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Latest revision as of 16:42, 7 September 2019

Heat that kills in the Global South

Tom Matthews explains why European heatwaves are nothing compared to climate impacts in other places.


In a heatwave that killed 65, people slept on pavements to escape heat and power cuts in Karachi, Pakistan. May 22, 2018. REUTERS/Akhtar Soomro

I am a scientist and I research climate dangers. Last month I published research on the potential for a terrible cyclone-heatwave in the Global South. But media want me to talk about the UK’s recent heatwave and climate change instead.

It is always good to respond to tell the public about weather extremes when they are interested. But there is a danger that people don’t find out important information about extreme heat in the world.

Everyone accepts that hot extreme temperatures are now more likely. But, every time it’s hot in the UK, we have to repeat the same story. We need to share more information about the global problems.

35°C or more is hot in the UK, but about 80 per cent of the world’s population has these temperatures. 46°C in France was unusual, but this is less than the 50°C in India earlier this year, or the 54°C in both Pakistan (in 2017) and Kuwait (in 2016). People in these hotter climates are better at living in high temperatures. But this heat kills.

Sometimes there are deadly heatwaves in Europe too. In 2003, 70,000 people died, and in 2010 more than 50,000 died in western Russia. Now, we are better prepared.

In places like South Asia and the Persian Gulf, the human body is often close to its limits. And yes, there is a limit.

When the air temperature is higher than 35°C, the body has to evaporate water – mainly through sweating – to keep the temperature at a safe level. This works until the ‘wetbulb’ temperature reaches 35°C. The wetbulb temperature includes the cooling effect of water evaporating from the thermometer, and so is normally much lower than the normal (‘drybulb’) temperature in weather forecasts.

When the wetbulb temperature is higher than the safe level, the air is so full of water vapour that sweat cannot evaporate. If we can’t sweat, our body temperature rises, even if we drink a lot of water, stay in the shade and rest. People start dying – first the very young, elderly or people with medical conditions.

There have not been many wetbulb temperatures of 35°C yet. But there is some evidence that they are starting in Southwest Asia. With climate change, some of the most densely populated regions on Earth could pass this safe level by the end of the century. The Persian Gulf, South Asia, and the North China Plain will be first. Billions of people live there.

As it gets hotter in the UK, people can slow down, drink more water, and go to cooler places. There is air conditioning, but this uses a lot of energy. By 2050, we will need as much electricity for cooling systems as US, EU and Japan together.

If we can get that electricity, it might be possible to live in that heat. But power cuts could be very dangerous.

So what would happen if we had big power cuts and extreme heat? Two colleagues and I recently investigated the possibility of this in a global study of storms and heat, (published in the journal Nature Climate Change).

We looked at tropical cyclones, which have already caused the biggest blackouts on Earth – the power cut that lasted months in Puerto Rico after Hurricane Maria was the most serious. This is what we found: as the climate warms it becomes more likely that these powerful cyclones are followed by dangerous heat, and we would have this every year if global warming reaches 4°C. During the emergency response to a tropical cyclone, it would be just as important to keep people cool as to get clean drinking water.

It is new for the UK to manage extreme heat. But the places that already have extreme heat will have the biggest increases in humid heat. Also, they often have the least resources to adapt to the danger. It is not surprising that extreme heat causes migration. A lot of migration means that extreme heat affects the whole world. Britain will feel the consequence of the faraway heat.

There are big challenges ahead. Adaptation has limits. We must keep looking at the whole world and find solutions for the whole world. We need to cut greenhouse gas emissions to keep to the Paris warming limits. This is how we have the biggest chance of not having deadly heat – at home and in other countries.

This article has been republished from The Conversation. Tom Matthews is a lecturer in Climate Science at Loughborough University

NOW READ THE ORIGINAL HERE: https://newint.org/features/2019/08/08/lethal-heat-has-taken-hold-global-south