More than a billion people could be forced to flee their homes because of global warming, according to new research.

The movement of people, as well as the various effects of climate change, could be about to trigger a major health crisis, according to a new study from The Lancet.

Global warming is already leading some to conclude the climate-change migrants are being forced to move because of extreme changes in the amount of rain and temperature changes destroying their ability to farm. It notes that some have blamed the Syrian conflict on migration into the cities that was caused by a drought that seems to have been induced by climate change.

It notes that “migration driven by climate change has potentially severe impacts on mental and physical health, both directly and through the disruption of essential health and social services”.

That is the conclusion of the sweeping new research, which brings together a range of different studies looking at the health impacts of climate change. It suggests that the possible impact of those changes on people’s health could be vast – and that governments must act quickly to clean up the air and address environmental problems before they begin to kill people.

The study concludes that people can adapt to some of the less dramatic changes. But there are powerful limits to the amount people can adapt, it says – and so governments need to work hard both to mitigate the effects of climate change and help people adapt to them, in an attempt to deal with that health crisis.

It says that if those recommendations are taken up, it could avoid the disasters that it sees in the future. “The indicators reveal some stark warnings for human health as well as some glimmers of hope,” said Dr Clare Goodess, a senior researcher at the Climatic Research Unit at the University of East Anglia.

The impact of air pollution in UK cities forms part of a major investigation looking at the health and social costs of climate change around the world led by a top medical journal.

The Lancet Countdown on Health and Climate Change brought together 24 institutions and inter-governmental organisations including the WHO and World Meteorological Organisation.

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It found that global exposure to dangerous levels of air pollution caused by burning fossil fuels had increased by 11.2 per cent since 1990 with more than 70 per cent of cities exceeding WHO PM2.5 limits.

Many British cities and towns also broke the WHO limits for PM10s, slightly larger sooty specks considered less of a hazard than ultra-fine particles but still harmful to health.

The authors acknowledged that European Union air quality guidelines were far less stringent than those of the WHO, with an upper safety limit for PM2.5s of 25 micrograms per cubic metre.

However, they said the WHO limits represented a “safer threshold”.

The report added that 802 London schools and a high proportion of the capital’s hospitals and clinics were located in highly polluted areas “potentially putting some of society’s most vulnerable people at risk”.

Diesel-powered vehicles, which generate pollution particles, were one of the “key drivers” of poor air quality in towns and cities in the UK, said Dr Hillman.

“Unfortunately previous policies about encouraging diesel adoption have led to an increase in the amount of diesel related pollution,” he said.

In a “briefing for UK policymakers” the report called for the expansion of Clean Air Zones nationwide and wider introduction of measures similar to London’s new T-charge, which imposes a levy on drivers of the most polluting vehicles.

The report pointed out that between 2000 and 2016 there had been a 46 per cent increase in the number of weather-related disasters around the world. During the same period of time 125 million vulnerable adults over the age of 65 had been exposed to heatwaves.

In addition, climate change had increased the threat from mosquito-borne infectious diseases.

Transmission of dengue fever by the Aedes agypti mosquito had increased by 9.4 per cent since 1950.

Professor Hugh Montgomery, co-chair of The Lancet Countdown and director of the Institute for Human Health and Performance at University College London, said: “We are only just beginning to feel the impacts of climate change.

“Any small amount of resilience we may take for granted today will be stretched to breaking point sooner than we may imagine.”