Heat stress may threaten more than one billion people’s ability to work

Increasing global temperatures may affect about one billion people’s ability to work and perform daily activities and around 20 million people’s ability to cope with heat this century, especially in tropical and sub-tropical developing countries, according to a recent study by a team of scientists led by Dr. Oliver Andrews at the University of Bristol contributing to Tyndall Centre research.

The study, published in the medical journal Lancet Planetary Health, looked at the risks associated with up to 3°C of global warming above pre-industrial levels. It calculates the wet-bulb globe temperature – an index which includes the effect of temperature and humidity on humans.

The threshold for risks to workability is a monthly average of daily maximum wet-bulb globe temperature of 34°C, after which it is suggested to be too hot to work safely for a large part of the month. This is supported by the recommended heat exposure limits of the US National Institute of Occupational Safety and Health.

Some countries have already seen the effect of rising temperatures. In 2015, India and Pakistan experienced a heat wave that caused the deaths of at least 3,500 people. Climate-change driven heat stress might have already caused rural to urban migration in Pakistan.

As global temperature change (GTC) increases, the study suggests more regions will be exposed to extreme heat and heat stress. At 1.5°C above pre-industrial levels, areas of Africa such as Mali and Niger, South Asia, and the Middle East including Iraq and Saudi Arabia may be exposed to extreme heat. At more than 2°C above pre-industrial levels, the risk of extreme heat stress is predicted to become more widespread across many tropical and subtropical areas.

Population growth is projected to be highest in regions where the highest risk of heat exposure is estimated to occur, including Central and West Africa and South and Southeast Asia. Heat exposure risks are predicted to affect urban more than rural areas. The study emphasises the importance of adaptation strategies to anticipate and prepare for the impacts of heat stress.

Increased heat stress reduces people’s capacity to work, which may also increase poverty and inequality in some regions. The authors note “the need to build on the Paris Agreement regarding global temperature targets, to protect populations who have contributed little to greenhouse gas emissions.”

The research paper is here in full in the Medical Journal The Lancet.

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