This was the sobering conclusion of a team of researchers led by Benjamin Cook, research scientist at NASA Goddard Institute for Space Studies, advanced in a paper published in the journal Science Advances in 2015. In an effort to frame the current drought in the western United States in the proper context, the group compared the climate of the Southwest and Central Plains over the past 1000 years, gleaned from natural archives of climate such as tree rings, with predictions of their climates over the next 100 years based on computer simulations.
“We are the first to do this kind of quantitative comparison between the projections and the distant past,” said co-author Jason Smerdon, “and the story is a bit bleak.” Estimates of past climates in these regions used the North American Drought Atlas (NADA), a reconstruction of climates based on data from tens of thousands of samples of tree rings from the United States, Canada, and Mexico. Trees are a natural archive of climate data, because they grow at varying rates depending on moisture, temperature, and other factors.
Using data from the recent past, scientists have determined the relationship between tree growth patterns and climatic factors, and they then use this relationship to reconstruct past climates for which they have data on tree growth from tree rings.