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The Fifth National Climate Assessment (NCA5) represents the latest science in assessing changes in the climate, its national and regional impacts, and options to reduce present and future risk. Every five years, the U.S. Global Change Research Program releases a new National Climate Assessment. The newest assessment, NCA5, is a resource to understand how drought will change as the climate changes, how we can adapt, and how future droughts might impact your region and livelihood.
Check out these 10 maps and graphics to learn more about drought in a changing climate.
Summer soil moisture will likely decrease
One of the ways we can understand drought is through the water stored in soil, soil moisture. Soil moisture supports agricultural crops and ecosystems and is a factor in how much precipitation and snowmelt becomes runoff in streams and rivers. Across most of the U.S., summer soil moisture is expected to decrease, with the greatest decreases in southern Alaska and the mountain ranges of the Western U.S.
For the most part, precipitation has increased in the Eastern U.S. and decreased in the Western U.S. over the 20th–21st centuries. But across nearly the entire nation, average annual temperatures are rising. That warming alters the amount of evapotranspiration, a measure of the water used by plants and evaporating from the earth’s surface into the atmosphere. Actual evapotranspiration represents evaporative demand limited by the amount of water available to evaporate or transpire from plants into the atmosphere. This measure of evapotranspiration has trended lower in the Southwest as water availability has decreased, while it increased in the East and North. These trends are expected to continue under climate change.
There are a number of other ways drought can drive mortality. Drought can lead to decreased air quality, resulting in an increase in cardiovascular and pulmonary disease and premature death. It can degrade water quantity and quality, increasing exposure to contaminants such as heavy metals and bacteria. And it is associated with worsening mental health among rural farmers in the U.S.
While all regions are impacted by drought, some people are more vulnerable to negative impacts of drought due to socioeconomic factors.
For example, climate stressors, including drought, disproportionately impact small-scale, Black, Indigenous, and economically disadvantaged farmers. These groups are more likely to be under-resourced, making adaptation to climate change more difficult. An increase in drought is also expected to drive a northward spread of Valley fever, a respiratory disease, which infects people when they inhale dust that contains the Valley fever fungus. Valley fever tends to afflict construction and agricultural workers, and the disease disproportionately impacts Black and Latinx populations, possibly due to occupational exposure.
Wildfires are worsening by a number of different metrics in a changing climate. The amount of forest burned in the Western U.S. has increased since the mid- to late-20th century, in part due to higher rates of evapotranspiration and warmer temperatures. Fires are not only burning more land; they are becoming more severe. The area burned by high-severity wildfires has also increased in warmer, drier conditions. Increased fire severity is expected to become more widespread in U.S. forests in the future as extreme weather conditions become more frequent.
Learn how climate change is impacting ecosystems, transportation, energy, and other sectors in topical chapters.
Drought impacts policy
Drought can result in competition, collaboration, or conflict over water. Historically, very wet and very dry years have inspired policy action. After 22 years of drought in the Colorado River basin, water managers created guidelines to restrict water use in times of shortage on the Colorado River in 2007. In contrast, after the wettest period in the past 1,200 years, the 1922 Colorado River Compact divided the river between seven western states, and it allocated more water than the river provided. As climate change continues, the variability of our natural systems is expected to continue as well, creating challenges to plan for and create policies to adapt to climate change.
A hotter, drier future can be scary to think about, but the NCA5 focuses on what we can do about it. Each chapter highlights adaptation strategies communities are already taking to manage drought, wildfire, and heat. It also describes transformations and adaptations we can implement as we plan for this future.
Art can help too; NCA5 showcases a gallery of art inspired by climate change in the U.S. Art X Climate is the first art gallery to be featured in the National Climate Assessment and was created with the understanding that, together, art and science move people to greater understanding and action. View the art gallery.