In many regions worldwide, climate change reduces the difference between the daily high and low temperatures. The difference between the two, termed the diurnal temperature range (DTR), substantially impacts growing seasons, crop yields, residential energy use, and heat-related human health issues.
Scientists involved in new international research of the DTR near the end of the 21st century think that they have discovered the answer as to why the DTR declines with climate change: An increase in clouds hinders incoming shortwave radiation from the sun throughout the day.
This indicates that, though the daily maximum and minimum temperatures are predicted to rise due to climate change, the daily maximum temperature will increase more slowly. According to the experts, the DTR will continue to decrease in many places, but the alterations may differ based on various local conditions.
The research, published in the journal AGU Geophysical Research Letters, is the first to investigate the issue of the Earth’s declining DTR, specifically how it is connected to cloud cover.
Clouds are one of the big uncertainties in terms of climate projections. When we do this with a very high spatial resolution modeling framework, it allows us to explicitly simulate clouds.
Dev Niyogi, Study Co-Author and Professor, Jackson School of Geosciences, The University of Texas at Austin
According to Lead Author Doan Quang Van, an Assistant Professor at Japan’s University of Tsukuba Center for Computational Sciences, this is critical for comprehending the DTR’s future.
Doan Quang Van says, “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.”
Researchers from the UT Jackson School’s Department of Geological Sciences, the National Center for Atmospheric Research in Boulder, Shanghai University of Engineering Science, the National Defense Academy of Japan, and the University of Tsukuba in Japan were among those who contributed to the study. Supercomputers at the University of Tsukuba Center for Computational Sciences were utilized in the modeling endeavor.
By employing supercomputers, the researchers could model the intricate interplay of land–surface processes on climate change. These included changes in land use (like deforestation), precipitation, soil moisture, cloud cover, and other factors that may impact temperature in a local region.
The scientists were able to more thoroughly assess the effects of climate change by developing a model with a finer resolution grid, using 2 km2 grids instead of the 100 km grids often used in climate models.
The team concentrated on Japan’s Kanto region and the Malaysian peninsula. They employed the ten years from 2005 to 2014 as a baseline and then ran various climatic scenarios to forecast what would happen to the DTR in the two regions by the end of the century.
Researchers discovered that the temperature difference reduces by about 0.5 ℃ in the temperate Kanto area and by 0.25 °C on the more tropical Malaysian peninsula. Experts partly attribute these changes to the increased daytime cloud cover anticipated under these climate conditions.
According to the researchers, the findings can help scientists enhance existing global climate models and better comprehend how the declining DTR will influence civilization and the environment as the climate continues to warm.
It is very important to know how DTR will change in the future because it modulates human, animal and plant metabolisms. It also modulates the local atmospheric circulation such as the land-sea breeze.
Doan Quang Van, Study Lead Author and Assistant Professor, Center for Computational Sciences, University of Tsukuba
The Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (KAKENHI), NASA Interdisciplinary Research in Earth Science, and the United States Department of Agriculture National Institute for Food and Agriculture provided financial support for the study.
Doan, Q. V., et al. (2022) Causes for Asymmetric Warming of Sub-Diurnal Temperature Responding to Global Warming. AGU Geophysical Research Letters. doi.org/10.1029/2022GL100029.