How does climate change affect health?

He climate change It is a multiple and growing threat to the health human, to the point that COP28which begins on Thursday, will dedicate a day to this topic for the first time.

“To avoid catastrophic health effects and prevent millions of deaths”it is necessary to limit the average increase in temperature on Earth to 1.5 ° C, the most ambitious goal of the Paris Agreement, maintains the World Health Organization, in unison with other health experts and environmental organizations.

Instead, the planet is on track to warm by 2.5°C to 2.9°C by 2100, according to the UN.

The most vulnerable and disadvantaged are children, women, the elderly, migrants or inhabitants of less developed countries, who are exposed in a more drastic and dangerous way, according to experts.

Heat waves

The year 2023 is shaping up to be the warmest ever recorded. More frequent and intense heat waves promise to increasingly put the human body to the test.

In 2022, Earth’s inhabitants were exposed, on average, to 86 days of life-threatening temperatures.

The most vulnerable pay the highest tax. For example, the number of people over 65 who died due to heat increased by 85% between 1991-2000 and 2013-2022, according to a landmark report published this week by the medical journal The Lancet.

In Europe alone, heat caused more than 70,000 deaths last summer, according to researchers who this week revised upwards the previous estimate of 62,000 victims.

Nearly five times as many people could die worldwide due to extreme heat by 2050, according to the “Countdown” from The Lancet.

More frequent droughts also expose millions of people to famine. With 2°C warming by 2100, around 520 million additional people would be moderately or severely food insecure by mid-century.

And other extreme weather events, such as storms, floods or fires, cause death or illness.

Air pollution

Near to 99% of the world’s population breathes air whose pollution exceeds the limits established by the World Health Organization.

Accentuated by climate change, air pollution increases the risk of respiratory diseases, cardiovascular accidents, diabetes or cancer and, according to some experts, has effects comparable to, and even greater than, those of tobacco or alcohol.

The presence of gases, heavy metals, particles and dust in the air, derived mainly from fossil fuels, can cross the lung barrier and enter the blood.

The most harmful effect on health is related to long-term exposure, particularly during pollution peaks, when respiratory infections and allergies increase.

More than four million premature deaths, according to the WHO, occur each year due to pollution.

These premature deaths have, however, decreased by almost 16% since 2005, mainly thanks to lower coal consumption, according to The Lancet.

Infectious diseases

By altering temperature and precipitation, climate change also aggravates infectious and parasitic diseases.

This is especially due to new areas of spread of mosquitoes, birds or mammals involved in epidemics caused by viruses (dengue, chikungunya, Zika, West Nile virus…), bacteria (plague, Lyme disease…), animals or parasites (malaria…).

Dengue transmission could increase 36% with global warming of 2°C by 2100, according to The Lancet report. And with warming oceans, more coastal areas are conducive to the transmission of the vibrio bacteria, responsible for cholera.

Storms or floods can also leave stagnant water, conducive to mosquito breeding, while heat waves increase waterborne infections.

Mental health

Anxiety, depression or post-traumatic stress: climate change also represents a risk for mental health, especially in people with mental disorders, according to specialists.

In addition to the direct repercussions of natural disasters or heat waves, there are indirect effects, such as eco-anxiety, especially in young adults.