A record 512bn of work hours were lost around the world in 2023 because of the risk of heat exposure, says a new report from the Lancet Countdown on Health and Climate Change.
Agricultural workers in low-income countries were disproportionately affected, the authors say, costing countries around 8% of their GDP in 2023.
The findings are part of the ninth iteration of the annual report, which features indicators of climate change and human health, such as heat mortality, air pollution exposure and how countries are adapting.
The report highlights the many health inequalities in how energy is used around the world. According to the report, the number of deaths caused by fossil fuel-derived air pollution decreased by 7% over 2016-21 – mainly due to wealthy nations phasing out coal.
However, the vast majority of low-income countries still rely heavily on biomass and other “dirty” fuels in their homes. Dr Marina Romanello, lead author and executive director of the Lancel Countdown, added that women and children are usually in charge of sourcing and burning the fuel, making them particularly vulnerable.
The authors also call out governments and fossil fuel companies for “fuelling the fire” through continuing investment into oil and gas assets that are likely to push the world past key warming targets. The study notes that fossil fuel subsidies exceeded national health spending in 2022 for more than 20 countries around the world.
Romanello told journalists her “concern” that governments and companies “keep on promoting fossil fuel expansion, to the detriment of health and survival of people worldwide”.
Extreme heat
The impacts of extreme heat are “insidious”, Prof Ollie Jay, director of the Heat and Health Research Centre at the University of Sydney and author on the report, told a press briefing.
He explained that certain groups of people are more vulnerable to heat – including infants, the elderly, pregnant women and people with pre-existing medical conditions.
In 2023, infants and adults older than 65 faced a new record high of 14 days of heatwaves per person, the report finds. This value exceeds the previous record, set in 2022, by more than 20%.
The combination of a warming and ageing world is putting more people at risk, the report says. For example, in 2023, demographic changes alone would have driven a 65% increase in heat-related deaths among over-65s, compared to the 1990-99 average. The addition of global warming pushes this percentage up to 167% – the highest highest level recorded.
Across the whole population, the authors find that people were exposed to an average of 50 more “health-threatening heat days” in 2023 than they would have been in a world without climate change. (These are defined as days when the daily average temperature exceeds the 84.5th percentile of the 1986-2005 daily regional average.)
Beyond this global average figure, less-developed countries are much more likely to see such health-threatening days. For example, 31 such countries experienced at least 100 more days of health-threatening heat due to climate change.
The map below shows the average number of days with health-threatening temperatures attributable to climate change per year, over 2019-23, by country. Darker colours mean more health-threatening days.
Heat stress is particularly dangerous for outdoors workers, who are often directly exposed to the heat while undertaking manual labour. In 2023, around one-quarter of the world’s population worked outdoors.
The report finds that countries with the lowest human development index (HDI) – a measure of a country’s development – have the highest proportion of outdoors workers, largely due to their reliance on the agricultural sector.
The report measures the number of “potential work hours lost” due to heat exposure, by considering temperature, humidity and “typical metabolic rate of workers in specific economic sectors”.
It finds that heat exposure drove a record high of 512bn potential work hours lost in 2023 – around 1.5 times the 1990-99 average. Approximately two-thirds of this loss was in the agricultural sector, mainly in low and medium HDI countries. In total, the global potential loss of income due to extreme heat reached a record high of $835bn in 2023, the report says.
Wealthy countries were generally the least impacted by heat stress. Very high HDI countries only saw around 41 lost hours per worker due to heat, causing an economic loss of around 1% of their GDP. Meanwhile, low HDI countries lost more than 200 hours per worker, and saw almost an 8% loss in their GDP.
The graph below shows percentage GDP loss due to heat stress in low, medium, high and very high HDI countries, in agriculture (light green), construction (dark green), manufacturing (orange) and services (purple).
This year’s report also introduces a new indicator assessing how night-time heat affects sleep loss. The authors estimate that high night-time temperatures led to 5% more sleep hours lost in 2019-23 than in 1986-2005.
The authors say that air conditioning is an “effective technology for reducing heat exposure”. However, they say that it can also be an example of “maladaptation”, as it is “expensive and energy-intensive, overwhelms energy grids on hot days, and can contribute to greenhouse gas emissions”.
They note that emissions from air conditioning increased by 8% over 2016-21. However, access to the technology is not universal. In 2021, 48% of households in very high HDI countries had air conditioning compared to only 5% of those in low HDI countries.
Malnutrition and disease
The report also unpacks how climate change is exacerbating food insecurity and malnutrition.
It finds that the total proportion of global land area affected by extreme drought for at least one month per year increased from 15% in 1951-60 to 44% in 2013-24.
The authors warn that “the higher frequency of heatwave days and drought months in 2022, compared with 1981-2010, was associated with 151 million more people experiencing moderate or severe food insecurity across 124 countries”.
This year, the authors also introduced a new indicator tracking changes in rainfall events. The authors divide up the world into 80km grid squares and monitor the number of rainfall events that exceed the 99th percentile of 1961-90 rainfall.
Over the last decade, extreme rainfall events increased in more than 61% of grid squares, the report finds. The authors warn that high rainfall can drive an increase in flooding, which can lead to a range of negative health incomes including outbreaks of certain diseases.
For example, Vibrio bacteria in coastal waters can cause “severe” gastrointestinal infections and “life-threatening sepsis”. The study finds that the length of coastlines with suitable conditions for the bacteria reached a new record high of more than 88,000km in 2023 – 32% above the 1990-99 average.
In addition, the total population living within 100km of coastal waters with conditions suitable for Vibrio transmission has reached a record high of 1.42 billion.
The authors also find that the climatic conditions for mosquitoes to transmit dengue, malaria and West Nile virus have increased between 1951-60 and 2014-23 as the world has warmed.
Fossil fuels
On energy use, the study notes that, “given the high greenhouse gas and air pollution emission intensity of coal, its phase-out is crucial to protect people’s health”.
Over 2016-21, very high HDI countries have seen a reduction in the share of energy that comes from coal. (The UK became the first G7 country to phase out coal power in September 2024.)
However, the report highlights that all low HDI countries are still very dependent on coal. Over 2016-21, the share of electricity that comes from coal in low HDI countries increased from less than 1% to 10%.
According to the report, the number of deaths caused by fossil fuel-derived air pollution – specifically, tiny particulate matter known as PM2.5 – decreased by 156,000 over 2016-21 – a drop of 7%. This is mainly due to reduced pollution from coal burning in high and very high HDI countries.
Dr Marina Romanello, the lead author of the report and executive director of the Lancet Countdown, told the press briefing that this an important result as it shows the “enormous potential of coal phase-out to improve health”.
However, the report also warns that biomass burning caused 1.24 million deaths in 2021 – an increase of 135,000 from 2016 levels.
For example, the report finds that 2.3bn people still cook using biomass. In low HDI countries, around 92% of countries use solid biomass for their household energy needs. Conversely, in very high HDI countries, this number is around 10%.
Romanello explained that biomass is “very unreliable, very unstable and particularly polluting”. She added:
“When households rely on biomass, it is often women and children that are in charge of sourcing the fuel, so it also generates disproportionate impacts on these groups.”
The authors also call out fossil fuel companies for “fuelling the fire”. One of the report’s indicators assesses the compatibility of fossil fuel company strategies with the Paris Agreement. It says:
“As of March 2024, the strategies of the 114 largest oil and gas companies have put them on track to exceed their share of greenhouse gas emissions consistent with limiting global heating to 1.5C by 189% in 2040, up from the 173% excess projected in March, 2023.”
The report analyses 86 countries that are collectively responsible for 93% of global CO2 emissions. They find that, in 2022, these countries awarded a record $1.2tn in fossil fuel subsidies. This funding exceeded 10% of national health spending in 47 countries and 100% in 23 countries.
Romanello shared her “concern” with the press briefing that “governments and companies keep fuelling the fire, keep on promoting fossil fuel expansion, to the detriment of health and survival of people worldwide”.
Adaptation
Finally, the report assesses countries’ preparedness for the health impacts of climate change. This section presents a mixed picture.
The report finds that, as of February 2024, fewer than half of the most recent country climate pledges made under the Paris Agreement mentioned a “health keyword”.
However, the report also finds areas of progress. For example, at the end of 2022, only four countries had put forward health national adaptation plans (HNAPs) outlining how they will plan for and adapt to the impacts of climate change on health. Just one year later, this number had jumped up to 40 countries.
Furthermore, the authors find that scientific engagement into the links between climate change and health is increasing. The number of scientific papers investigating the link between climate change and health reached a record high in 2023, with the vast majority of papers focusing on impacts, rather than mitigation or adaptation.
The graph below shows the number of academic papers published each year over 1990-2023 on climate change and health, focused on mitigation (orange), adaptation (green) and impacts (purple).
The report finds that some countries are already implementing successful adaptation measures. For example, it explains that countries with health early warning systems saw a 73% decrease in the number of people killed per extreme weather event between 2000-09 and 2014-23. In countries without such early warning systems, the decrease was only 21%.
The authors note that “the reduction cannot be directly attributed to the implementation of health early warning systems”, but suggest that countries that implement these systems likely have higher “engagement with climate change adaptation efforts”.
The positive news in this report is “not enough to tip the balance” or to “secure a healthy future”, Romanello told the press briefing. However, she said it is “meaningful progress” which can be “built on”.
Dr Jeremy Farrar served as chief scientist of the World Health Organisation, and was previously the director of the Wellcome Trust – the main funding body behind this report. He told journalists at the press briefing that despite the “incredible evidence base” available, the health community “have been too slow to make the case that climate change is a health crisis”.
However, he praised the intersectoral collaboration between health and climate experts, and said he hopes we are “turning a corner” on making sure that climate change is seen as a “health issue”.
The post More than half a trillion hours of work lost in 2023 due to ‘heat exposure’ appeared first on Carbon Brief.
More than half a trillion hours of work lost in 2023 due to ‘heat exposure’
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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