Israeli airstrikes on oil facilities in Tehran on 7 March led to sulphur dioxide emissions equivalent to a small volcanic eruption, potentially exposing people as far away as China to acid rain and toxic air pollution.

As part of the US and Israeli campaign against Iran, warplanes several oil depots and a refinery that night, sparking that lit up the sky and smoke for days. Black rain containing soot and hydrocarbons fell on the Iranian capital, and residents reported eye and skin irritation and difficulty breathing.

Now, data from a new generation of Chinese satellites has shown that the plume of sulphur dioxide released by these explosions and fires covered 300,000 square kilometres, passing over Turkmenistan, Uzbekistan, Kyrgyzstan, Kazakhstan and China.

The brief attack prompted a days-long spike in emissions, injecting a total of 29,800 tonnes of sulphur dioxide, according to at Wuhan University in China and his colleagues. For comparison, Iceland’s Eyjafjallajökull volcano was emitting about  per day when its ash cloud shut down air travel in Europe in 2010.

The concentrations of sulphur dioxide measured by the satellites reached levels that could impair lung function, irritate the eyes and throat, and exacerbate asthma or bronchitis, especially among children and older people, says .

“Although the major emission event lasted only one to two days, the research notes that the potential impact on the regional atmosphere should not be neglected,” he says. Pollutants may have been rained out over water sources and agricultural land, potentially contaminating drinking water and food, he adds.

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Sulphur dioxide reacts with different compounds of hydrogen and oxygen in the air to form sulphuric acid, leading to smog and acid rain. During the Great Smog of 1952, sulphuric acid and other pollution from burning coal killed an .

The attack on Tehran released about sulphur dioxide than some coal-fired power plants in high-income countries emit in a year, although a coal plant in a nation that doesn’t require scrubbers on smokestacks can emit far more of it.

Besides sulphur dioxide, the burning oil facilities emitted soot and heavy metals. According to at the University of York, UK, the massive quantity of sulphur dioxide emitted suggests the plume held harmful quantities of even more dangerous pollution. This might include nitrogen oxides and polycyclic aromatic hydrocarbons, as well as unburned hydrocarbons like benzene, all of which to cancer.

“[Sulphur dioxide] would be emitted with a whole range of other things,” says Carpenter. “That amount in one single fire has huge implications for people’s health… over thousands of kilometres.”

These fine particles can stay aloft for days, travelling with the wind. It was impressive that the study was able to trace the evolution of the plume over such a wide area, she says.

The plume only lasted for about three days, which probably isn’t enough time to cause cancer. And the satellites measure sulphur-dioxide concentrations through the entire atmosphere, so the toxin concentration at ground level is unclear. But the pollution could potentially have triggered asthma attacks, strokes or even heart attacks in especially vulnerable people, according to Carpenter.

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The Fengyun 3 satellite constellation that the study drew upon provides atmospheric concentrations of sulphur dioxide and other major pollutants to the public within three hours, which could improve disaster response, says Yin. “Satellite data are useful for pollution assessment and early warning for downstream areas.”

Widespread firings and staffing changes at the US National Oceanic and Atmospheric Administration (NOAA) could make the country’s weather forecasts less reliable, according to multiple researchers and the American Meteorological Society.

“The consequences to the American people will be large and wide-ranging, including increased vulnerability to hazardous weather,” the organisation said in a .

More than 880 NOAA employees have been fired under the administration of President Donald Trump, according to a from US Senator Maria Cantwell. That includes researchers working to improve hurricane forecasts and build the next generation of weather models, and more than 200 people within the National Weather Service, which is part of NOAA. An additional 500 people also accepted an earlier “fork in the road” offer to resign, further hollowing out the agency – which was already understaffed, according to two former NOAA employees.

A spokesperson for NOAA declined to discuss the firings and staffing changes. They said the agency will “continue to provide weather information, forecasts and warnings pursuant to our public safety mission”. But outside researchers and former NOAA employees say the cuts could degrade the quality of the agency’s weather forecasts.

The changes will have “definite cascading effects that will impact the forecast, even what people see on their phone via a third party”, says at the University of Colorado Boulder.

The cuts could start to affect alerts about extreme weather like tornadoes and hurricanes immediately, and in the longer term, they could make general weather reports less accurate, as even commercial weather apps rely on data and modelling from NOAA. Here are four ways experts predict the storm of firings and resignations will affect weather forecasts.

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Delayed tornado warnings

The National Weather Service runs a network of 122 weather forecasting offices across the country. At least 16 of the offices in the tornado-prone central part of the country are now understaffed, says at Iowa State University. More than a dozen offices in this central region saw their head meteorologists resign, according to the former NOAA employees. And the region’s severe weather season is about to begin.

Neighbouring offices may be able to help understaffed sites track tornadoes and issue alerts, but the disruption could result in delays. “It is more likely there will be some mistakes,” says Gallus.

Such delays were evident last year, when a tornado forced a local forecast office in Iowa to evacuate, says Gallus. A neighbouring station stepped in to help track the storm. But in the confusion, some residents got only a 5-minute warning that a tornado was headed their way, rather than the 15-minute minimum that forecasters aim to provide. In an emergency situation, those lost minutes can make the difference between being able to get to safety or not.

Not knowing when hurricanes will suddenly get stronger

Some employees fired from NOAA were working on improving hurricane forecasts, in particular estimating when they will rapidly intensify. Rapid intensification can make hurricanes more dangerous by leaving people with less time to prepare. But these events are notoriously challenging to predict.

Hurricane modellers at NOAA and at other institutions have made substantial progress in forecasting rapid intensification in recent years, says at the University at Albany in New York. This has been due to better modelling, data collection and data integration efforts by NOAA researchers. Now staffing cuts are “destabilising the whole process that makes for improvements into hurricane track and intensity forecasts”, he says.

“It’s going to be slower going to make the improvements that we have counted on to make hurricane forecasts better over the last 30 years,” says , who had worked on improving NOAA’s hurricane forecasts before he was fired from his position at the agency’s Environmental Modeling Center last week. He says several people were also fired from the “Hurricane Hunters” group that flies planes into storms to collect data, including two flight directors.

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Less reliable weather data

Accurate weather forecasts rely on a continuous stream of information about real-time conditions around the world, collected from ocean buoys, satellites, radar and other sensors. The data is then fed into global weather models that underlie both public and private forecasts. Much of the world’s data and modelling is provided by NOAA.

Staffing cuts could affect these vital data-gathering efforts, which would degrade the quality of forecasts. In fact, some local have already suspended regular weather balloon launches because of staffing shortages.

“All of those observing networks are maintained and run by people,” says at the University of Miami in Florida. “And we have already lost many people from those teams. It’s going to be an aggregate effect.”

Stalled improvements to future weather forecasts

At least eight people, a quarter of its staff, were fired from the Environmental Modeling Center, which is responsible for validating weather data and integrating it into the models that underlie more or less all forecasting, says Hazelton. “Everything from ‘What’s the temperature this weekend?’ to ‘Is there going to be a tornado outbreak?’”

Staffing cuts at the Environmental Modeling Center will also slow down research to improve current global weather models, he says. Ten people were also fired from the Geophysical Fluid Dynamics Laboratory, where researchers were building the of global weather and climate models.

Such cuts are “extremely harmful” to efforts to make forecasts more reliable, says Gallus. He says almost all the improvements in forecasts in the past few decades have been down to improvements in modelling. “If we’re losing a large amount of researchers working on them, you’re basically saying my forecasts are never going to get better.”