Picture the world 100 or 200 years from now. What are you imagining? Hotter temperatures, melting glaciers or alpine places without snow? With heatwaves happening across Europe this summer, it’s not that hard to visualise.

Now picture Europe in a deep freeze where temperatures hit -20°C in London. Both of these scenarios might be the future we’re heading for, thanks to climate change. And there’s an even more worrying indicator: while almost the entire planet has been warming, there’s one patch in the North Atlantic Ocean just south of Greenland where temperatures have been falling.

Scientists call it the “cold blob”, and some think it could be a warning that one of Earth’s most important climate systems is beginning to change and may soon hit a tipping point where climate change no longer happens gradually. If this system flips, it could have devastating consequences that change all of our lives as we know them.

The full extent of the deaths and damage caused by the enormous flash flood that swept down a river valley in Nepal and Tibet today won’t be clear for weeks. But initial analyses of satellite images and seismic data suggest that the collapse of a high glacier caused the disaster.

“There’s a glacier that rolls over a cliff at about 5200 metres,” says at the University of Calgary in Canada. “It’s just like a perfect straight line where it snapped off and dropped over a kilometre vertically to the valley bottom.”

This collapse could be a result of global heating. “It’s not that much of a stretch to think, yes, we’re seeing one terrible ramification of human-caused climate change,” he says.

As the glacier flowed over the cliff and moved down the steep slope, deep crevasses would have formed in the ice. Warm weather in the past day or so may have melted a lot of snow and some glacier ice, with this liquid water weakening the glacier and causing the entire section flowing down the steep slope to collapse.

“Comparing satellite imagery from yesterday and today, the glaciers in the vicinity do seem to have lost a fair bit of snow in the last 24 hours,” says Shugar. “My guess is that snow melt, and glacier ice melt as well, injected a lot of liquid water into the glacier, which percolated down to the bed and lubricated it. That was enough for it to collapse.”

The potential energy released as heat when millions of tonnes of ice fell a kilometre may have melted large quantities of it, producing enough liquid water to generate the huge flash flood.

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“Maybe the glacier breaking is only part of the story and there’s something else that we can’t see yet,” says Shugar. “But as of now, that’s what it looks like.”

The melting of ice due to the release of potential energy caused the Chamoli flash flood in India in February 2021. “In that case, it was a large landslide but with a bit of glacier ice on top of it,” says Shugar. “When that much ice falls, there’s a lot of heat generated and it can melt.”

This event, however, was much larger. “These videos that we’re seeing are off the charts. This is horrific,” he says. “It looks like this will rank very high on the list of historic mountain disasters in terms of people killed, and cost.”

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Some reports have suggested that an earthquake triggered the event, but this isn’t the case, says at the University of Grenoble Alpes in France. “I have looked at the data from a few stations in the region, including a station from the Nepali national seismic network near Kathmandu, and we see the event very clearly in this record.”

The record begins with a strong signal of a form typically associated with the mass movement of material, rather than with an earthquake, says Cook. “Then we see a long seismic signal typical of a large debris flow that lasts for hours.”

The initially described the seismic event as an earthquake, but now says further analysis shows it was a landslide.

The signal is similar to one observed during the 2021 Chamoli event, says Cook.

Global heating may have and to the collapse of a glacier above the village of Blatten in Switzerland in 2025. Steep glaciers can break for reasons unrelated to climate change, says Shugar, but an increase in the frequency of this kind of disaster points to warming as a contributing factor.

“Mountain communities around the world, from the Alps to the Andes and the Himalayas, are threatened by increasing intensity and frequency of mountain-related hazards,” said , head of the United Nations Office for Disaster Risk Reduction,. “Their lives, ways of life, culture, and heritage are all threatened.”

Winter has traditionally been the most deadly season in the UK. But that is changing, thanks to searing summer heatwaves, with the number of heat-related deaths in England and Wales each year now rivalling deaths from cold weather.

Across England and Wales, just over 40,000 more people died on the hottest days between 1988 and 2025 than would be expected under normal temperatures, new figures released today by the UK’s Office for National Statistics (ONS) show.

By comparison, across the 37-year period, almost 139,000 deaths were associated with the coldest days.

But as summer temperatures rise, the number of heat-related and cold-related deaths each year is starting to converge, the ONS said.

In 1992, hot weather was associated with the deaths of 722 people, compared to 3412 deaths for cold weather. By 2023, hot weather was linked to 2234 deaths in England and Wales, with cold weather during the same year linked to 3294 deaths.

The ONS estimated deaths associated with the coldest 2.5 per cent and hottest 2.5 per cent of days between 1988 and 2025, accounting for other factors such as air pollution.

A series of hot summers, fuelled by a warming climate, has driven the trend in rising heat deaths. All five of the UK’s warmest summers on record have occurred since 2000, with 2022 being the first summer to record a 40°C day in the UK. Deaths associated with hot weather have been rising since 2011.

The ONS data didn’t include 2026 in its assessment, but prolonged high temperatures and successive heatwaves mean England is widely expected to log a record number of heat-related deaths this summer. In July, the UK’s Health Security Agency (UKHSA) said heatwaves in May and June 2026 had caused 2877 heat-associated deaths in England, almost double the entire 2025 total. That is also higher than the total number of deaths associated with cold weather in England during winter 2024-25, which the UKHSA has at 2544, raising the possibility that heat-related deaths in 2026 could outstrip cold-related deaths for the first time on record.

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Summer heat is “now killing almost as many people as winter cold each year in England and Wales,” said at the Grantham Research Institute on Climate Change and the Environment in London in a statement. “The deaths during the record heat of summer 2026 may be higher than the mortality we experienced last winter.”

 at the University of Surrey says the gap between hot weather deaths and cold weather deaths is “narrowing a lot quicker than anyone anticipated it would”. Without action to help people better cope with high temperatures, we will see “high and rapid growth” in the number of hot weather deaths in the UK over the coming years, he warns.

Climate change is expected to bring even hotter, drier summers to the UK, further increasing the public health risk. Already, more than half of UK homes are at risk of overheating during hot weather – that is projected to rise to 92 per cent by 2050, according to the UK’s Climate Change Committee.

at Warwick University, UK, says factors such as age, chronic disease, social isolation and housing conditions all determine how vulnerable a person is to extreme heat. “Whether deaths from heat will ultimately exceed deaths from cold is still unclear, yet that may not even be the most relevant question,” she says. “The more urgent concern is that heat-related mortality is rising, and many of these deaths could be avoided. How far this pattern persists will depend not just on future warming, but also on how well we adjust our homes, communities, health systems, and cities to a hotter climate.”

“The El Niño has blossomed. It is off the charts. Usual measures of El Niño have blown past prior record levels in the period with good data, even though maximum effects are still several months in the future.”

So writes renowned climate scientist James Hansen at Columbia University in New York in .

There are different ways of measuring El Niños, which occur when warm surface waters spread eastwards along the equator across the surface of the tropical Pacific Ocean. Hansen thinks the best measure is how much warmer than usual the upper 300 metres of the eastern tropical Pacific becomes.

“Our preferred metric, the heat anomaly in the upper 300 meters of the Equatorial Pacific Ocean… already exceeds the 1997-98 super El Niño,” he writes.

A more common measure, called the Niño3.4 index, is based on how much warmer than usual the sea surface temperature is in the Pacific in the long rectangle between 5 degrees north and south of the equator, and between 120 and 170 degrees west.

“The more common Niño3.4 metric, sea surface temperature… in the equatorial Pacific, also far exceeds prior values,” Hansen writes.

But at the Met Office, the UK’s national weather service, says the Niño3.4 index has not yet exceeded previous super El Niños. “The anomaly in Niño3.4 is currently about 2 degrees above the norm which is very high for this time of year but not quite as high as the anomaly at the peak of the 1997/1998 El Niño which was around 2.5 degrees,” Scaife told 91av.

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The disagreement on the Niño3.4 index might partly be because this index is usually expressed . By contrast, the daily Niño3.4 value before dropping back slightly.

“In this case, I would agree with Jim,” says at the California Institute for Water Resources. “Niño3.4 values are clearly now the highest on record for the time of year, and are expected to remain so for the rest of the calendar year.”

Using a running mean with a long lag is misleading in a rapidly evolving situation like this, says Swain.

However, during November 2015 the daily Niño3.4 reached nearly 3.1°C, so the current event is not yet as strong as the 2015 one on this measure, either. It appears Hansen meant to say the Niño3.4 index exceeds values for this time of year, as Swain says. 91av has asked Hansen for clarification, but had no response at the time of publication.

“Under the standard El Niño metric region it’s still currently the third strongest event on record,” says at Berkeley Earth. “But upper 300m heat is generally a leading indicator of what we will see at the surface.”

“I agree that this El Nino is the biggest on record,” says at the National Center of Atmospheric Research.

What’s clear is that this developing super El Niño will soon exceed previous events on all measures. “I have never seen an El Niño signal this intense in our forecasts,” Scaife said in . “If the forecast is accurate… then 2026 will far exceed our recent experience of El Niño and its worldwide climate influences.”

While Hansen is comparing the developing super El Niño to other modern events for which we have direct temperature records, at Newcastle University in the UK thinks it could also exceed historical events suspected to be even larger.

“The super El Niño evolving in the Pacific will likely be the biggest ever recorded, reaching or exceeding the levels of the 1877-1878 El Niño which caused widespread impacts, including famines and around 50 million deaths (3-4 percent of the global population at the time), mostly across Asia and South America,” Fowler said in a statement.

Climate models projecting higher warming for a given level of carbon dioxide have been discounted as unrealistic, but a new way of assessing models suggests they are accurate.

“For a given emission trajectory, we expect warming to be 25 per cent higher,” says at ETH Zurich in Switzerland.

The conclusion has enormous implications. For instance, a project called the currently projects that average global surface temperatures will rise by 2.6°C above pre-industrial levels by 2100 if countries implement existing policies. Gyuleva’s team’s results suggest we are instead heading for 3.25°C.

How much the world will warm depends on how much more CO2 we put into the atmosphere and how the planet responds to that CO2. Different climate models vary in how much warming they project for a given CO2 level. For instance, some models suggest that a doubling of CO2 will result in the average global surface temperature increasing by around 1.6°C above pre-industrial levels in the short term. Others suggest it could be as high as 3°C.

“The range is big, and it really matters,” says Gyuleva. “So the point is to find out which ones are right.”

Previously, this was done by using climate models to simulate the recent past. The models are fed data on greenhouse emissions over the past century or so, and their projected climate response is compared with what actually happened.

For the last report by the Intergovernmental Panel on Climate Change, a lot of these models simulated more warming than had happened, so were discounted. Based on the remaining models, the panel’s last report concluded that a doubling of CO2 would result in between 1.2°C and 2.4°C of warming in the short term, with a best estimate of 1.8°C.

But there is lots of variability in Earth’s climate. For instance, during the La Niña climate pattern, cooler seawater from deeper down spreads across the ocean, resulting in cooler surface temperatures. So, Gyuleva and her colleagues have filtered the historical climate record to try to remove the effect of variability due to phenomena like La Niña.

Their results suggest that natural variability limited temperature rises between 1981 and 2014 – a period that includes the so-called global warming hiatus in the first decade of the 21st century. “It’s really exactly this period 1981 to 2014, which was used in the previous papers, where you see the strongest bias down,” she says. “It was really bad luck.”

Correcting for this bias alone leads to higher estimates of the warming expected from a doubling of CO2. But Gyuleva’s team also assessed models using a new approach. Instruments on several satellites have been measuring how much short-wave radiation from the sun enters the atmosphere, and how much long-wave radiation is emitted. The difference between how much heat energy enters the atmosphere and how much leaves is the most fundamental measure of global warming.

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So, how well models project the trends in incoming and outgoing radiation as the world warms can be seen as a better measure of their performance than their projections of surface temperatures. But because the satellite measurements required to do this only began in 2001, this kind of assessment has only recently become possible.

The team found the models that best match the observed trends in short-wave and long-wave radiation project much greater warming. Based on the models that perform best at both kinds of assessments, the team concludes that a doubling of CO2 will lead to a rise of between 1.9°C and 2.6°C, with a best estimate of 2.25°C. “Our results need to be confirmed by more evidence from different sources before we can be fully confident,” says Gyuleva.

“This seems to be a sound approach,” says at the University of Oslo in Norway.

“In my opinion, the filtering out of natural variability is a valuable step forward,” says at Duke University in North Carolina, although he isn’t yet convinced that the short-wave and long-wave trends are a good way to assess models.

“I think it’s a plausible conclusion and a reasonable approach,” says at the University of New South Wales in Sydney.

But the findings are based on climate models, and none of them reproduces the key phenomena very well, says Sherwood. “To do a better job of this we really need better climate models. On the other hand, the steep temperature rises of the last few years are going to lead to higher estimated ranges regardless of method.”

In climate jargon, what Gyuleva’s team has estimated is known as the transient climate response. It is just one of three types of climate sensitivity, which vary in terms of the timescales involved.

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In the decades after a doubling of CO2, various feedbacks will kick in that lead to further warming, such as the continued warming of the oceans. The response after these medium-term feedbacks have kicked in is known as the equilibrium climate sensitivity. Last year, it was shown that the trends in short-wave and long-wave radiation suggest the equilibrium climate sensitivity is higher than previous estimates.

There are also very slow feedbacks that take centuries or more, such as the melting of ice sheets. Estimates of this earth system sensitivity – the full response to a doubling of CO2 over many millennia – are as high as 7°C.

However, if atmospheric CO2 levels were lowered by carbon removal, some of the longer-term consequences would be avoided.

Planes flying across the North Atlantic Ocean later this year will be re-routed to avoid causing condensation trails, in a first-of-a-kind trial to address the global warming impact of contrails across an entire airspace.

Starting in November, air traffic controllers managing the Shanwick airspace on the eastern side of the North Atlantic will advise planes to adjust their altitude to avoid creating fresh contrails. The controllers will be using AI-generated forecasts of atmospheric conditions from Google that predict where contrails will form.

“We can predict the regions that are going to form persistent climate-warming contrails, and we can re-route planes around them,” at Contrails.org, a research organisation that is participating in the project, said during a press briefing on 17 August.

Contrails are formed when soot particles emitted by jet engines trigger the formation of ice particles, leaving a condensation trail that can last for hours. During the day, these persistent contrails help to reflect solar radiation back to space, which has a cooling effect. But they also trap heat below them, causing warming. Overall, contrails are thought to account for around one-third of aviation’s climate impact.

The Shanwick airspace is a contrail hotspot and a busy area for planes crossing the North Atlantic. suggests the airspace is responsible for about 5 per cent of global contrail warming, and most of this effect occurs during the winter season between November and February.

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The £5 million Operation Blue Skies project will re-route flights in the evening and night, which have the biggest warming effect. Pilots entering the Shanwick airspace will be instructed to adjust their altitude by up to 2000 feet (600 metres) to avoid atmospheric conditions where contrail formation is likely. The advice will be issued under the same procedures already used by air traffic controllers to help pilots avoid turbulence or other weather conditions.

The trial will run during two four-month winter trials over 2026-2027 and 2027-2028, with approximately 20 to 40 test days during each winter season. Around 10,000 flights are expected to pass through the airspace during trial hours each year, and hundreds will need to be re-routed to produce a statistically significant data set for analysis. Researchers from the University of Cambridge and Imperial College London will analyse the data from the trial.

The climate benefit of avoiding contrails is worth any extra fuel burn from shifting flight paths, at Google UK said during the briefing. Re-routed flights may have to burn an additional 100 kilograms of fuel per aircraft while crossing the airspace, resulting in an additional few hundred kilograms of CO2 emitted. By comparison, “the contrail impact on those flights, especially at those times of day, is measured in the tonnes or even the tens of tonnes”, he said.

The project follows previous trials of Google’s AI contrail forecasts, which have been used to inform airlines’ flight plans before take-off and routes set by air traffic dispatchers. This work suggests re-routing a plane can cut contrail formation by 50 to 60 per cent.

But this is the first time contrail forecasts will be used across an entire airspace, and airlines will not be able to opt out. “This is what we call an airspace-scale trial, where deviations will effectively be instructed from the air traffic controller and affect all of the aircraft that are flying in this particular region,” said Hodgson.