The effects of climate change are underway for parts of the western United States, manifesting in a severe megadrought.
A new study published in the journal Science titled “Anthropogenic megadrought” tracks anecdotal data going back to the 16th century Spanish Entrada expeditions across the U.S. Southwest, formerly called New Spain.
Updated quantitative analyses that were collected from tree rings show that during this period, a megadrought occurred that researchers describe as “the worst multidecadal drought episode in the Southwest over the past 1,200 years.”
The same data also reveal that the second-worst drought occurred from 2000 to 2018 — and may still be occurring.
A megadrought is different from a standard drought; they are defined as lasting for as long as multiple decades or centuries. A standard drought can last for several months to more than a decade.
CNN reports that the study confirms a very wet period occurred from about 1980 to 1998, right before the onset of the latest megadrought. This sudden shift in environmental conditions from wet to arid “was hastened by the background drying forced from anthropogenic warming,” according to the study.
This conclusion implies a second megadrought caused by climate change rather than natural meteorological conditions. The Washington Post writes that historically, megadroughts are caused by fluctuations in tropical oceanic conditions, such as the cyclic cooling of tropical Pacific waters known as La Niña.
“The megadrought era seems to be reemerging, but for a different reason than the [past] megadroughts,” Park Williams, the study’s lead author and a researcher at the Lamont-Doherty Earth Observatory at Columbia University, told the Post.
CNN notes that instances of megadroughts are likely to worsen; the study reportedly notes that anthropogenic global warming — or human-caused climate change — is likely to bring more changes in the environment.
“The magnitude of future droughts in North America and elsewhere will depend greatly on future rates of anthropogenic greenhouse gas emissions globally,” the study notes.
The effects of a parched landscape obviously include a shortage of water flow in rivers and reservoirs, resulting in less groundwater available for human use, like drinking and irrigation.
“I think the important lesson that comes out of this is that climate change is not a future problem,” Benjamin I. Cook, a NASA climate scientist and co-author of the study, told the Post. “Climate change is a problem today. The more we look, the more we find this event was worse because of climate change.”
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