Daniel Lawler and Isabelle Cortes highlight the growing urgency for the world to confront the various ways global warming impacts human health. This concern has led to the establishment of the first dedicated day on this issue at the upcoming U.N. climate talks.

The World Health Organization (WHO) identifies climate change as the paramount health threat to humanity, citing reasons such as extreme heat, air pollution and the escalating prevalence of deadly infectious diseases.

Global warming must be limited to the Paris Agreement target of 1.5 degrees Celsius "to avert catastrophic health impacts and prevent millions of climate change-related deaths," according to the WHO.

However, under current national carbon-cutting plans, the world is on track to warm up to 2.9 degrees Celsius this century, the U.N. said this week.

While no one will be completely safe from the effects of climate change, experts expect that those most at risk will be children, women, the elderly, migrants, and people in less developed countries that have emitted the least planet-warming greenhouse gases.

On Dec. 3, the COP28 negotiations in Dubai will host the first "health day" ever held at the climate negotiations.

Extreme heat

This year is widely expected to be the hottest on record. And as the world continues to warm, even more, frequent and intense heat waves are expected to follow.

Heat is believed to have caused more than 70,000 deaths in Europe during summer last year, researchers said this week, revising the previous number up from 62,000.

Worldwide, people were exposed to an average of 86 days of life-threatening temperatures last year, according to the Lancet Countdown report earlier this week.

The number of people over 65 who died from heat rose by 85% from 1991-2000 to 2013-2022, it added.

And by 2050, more than five times more people will die from the heat each year under a 2 degrees Celsius warming scenario, the Lancet Countdown projected.

More droughts will also drive rising hunger. Under the scenario of 2 degrees Celsius warming, by the end of the century, 520 million more people will experience moderate or severe food insecurity by 2050.

Meanwhile, other extreme weather events such as storms, floods and fires will continue to threaten the health of people across the world.

Air pollution

Almost 99% of the world's population breathes air that exceeds the WHO's guidelines for air pollution.

Outdoor air pollution driven by fossil fuel emissions kills more than four million people every year, according to the WHO.

It increases the risk of respiratory diseases, strokes, heart disease, lung cancer, diabetes and other health problems, posing a threat that has been compared to tobacco.

The damage is caused partly by PM 2.5 microparticles, which are mostly from fossil fuels. People breathe these tiny particles into their lungs, where they can then enter the bloodstream.

While spikes in air pollution, such as extremes seen in India's capital, New Delhi, earlier this month, trigger respiratory problems and allergies, long-term exposure is believed to be even more harmful.

However, it is not all bad news.

The Lancet Countdown report found that deaths from air pollution due to fossil fuels have fallen 16% since 2005, mostly due to efforts to reduce the impact of coal burning.

Infectious diseases

The changing climate means that mosquitoes, birds and mammals will roam beyond their previous habitats, raising the threat that they could spread infectious diseases with them.

Mosquito-borne diseases that pose a greater risk of spreading due to climate change include dengue, chikungunya, Zika, West Nile virus and malaria.

The transmission potential for dengue alone will increase by 36% with 2 degrees Celsius warming, the Lancet Countdown report warned.

Storms and floods create stagnant water breeding grounds for mosquitoes and increase the risk of water-borne diseases such as cholera, typhoid and diarrhea.

Scientists also fear that mammals straying into new areas could share diseases, potentially creating new viruses that could then jump over to humans.

Mental health

Worrying about the present and future of our warming planet has also provoked rising anxiety, depression and even post-traumatic stress – particularly for people already struggling with these disorders, psychologists have warned.

In the first 10 months of the year, people searched online for the term "climate anxiety" 27 times more than during the same period in 2017, according to data from Google Trends cited by the BBC this week.