Because of the ‘urban heat island effect’ cities are already warmer than their rural surroundings. If we do not curb emissions (Business-As-Usual scenario – RCP 8.5) by 2100 they will be much hotter still. Climate Central in 2017 created the interactive map below in partnership with the World Meteorological Organization.
Under the BAU-scenario cities in the Balkans will experience the most extreme temperature rise, varying between 7.5°C and 8.5°C increase. For example Budapest will reach an average summer daily maximum temperature of 32.2 °C (from 24.8°C ), Sofia 32.6°C (from 24.3°C) and Bucharest 36.4°C (from 28.1°C ). Temperature-wise this would transform the Balkans into the Middle East.
At their turn some cities in the Middle East will get so hot that they have no current-day equivalents. For example, Riyadh will reach 48 °C Celsius and Baghdad a blistering 49,5 °C .
The temperatures in the graph refer to average daily maximum temperatures over June, July and August on the Northern Hemisphere (Dec, Jan & Feb on the Southern Hemisphere).
Researchers at MIT warn that if climate change remains unchecked (Business As Usual-scenario = RCP 8.5) over half a billion people will, from 2070 onwards, experience humid heat waves that will kill even healthy people in the shade within 6 hours. The Wet Bulb Temperature (WBT) would exceed 35°C (95°F), at which the body – of any mammal – cannot cool itself, overheats and shuts down.
Three regions were studied: China (2018), South Asia (2017) and the Persian Gulf (2015). The researchers predict (at RCP 8.5) WBT exceeding 35°C about once every decade for the Northern Plains in China (400+ million people), at locations in the Chota Nagpur plateau, northeastern India, and Bangladesh in South Asia (70+ million people). Persian Gulf regions that would be affected include cities such as Doha, Qatar, Abu Dhabi, Dubai (UAE) and Bandar Abbas (Iran).
The total number of people affected will be higher than 0.5 billion. A study in Nature (2017) identifies regions worldwide that are likely to exceed the survivability threshold from 2070 onwards (see Fig. 2). These also include the Eastern United States, Northern Latin America and Northern Australia.
Wet bulb temperatures higher than 33.5°C for more than a few hours have not been measured in human history (yet). In 2015 there was a severe episode in South Asia with 30°C WBT. This led to 3,500 deaths. According to this article the largest hospital in Karachi was receiving 1 patient per minute and the morgue was overflowing.
Would airconditioning be to avail? Podcast Ashesashes describes that a ‘perfect storm’ will hit power supply at extreme temperatures. Airconditioning at high temperatures leads to more than 20% extra power demand, while at the same the power grid becomes less effective, nuclear and gas fuel plants provide less power because of warmer cooling water and transformers are more likely to overheat leading to power outages. Also, it is hard to see how renewable energy could meet the peak demand. Without solutions, the areas mentioned would effectively become uninhabitable.
At the Business as Usual-scenario many billions of people would experience WBT higher than 32°C on a regular (e.g. yearly) basis, which is already deadly for the less fit and makes working outside impossible.