India heatwave
An Indian minister has blamed the country's recent deadly heatwave on climate changeGetty

Climate change threatens to wipe out many improvements to human health made in the past 50 years around the world, according to a new study.

The "impact of climate change on global health could be enormous, not only through the direct health effects, but also because of reduced social stability if people are forced to move or flee," said Peter Byass, a senior adviser to the work of the Lancet Commission on Health and Climate Change and professor of global health at Umeå University in Sweden.

It is predicted there could be as many as 200 million climate refugees by 2050, according to the International Bar Association.

Published by the medical journal The Lancet on 23 June, the study lays out a plan to get the problem under control. First is the "recommendation to scale up financing for climate-resilient health systems worldwide," writes Margaret Chan, director-general of the World Health Organization (WHO) in the study.

The journal's 2015 Commission on Health and Climate Change puts forward eight other ideas governments around the world should consider to mitigate the health effects. Among the suggestions are rapidly phasing out coal power plants, setting up an international carbon pricing mechanism, and giving people in developing countries access to renewable energy.

It also calls for the creation of a new organization: the "Countdown to 2030: Climate Change and Health Action" group. Its job would be to monitor and report every two years to the UN on the impact of climate change on health globally.

Chan said that WHO estimates climate change would cause 250,000 extra deaths around the world each year by the 2030s. In India this year an extreme heatwave has left 1,700 dead. On 22 June, Pakistan reported as many as 224 people have also died there from 45C temperatures.

Severe droughts in California and South America are ongoing. Scientists say that climate change is having an impact on the frequency, intensity, and duration of these events.

"Hundreds of millions, probably billions, of people would have to move if you talk about 4, 5, 6 degree increases" in the Earth's median temperature, British economist Nick Stern, and author of the Stern Review on the Economics of Climate Change, predicted in 2009. "There's no way the world can handle that kind of population move in the time in which it would take place."

Countries around the world are already grappling with the issue. A new study has linked 2012's Hurricane Sandy to climate change. And Bangladesh and Pakistan have seen many people displaced by flooding linked to climate change in recent years.

A random survey of 30,000 people in Pakistan, Nepal, India, Bangladesh, China, Vietnam and Indonesia by the Environmental Justice Foundation found that 68% of them believe they are likely to face extreme weather events. Even more - 87% - said that changes in the weather and the resulting access to food and water would have a significant impact on them.

Nevertheless, if all of the report's recommendations are taken up, said Byass, "effective climate action may actually prove to be one of the greatest opportunities to also improve global health that we have ever had."