For decades, long spells of suffocating heat followed by explosive thunderstorms were largely confined to the tropics. But that pattern is now spreading into the planet’s midlatitudes, and researchers at the Massachusetts Institute of Technology believe they know why.

In a new study published in Science Advances, MIT scientists have identified atmospheric inversions — layers of warm air sitting over cooler air near the ground — as a critical factor controlling how hot, humid, and storm-prone a region can become. Their findings suggest that parts of the United States and East Asia could face unfamiliar and dangerous combinations of oppressive heat and extreme rainfall as the climate continues to warm.

Inversions are already notorious for trapping air pollution close to the ground. The MIT team now shows they also act like thermal lids, allowing heat and moisture to accumulate near the surface for days at a time. The longer an inversion persists, the more unbearable the humid heat becomes. And when that lid finally breaks, the stored energy can be released violently, fuelling intense thunderstorms and heavy downpours.

“Our analysis shows that the eastern and midwestern regions of U.S. and the eastern Asian regions may be new hotspots for humid heat in the future climate,” said Funing Li, a postdoctoral researcher in MIT’s Department of Earth, Atmospheric and Planetary Sciences, in a media statement.

The mechanism is especially important in midlatitude regions, where inversions are common. In the US, areas east of the Rocky Mountains frequently experience warm air aloft flowing over cooler surface air — a configuration that can linger and intensify under climate change.

“As the climate warms, theoretically the atmosphere will be able to hold more moisture,” said Talia Tamarin-Brodsky, an assistant professor at MIT and co-author of the study, in a media statement. “Which is why new regions in the midlatitudes could experience moist heat waves that will cause stress that they weren’t used to before.”

Why heat doesn’t always break

Under normal conditions, rising surface temperatures trigger convection: warm air rises, cool air sinks, clouds form, and storms develop that can eventually cool things down. But the researchers approached the problem differently, asking what actually limits how much heat and moisture can build up before convection begins.

By analysing the total energy of air near the surface — combining both dry heat and moisture — they found that inversions dramatically raise that limit. When warm air caps cooler air below, surface air must accumulate far more energy before it can rise through the barrier. The stronger and more stable the inversion, the more extreme the heat and humidity must become.

“This increasing inversion has two effects: more severe humid heat waves, and less frequent but more extreme convective storms,” Tamarin-Brodsky said.

A Midwest warning sign

Inversions can form overnight, when the ground cools rapidly, or when cool marine air slides under warmer air inland. But in the central United States, geography plays a key role.

“The Great Plains and the Midwest have had many inversions historically due to the Rocky Mountains,” Li said in a media statement. “The mountains act as an efficient elevated heat source, and westerly winds carry this relatively warm air downstream into the central and midwestern U.S., where it can help create a persistent temperature inversion that caps colder air near the surface.”

As global warming strengthens and stabilises these atmospheric layers, the researchers warn that regions like the Midwest may be pushed toward climate extremes once associated with far warmer parts of the world.

“In a future climate for the Midwest, they may experience both more severe thunderstorms and more extreme humid heat waves,” Tamarin-Brodsky said in a media statement. “Our theory gives an understanding of the limit for humid heat and severe convection for these communities that will be future heat wave and thunderstorm hotspots.”

The study offers climate scientists a new way to assess regional risk — and a stark reminder that climate change is not just intensifying known hazards, but exporting them to places unprepared for their consequences.

Extreme weather events intensified across the globe in 2025, disproportionately impacting vulnerable communities and pushing many regions close to the limits of adaptation, according to the latest annual report by World Weather Attribution (WWA). Despite the absence of a strong El Niño, global temperatures remained exceptionally high, making 2025 one of the hottest years on record and underscoring the growing influence of human-induced climate change.

The report, Unequal Evidence and Impacts, Limits to Adaptation: Extreme Weather in 2025, analysed 22 major extreme weather events in depth, selected from 157 climate disasters that met humanitarian impact thresholds worldwide. Floods and heatwaves were the most frequent, with 49 events each, followed by storms (38), wildfires (11), droughts (7) and cold spells (3).

Although 2025 occurred under weak La Niña conditions—typically associated with cooler global temperatures—the three-year global temperature average crossed the 1.5°C warming threshold for the first time. Scientists attribute this persistent heat to rising greenhouse gas emissions, which continue to override natural climate variability.

“Each year, the risks of climate change become less hypothetical and more brutal reality,” said Friederike Otto, Professor of Climate Science at Imperial College London and co-founder of World Weather Attribution, in a statement. “Our report shows that despite efforts to cut carbon emissions, they have fallen short in preventing global temperature rise and the worst impacts. Decision-makers must face the reality that their continued reliance on fossil fuels is costing lives, billions in economic losses, and causing irreversible damage to communities worldwide”

Heatwaves: the deadliest disaster of 2025

Heatwaves emerged as the deadliest extreme weather event of the year. In Europe alone, an estimated 24,400 people died during a single summer heatwave between June and August, across 854 cities representing nearly 30% of the continent’s population.

In South Sudan, human-induced climate change made a February heatwave 4°C hotter than it would have been in a pre-industrial climate, turning what was once a rare event into one expected every two years. Schools were closed nationwide after dozens of children collapsed from heat exhaustion, highlighting how extreme heat disrupts education and deepens gender and social inequalities.

Floods, storms and data gaps in the Global South

Floods were the most frequently triggered hazard studied by WWA in 2025, with devastating impacts reported in Pakistan, Sri Lanka, Indonesia, Botswana and the Mississippi River Basin. However, nearly one-quarter of attribution studies remained inconclusive, largely due to poor weather data and limitations in climate models, particularly in the Global South.  

This uneven scientific evidence mirrors broader climate injustice. Many regions experiencing the most severe impacts lack dense weather station networks, making it difficult to quantify the role of climate change precisely—even when human suffering is evident.

Wildfires and storms pushed adaptation limits

The report also documented record-breaking wildfires, including the most economically destructive fires in modern US history in Los Angeles, which caused an estimated $30 billion in insured losses and were linked to around 400 deaths. Climate change increased the likelihood of extreme fire weather by 35%, driven by hotter, drier, and windier conditions.  

Tropical cyclones further illustrated the limits of adaptation. Hurricane Melissa, which struck the Caribbean, produced rainfall intensities at least 9% higher due to climate change. While early warnings and evacuations in Jamaica and Cuba saved lives, the storm still caused widespread damage, demonstrating that preparedness alone cannot fully offset intensifying extremes

A new era of dangerous extremes

“2025 showed us that we are now in a persistent new era of dangerous, extreme weather,” said Theodore Keeping, researcher at Imperial College London, in a statement. “The evidence of the severe, real impacts of climate change are more clear than ever, and it is essential that action is taken to stop fossil fuel emissions, and to help the world’s most vulnerable prepare for the devastating impacts of increasingly extreme weather.”

Echoing this concern, Sjoukje Philip, researcher at the Royal Netherlands Meteorological Institute (KNMI), noted in a statement that natural climate variability alone cannot explain the year’s extreme heat. “The continuous rise in greenhouse gas emissions has pushed our climate into a new, more extreme state, where even small increases in global temperatures now trigger disproportionately severe impacts”

Emissions cuts are non-negotiable

While the report emphasises the importance of adaptation—such as early warning systems, urban planning, and ecosystem restoration—it concludes that rapid and deep reductions in fossil fuel emissions remain essential to avoid the worst climate impacts.

As the WWA scientists warn, without decisive global action, extreme weather events like those seen in 2025 will no longer be exceptions, but the defining feature of a warming world.

When fires swept through the Palisades and Eaton neighbourhoods of Los Angeles in January, turning entire streets into ash, the scale of destruction stunned even disaster-hardened California. By the time the flames were finally contained, the damage bill had crossed $60 billion, making it the costliest wildfire event ever recorded in the United States. Dozens were killed directly, and later studies linked the smoke and prolonged exposure to hundreds more deaths.

That inferno was not an outlier. It was the opening chapter of what humanitarian organisation Christian Aid now calls “a year of climate breakdown.”

According to Counting the Cost 2025, a new global assessment released this week by Christian Aid, climate-driven disasters — from wildfires and cyclones to floods and droughts — caused more than $120 billion in economic losses worldwide in 2025. And even that staggering figure, the report cautions, captures only a fraction of the real damage .

>> Seasonal flooding in China causing $11.7 billion in losses

>> Hurricane Melissa in the Caribbean, with damages nearing $8 billion

>> Severe monsoon floods in India and Pakistan, killing over 1,860 people

>> Back-to-back typhoons in the Philippines, displacing more than 1.4 million people

The report identifies ten extreme weather events, each costing over $1 billion, spread across every inhabited continent. Together, they paint a picture of a planet where climate shocks are no longer exceptional, but routine — and increasingly deadly.

After the California fires, the world watched as powerful cyclones tore through South and Southeast Asia in November. A rare convergence of storms battered Thailand, Sri Lanka, Indonesia, Viet Nam and Malaysia, triggering floods and landslides that killed more than 1,750 people. Economic losses are estimated at around $25 billion, though final figures are still emerging.

In China, months of relentless rain between June and August submerged cities and farmland, killing dozens and causing nearly $12 billion in damage. In the Caribbean, Hurricane Melissa rapidly intensified over unusually warm waters, striking Jamaica, Cuba and the Bahamas and leaving destruction valued at close to $8 billion in its wake.

South Asia experienced one of its deadliest monsoon seasons in years. Torrential rains across India and Pakistan displaced millions, damaged crops and infrastructure, and claimed more than 1,860 lives. The Philippines, meanwhile, endured a relentless parade of typhoons that forced over 1.4 million people from their homes.

“These disasters are not ‘natural’,” said Joanna Haigh, Emeritus Professor of Atmospheric Physics at Imperial College London, responding to the findings. “They are the predictable result of continued fossil fuel expansion and political delay.”

What stands out in the report is not just the scale of losses, but how unevenly they are counted. Most of the headline figures rely on insured losses, which are far higher in wealthy countries with strong insurance markets. In poorer regions, where insurance is rare or nonexistent, devastation often goes largely unpriced.

Christian Aid highlights another set of disasters — floods in Nigeria and the Democratic Republic of Congo, drought across Iran and West Asia, wildfires in the UK and southern Europe — that caused immense human suffering but failed to make the top ten simply because reliable economic data was unavailable.

“It is the present reality of climate breakdown.”

“The poorest communities are first and worst affected,” said Patrick Watt, Chief Executive Officer of Christian Aid. “While wealthy countries count the financial cost, millions of people elsewhere are counting lost lives, homes and futures.”

The science behind these events is becoming harder to ignore. Attribution studies cited in the report show that rising global temperatures are intensifying rainfall, fuelling stronger cyclones, prolonging droughts and creating the hot, dry conditions that allow fires to explode — even in places like Scotland and northern Europe, once considered low-risk.

“What we are seeing in 2025 is not a warning of the future,” said Davide Faranda, Research Director at France’s Laboratoire de Science du Climat et de l’Environnement. “It is the present reality of climate breakdown.”

Christian Aid argues that the consequences documented this year are the result of political choices — continued investment in fossil fuels, slow emissions cuts, and repeated failures to deliver climate finance to vulnerable countries. With global leaders heading into 2026 negotiations, the organisation warns that without urgent action, today’s billion-dollar disasters may soon look modest by comparison.

As the report makes clear, the climate bill is no longer coming due. It has arrived — and the world’s most vulnerable are paying first.