As the planet heats up, animals big and small, on land and in the sea, are headed to the poles to get out of the heat. That means animals are coming into contact with other animals they normally wouldn’t, and that creates an opportunity for pathogens to get into new hosts.

Many of the root causes of climate change also increase the risk of pandemics. Deforestation, which occurs mostly for agricultural purposes, is the largest cause of habitat loss worldwide. Loss of habitat forces animals to migrate and potentially contact other animals or people and share germs. Large livestock farms can also serve as a source for spillover of infections from animals to people. Less demand for animal meat and more sustainable animal husbandry could decrease emerging infectious disease risk and lower greenhouse gas emissions.

We have many reasons to take climate action to improve our health and reducing risks for infectious disease emergence is one of them.

A series of fires in Indonesia in 2015 to clear land for agriculture caused an estimated 100,000 premature deaths in Indonesia, Malaysia, and Singapore. That’s according to a new study from Harvard T.H. Chan School of Public Health and Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with colleagues from Columbia University.

According to an August 20, 2016 New York Times article, the fires were deliberately set in August 2015 to clear land for palm oil plantations and other agricultural uses. By the fall, smoke from the fires blanketed large portions of Southeast Asia, closing schools and businesses, grounding planes, and forcing tens of thousands of people to seek medical treatment for respiratory illness. The researchers say exposure to fine particle pollution from burning forests, in particular carbon-rich peatlands, is responsible for premature deaths across the region.

Death Valley is set to experience what could be the hottest week recorded anywhere on Earth, with temperatures predicted to reach a high of 133F.

Fourth of July week will see “record-breaking and dangerous heat”, beginning on Independence Day itself when the mercury is predicted to hit 125F.

Temperatures are predicted to climb steadily over the following days, peaking at 133F on July 9 – just shy of the hottest air temperature ever recorded there over 100 years ago.

The inset shows that a temperature of 113°F or 45°C and a Wet Bulb Globe Temperature of 95°F or 35°C is forecast for a location 8 miles south of Parker, Arizona, on July 26, 2024 at 21 UTC. 

The above map illustrates that extreme heat stress can occur at higher latitudes, e.g. the grey areas in the north of the United States that extend into Canada. The danger occurs where high temperatures coincide with high relative humidity. 

The image below further illustrates the danger. It shows that a 'feel like' temperature of 54°C (129.1°F) and a wet bulb temperature of 31°C (87.7°F) hit an area west of Wuhan, China, on July 23, 2024 at 10:00 UTC (green circle). 

A 2022 study (by Vecellio et al.) finds that the actual limit is lower — about 31°C wet-bulb or 87°F at 100% humidity — even for young, healthy subjects. The temperature for older populations, who are more vulnerable to heat, is likely even lower. In practice the limit will typically be lower and depending on circumstances could be as low as a wet-bulb temperature of 25°C.

Climate change danger assessment

The image below, earlier discussed here, expands risk assessment beyond its typical definition as the product of the severity of impact and probability of occurrence, by adding a third dimension: timescale, in particular imminence.

Imminence alone could make that the danger constituted by rising temperatures needs to be acted upon immediately, comprehensively and effectively. While questions may remain regarding probability, severity and timescale of the dangers associated with climate change, the precautionary principle should prevail and this should prompt for action, i.e. comprehensive and effective action to reduce damage and improve the situation is imperative and must be taken as soon as possible.