Drought defines the American West; dry, dusty and unforgiving. However, these periodic droughts are not caused only by lack of rainfall, as previously thought. A recent study points to another reason, blaming rising temperatures caused by anthropogenic climate change.
The study suggests that increased evaporation caused by rising temperatures played a more important role than decreased precipitation in causing droughts in the American West, especially since 2000. The study was conducted by scientists from the University of California, Los Angeles and the National Oceanic and Atmospheric Administration (NOAA).
Increasing temperature and drought intensity
Researchers concluded that evaporation accounted for 61 percent of the severity of drought during the 2020-2022 drought, while the decrease in precipitation accounted for only 39 percent. The lead author of the study, Rong Fu, a professor of atmospheric and oceanic sciences at the University of California, Los Angeles, made an interesting statement.
“Studies have already shown that rising temperatures contribute to drought, but to our knowledge, this is the first study to show that moisture loss from demand is greater than moisture loss from lack of precipitation,” Professor Fu said.
perspective change
Historically, drought in the West has been associated with decreased precipitation. However, warming caused by burning fossil fuels increased the demand for evaporation. It certainly expands our understanding of the causes of drought, highlighting the need to consider human activities and their impacts on the environment.
Veva Deheza, managing director of NOAA’s National Integrated Drought Information System and co-author of the study, talked about this shift in understanding.
“For generations, drought has been associated with drier-than-normal weather conditions. This study reaffirms that we have entered a new paradigm where rising temperatures lead to intense droughts and rainfall is a secondary factor,” Deheza said.
The rain that never falls
Our climate is a complex system. As the planet warms, the amount of evaporation increases. Although a warmer atmosphere can hold more water vapor, this does not necessarily lead to precipitation.
Heat keeps water molecules in constant motion, making it difficult for condensation and therefore precipitation to occur. This cyclical process means that droughts will last longer, cover larger areas, and become drier with each degree of global warming.
Heat, evaporation and drought
What happens when we analyze a 70-year observational record of “natural” droughts and droughts caused by anthropogenic climate change?
Surprisingly, researchers found that 80 percent of the increase in evaporative demand since 2000 was due to climate change. During dry periods, this figure rises to over 90 percent. These figures reveal that the main reason for the increase in the severity and spread of droughts since 2000 is climate change.
Climate change and the intensity of droughts
Researchers have made a dramatic comparison of drought patterns. By 2000, only 26 percent of droughts were caused by high evaporative demand. Since 2000, that number has increased to 66 percent. Professor Fu emphasized the impact of climate change on drought severity.
“Although the drought began due to a natural decrease in rainfall, I would say that due to climate change the severity of the drought has increased from the equivalent of ‘moderate’ on the drought severity scale to ‘exceptional’.”
The future of drought
The study ends with a warning. If greenhouse gas emissions are not reduced, droughts that we once thought of as severe will become more frequent in the near future.
“Even if rain seems normal, we may still face drought because the demand for moisture has increased so much that there is not enough water to meet this increased demand,” Professor Fu said.
“This is not something you can avoid by building larger reservoirs because as the atmosphere warms it will absorb more moisture from everywhere. “The only way to prevent this is to stop the temperature rising, which means we have to stop emitting greenhouse gases.”
The research was supported by NOAA’s National Integrated Drought and Climate Information System and the National Science Foundation. The results of the research emphasize that the problem of climate change must be solved urgently. The future of the American West depends on us, our actions, and our commitment to protecting the environment. The study was published in the journal Science Advances.
Source: Port Altele
