The effects of climate change mean the world can expect higher temperatures and more frequent heat waves, climate experts have warned, with poor communities likely to be worst affected.

Heat is neglected because it is both an invisible and hard-to-document disaster that claims lives largely behind closed doors, they said, and because hot weather does not strike many people as a serious threat.

The warning comes as hot weather has swept the northern hemisphere. Britain has sweltered in a prolonged heat wave, with temperatures set to test national records, the country's Meteorological Office said.

"We will have to get used to these kinds of summers," said Friederike Otto, deputy director at the Environmental Change Institute at Oxford University.

"There is no doubt that there is a link to climate change. We need to take heat waves seriously around the world as something that we need to adapt to," Otto told the Thomson Reuters Foundation.

Fires have also caused devastation in Greece, Sweden and the United States. In Greece, rescuers are searching scorched land and the coastline for survivors three days after a wildfire destroyed a village outside Athens killing at least 82 people.

Health risks

The past three years were the hottest on record, the United Nations' World Meteorological Organization said in March.

The World Health Organization says heat stress, linked to climate change, is likely to cause 38,000 extra deaths a year worldwide between 2030 and 2050.

Image: WHO

Two weeks into Japan's blistering heat wave, at least 80 people have died and thousands have been rushed to emergency rooms, as officials urged citizens to stay indoors to avoid temperatures exceeding 40 degrees Celsius (104°F) in some areas.

In a heat wave in May, more than 60 people died in Karachi, Pakistan, when the temperature rose above 40C (104F).

"Heat waves are becoming more frequent, and that is likely due to climate change because the global temperature is rising," Sven Harmeling, head of climate change and resilience policy at aid group CARE International, said by phone.

He said climate change was altering weather patterns, and "we have to prepare for more of these consequences".

Stanford University researchers on Monday said hotter weather was linked to increases in suicides, after examining decades worth of temperature data against suicide rates in U.S. counties and Mexican municipalities, some dating back to the 1960s.

The report projected that if global warming were not capped by 2050, there could be at least an additional 21,000 suicides in the U.S. and Mexico alone.

Carbon emissions

In 2015, countries signing the Paris Agreement set a goal of limiting a rise in average world surface temperatures to "well below" 2C (3.6F) above pre-industrial times, while "pursuing efforts" to limit rising temperatures to 1.5C (2.7F).

U.S. President Donald Trump has vowed to pull out of the accord, which would make his country the only one to do so.

Nearly one in three people around the world are already exposed to deadly heat waves, and that will rise to nearly half of people by 2100 even if the world moves aggressively to cut climate-changing emissions, a University of Hawaii study found in 2017.

But poorer communities will suffer the most, said Frank Rijsberman, head of the Global Green Growth Institute, which helps developing countries adopt clean energy to boost their economies and reduce carbon emissions.

"In developed countries, we have resources, we have money, we have systems, we can manage. But in developing countries, where resilience is very low, people are hit much harder," he said in an interview.

About 1.1 billion people in Asia, Africa and Latin America are at risk from a lack of air conditioning to keep them cool as global warming brings more high temperatures, the non-profit Sustainable Energy for All said in a study last week.

"The most vulnerable in society will be most affected because those are the people who do not have the air-conditioned offices to go to, the people who have to work outside to make a living," said Otto.