no government spokesman was available to confirm the number of heatstroke-related deaths”. However, the Edhi ambulance service told BBC News it had taken around 568 people’s bodies to the Karachi city morgue in Pakistan over the past six days – up from its usual rate of 30-40 bodies a day.
‘TOLLS APART’: In neighbouring India, the country’s health ministry said 143 people across the country had died of heatstroke from the start of summer until 20 June, far lower than 209 confirmed and 448 suspected deaths tallied by Times of India. Meanwhile, a non-profit report estimated that “192 homeless individuals died from the heat in just nine days” in the national capital region alone, experts in India Development Review Online wrote, “highlighting the significant underreporting of heat-related deaths” in the country.
CULPABLE HEAT: In the US, the Boston Globe reported that New England experienced the “highest rate of heat-related emergency department visits” in the country, with temperatures in the region crossing 32C. Meanwhile, prosecutors in Arizona could “reasonably press homicide charges against big oil” for heat deaths in the state last year, the Guardian reported. Finally, Reuters wrote that the “sweltering summer” is worsening conditions in Gaza, where “nearly all the 2.3 million inhabitants have been driven from their homes by Israel’s military campaign” with almost no access to electricity and little clean water.
Around the world
- COW TAX: Denmark is set to introduce the world’s first carbon tax on agriculture after a historic agreement on Monday, Politico reported. Farmers will be charged “almost €100 a year” per cow once the levy rolls out in 2030, Financial Times said.
- PARLEY VOUS: In a “new and surprising” move, South China Morning Post reported that China agreed to talks with the EU over its plans to raise tariffs on electric vehicle imports by 48%.
- MAI KUHIHEWA: Youth in the US state of Hawaii who sued transport authorities for their use of fossil fuels reached a “first-of-its-kind” settlement that recognised their “constitutional rights to a life-sustaining climate”, Teen Vogue reported.
- OILSTRUCK: Financial Times reported on ExxonMobil’s development of “one of the largest offshore oil developments in history” and what it could mean for Guyana.
- BP U-TURN: Oil and gas giant BP has imposed a hiring freeze and paused new offshore wind projects to place a greater emphasis on oil and gas rather than renewables amid investor discontent, sources at the company told Reuters.
- PIPELINE PROTESTS: 37 activists in Uganda were arrested for protesting the East African Crude Oil Pipeline (EACOP), calling on China to “reject financial support” to the project, All Africa reported.
£116bn £30bn £2.8tn
Some of the “scary-sounding” numbers being used to mislead the public about the “cost” of net-zero in the UK general-election campaign. Carbon Brief’s Dr Simon Evans has factchecked them.
Latest climate research
- A new study in Nature Ecology and Evolution found that Earth’s most extreme wildfires increased 2.2-fold in the past 20 years, with the last seven years seeing the six most extreme fires on record.
- According to new research in Nature Climate Change, a 1C rise in average temperatures would mean four extra minutes every day spent collecting water for women. By 2050, women could spend 30% and 100% more time – globally and regionally – collecting water, “undermining” their welfare.
- New research on grounding zones – where ice transitions from land to water – suggests that sea-level rise projections could be substantially underestimated, according to a Carbon Brief guest post.
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
New Carbon Brief analysis found that UK governments in England, Scotland, Wales and Northern Ireland have missed their tree-planting targets set in 2020 and failed to plant an area of forest nearly the size of Birmingham. Tree-planting is a “significant” part of the UK’s net-zero strategy to compensate for other polluting sectors. By 2050, the unplanted trees would have removed some 8.5m tonnes of CO2 from the atmosphere, roughly 2% of the UK’s annual emissions in 2023. This shortfall will need to be made up for with stronger efforts elsewhere if the UK’s net-zero by 2050 target is to be met.
Spotlight
Monsoon mixtape
As the UK gears up for Glastonbury, Carbon Brief interviews pioneering Indian hip-hop and folk artists about protest music and the role of artists in an era of climate change.
When Carbon Brief spoke to the Marathi-language rapper MC Mawali from the hip-hop collective Swadesi, Mumbai was under an orange alert for extremely heavy rains, after stalling for most of the month.
The monsoon has changed along with the mega-city most defined by it. Massive infrastructure projects have cost the island city its flood buffers, including the much-diminished Aarey forest, home to the Indigenous Warli tribe and the only urban leopard population in the world.
In 2019, Mawali, along with fellow Swadesi rappers and Warli bard Prakash Bhoir, gave Mumbai’s #SaveAarey movement its protest anthem, The Warli Revolt – its chorus warning of a dystopian climate future to come.
“I used to go to Aarey to swim in the Vihar lake as a kid, but I didn’t know about [Warli] culture, their instruments, their songs going extinct that are not on the internet,” said Mawali.
When the chainsaws came for the forest, Mawali says he “felt helpless”, but he’s happy to hear that Warli Revolt has become a go-to anti-deforestation anthem across the country since. He added:
“Today’s music business is about labels pouring in music and splashing their artists all over platforms that censor messages like ours, but, through hip-hop, we’ve learned to hijack that same system to keep folk, tribal and conscious music alive.”
To anti-caste singer-poet Dhammarakshit Randive from the Yalgaar Sanskrutik Manch collective, the word “green” has turned into “its own kind of propaganda” that justifies “ask-no-questions development”, with high displacement of people and a large emissions footprint.
“‘Green’ often becomes propaganda, telling us you can offset 100 trees in a biodiverse forest that Adivasis (Indigenous peoples) depend on by planting another 1,000 somewhere else,” he told Carbon Brief.
Randive sees climate change, anti-caste and “movements to centre democracy” as interlinked, “affecting all our lives, everywhere”. To him, the main role of musicians and artists in responding to climate change is to establish that intersectionality. He told Carbon Brief:
“Otherwise, those fighting for forests are dying unheard in those same forests, sanitation workers are dying in the same sewers, factory workers are dying in the heat and there’s no one to widen peoples’ perspectives to say ‘this is all part of the same struggle’.”
Taru Dalmia, also known as Delhi Sultanate, was among the earliest pioneers to fuse dub and dancehall with protest anthems penned by Indigenous singers, such as Bhagaban Majhi, protesting mining projects in central India. Blood Earth, the album Dalmia made with producer Chris McGuiness, is now 12-years-old, but remains just as relevant.
“At that time we made it, I felt that there was a kind of hidden violence and not as much discourse about a war-like situation in [mineral-rich Indian states],” said Dalmia, speaking to Carbon Brief. He feels that, since then, “there’s definitely more awareness and politicisation which has to do with how much more repressive things have gotten and [environmental and other] issues staring at us in the face”.
While hip-hop has “blown up” over the past half-decade, he feels that little has changed as far as mining companies are concerned, since “profit margins remain huge”. Dalmia added:
“This awareness of how fundamentally our way of life is based on extraction, extractive industries and destruction and how that’s a direct continuation of the colonial project…sure, there’s more politicisation, but the depth of it is still missing.”
While extreme weather has not quite made its way to the airwaves, aside from boilerplate Bollywood songs invoking heat and rain, mercury levels were the subject of one of India’s earliest environmental campaign songs.
In 2015, a young Sofia Ashraf dropped the single Kodaikanal Won’t, a rap parody of Nicki Minaj’s Anaconda, demanding that Unilever clean up toxic waste from its thermometer factory dumped in the rainforest and compensate its workers for mercury poisoning. It drew over 2m views, praise from Minaj and a public apology and settlement from Unilever. Speaking to Carbon Brief, Ashraf said:
“Since Kodaikanal Won’t, there has been a whole gamut of songs around climate change, from general awareness-building to pointed information-sharing, music has been used effectively to express the dread a lot of us live under. The downside is that greenwashing is constantly on the rise and there is too much onus on the audience to parse this content for the truth.”
But she remains optimistic, telling Carbon Brief:
“As long as art still strives to build conscious narratives, I feel we are headed in the right direction.”
Watch, read, listen
PETROCENTRIC: Adam Hanieh, author and professor of political economy at the University of Exeter, spoke to the Break Down about all the ways in which oil came to “permeate” our lives.
MIC TEST: Vox tuned in to how scientists are listening to Puerto Rico’s frogs to understand how climate change is altering life on the rainforest island.
NON-ALIGNED: A piece in Drilled unpacked new research prompting questions of what “Paris-aligned” means and whether “climate pledges…need a terminology overhaul”.
Coming up
- 22-30 June: London climate action week
- 30 June: France national assembly elections, first round
- 4 July: UK general election
Pick of the jobs
- International Institute for Environment and Development (IIED), head of global climate law, policy and governance programme (maternity cover) | Salary: £64,814-£80,654. Location: UK (hybrid) with access to London office
- Sustainable Futures Collaborative, senior research associate, climate policy | Salary: Unknown. Location: New Delhi
- Climate and Community Project, data communications manager | Salary: $105,000. Location: US (fully remote), one week of travel every two months
- Global Campaign to Demand Climate Justice (DCJ), communications coordinator. Salary: $38,400. Location: Remote. Preference for candidates from the global south
- Chr. Michelsen Institute (CMI), global fellowships for scholars from non-OECD countries | Stipend: NOK 15,000 per month, plus travel, accommodation and insurance coverage. Location: Bergen, Norway
- Climate News Tracker, managing editor | Salary: £70,000-£80,000. Location: Remote, with occasional UK travel for meetings
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 28 June 2024: Global floods; Heat deaths uncertainty; India’s climate protest music appeared first on Carbon Brief.
DeBriefed 28 June 2024: Global floods; Heat deaths uncertainty; India’s climate protest music
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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