Day-night temperature gap shrinking due to climate change: Study
The gap, called Diurnal Temperature Range, is considered crucial because it has a significant impact on crop yields, change of seasons, and human health issues related to heat stress and more
Clouds, the atmospheric blanket that envelopes the earth, offer us respite from the heat, besides bringing us rain. According to a team of researchers in the US, clouds also have another significant impact on our everyday lives.
Their study, published in Geophysical Research Letters, a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union, has found that the difference between the daily maximum and minimum temperatures across the globe is shrinking because of climate change-induced increase in cloud cover.
The gap between the daily highs and lows in temperature is known as the diurnal temperature range (DTR). DTR is considered to be crucial because it has a significant impact on crop yields, change of seasons, and human health issues related to heat stress and more.
How cloud cover impacts DTR
The research team, in their bid to decode the phenomenon of shrinking DTR, listed down some factors that influence regional temperatures — changes in land use, soil moisture, rainfall, cloud cover, etc. — and simulated their effects on climate change, using supercomputers.
The team was able to conduct a close analysis of the complex interplay between land-surface processes and climate change because the simulation helped them create a first-of-its-kind finer-resolution climate model with two square kilometre grids instead of the commonly used 100-kilometre grids.
The Kanto region of Japan and the Malaysian peninsula were chosen as the two focus areas for the model. Using the period between 2005-2014 as the baseline decade, the researchers ran different climate scenarios to project how the DTR in the two regions under the focus will change by the end of the century.
The temperature gap closed by about 0.5°C in the temperate Kanto region and 0.25°C in the more tropical Malaysian peninsula, the subsequent results revealed. These changes were largely attributed to increased daytime cloud coverage expected to develop under these climate conditions.
Why DTR impact is crucial
According to Doan Quang Van, the lead author of the paper, “Clouds play a vital role in the diurnal temperature variation by modulating solar radiative processes, which consequently affect the heat exchange at the land surface.”
In simple terms, an increase in cloud cover reduces the incoming solar shortwave radiations during the daytime. This brings down the daily maximum temperatures, which is instrumental in closing the gap between daily high and low temperatures.
Climate projections, however, indicate that both daily high and low temperatures will continue to increase as a consequence of climate change, although the former will do so at a slower rate.
With the shrinking of DTR also certain, a better understanding of its impacts can equip us to be better prepared to tackle the threat of global warming. “It is very important to know how DTR will change in the future because it modulates human, animal and plant metabolism. It also modulates the local atmospheric circulation, such as the land-sea breeze,” Quang Van added.
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The journal
Geophysical Research Letters was established in 1974. Its current editor-in-chief, Harihar Rajaram, is a professor of environmental health and engineering, who uses mathematical models to shed light on complex environmental and earth systems and to predict future trends within those systems.
Rajaram received his PhD from the Massachusetts Institute of Technology in 1991. His recent investigations have explored the environmental impacts of hydraulic fracturing, including human-produced earthquakes resulting from the injection of fracking fluids into deep geologic formations, the biogeochemical impacts of climate warming in alpine and other environments, and the response of glaciers and ice sheets to climate warming — research that is illuminating the climate change’s subtle public health effects.
