Extreme heat in India and anthropogenic climate change
On 19 May 2016 the afternoon temperature reached 51.0 °C in Phalodi in the northwest of India – a new record for the highest observed maximum temperature in India. The previous year, a widely reported very lethal heat wave occurred in the southeast, in Andhra Pradesh and Telangana, kill...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-01-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://www.nat-hazards-earth-syst-sci.net/18/365/2018/nhess-18-365-2018.pdf |
| Summary: | On 19 May 2016 the afternoon temperature reached 51.0 °C in Phalodi
in the northwest of India – a new record for the highest observed maximum
temperature in India. The previous year, a widely reported very lethal
heat wave occurred in the southeast, in Andhra Pradesh and Telangana, killing
thousands of people. In both cases it was widely assumed that the probability
and severity of heat waves in India are increasing due to global warming, as
they do in other parts of the world. However, we do not find positive trends
in the highest maximum temperature of the year in most of India since the 1970s
(except spurious trends due to missing data). Decadal variability
cannot explain this, but both increased air pollution with aerosols blocking
sunlight and increased irrigation leading to evaporative cooling have
counteracted the effect of greenhouse gases up to now. Current climate models
do not represent these processes well and hence cannot be used to attribute
heat waves in this area.
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The health effects of heat are often described better by a combination of
temperature and humidity, such as a heat index or wet bulb temperature. Due
to the increase in humidity from irrigation and higher sea surface temperatures
(SSTs), these indices have increased over the last decades even when extreme temperatures have not. The extreme air pollution also exacerbates the health impacts of heat. From these factors it follows that, from a health impact point of view, the severity of heat waves has increased in India.
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For the next decades we expect the trend due to global warming to continue
but the surface cooling effect of aerosols to diminish as air quality
controls are implemented. The expansion of irrigation will likely continue,
though at a slower pace, mitigating this trend somewhat. Humidity will
probably continue to rise. The combination will result in a strong rise in the
temperature of heat waves. The high humidity will make health effects worse,
whereas decreased air pollution would decrease the impacts. |
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| ISSN: | 1561-8633 1684-9981 |