Global warming is making us sick.

The proportion of Earth's population that's vulnerable to heat-related death and disease continues to grow around the world because of human-caused climate change, according to a report released this week.

"Climate change is a medical emergency," said report co-author Renee Salas, a doctor of emergency medicine at Massachusetts General Hospital. "It is truly harming the health of Americans and especially the most vulnerable ... children, the elderly, minorities and the poor."

Growing populations of older people, people living in cities and people with diseases are the prime reasons for our increasing vulnerability, according to the report, which was released Wednesday and published by The Lancet, a British medical journal.

Last year, about 157 million vulnerable people were exposed to heat waves globally. That's 18 million more than in 2016.

"We're seeing increases in the frequency, intensity and duration of heat waves," said report co-author Kristie Ebi of the University of Washington. "As our populations age and as they move into cities that have got urban heat islands, we're seeing a large increase in the number of people who are vulnerable to high temperatures."

She said another concern is that the potential geographic range of the mosquito, which can carry diseases such as dengue fever and Zika, has increased dramatically in higher temperatures.

Climate change, aka global warming, is caused by the burning of fossil fuels such as oil, gas and coal, which release greenhouse gases such as carbon dioxide and methane into the Earth's atmosphere and oceans. This has caused the planet to warm to levels that cannot be explained by natural factors.

The report, officially titled "The Lancet Countdown on Health and Climate Change," said that in 2017, 153 billion hours of labor was lost worldwide because of heat exposure.

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In 2017, the report said, there were 16 extreme weather disasters in the USA, from powerful hurricanes to catastrophic wildfires, each of which caused more than $1 billion in damage and together cost more than $313 billion.

"While each type of disaster poses different threats to human health, they all can lead to death," according to the report. "The official death toll was estimated at 3,278 lives, though the actual number is likely much higher, highlighting the need for better surveillance."

In an editorial that accompanied the report, The Lancet warned that in the next few decades, "heatstroke and extreme weather will have redefined global labor and production beyond recognition. Multiple cities will be uninhabitable, and migration patterns will be far beyond those levels already creating pressure worldwide."

The report was written by experts from 27 academic institutions, the United Nations and intergovernmental agencies from every continent, The Lancet said.

Calling climate change a dire health crisis, Salas concluded that "if we don't start taking these preventative measures, mitigating the greenhouse gas pollution that is choking us every day, many more Americans will continue to suffer and die. This doesn't have to be."

"We must take aggressive action to combat climate change today, so that by the end of this century, we'll have saved thousands of lives each year, along with hundreds of billions of dollars in public health costs," she said.