Published

1 year ago

April 4, 2024

Alice Rush

Over the past year, there has been a vigorous debate among scientists – and more broadly – about whether global warming is “accelerating”.

This, in turn, has led to questions about whether the world is warming “faster than scientists expected”.

Here, Carbon Brief takes a detailed look at the issue and finds that there is increasing evidence of an acceleration in the rate of warming over the past 15 years.

However, this acceleration is broadly in line with projections from the latest generation of climate models and the recent sixth assessment report (AR6) from the Intergovernmental Panel on Climate Change (IPCC). They all expect the world to warm notably faster in both current and future decades than the rate the world has experienced since 1970.

Carbon Brief’s analysis also reveals that the speed up in warming projected in the latest climate models (known as CMIP6) is similar to the acceleration estimated by prominent climate scientist Dr James Hansen and colleagues in their much-discussed 2023 paper in Oxford Open Climate Change.

The IPCC’s AR6 also produced a set of “assessed warming projections” that incorporate multiple lines of evidence. While these project future warming levels a bit below the average of CMIP6 models, they still expect the rate of warming up to 2050 to be around 26% faster than the world has experienced to date since 1970.

Even with an apparent acceleration in recent warming, there remain major questions regarding drivers of 2023’s record-breaking heat relative to 2022, though annual temperatures still remain well within the range of climate-model projections.

An accelerating debate

Between 1970 and 2008, the world warmed at an approximately linear rate – by 0.18C per decade.

However, in recent years, the rise in global surface temperatures has climbed above this long-term trend, with eight of the past nine years showing warming levels above what would be expected given the historical warming rate.

In December 2022, former NASA scientist Dr James Hansen and colleagues published a preprint (later published as a peer-reviewed paper in 2023) projecting an acceleration in the rate of warming over the next few decades. Hansen and colleagues argued that the rate of warming would increase to between 0.27C and 0.36C per decade – or a 50-to-100% increase in the warming rate since 1970 – over the next 30 years.

These projections – coupled with the exceptional and unusual temperatures in 2023 – has fuelled a debate within the scientific community and among the broader public about a potential acceleration in warming in recent years.

This potential acceleration is illustrated in the figure below, which shows a composite of global surface temperatures from five different groups – NASA GISTEMP, NOAA’s GlobalTemp, the UK Met Office/University of East Anglia’s HadCRUT5, Berkeley Earth and Copernicus’ ERA5 – following an approach used by the World Meteorological Organization.

The circles indicate individual years and the dashed lines show the trend over 1970-2008 (blue) and 2009-23 (red). (The past 15 years are highlighted here as that is the time period that has previously been used to assess potential changes in the underlying trend in the scientific literature.)

Annual global average surface temperatures from a composite of NASA GISTEMP, NOAA’s GlobalTemp, the UK MET Office/UEA’s HadCRUT5, Berkeley Earth, and Copernicus’ ERA5 following an approach used by the World Meteorological Organization, with linear trends between 1970 and 2008 (blue) and 2009 and 2023 (red) shown by the dashed lines. Chart by Carbon Brief.

The chart shows how the warming rate of 0.18C per decade seen since 1970 has almost doubled to roughly 0.3C per decade over the past 15 years.

Researchers have proposed a number of potential contributors to the increased rate of warming seen in recent years.

One is the significant decline in global air pollution over the past few decades, as well as a 2020 phase-out of sulphur in marine fuels, which have reduced the levels of cooling aerosols in the atmosphere.

Other suggested factors include an approaching peak in the 11-year solar cycle, the 2022 eruption of the Hunga Tonga volcano and the continued increases in atmospheric greenhouse gas concentrations.

The fact that the past 15 years ended on a particularly high point due to the current El Niño event might also result in higher warming rates – although the contribution of El Niño to overall 2023 temperatures remains an area of vigorous scientific debate.

It is possible to remove the estimated influence of some of the natural factors – such as El Niño and La Niña events, volcanic eruptions and variations in solar output – from the global temperature record.

The figure below shows a version of the temperature record above where these natural factors are removed. The recent warming (red dashed line) is even more evident in this chart compared to the prior trend (blue).

Composite of five annual global average surface temperature records with the El Niño-Southern Oscillation (ENSO), volcanic eruptions and solar variations removed. Linear trends between 1970 and 2008 (blue) and 2009 and 2023 (red) shown by dashed lines. Data from Tamino following an updated version of the methodology in Foster and Rahmstorf 2011. Chart by Carbon Brief.

However, despite this spate of very warm years, it is challenging to draw firm conclusions on the overall rate of global warming based on a time period as short as 15 years.

Even though recent trends appear to show significant acceleration, the long-term trend remains – just barely – within the full range of uncertainty in climate model projections.

There is a risk of conflating shorter-term climate variability with longer-term changes – a pitfall that the climate science community has encountered before.

Parallels with the warming ‘hiatus’

The debate around a potential acceleration in warming shares similarities with another scientific contretemps – the so-called “hiatus” in warming of the early 21st century.

During the 15-year period from 1998 to 2012, the rate of warming at the surface appeared to nearly “pause” – or at least slow down dramatically compared to climate-model projections.

The debate so consumed the scientific community – and some sections of the media – that there was a running joke among scientists that the journal Nature Climate Change should be renamed “Nature Hiatus” for the number of studies it published trying to explain the apparent slowdown.

In retrospect, the apparent hiatus and associated disagreement between climate models and observations was caused by a number of different factors. Key among them were natural variability (in the form of more heat uptake by the oceans), disparities in surface temperature records associated with a transition from ship engine room to automated buoy-based measurements of sea surface temperatures, and incomplete comparisons between climate models and observations that excluded areas such as the Arctic that had sparser observational coverage.

With the development of the 2015-16 “super” El Niño, any sign of a “pause” in warming quickly vanished and the argument faded away – though it made a brief return in climate-sceptic circles in more recent years. However, it left behind a lasting appreciation among many scientists for the danger of overinterpreting short-term climate variability and is one of the reasons why there has been reticence in some circles about current claims of an acceleration.

Nonetheless, there are a number of reasons to expect that what the world is currently experiencing is not just the influence of natural variability on top of human-caused warming. An acceleration of warming in recent decades also shows up in ocean heat content and in satellite measurements of the Earth’s energy imbalance.

And, perhaps most importantly, an acceleration in the rate of warming in recent years – and over the coming decades – is exactly what is seen in climate models under a scenario in keeping with current global policies (known as SSP2-4.5). Under this scenario, greenhouse gas emissions remain around current levels until the middle of the century, alongside a decline in emissions of planet-cooling aerosols such as sulphur dioxide.

An expected acceleration

The most notable thing about the current apparent acceleration in warming is that it was expected.

Climate models have long shown a faster rate of warming in current and future decades than has been observed to date, though there is some disagreement among modelling estimates.

The table below shows a compilation of both observed rates of warming to date and different model projections out to 2050.

Projection	Time period	Trend (C/decade)
Observed trend since 1970	1970-2023	0.19 (0.17 to 0.21)
Observed trend since 2009	2009-2023	0.30 (0.17 to 0.43)
Estimated human contribution (Forster et al, 2023)	2013-2022	0.23
IPCC AR6 assessed warming projections under SSP2-4.5	2015-2050	0.24 (0.17 to 0.34)
Full CMIP6 ensemble under SSP2-4.5	2015-2050	0.29 (0.2 to 0.4)
Hansen et al, 2023	2011-2050	0.32 (0.27 to 0.36)

Global surface temperatures have warmed at a rate of 0.19C per decade between 1970 and 2023. They have warmed at a faster rate (~0.3C per decade) over the past 15 years – though with large uncertainties of 0.17C to 0.43C given the shorter time period.

The estimated human contribution to global warming of 0.23C for the past decade (2013 to 2022), as published in Earth System Science Data by Prof Piers Forster and colleagues, is based on a climate model emulator that is driven by an updated estimate of factors including the influence of greenhouse gases and aerosols on the Earth’s climate in recent years.

The IPCC’s AR6 provided “assessed warming projections” based on CMIP6 models – weighted based on their ability to accurately reproduce historical temperatures – and the recent synthesis of climate sensitivity estimates. These assessed warming projections show 0.24C warming per decade between 2015 and 2050 with an uncertainty range of 0.17C to 0.34C in the current-policy-type SSP2-4.5 scenario. This represents approximately 26% faster warming than the world has experienced since 1970.

The full CMIP6 ensemble of models has notably more warming than the IPCC-assessed warming projections. CMIP6 models, on average, warm by 0.29C per decade with a range of 0.2C to 0.4C, or 53% faster than historical warming since 1970.

The recent projections by Dr James Hansen and colleagues has a very similar projection of future warming rates to the CMIP6 ensemble, estimating warming of around 0.32C per decade with an uncertainty of 0.27C to 0.36C.

These estimates are summarised in the charts below, which show the historical warming rate (top left), the AR6 assessed range under SSP2-4.5 (top right), the CMIP6 models under SSP2-4.5 (bottom left) and Hansen et al’s future warming projection (bottom right). The blue dots and red dashed lines show observed data and the long-term trend, while the black lines and yellow shading show the average of model projections and their ranges.

Comparison of historical and future warming projections from a continuation of the 1970-2023 linear trend (top left), the IPCC AR6 assessed warming range for SSP2-4.5 (top right), the CMIP6 multimodal mean and range for SSP2-4.5 (bottom left) and Hansen et al 2023 (bottom right). Blue dots and red dashed lines show observations and trends, while the black lines and yellow shading show model projections and their ranges. Chart by Carbon Brief.

In all three cases, there is an expectation of acceleration of warming both at present and in coming decades compared to the warming the world has experienced since 1970.

However, this does not mean that the world will pass climate limits such as 1.5C sooner than expected. The current best estimates of when these thresholds will be passed are based on climate models that include the near-term warming acceleration.

The apparent acceleration of warming in recent years is well in line with climate model projections, which lends confidence that what the world is experiencing is a result of human activity rather than a result of natural variability.

However, this does not mean that the world will not experience cool years in the future; the next La Niña year – likely in 2025 – will probably end up well below some of the prior record-setting years.

But, as long as global emissions of CO2 and other greenhouse gases fail to decline and the world continues to tackle aerosol pollution, the world will likely warm faster than experienced in the past.

The post Factcheck: Why the recent ‘acceleration’ in global warming is what scientists expect appeared first on Carbon Brief.

Factcheck: Why the recent ‘acceleration’ in global warming is what scientists expect

Climate Change

DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report

Published

3 weeks ago

August 15, 2025

Alice Rush

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

This week

Blazing heat hits Europe

FANNING THE FLAMES: Wildfires “fanned by a heatwave and strong winds” caused havoc across southern Europe, Reuters reported. It added: “Fire has affected nearly 440,000 hectares (1,700 square miles) in the eurozone so far in 2025, double the average for the same period of the year since 2006.” Extreme heat is “breaking temperature records across Europe”, the Guardian said, with several countries reporting readings of around 40C.

HUMAN TOLL: At least three people have died in the wildfires erupting across Spain, Turkey and Albania, France24 said, adding that the fires have “displaced thousands in Greece and Albania”. Le Monde reported that a child in Italy “died of heatstroke”, while thousands were evacuated from Spain and firefighters “battled three large wildfires” in Portugal.

UK WILDFIRE RISK: The UK saw temperatures as high as 33.4C this week as England “entered its fourth heatwave”, BBC News said. The high heat is causing “nationally significant” water shortfalls, it added, “hitting farms, damaging wildlife and increasing wildfires”. The Daily Mirror noted that these conditions “could last until mid-autumn”. Scientists warn the UK faces possible “firewaves” due to climate change, BBC News also reported.

Around the world

GRID PRESSURES: Iraq suffered a “near nationwide blackout” as elevated power demand – due to extreme temperatures of around 50C – triggered a transmission line failure, Bloomberg reported.
‘DIRE’ DOWN UNDER: The Australian government is keeping a climate risk assessment that contains “dire” implications for the continent “under wraps”, the Australian Financial Review said.
EXTREME RAINFALL: Mexico City is “seeing one of its heaviest rainy seasons in years”, the Washington Post said. Downpours in the Japanese island of Kyushu “caused flooding and mudslides”, according to Politico. In Kashmir, flash floods killed 56 and left “scores missing”, the Associated Press said.
SOUTH-SOUTH COOPERATION: China and Brazil agreed to “ensure the success” of COP30 in a recent phone call, Chinese state news agency Xinhua reported.
PLASTIC ‘DEADLOCK’: Talks on a plastic pollution treaty have failed again at a summit in Geneva, according to the Guardian, with countries “deadlocked” on whether it should include “curbs on production and toxic chemicals”.

15

The number of times by which the most ethnically-diverse areas in England are more likely to experience extreme heat than its “least diverse” areas, according to new analysis by Carbon Brief.

Latest climate research

As many as 13 minerals critical for low-carbon energy may face shortages under 2C pathways | Nature Climate Change
A “scoping review” examined the impact of climate change on poor sexual and reproductive health and rights in sub-Saharan Africa | PLOS One
A UK university cut the carbon footprint of its weekly canteen menu by 31% “without students noticing” | Nature Food

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

Captured

Factchecking Trump’s climate report

A report commissioned by the US government to justify rolling back climate regulations contains “at least 100 false or misleading statements”, according to a Carbon Brief factcheck involving dozens of leading climate scientists. The report, compiled in two months by five hand-picked researchers, inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed” and misleadingly states that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”80

Spotlight

Does Xi Jinping care about climate change?

This week, Carbon Brief unpacks new research on Chinese president Xi Jinping’s policy priorities.

On this day in 2005, Xi Jinping, a local official in eastern China, made an unplanned speech when touring a small village – a rare occurrence in China’s highly-choreographed political culture.

In it, he observed that “lucid waters and lush mountains are mountains of silver and gold” – that is, the environment cannot be sacrificed for the sake of growth.

(The full text of the speech is not available, although Xi discussed the concept in a brief newspaper column – see below – a few days later.)

In a time where most government officials were laser-focused on delivering economic growth, this message was highly unusual.

Forward-thinking on environment

As a local official in the early 2000s, Xi endorsed the concept of “green GDP”, which integrates the value of natural resources and the environment into GDP calculations.

He also penned a regular newspaper column, 22 of which discussed environmental protection – although “climate change” was never mentioned.

This focus carried over to China’s national agenda when Xi became president.

New research from the Asia Society Policy Institute tracked policies in which Xi is reported by state media to have “personally” taken action.

It found that environmental protection is one of six topics in which he is often said to have directly steered policymaking.

Such policies include guidelines to build a “Beautiful China”, the creation of an environmental protection inspection team and the “three-north shelterbelt” afforestation programme.

“It’s important to know what Xi’s priorities are because the top leader wields outsized influence in the Chinese political system,” Neil Thomas, Asia Society Policy Institute fellow and report co-author, told Carbon Brief.

Local policymakers are “more likely” to invest resources in addressing policies they know have Xi’s attention, to increase their chances for promotion, he added.

What about climate and energy?

However, the research noted, climate and energy policies have not been publicised as bearing Xi’s personal touch.

“I think Xi prioritises environmental protection more than climate change because reducing pollution is an issue of social stability,” Thomas said, noting that “smoggy skies and polluted rivers” were more visible and more likely to trigger civil society pushback than gradual temperature increases.

The paper also said topics might not be linked to Xi personally when they are “too technical” or “politically sensitive”.

For example, Xi’s landmark decision for China to achieve carbon neutrality by 2060 is widely reported as having only been made after climate modelling – facilitated by former climate envoy Xie Zhenhua – showed that this goal was achievable.

Prior to this, Xi had never spoken publicly about carbon neutrality.

Prof Alex Wang, a University of California, Los Angeles professor of law not involved in the research, noted that emphasising Xi’s personal attention may signal “top” political priorities, but not necessarily Xi’s “personal interests”.

By not emphasising climate, he said, Xi may be trying to avoid “pushing the system to overprioritise climate to the exclusion of the other priorities”.

There are other ways to know where climate ranks on the policy agenda, Thomas noted:

“Climate watchers should look at what Xi says, what Xi does and what policies Xi authorises in the name of the ‘central committee’. Is Xi talking more about climate? Is Xi establishing institutions and convening meetings that focus on climate? Is climate becoming a more prominent theme in top-level documents?”

Watch, read, listen

TRUMP EFFECT: The Columbia Energy Exchange podcast examined how pressure from US tariffs could affect India’s clean energy transition.

NAMIBIAN ‘DESTRUCTION’: The National Observer investigated the failure to address “human rights abuses and environmental destruction” claims against a Canadian oil company in Namibia.

‘RED AI’: The Network for the Digital Economy and the Environment studied the state of current research on “Red AI”, or the “negative environmental implications of AI”.

Coming up

17 August: Bolivian general elections
18-29 August: Preparatory talks on the entry into force of the “High Seas Treaty”, New York
18-22 August: Y20 Summit, Johannesburg
21 August: Advancing the “Africa clean air programme” through Africa-Asia collaboration, Yokohama

Pick of the jobs

Lancaster Environment Centre, senior research associate: JUST Centre | Salary: £39,355-£45,413. Location: Lancaster, UK
Environmental Justice Foundation, communications and media officer, Francophone Africa | Salary: XOF600,000-XOF800,000. Location: Dakar, Senegal
Politico, energy & climate editor | Salary: Unknown. Location: Brussels, Belgium
EnviroCatalysts, meteorologist | Salary: Unknown. Location: New Delhi, India

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 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report appeared first on Carbon Brief.

DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report

Climate Change

New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit

Published

3 weeks ago

August 15, 2025

Alice Rush

The specter of a “gas-for-wind” compromise between the governor and the White House is drawing the ire of residents as a deadline looms.

By Deep Vakil

Hundreds of New Yorkers rallied against new natural gas pipelines in their state as a deadline loomed for the public to comment on a revived proposal to expand the gas pipeline that supplies downstate New York.

New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit

Climate Change

Factcheck: Trump’s climate report includes more than 100 false or misleading claims

Published

3 weeks ago

August 14, 2025

Alice Rush

A “critical assessment” report commissioned by the Trump administration to justify a rollback of US climate regulations contains at least 100 false or misleading statements, according to a Carbon Brief factcheck involving dozens of leading climate scientists.

The report – “A critical review of impacts of greenhouse gas emissions on the US climate” – was published by the US Department of Energy (DoE) on 23 July, just days before the government laid out plans to revoke a scientific finding used as the legal basis for emissions regulation.

The executive summary of the controversial report inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed”.

It also states misleadingly that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”.

Compiled in just two months by five “independent” researchers hand-selected by the climate-sceptic US secretary of energy Chris Wright, the document has sparked fierce criticism from climate scientists, who have pointed to factual errors, misrepresentation of research, messy citations and the cherry-picking of data.

Experts have also noted the authors’ track record of promoting views at odds with the mainstream understanding of climate science.

Wright’s department claims the report – which is currently open to public comment as part of a 30-day review – underwent an “internal peer-review period amongst [the] DoE’s scientific research community”.

The report is designed to provide a scientific underpinning to one flank of the Trump administration’s plans to rescind a finding that serves as the legal prerequisite for federal emissions regulation. (The second flank is about legal authority to regulate emissions.)

The “endangerment finding” – enacted by the Obama administration in 2009 – states that six greenhouse gases are contributing to the net-negative impacts of climate change and, thus, put the public in danger.

In a press release on 29 July, the US Environmental Protection Agency said “updated studies and information” set out in the new report would “challenge the assumptions” of the 2009 finding.

Carbon Brief asked a wide range of climate scientists, including those cited in the “critical review” itself, to factcheck the report’s various claims and statements.

The post Factcheck: Trump’s climate report includes more than 100 false or misleading claims appeared first on Carbon Brief.

https://www.carbonbrief.org/factcheck-trumps-climate-report-includes-more-than-100-false-or-misleading-claims/