Climate Change's Impact on Global Health

Heat stress, lung damage from wildfire smoke. The spread of disease-carrying mosquitoes into new regions as temperatures rise.

These are only a few of how public health has been affected and compounded by climate change - a focus for the first time at the annual U.N. climate summit COP28.

Government ministers are expected to discuss ways they can protect people from climate-driven health threats, which currently threaten to fix decades of progress in public health.

From 2030, experts expect that only four of these threats - malnutrition, malaria and dengue, diarrhea, and heat stress - will push global death tolls up by 250,000 every year, as per the World Health Organisation (WHO).

"Extreme weather events are becoming extreme health events," said Martin Edlund, CEO of global health nonprofit Malaria No More.

Here's how climate change is harming individuals' health across the world, and what countries could expect in the future.

Vector-borne diseases:

Mosquitoes that carry viruses including dengue, malaria, West Nile, and Zika are shifting into new regions of the world as warmer temperatures and heavy downpours create more hospitable conditions for them to breed.

Reported dengue cases have grown from around half a million in 2000 to more than 5 million in 2019, according to the WHO. Just this year, cases in Brazil are up 73% against the five-year average, said Edlund, with Bangladesh suffering a record dengue outbreak.

Climate change is also having an unpredictable impact on malaria, with 5 million more cases registered in 2022 than the previous year, reaching a total of 249 million, the WHO's World Malaria Report found.

Floods in Pakistan last year, for example, led to a 400%increase in malaria cases in the country, the report said.

The disease has also spread into the highlands of Africa that previously had been cold for mosquitoes.

Two new malaria vaccines expected to be available next year offer some hope of combating the scourge.

Murky waters:

Storms and flooding wrought by climate change are allowing other infectious water-borne diseases to proliferate as well.

After decades of progress against cholera, an intestinal disease spread by contaminated food and water, case numbers are rising again, including in countries that had all but extirpated the disease.

Without treatment, cholera can kill within hours.

In 2022, 44 countries reported cholera cases, a 25% increase over 2021, according to the WHO, which noticed the role played by cyclones, floods, and drought in cutting off clean water and helping bacteria to thrive.

Recent outbreaks have also been far deadlier, with fatality rates now at the most elevated level in more than a decade, the WHO said.

Diarrhea, too, receives a boost from climate change, with increasing erratic rainfall - resulting in either wet or dry conditions - yielding a higher risk, research has found.

Diarrhea is the world's second leading cause of death among children under 5, after pneumonia, claiming the lives of more than half a million kids every year.

Intense heatwaves and smoky skies:

Heat stress - one of the more obvious health impacts of global warming - is projected to impact hundreds of millions of individuals as temperatures continue to increase through the next few decades.

With the world already around 1.1 degrees C warmer than the average preindustrial temperature, individuals in 2022 experienced about 86 days on average of dangerously high temperatures, a report from the Lancet medical journal found last month.

If the world warms by 2 degrees C above preindustrial levels, the report said, yearly heat deaths could more than quadruple.

A July study in the journal Nature Medicine estimated that some 61,000 people died during European heatwaves in the summer of 2022.

The heat has also made forests drier, fuelling extreme wildfires that have swept across larger swathes of the world in recent years.

During the decade starting in 2010, more than 2 billion individuals were exposed to at least one day per year of unhealthy air pollution from fire smoke, as per a September study in the journal Nature. That was up by 6.8% compared with the previous decade.

In the United States, wildfire air pollution now kills somewhere between 4,000 and 28,000 individuals annually, according to the American Thoracic Society.