Climate change: 1.5 °C target keeps the tropics under human adaptability limit

Limiting global warming to 1.5 °C could prevent tropical regions between 20°S and 20°N of the equator from reaching the limit of human adaptability, suggests a paper published this week in Nature Geoscience.

Humans’ ability to regulate body heat is dependent on the temperature and humidity of the surrounding air. There exists an upper survival limit, beyond which humans are no longer able to effectively cool themselves. This threshold is reached when the wet-bulb temperature — a measure of air temperature and humidity — passes 35 °C. There is concern that ongoing climate warming could result in extreme heat events that exceed this limit.

Yi Zhang and colleagues analysed numerical model simulations and observations to investigate how wet-bulb temperature extremes are likely to respond to future warming. They find that relatively simple atmospheric dynamics control the maximum wet-bulb temperature in the tropics. Based on their modelling and observations, the authors suggest that wet-bulb temperature extremes in the tropics increase at approximately the same rate as the tropical mean temperature.

These findings suggest that keeping global mean warming below 1.5 °C should ensure that no region in the tropics will experience extreme heat events that exceed the human survival limit. However, the authors indicate further research will be needed as serious health impacts can still occur well below this limit.