The U.S. may face a future marked by diminished water availability, deteriorating crop yields and worsening droughts if climate trends continue, a new study from experts at AccuWeather suggests.
The study, based on data from official government weather stations in 44 regions across the U.S, had several findings, including:
- Over the last 70 years, temperatures have risen by an average of 0.5°F.
- Relative humidity stayed fairly stable up to 1995, but then fell by 5.3 percent overall, averaging about 1.7 percent per decade.
- Average annual rainfall has fallen 2.7 percent since 1995 (about 0.9 percent per decade), even as heavier rainfall events have increased: 24-hour totals over four inches are up 70 percent, and over two inches are up 23 percent.
“If these trends continue, the well known climate models may not be capturing all of the important changes our studies have revealed,” said Joel Myers, founder and executive chair of AccuWeather, in a media advisory from the outlet provided to Newsweek on Monday.
“What has been surprising in our detailed analysis is the significant decline of rainfall amounts, especially since 1995. Over the last 30 years, average rainfall has been declining by an average of one percent every 11 years, and the rain that does fall is less effective for crop production and maintaining our water supply because it tends to come in shorter bursts. Furthermore, the average relative humidity during the same 30-year period has declined by a very significant 5.3 percent, which is 1.7 percent per decade.”
This means rainfall evaporates faster and is less useful for crops, water supplies, and refilling reservoirs, lakes, and other sources; together, these factors suggest “effective” U.S. average rainfall is declining by two to three percent per decade, Myers said.
“If these trends continue, we expect to see accelerating harmful impacts on crop production, more frequent wildfires, and less available water due to greater drought. Furthermore, the crop-growing areas in the United States may shrink as soil becomes more arid. Even in productive growing areas, crop yields may decline. These effects could become more obvious over the next decade or two,” added Myers.
Myers explained that warmer air can hold more water vapor, so rising temperatures can increase atmospheric moisture; when events like thunderstorms convert that vapor into rain, those events tend to produce heavier rainfall.
Myers also noted that temperature and dew point rose together until 1995, keeping relative humidity fairly steady, but since then temperatures have continued to climb while the dew point has leveled off, causing a “significant” drop in relative humidity.
“This suggests we reached a tipping point around 1995, as the temperature continued to increase, evaporation from the ground and vegetation could not keep up with the increase in temperature, and so the dew point has not been able to increase as quickly as the temperature over the last 30 years, resulting in a decline of relative humidity,” said Myers. “If this trend continues, desert areas will expand.”
AccuWeather said that should the trends highlighted in its study continue, this could have serious consequences for industries like agriculture, those affected by water supply declines, and an increase in wildfire frequency as drying will accelerate: with less soil moisture to absorb heat through evaporation, temperatures could rise even faster.
Dry soil reduces heat transfer into deeper ground, trapping solar heating near the surface and driving higher air temperatures, the outlet said, adding that while this link is well known, it may not be fully reflected in current climate predictions.
“Furthermore, when the soil is drier, there tends to be more dust and soil in the air,” said Myers. “Heat then leads to increased drought. You have more soil particles in the atmosphere, more dust competing for nuclei for droplets, so you get more water droplets that are smaller and have trouble falling out of the clouds, so you get less rain. Less rain means drier and hotter soil which brings drought and drought brings heat and you have a cycle that is running away. That is the concern.”
AccuWeather said it should be noted that climate trends and fluctuations over 10, 20, or 30 years can reverse, and there’s no guarantee the patterns it identified will continue, slow, or reverse. It also noted that its averages are national, and impacts may vary by region.
