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
In 2026, the dangers of fossil fuel dependence have been laid bare like never before. The illegal invasion of Iran has brought pain and destruction to millions across the Middle East and triggered a global energy crisis impacting us all. Communities in the Pacific have been hit especially hard by rising fuel prices, and Australians have seen their cost-of-living woes deepen.
Such moments of crisis and upheaval can lead to positive transformation. But only when leaders act with courage and foresight.
There is no clearer statement of a government’s plans and priorities for the nation than its budget — how it plans to raise money, and what services, communities, and industries it will invest in.
As we count down the days to the 2026-27 Federal Budget, will the Albanese Government deliver a budget for our times? One that starts breaking the shackles of fossil fuels, accelerates the shift to clean energy, protects nature, and sees us work together with other countries towards a safer future for all? Or one that doubles down on coal and gas, locks in more climate chaos, and keeps us beholden to the whims of tyrants and billionaires.
Here’s what we think the moment demands, and what we’ll be looking out for when Treasurer Jim Chalmers steps up to the dispatch box on 12 May.
1. Stop fuelling the fire
2. Make big polluters pay
3. Support everyone to be part of the solution
4. Build the industries of the future
5. Build community resilience
6. Be a better neighbour
7. Protect nature
1. Stop fuelling the fire
In mid-April, Pacific governments and civil society met to redouble their efforts towards a Fossil Fuel Free Pacific. Moving beyond coal, oil and gas is fundamental to limiting warming to 1.5°C — a survival line for vulnerable communities and ecosystems. And as our Head of Pacific, Shiva Gounden, explained, it is “also a path of liberation that frees us from expensive, extractive and polluting fossil fuel imports and uplifts our communities”.
Pacific countries are at the forefront of growing global momentum towards a just transition away from fossil fuels, and it is way past time for Australia to get with the program. It is no longer a question of whether fossil fuel extraction will end, but whether that end will be appropriately managed and see communities supported through the transition, or whether it will be chaotic and disruptive.
So will this budget support the transition away from fossil fuels, or will it continue to prop up coal and gas?
When it comes to sensible moves the government can make right now, one stands out as a genuine low hanging fruit. Mining companies get a full rebate of the excise (or tax) that the rest of us pay on diesel fuel. This lowers their operating costs and acts as a large, ongoing subsidy on fossil fuel production — to the tune of $11 billion a year!
Greenpeace has long called for coal and gas companies to be removed from this outdated scheme, and for the billions in savings to be used to support the clean energy transition and to assist communities with adapting to the impacts of climate change. Will we see the government finally make this long overdue change, or will it once again cave to the fossil fuel lobby?
2. Make big polluters pay
While our communities continue to suffer the escalating costs of climate-fuelled disasters, our Government continues to support a massive expansion of Australia’s export gas industry. Gas is a dangerous fossil fuel, with every tonne of Australian gas adding to the global heating that endangers us all.
Moreover, companies like Santos and Woodside pay very little tax for the privilege of digging up and selling Australians’ natural endowment of fossil gas. Remarkably, the Government currently raises more tax from beer than from the Petroleum Resource Rent Tax (PRRT) — the main tax on gas profits.
Momentum has been building to replace or supplement the PRRT with a 25% tax on gas exports. This could raise up to $17 billion a year — funds that, like savings from removing the diesel tax rebate for coal and gas companies, could be spent on supporting the clean energy transition and assisting communities with adapting to worsening fires, floods, heatwaves and other impacts of climate change.
As politicians arrive in Canberra for budget week, they will be confronted by billboards calling for a fair tax on gas exports. The push now has the support of dozens of organisations and a growing number of politicians. Let’s hope the Treasurer seizes this rare window for reform.
3. Support everyone to be part of the solution
As the price of petrol and diesel rises, electric vehicles (EVs) are helping people cut fuel use and save money. However, while EV sales have jumped since the invasion of Iran sent fuel prices rising, they still only make up a fraction of total new car sales. This budget should help more Australians switch to electric vehicles and, even more importantly, enable more Australians to get around by bike, on foot, and on public transport. This means maintaining the EV discount, investing in public and active transport, and removing tax breaks for fuel-hungry utes and vans.
Millions of Australians already enjoy the cost-saving benefits of rooftop solar, batteries, and getting off gas. This budget should enable more households, and in particular those on lower incomes, to access these benefits. This means maintaining the Cheaper Home Batteries Program, and building on the Household Energy Upgrades Fund.
4. Build the industries of the future
If we’re to transition away from fossil fuels, we need to be building the clean industries of the future.
No state is more pivotal to Australia’s energy and industrial transformation than Western Australia. The state has unrivaled potential for renewable energy development and for replacing fossil fuel exports with clean exports like green iron. Such industries offer Western Australia the promise of a vibrant economic future, and for Australia to play an outsized positive role in the world’s efforts to reduce emissions.
However, realising this potential will require focussed support from the Federal Government. Among other measures, Greenpeace has recommended establishing the Australasian Green Iron Corporation as a joint venture between the Australian and Western Australian governments, a key trading partner, a major iron ore miner and steel makers. This would unite these central players around the complex task of building a large-scale green iron industry, and unleash Western Australia’s potential as a green industrial powerhouse.
5. Build community resilience
Believe it or not, our Government continues to spend far more on subsidising fossil fuel production — and on clearing up after climate-fuelled disasters — than it does on helping communities and industries reduce disaster costs through practical, proven methods for building their resilience.
Last year, the Government estimated that the cost of recovery from disasters like the devastating 2022 east coast floods on 2019-20 fires will rise to $13.5 billion. For contrast, the Government’s Disaster Ready Fund – the main national source of funding for disaster resilience – invests just $200 million a year in grants to support disaster preparedness and resilience building. This is despite the Government’s own National Emergency Management Agency (NEMA) estimating that for every dollar spent on disaster risk reduction, there is a $9.60 return on investment.
By redirecting funds currently spent on subsidising fossil fuel production, the Government can both stop incentivising climate destruction in the first place, and ensure that Australian communities and industries are better protected from worsening climate extremes.
No communities have more to lose from climate damage, or carry more knowledge of practical solutions, than Aboriginal and Torres Strait Islander peoples. The budget should include a dedicated First Nations climate adaptation fund, ensuring First Nations communities can develop solutions on their own terms, and access the support they need with adapting to extreme heat, coastal erosion and other escalating challenges.
6. Be a better neighbour
The global response to climate change depends on the adequate flow of support from developed economies like Australia to lower income nations with shifting to clean energy, adapting to the impacts of climate change, and addressing loss and damage.
Such support is vital to building trust and cooperation, reducing global emissions, and supporting regional and global security by enabling countries to transition away from fossil fuels and build greater resilience.
Despite its central leadership role in this year’s global climate negotiations, our Government is yet to announce its contribution to international climate finance for 2025-2030. Greenpeace recommends a commitment of $11 billion for this five year period, which is aligned with the global goal under the Paris Agreement to triple international climate finance from current levels.
This new commitment should include additional funding to address loss and damage from climate change and a substantial contribution to the Pacific Resilience Facility, ensuring support is accessible to countries and communities that need it most. It should also see Australia get firmly behind the vision of a Fossil Fuel Free Pacific.
7. Protect nature
There is no safe planet without protection of the ecosystems and biodiversity that sustain us and regulate our climate.
Last year the Parliament passed important and long overdue reforms to our national environment laws to ensure better protection for our forests and other critical ecosystems. However, the Government will need to provide sufficient funding to ensure the effective implementation of these reforms.
Greenpeace has recommended $500 million over four years to establish the National Environment Agency — the body responsible for enforcing and monitoring the new laws — and a further $50 million to Environment Information Australia for providing critical information and tools.
Further resourcing will also be required to fulfil the crucial goal of fully protecting 30% of Australian land and seas by 2030. This should include $1 billion towards ending deforestation by enabling farmers and loggers to retool away from destructive practices, $2 billion a year for restoring degraded lands, $5 billion for purchasing and creating new protected areas, and $200 million for expanding domestic and international marine protected areas.
Conclusion
This is not the first time that conflict overseas has triggered an energy crisis, or that a budget has been preceded by a summer of extreme weather disasters, highlighting the urgent need to phase out fossil fuels. What’s different in 2026 is the availability of solutions. Renewable energy is now cheaper and more accessible than ever before. Global momentum is firmly behind the transition away from fossil fuels. The Albanese Government, with its overwhelming majority, has the chance to set our nation up for the future, or keep us stranded in the past. Let’s hope it makes some smart choices.
The 2026 budget test: Will Australia break free from fossil fuels?
Anne Jellema is Executive Director of 350.org.
The war on Iran and Lebanon is a deeply unjust and devastating conflict, killing civilians at home, destroying lives, and at the same time sending shockwaves through the global economy. We, at 350.org, have calculated, drawing on price forecasts from the International Monetary Fund (IMF) and Goldman Sachs, just how much that volatility is costing us.
Even under the IMF’s baseline scenario – a de facto “best case” scenario with a near-term end to the war and related supply chain disruptions – oil and gas price spikes are projected to cost households and businesses globally more than $600 billion by the end of the year. Under the IMF’s “adverse scenario”, with prolonged conflict and sustained price pressures, we estimate those additional costs could exceed $1 trillion, even after accounting for reduced demand.
Which is why we urgently need a power shift. Governments are under growing pressure to respond to rising fuel and food costs and deepening energy poverty. And it’s becoming clearer to both voters and elected officials that fossil dependence is not only expensive and risky, but unnecessary.
People who can are voting with their wallets: sales of solar panels and electric vehicles are increasing sharply in many countries. But the working people who have nothing to spare, ironically, are the ones stuck with using oil and gas that is either exorbitantly expensive or simply impossible to get.
Drain on households and economies
In India, street food vendors can’t get cooking gas and in the Philippines, fishermen can’t afford to take their boats to sea. A quarter of British people say that rising energy tariffs will leave them completely unable to pay their bills. This is the moment for a global push to bring abundant and affordable clean energy to all.
In April, we released Out of Pocket, our new research report on how fossil fuels are draining households and economies. We were surprised by the scale of what we found. For decades, governments have reassured people that energy price spikes are unfortunate but unavoidable – the result of distant conflicts, market forces or geopolitical shocks beyond anyone’s control. But the numbers tell a different story.
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Santa Marta: Ministers grapple with practicalities of fossil fuel phase-out
Around 60 governments that want to make progress on transitioning away from coal, oil and gas are meeting in Colombia to work out how they can do it an equitable way -
Why the transition beyond fossil fuels depends on cities and collective action
Cities will help identify concrete pathways for an equitable shift to clean energy at the Santa Marta conference, with C40 members aiming to halve their fossil fuel use by 2030
What we are living through today is not an energy crisis. It is a fossil fuel crisis. In just the first 50 days of the Middle East conflict, soaring oil and gas prices have siphoned an estimated $158 billion–$166 billion from households and businesses worldwide. That is money extracted directly from people’s pockets and transferred, almost instantly, into fossil fuel company balance sheets. And this figure only captures the immediate impact of price spikes, not the permanent economic drain of fossil dependence. Fossil fuels don’t just cost us once, they cost us over and over again.
First, through our bills. Every time there is a war, an embargo or a supply disruption, fossil fuel prices surge. For ordinary people, this means higher costs for energy, transport and food. Many Global South countries have little or no fiscal space to buffer the shock; instead, workers and families pay the price.
Second, through our taxes. Governments around the world continue to pour vast sums of public money into fossil fuel subsidies. These are often justified as a way to protect the most vulnerable at the petrol pump or in their homes. But in reality, the benefits are overwhelmingly captured by wealthier households and corporations. The poorest 20% receive just a fraction of this support, while public finances are drained.
Third, through climate impacts. New research across more than 24,000 global locations gives a granular account of the true costs of extreme heat, sea level rise and falling agricultural yields. Using this data to update IMF modelling of the social cost of carbon, we found that fossil fuel impacts on health and livelihoods amount to over $9 trillion a year. This is the biggest subsidy of all, because these massive and mounting costs are not charged to Big Oil – they are paid for by governments and households, with the poorest shouldering the lion’s share.
Massive transfer of wealth to fossil fuel industry
Adding up direct subsidies, tax breaks and the unpaid bill for climate damages, the total transfer of wealth from the public to the fossil fuel industry amounts to $12 trillion even in a “normal” year without a global oil shock. That’s more than 50% higher than the IMF has previously estimated, and equivalent to a staggering $23 million a minute.
The fossil fuel industry has become extraordinarily adept at profiting from instability. When conflict drives up prices, companies do not lose, they gain. In the current crisis, oil producers and commodity traders are on track to secure tens of billions of dollars in additional windfall profits, even as households face rising bills and governments struggle to manage the fallout.
Fossil fuel crisis offers chance to speed up energy transition, ministers say
This growing disconnect is impossible to ignore. Investors are advised to buy into fossil fuel firms precisely because of their ability to generate profits in times of crisis. Meanwhile, ordinary people are told to tighten their belts.
In 2026, unlike during the oil shocks of the 1970s, clean energy is no longer a distant alternative. Now, even more than when gas prices spiked due to Russia’s invasion of Ukraine in 2022, renewables are often the cheapest option available. Solar and wind can be deployed quickly, at scale, and without the volatility that defines fossil fuel markets.
How to transition from dirty to clean energy
The solutions are clear. Governments must implement permanent windfall taxes on fossil fuel companies to ensure that extraordinary profits generated during crises are redirected to support households. These revenues can be used to reduce energy bills, invest in public services, and accelerate the rollout of clean energy.
Second, we must shift subsidies away from fossil fuels and towards renewable solutions, particularly those that can be deployed quickly and equitably, such as rooftop and community solar. This is not just about cutting emissions. It is about building a more stable, fair and resilient energy system.
Finally, we need binding plans to phase out fossil fuels altogether, replacing them with homegrown renewable energy that can shield economies from future shocks. Because what the current crisis has made clear is this: as long as we remain dependent on fossil fuels, we remain vulnerable – to conflict, to price volatility and to the escalating impacts of climate change.
The true price of fossil fuels is no longer hidden. It is visible in rising bills, strained public finances and communities pushed to the brink. And it is being paid, every day, by ordinary people around the world.
It’s time for the great power shift.
Full details on the methodology used for this report are available here.
The Great Power Shift is a new campaign by 350.org global campaign to pressure governments to bring down energy bills for good by ending fossil fuel dependence and investing in clean, affordable energy for all
The post What fossil fuels really cost us in a world at war appeared first on Climate Home News.
Computer models that use artificial intelligence (AI) cannot forecast record-breaking weather as well as traditional climate models, according to a new study.
It is well established that AI climate models have surpassed traditional, physics-based climate models for some aspects of weather forecasting.
However, new research published in Science Advances finds that AI models still “underperform” in forecasting record-breaking extreme weather events.
The authors tested how well both AI and traditional weather models could simulate thousands of record-breaking hot, cold and windy events that were recorded in 2018 and 2020.
They find that AI models underestimate both the frequency and intensity of record-breaking events.
A study author tells Carbon Brief that the analysis is a “warning shot” against replacing traditional models with AI models for weather forecasting “too quickly”.
AI weather forecasts
Extreme weather events, such as floods, heatwaves and storms, drive hundreds of billions of dollars in damages every year through the destruction of cropland, impacts on infrastructure and the loss of human life.
Many governments have developed early warning systems to prepare the general public and mobilise disaster response teams for imminent extreme weather events. These systems have been shown to minimise damages and save lives.
For decades, scientists have used numerical weather prediction models to simulate the weather days, or weeks, in advance.
These models rely on a series of complex equations that reproduce processes in the atmosphere and ocean. The equations are rooted in fundamental laws of physics, based on decades of research by climate scientists. As a result, these models are referred to as “physics-based” models.
However, AI-based climate models are gaining popularity as an alternative for weather forecasting.
Instead of using physics, these models use a statistical approach. Scientists present AI models with a large batch of historical weather data, known as training data, which teaches the model to recognise patterns and make predictions.
To produce a new forecast, the AI model draws on this bank of knowledge and follows the patterns that it knows.
There are many advantages to AI weather forecasts. For example, they use less computing power than physics-based models, because they do not have to run thousands of mathematical equations.
Furthermore, many AI models have been found to perform better than traditional physics-based models at weather forecasts.
However, these models also have drawbacks.
Study author Prof Sebastian Engelke, a professor at the research institute for statistics and information science at the University of Geneva, tells Carbon Brief that AI models “depend strongly on the training data” and are “relatively constrained to the range of this dataset”.
In other words, AI models struggle to simulate brand new weather patterns, instead tending forecast events of a similar strength to those seen before. As a result, it is unclear whether AI models can simulate unprecedented, record-breaking extreme events that, by definition, have never been seen before.
Record-breaking extremes
Extreme weather events are becoming more intense and frequent as the climate warms. Record-shattering extremes – those that break existing records by large margins – are also becoming more regular.
For example, during a 2021 heatwave in north-western US and Canada, local temperature records were broken by up to 5C. According to one study, the heatwave would have been “impossible” without human-caused climate change.
The new study explores how accurately AI and physics-based models can forecast such record-breaking extremes.
First, the authors identified every heat, cold and wind event in 2018 and 2020 that broke a record previously set between 1979 and 2017. (They chose these years due to data availability.) The authors use ERA5 reanalysis data to identify these records.
This produced a large sample size of record-breaking events. For the year 2020, the authors identified around 160,000 heat, 33,000 cold and 53,000 wind records, spread across different seasons and world regions.
For their traditional, physics-based model, the authors selected the High RESolution forecast model from the Integrated Forecasting System of the European Centre for Medium-Range Weather Forecasts. This is “widely considered as the leading physics-based numerical weather prediction model”, according to the paper.
They also selected three “leading” AI weather models – the GraphCast model from Google Deepmind, Pangu-Weather developed by Huawei Cloud and the Fuxi model, developed by a team from Shanghai.
The authors then assessed how accurately each model could forecast the extremes observed in the year 2020.
Dr Zhongwei Zhang is the lead author on the study and a researcher at Karlsruhe Institute of Technology. He tells Carbon Brief that many AI weather forecast models were built for “general weather conditions”, as they use all historical weather data to train the models. Meanwhile, forecasting extremes is considered a “secondary task” by the models.
The authors explored a range of different “lead times” – in other words, how far into the future the model is forecasting. For example, a lead time of two days could mean the model uses the weather conditions at midnight on 1 January to simulate weather conditions at midnight on 3 January.
The plot below shows how accurately the models forecasted all extreme events (left) and heat extremes (right) under different lead times. This is measured using “root mean square error” – a metric of how accurate a model is, where a lower value indicates lower error and higher accuracy.
The chart on the left shows how two of the AI models (blue and green) performed better than the physics-based model (black) when forecasting all weather across the year 2020.
However, the chart on the right illustrates how the physics-based model (black) performed better than all three AI models (blue, red and green) when it came to forecasting heat extremes.
The authors note that the performance gap between AI and physics-based models is widest for lower lead times, indicating that AI models have greater difficulty making predictions in the near future.
They find similar results for cold and wind records.
In addition, the authors find that AI models generally “underpredict” temperature during heat records and “overpredict” during cold records.
The study finds that the larger the margin that the record is broken by, the less well the AI model predicts the intensity of the event.
‘Warning shot’
Study author Prof Erich Fischer is a climate scientist at ETH Zurich and a Carbon Brief contributing editor. He tells Carbon Brief that the result is “not unexpected”.
He adds that the analysis is a “warning shot” against replacing traditional models with AI models for weather forecasting “too quickly”.
The analysis, he continues, is a “warning shot” against replacing traditional models with AI models for weather forecasting “too quickly”.
AI models are likely to continue to improve, but scientists should “not yet” fully replace traditional forecasting models with AI ones, according to Fischer.
He explains that accurate forecasts are “most needed” in the runup to potential record-breaking extremes, because they are the trigger for early warning systems that help minimise damages caused by extreme weather.
Leonardo Olivetti is a PhD student at Uppsala University, who has published work on AI weather forecasting and was not involved in the study.
He tells Carbon Brief that “many other studies” have identified issues with using AI models for “extremes”, but this paper is novel for its specific focus on extremes.
Olivetti notes that AI models are already used alongside physics-based models at “some of the major weather forecasting centres around the world”. However, the study results suggest “caution against relying too heavily on these [AI] models”, he says.
Prof Martin Schultz, a professor in computational earth system science at the University of Cologne who was not involved in the study, tells Carbon Brief that the results of the analysis are “very interesting, but not too surprising”.
He adds that the study “justifies the continued use of classical numerical weather models in operational forecasts, in spite of their tremendous computational costs”.
Advances in forecasting
The field of AI weather forecasting is evolving rapidly.
Olivetti notes that the three AI models tested in the study are an “older generation” of AI models. In the last two years, newer “probabilistic” forecast models have emerged that “claim to better capture extremes”, he explains.
The three AI models used in the analysis are “deterministic”, meaning that they only simulate one possible future outcome.
In contrast, study author Engelke tells Carbon Brief that probabilistic models “create several possible future states of the weather” and are therefore more likely to capture record-breaking extremes.
Engelke says it is “important” to evaluate the newer generation of models for their ability to forecast weather extremes.
He adds that this paper has set out a “protocol” for testing the ability of AI models to predict unprecedented extreme events, which he hopes other researchers will go on to use.
The study says that another “promising direction” for future research is to develop models that combine aspects of traditional, physics-based weather forecasts with AI models.
Engelke says this approach would be “best of both worlds”, as it would combine the ability of physics-based models to simulate record-breaking weather with the computational efficiency of AI models.
Dr Kyle Hilburn, a research scientist at Colorado State University, notes that the study does not address extreme rainfall, which he says “presents challenges for both modelling and observing”. This, he says, is an “important” area for future research.
The post Traditional models still ‘outperform AI’ for extreme weather forecasts appeared first on Carbon Brief.
Traditional models still ‘outperform AI’ for extreme weather forecasts
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