Extreme temperatures — mostly heat — are projected to kill as many as 2.3 million people in Europe by the end of the century unless countries get better at reducing carbon pollution and adapting to hotter conditions, a new study says.

Currently, cold temperatures kill more people in Europe than heat by large margins. But a team from the London School of Hygiene and Tropical Medicine used climate simulations of different scenarios and looked at death rates in 854 cities. They found as it warms cold deaths lessen slowly, but heat deaths soar rapidly.

With few reductions in emissions of greenhouse gases and little adaptation like air conditioning and cooling centers, Italy, southern Spain and Greece should see massive increases in the rate of heat deaths due to climate change. On the flip side, much of Scandinavia and the United Kingdom will see fewer temperature-related deaths, mostly due to moderating cold temperatures, the study in Monday's journal Nature Medicine found.

But even in the most optimistic scenarios — with carbon dioxide emissions from coal, oil and gas cut sharply and massive increases in adaptation — there's a net increase in temperature-related deaths as the world warms, said study lead author Pierre Masselot, an environmental epidemiologist and statistician.

The drop in cold deaths up north are in places not as populated as places further south, where the heat really kicks in and hurts, Masselot said.

“The Mediterranean is a so-called climate hotspot," Masselot said. "It's a region that is warming much quicker than the rest of the world. And Malta is right in the middle of it.”

The study projects Malta's temperature-related death rate to increase by 269 people for every 100,000 by the end of the century. By contrast, Ireland's will go down slightly, 15 per 100,000 people.

In general, western Europe being wealthier fares better than eastern Europe, Masselot said.

Several heat waves have killed thousands of people in the last few years in Europe, but one in 2003 is the biggest with about 70,000 deaths.

Big cities with lots of people near the Mediterranean can see the bodies pile up through the rest of the century. The study says in the worst case they studied Barcelona could see nearly a quarter million extra temperature-related deaths, while Rome and Naples get close to 150,000 deaths.

In a scenario with carbon pollution only slightly worse than current trends and no extra adaptation to heat, Masselot's team found more than 5.8 million excess heat deaths just from climate change, but nearly 3.5 million fewer cold deaths too. The team has a interactive website where cities and different factors can be adjusted.

Masselot's team was also able to isolate out climate change, removing a major factor of an aging population which made the study even more useful and impressive, said University of Washington public health and climate scientist Kristie Ebi, who wasn't part of the study.

“This very much lines up with what we would expect,” said Dr. Courtney Howard, a Canadian emergency room physician and vice chair of the Global Climate and Health Alliance. She was not part of the study. “When you think about summertime daytime temperatures in places like Rome — they start to get up into the 40s (104 to 122 degrees Fahrenheit).... That's very heat stress/heat stroke territory for healthy young people and very dangerous for older people, particularly if they don't have air conditioning.”

Europe having older housing stock and not much air conditioning needs massive amount of adaptation, such as central air, more green space and cooling centers, to lower the projected death rates, Masselot said. North America is less likely to have such a strong trend, he said.

Another factor is the aging of Europe makes its population more vulnerable, Masselot said.

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