Scientists have challenged the conclusions of a new study suggesting that the planet has already exceeded the 1.5C warming threshold set under the Paris Agreement.
Climate change is typically measured as the average global temperature increase relative to a “pre-industrial baseline”. The UN Intergovernmental Panel on Climate Change (IPCC), for example, uses the average temperature over 1850-1900 as their historical baseline. The planet has already warmed by around 1.2C compared to this period.
The new study, published in Nature Climate Change, uses proxy data from sea sponges in the Caribbean Sea to create a record of ocean temperatures from 1700 to the present day. This data suggests that warming started 40 years before the IPCC’s pre-industrial baseline period began.
Based on this new record, the authors say “warming is 0.5C higher than IPCC estimates”.
This means that “the global warming clock for emission reductions to minimise the risk of dangerous climate change has been brought forward by at least a decade”, the lead author told a press briefing.
However, many experts have warned that the framing of the study is misleading, arguing that the finding has no bearing on the Paris Agreement 1.5C limit, because it specifically “describes temperature rise relative to the late 19th century”.
Prof Richard Betts, head of climate impacts research at the UK Met Office Hadley Centre, who was not involved in the study, tells Carbon Brief that, crucially, the study “does not mean that impacts of climate change will occur earlier than expected”.
Other experts raised doubts that the 0.5C warming in the 1800s is human-caused, while many cautioned that proxy data from a single location should not be used to make assumptions about the entire planet.
The University of Oxford’s Prof Yadvinder Malhi, who was also not involved in the study, cautions that “the way these findings have been communicated is flawed, and has the potential to add unnecessary confusion to public debate on climate change”.
Shifting baselines
Humans have been releasing greenhouse gases into the atmosphere for centuries, causing global temperatures to rise.
In IPCC reports – considered the most authoritative summaries on climate science – scientists use a combination of land surface air temperatures and sea surface temperatures to assess changes in global mean surface temperatures (GMST).
The UN body reports global warming against a “pre-industrial baseline” of 1850-1900. It describes this baseline as “a pragmatic choice based upon data availability considerations” – in part because much of the observed climate data they use is only available from 1850.
For example, the Met Office’s HadSST4 dataset – one of the three datasets used in IPCC estimates of sea surface temperatures – goes back as far as 1850.
The IPCC also recognises that “both anthropogenic and natural changes to the climate occurred” before the 1850-1900 baseline. For example, in its 2021 report on climate science, the IPCC estimates that between 1750 and 1850-1900, GMST increased by around 0.1C. Of this, human activity was responsible for 0.0-0.2C, it says.
Nonetheless, researchers have typically followed suit in using the 1850-1900 average as their “pre-industrial baseline” to measure global warming.
In 2015, countries agreed under the Paris Agreement to hold the increase in the global average temperature to well below 2C above pre-industrial levels and pursue efforts to limit warming to 1.5C. “Pre-industrial” was not clearly defined in the agreement, but it has generally been taken to mean the average temperature over 1850-1900.
However, some scientists argue that the “pre-industrial baseline” period should begin before 1850.
The new study uses proxy data taken from sea sponges from the Caribbean sea, to present a timeseries of regional ocean temperatures from 1700 to the present day. Scientists collected sclerosponges from the ocean mixed layer – a region of ocean where heat is exchanged between the atmosphere and the ocean interior.
Between 1700-90 and 1840-60, the proxy data shows ocean warming of around 0.9C, according to the study. In the intervening time, there was some cooling, largely caused by volcanic eruptions, the authors say.
The plot below shows the proxy data (blue) from the year 1770, alongside the HadSST4 observed temperature record (purple), which begins in 1850, relative to a 1961-90 reference period. The authors have applied a 0.9C “offset” to their proxy data to account for pre-industrial temperature increase.
By comparing their proxy data against existing records of global temperature changes, the authors find “strong empirical evidence that the Caribbean ocean mixed layer has warmed proportionately to the average global increase in sea surface temperature, over the last ~50 years”.
The authors assume that the 0.9C offset “can be applied to land-air as well as the ocean mixed layer anomalies”, therefore concluding that GMST increased by 0.9C between 1700-1860 and 1961-90.
Meanwhile, global ocean temperatures measured using HadSST4 show only 0.4C of warming relative to the IPCC’s 1850-1900 pre-industrial period.
As such, the authors suggest that human-caused warming to date is actually 0.5C higher than IPCC estimates.
Dr Malcolm McCulloch – an emeritus professor at the University of Western Australia and lead author on the study – told a press briefing that, according to his study, the 1.5C Paris temperature threshold has already been crossed in around 2010-12.
He continued:
“It means that now, temperatures are at least 1.7C above the pre-industrial level. It also means that the 2C target will be passed in late 2020 unless there are major reductions in emissions…
“The big picture is that the global warming clock for emission reductions to minimise the risk of dangerous climate change has been brought forward by at least a decade”.
However, many scientists are concerned about this framing of the study.
Warming limits
Dr Friederike Otto, who was not involved in the study, is a senior lecturer in climate science at Imperial College London’s Grantham Institute. She says the paper “does not tell us anything about whether we have exceeded the 1.5C temperature limit set in the Paris Agreement”.
She continues:
“That limit was established as the threshold of unacceptably dangerous warming and describes temperature rise relative to the late 19th century. If this study has indeed identified warming from before the mid-1800s, that doesn’t mean the planet is any closer to breaking the 1.5C limit as it is widely understood.”
(The IPCC best estimate – in all but the highest emission scenario – is that global warming will pass 1.5C in the first half of the 2030s.)
Mahli adds:
“Our models of climate warming impacts are based on warming relative to 1850-1900 and moving the baseline definition of pre-industrial does not make these expected impacts worse…
“It is the date of the reference period that matters rather than whether it is labelled pre-industrial or not. The period 1850-1900 is a period of relatively reliable global data when industrial era human-caused climate change was likely negligible.”
Dr Andrew King is a senior lecturer in climate science at the University of Melbourne and was not involved in the study. He tells Carbon Brief that the findings of the study do not have any implications for the Paris Agreement warming limits, because these were “written in 2015 with a view to limiting further global warming from that point onwards”.
He adds:
“While the lack of clarity on what pre-industrial means was problematic, it doesn’t really affect that goal or any of the analyses on climate impacts at global warming levels that have been performed.”
King also tells Carbon Brief that the authors have not demonstrated that pre-1850s warming is due to human activity.
Malhi agrees that “this early industrial-era warming, if real, is almost certainly not human-caused”. He notes that human-caused emissions over 1750-1900 account for only 2.5% of total emissions to date, and says they are “unlikely to have caused substantial warming compared to the 1.4C of warming caused by the remaining 97.5% of cumulative emissions”.
Dr Duo Chan, a lecturer in climate sciences at the University of Southampton, also advises “caution” when interpreting the results, noting that “this new warming estimate does not align” with historical estimates of the different factors that affect the climate.
He notes that, according to Berkeley Earth temperature estimates, the land warmed by around 0.05C per decade over 1850-1900. The new proxy data from the sponges suggests that the ocean warmed almost twice as quickly as the land over this time – a “puzzling observation given the ocean warms more slowly than land”, he says.
Dr Zeke Hausfather, Carbon Brief’s contributing science writer, adds that the study authors are “conflating ocean mixed layer temperature with sea surface temperature in a way that is confusing”. He adds that “their reconstruction also seems a bit at odds with other palaeoclimate reconstructions – such as PAGES2k – that do not see large differences in pre-1900 temperatures”.
The sclerosponge record
Coralline sclerosponges are an ancient type of calcifying sea sponge which can live for hundreds of years. As they grow, chemicals called strontium and calcium build up in their skeletons. The ratio of strontium to calcium in their skeletons is higher during warm periods and lower during cool periods.
Scientists collected live specimens of sclerosponge from the Caribbean sea and analysed the ratios of strontium to calcium in their skeletons to reproduce a timeseries of ocean temperatures in the region from the year 1700 to the present day.
Dr Amos Winter is a professor of Earth and environmental systems at Indiana State University and author on the study. He told the press briefing that there is no such thing as a “perfect proxy”, but said the sclerosponge record is “as good as possible – the holy grail of reconstruction”.
He explained that the Caribbean is “the ideal location to measure global trends”. According to the paper, the region is “ideally positioned” to have a “minimal” impact from the Atlantic Meridional Overturning Circulation, while “still registering the broader effects” of the El Niño-Southern Oscillation climate phenomenon.
He adds that the sclerosponge temperature reconstruction is “very robust” when compared to other assessments of temperature trends.
Dr Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, says that the new data is a “useful addition to the database” of palaeoclimate proxies. However, he adds:
“Estimates of the global mean temperatures before 1850 require multiple proxies from as wide a regional variation as possible, thus claims that records from a single record can confidently define the global mean warming since the pre-industrial are probably overreaching.”
Prof Gabi Hegerl, a professor of climate system science at the University of Edinburgh, says that the paper presents a “nice new record” of ocean temperatures, but says that “the interpretation in terms of global warming goals overstretches it”.
She warns that “a single location cannot substitute global data, as climate varies across the globe, which is why the only way to measure global temperature is to get data from across the globe”.
Similarly, Hausfather calls the finding “interesting”, but says it “should be combined with other proxy records in a larger synthesis before it will change our prevailing views here”.
The post Scientists challenge ‘flawed communication’ of study claiming 1.5C warming breach appeared first on Carbon Brief.
Scientists challenge ‘flawed communication’ of study claiming 1.5C warming breach
Countries are still debating whether to mine the seafloor for minerals, but exploratory efforts have already begun.
As demand for critical minerals surges around the world, countries are debating whether to mine the untapped deep-sea reserves of cobalt, copper and manganese, miles below the surface. But a growing body of research shows that these activities could have profound consequences for ocean ecosystems, and the industries and communities that rely on them.
Climate Change
IEA: Slow transition away from fossil fuels would cost over a million energy sector jobs
A slower shift to clean energy could leave the world with 1.3 million fewer energy sector jobs by 2035 compared with a scenario in which governments fully implement their green policies, the International Energy Agency (IEA) has found.
In its annual World Energy Employment report, the Paris-based watchdog said on Friday that the Current Policies Scenario (CPS), which it reintroduced under pressure from the Trump administration, has “more muted” employment growth than the Stated Policies Scenario.
The CPS sees oil and gas demand continuing to rise until at least 2050 – a scenario that the IEA described as “cautious” and “anchored in enacted laws and measures” and was widely criticised by clean energy experts.
A fast energy transition would spur investment in construction, creating more jobs across the sector. New roles for electricians, building insulators, solar panel and energy-efficient lightbulb installers, and transition mineral miners would more than offset job losses in coal mines, power plants and oil and gas fields, the report found.
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Anabella Rosemberg, Just Transition lead at Climate Action Network International, lamented that the clean energy sector is “being undermined at a time when employment creation is of utmost priority”.
“Climate ambition and decent job creation must go hand in hand – but as the recent conversations at COP30 showed, there is a need for both the right targets and just transition strategies to make it happen,” she added.
A more ambitious Net Zero Emissions scenario, aligned with the Paris Agreement goal of limiting global warming to 1.5C, would see roughly ten million more energy jobs created than under the CPS, report author Daniel Wetzel told Climate Home News at a press conference.
Bottleneck warnings
The IEA warned that governments must act to train workers for these roles or risk facing shortages of electricians, welders, and grid specialists – a gap that could slow the energy transition and drive up wages and energy costs.
IEA head Fatih Birol highlighted a particular shortage of qualified workers in the nuclear industry, warning that the problem could worsen as the sector’s workforce continues to age. “I hear nuclear is making a comeback, but the interest in the nuclear sector for the jobs is rather weak,” he said.
Laura Cozzi, IEA’s Director of Sustainability, Technology and Outlooks, warned of a shortage of skilled workers in electricity grids. “That is one of the key ingredients why we are not seeing grids ramp up as [they] should,” she said. Over 60 governments pledged at COP29 to improve and expand their grids to enable clean electricity to flow to where it is needed.
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Bert De Wel, Global Coordinator for Climate Policy at the International Trade Union Confederation, celebrated that the energy transition is creating jobs but added that they should be good jobs with decent pay, conditions and union rights. Decent work would attract skilled workers, he added.
The report found that wages in the oil and gas industry have generally risen faster over the past year than in the solar – and especially the wind – sectors. It noted that the oil and gas industry has a “historical tendency to offer highly competitive wages to attract and retain top talent”.
At the COP30 climate summit, governments agreed to set up the Belém Action Mechanism to try and make the energy transition fairer to groups such as workers in the energy industry. It will give trade unions a formal role in shaping just transition policies, for what the ITUC says is the first time.
ITUC General Secretary Luc Triangle called it a “decisive win for the union movement and working people across the world, in all sectors but especially those in transition industries.”
The post IEA: Slow transition away from fossil fuels would cost over a million energy sector jobs appeared first on Climate Home News.
IEA: Slow transition away from fossil fuels would cost over a million energy sector jobs
Climate Change
DeBriefed 5 December: Deadly Asia floods; Adaptation finance target examined; Global south IPCC scientists speak out
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Deadly floods in Asia
MOUNTING DEVASTATION: The Associated Press reported that the death toll from catastrophic floods in south-east Asia had reached 1,500, with Indonesia, Sri Lanka and Thailand most affected and hundreds still missing. The newswire said “thousands” more face “severe” food and clean-water shortages. Heavy rains and thunderstorms are expected this weekend, it added, with “saturated soil and swollen rivers leaving communities on edge”. Earlier in the week, Bloomberg said the floods had caused “at least $20bn in losses”.
CLIMATE CHANGE LINKS: A number of outlets have investigated the links between the floods and human-caused climate change. Agence France-Presse explained that climate change was “producing more intense rain events because a warmer atmosphere holds more moisture and warmer oceans can turbocharge storms”. Meanwhile, environmental groups told the Associated Press the situation had been exacerbated by “decades of deforestation”, which had “stripped away natural defenses that once absorbed rainfall and stabilised soil”.
‘NEW NORMAL’: The Associated Press quoted Malaysian researcher Dr Jemilah Mahmood saying: “South-east Asia should brace for a likely continuation and potential worsening of extreme weather in 2026 and for many years.” Al Jazeera reported that the International Federation of Red Cross and Red Crescent Societies had called for “stronger legal and policy frameworks to protect people in disasters”. The organisation’s Asia-Pacific director said the floods were a “stark reminder that climate-driven disasters are becoming the new normal”, the outlet said.
Around the world
- REVOKED: The UK and Netherlands withdrew $2.2bn of financial backing from a controversial liquified natural gas (LNG) project in Mozambique, Reuters reported. The Guardian noted that TotalEnergies’ “giant” project stood accused of “fuelling the climate crisis and deadly terror attacks”.
- REVERSED: US president Donald Trump announced plans to “significantly weaken” Biden-era fuel efficiency requirements for cars, the New York Times said.
- RESTRICTED: EU leaders agreed to ban the import of Russian gas from autumn 2027, the Financial Times reported. Meanwhile, Reuters said it is “likely” the European Commission will delay announcing a plan on auto sector climate targets next week, following pressure to “weaken” a 2035 cut-off for combustion engines.
- RETRACTED: An influential Nature study that looked at the economic consequences of climate change has been withdrawn after “criticism from peers”, according to Bloomberg. [The research came second in Carbon Brief’s ranking of the climate papers most covered by the media in 2024.]
- REBUKED: The federal government of Canada faced a backlash over an oil pipeline deal struck last week with the province of Alberta. CBC News noted that First Nations chiefs voted “unanimously” to demand the withdrawal of the deal and Canada’s National Observer quoted author Naomi Klein as saying that the prime minister was “completely trashing Canada’s climate commitments”.
- RESCHEDULED: The Indonesian government has cancelled plans to close a coal plant seven years early, Bloomberg reported. Meanwhile, Bloomberg separately reported that India is mulling an “unprecedented increase” in coal-power capacity that could see plants built “until at least 2047”.
$518 billion a year
The projected coastal flood damages for the Asia-Pacific region by 2100 if current policies continue, according to a Scientific Reports study covered this week by Carbon Brief.
Latest climate research
- More than 100 “climate-sensitive rivers” worldwide are experiencing “large and severe changes in streamflow volume and timing” | Environmental Research Letters
- Africa’s forests have switched from a carbon sink into a source | Scientific Reports
- Increasing urbanisation can “substantially intensify warming”, contributing up to 0.44C of additional temperature rise per year through 2060 | Communications Earth & Environment
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
A new target for developed nations to triple adaptation finance by 2035, agreed at the COP30 climate summit, would not cover more than a third of developing countries’ estimated needs, Carbon Brief analysis showed. The chart above compares a straight line to meeting the adaptation finance target (blue), alongside an estimate of countries’ adaptation needs (grey), which was calculated using figures from the latest UN Environmental Programme adaptation gap report, based on countries’ UN climate plans (called “nationally determined contributions” or NDCs) and national adaptation plans (NAPs).
Spotlight
Inclusivity at the IPCC
This week, Carbon Brief speaks to an IPCC lead author researching ways to improve the experience of global south scientists taking part in producing the UN climate body’s assessments.
Hundreds of climate scientists from around the world met in Paris this week to start work on the Intergovernmental Panel on Climate Change’s (IPCC’s) newest set of climate reports.
The IPCC is the UN body responsible for producing the world’s most authoritative climate science reports. Hundreds of scientists from across the globe contribute to each “assessment cycle”, which sees researchers aim to condense all published climate science over several years into three “working group” reports.
The reports inform the decisions of governments – including at UN climate talks – as well as the public understanding of climate change.
The experts gathering in Paris are the most diverse group ever convened by the IPCC.
Earlier this year, Carbon Brief analysis found that – for the first time in an IPCC cycle – citizens of the global south make up 50% of authors of the three working group reports. The IPCC has celebrated this milestone, with IPCC chair Prof Jim Skea touting the seventh assessment report’s (AR7’s) “increased diversity” in August.
But some IPCC scientists have cautioned that the growing involvement of global south scientists does not translate into an inclusive process.
“What happens behind closed doors in these meeting rooms doesn’t necessarily mirror what the diversity numbers say,” Dr Shobha Maharaj, a Trinidadian climate scientist who is a coordinating lead author for working group two (WG2) of AR7, told Carbon Brief.
Global south perspective
Motivated by conversations with colleagues and her own “uncomfortable” experience working on the small-islands chapter of the sixth assessment cycle (AR6) WG2 report, Maharaj – an adjunct professor at the University of Fiji – reached out to dozens of fellow contributors to understand their experience.
The exercise, she said, revealed a “dominance of thinking and opinions from global north scientists, whereas the global south scientists – the scientists who were people of colour – were generally suppressed”.
The perspectives of scientists who took part in the survey and future recommendations for the IPCC are set out in a peer-reviewed essay – co-authored by 20 researchers – slated for publication in the journal PLOS Climate. (Maharaj also presented the findings to the IPCC in September.)
The draft version of the essay notes that global south scientists working on WG2 in AR6 said they confronted a number of diversity, equity and inclusion (DEI) issues, including “skewed” author selection, “unequal” power dynamics and a “lack of respect and trust”. The researchers also pointed to logistical constraints faced by global south authors, such as visa issues and limited access to journals.
The anonymous quotations from more than 30 scientists included in the essay, Maharaj said, are “clear data points” that she believes can advance a discussion about how to make academia more inclusive.
“The literature is full of the problems that people of colour or global south authors have in academia, but what you don’t find very often is quotations – especially from climate scientists,” she said. “We tend to be quite a conservative bunch.”
Road to ‘improvement’
Among the recommendations set out in the essay are for DEI training, the appointment of a “diversity and inclusion ombudsman” and for updated codes of conduct.
Marharaj said that these “tactical measures” need to occur alongside “transformative approaches” that help “address value systems, dismantle power structures [and] change the rules of participation”.
With drafting of the AR7 reports now underway, Maharaj said she is “hopeful” the new cycle can be an improvement on the last, pointing to a number of “welcome” steps from the IPCC.
This includes holding the first-ever expert meeting on DEI this autumn, new mechanisms where authors can flag concerns and the recruitment of a “science and capacity officer” to support WG2 authors.
The hope, Maharaj explained, is to enhance – not undermine – climate science.
“The idea here was to move forward and to improve the IPCC, rather than attack it,” she said. “Because we all love the science – and we really value what the IPCC brings to the world.”
Watch, read, listen
BROKEN PROMISES: Climate Home News spoke to communities in Nigeria let down by the government’s failure to clean up oil spills by foreign companies.
‘WHEN A ROAD GOES WRONG’: Inside Climate News looked at how a new road from Brazil’s western Amazon to Peru has become a “conduit for rampant deforestation and illegal gold mining”.
SHADOWY COURTS: In the Guardian, George Monbiot lamented the rise of investor-state dispute settlements, which he described as “undemocratic offshore tribunals” that are already having a “chilling effect” on countries’ climate ambitions.
Coming up
- 1-12 December: UN Environment Assembly 7, Nairobi, Kenya
- 7 December: Hong Kong legislative elections
- 11 December: Falkland Islands legislative assembly elections
Pick of the jobs
- Greenpeace International, engagement manager – climate and energy | Salary: Unknown. Location: Various
- The Energy, newsletter editor | Salary: Unknown. Location: Australia (remote)
- University of Groningen, PhD position in motivating people to contribute to societal transitions | Salary: €3,059-€3,881 per month. Location: Groningen, the Netherlands
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
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The post DeBriefed 5 December: Deadly Asia floods; Adaptation finance target examined; Global south IPCC scientists speak out appeared first on Carbon Brief.
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