Early life on Earth has found an interetsing turning point. A new study by researchers at Massachusetts Institute of Technology suggests that some of Earth’s earliest life forms may have evolved the ability to use oxygen hundreds of millions of years before it became a permanent part of the planet’s atmosphere.

Oxygen is essential to most life on Earth today, but it was not always abundant. Scientists have long believed that oxygen only became a stable component of the atmosphere around 2.3 billion years ago, during a turning point known as the Great Oxidation Event (GOE). The new findings indicate that biological use of oxygen may have begun much earlier, potentially reshaping scientists’ understanding of how life evolved on Earth.

The study, published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, traces the evolutionary origins of a key enzyme that allows organisms to use oxygen for aerobic respiration. This enzyme is present in most oxygen-breathing life forms today, from bacteria to humans.

Scientists have long believed that oxygen only became a stable component of the atmosphere around 2.3 billion years ago, during a turning point known as the Great Oxidation Event (GOE). The new findings indicate that biological use of oxygen may have begun much earlier, potentially reshaping scientists’ understanding of how life evolved on Earth

MIT geobiologists found that the enzyme likely evolved during the Mesoarchean era, between 3.2 and 2.8 billion years ago—several hundred million years before the Great Oxidation Event.

The findings may help answer a long-standing mystery in Earth’s history: why it took so long for oxygen to accumulate in the atmosphere. Scientists know that cyanobacteria, the first organisms capable of producing oxygen through photosynthesis, emerged around 2.9 billion years ago. Yet atmospheric oxygen levels remained low for hundreds of millions of years after their appearance.

While geochemical reactions with rocks were previously thought to be the main reason oxygen failed to build up early on, the MIT study suggests biology itself may also have played a role. Early organisms that evolved the oxygen-using enzyme may have consumed small amounts of oxygen as soon as it was produced, limiting how much could accumulate in the atmosphere.

“This does dramatically change the story of aerobic respiration,” said Fatima Husain, postdoctoral researcher in MIT’s Department of Earth, Atmospheric and Planetary Sciences, said in a media statement. “Our study adds to this very recently emerging story that life may have used oxygen much earlier than previously thought. It shows us how incredibly innovative life is at all periods in Earth’s history.”

The research team analysed thousands of genetic sequences of heme-copper oxygen reductases—enzymes essential for aerobic respiration—across a wide range of modern organisms. By mapping these sequences onto an evolutionary tree and anchoring them with fossil and geological evidence, the researchers were able to estimate when the enzyme first emerged.

“The puzzle pieces are fitting together and really underscore how life was able to diversify and live in this new, oxygenated world

Tracing the enzyme back through time, the team concluded that oxygen use likely appeared soon after cyanobacteria began producing oxygen. Organisms living close to these microbes may have rapidly consumed the oxygen they released, delaying its escape into the atmosphere.

“Considered all together, MIT research has filled in the gaps in our knowledge of how Earth’s oxygenation proceeded,” Husain said. “The puzzle pieces are fitting together and really underscore how life was able to diversify and live in this new, oxygenated world.”

The study adds to a growing body of evidence suggesting that life on Earth adapted to oxygen far earlier than previously believed, offering new insights into how biological innovation shaped the planet’s atmosphere and the evolution of complex life.

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.