File:History of drought in the US Southwest.png

A history of drought in the Southwest

This chart shows the cumulative effects of rain and drought in the Southwest over five centuries, measured on decades-long time spans that climatologists use to identify megadroughts.

'Megadrought': Worst drought in the Southwest in the past 1,200 years

We have spiked the climate system, releasing heat-trapping carbon dioxide into the atmosphere faster than at any other time in at least the past 50 million years. Human-fueled megadroughts like this one will be more frequent and severe in the future. In the Southwest, there will be more years with declining snowpack, more years with water shortages and a more dire mismatch between where water is available and where it is needed...

Ancient tree rings tell a story

Across the Southwest, forests are now living on a knife’s edge

• https://www.nytimes.com/interactive/2022/07/20/opinion/ancient-trees-climate-change.html

As a dendrochronologist, I examine tree rings to study climate. I hunt for old trees and use a simple hand tool — which does not harm the tree — to bore deep into trunks looking for evidence of ancient drought and deluge. For 20 years, first with my teachers and later with my students, I’ve visited old-growth forests across the American Southwest, watching dry season after dry season pile up.

These withering years are killing trees. We have watched their habitats shrink, as warmer temperatures pull moisture out of the ground at lower elevations and drive woodlands to higher, cooler slopes. I’ve taken samples from healthy younger trees and returned years later to find them dead or dying. The matriarchs, the largest, oldest and most deeply established trees in many groves, seem to be hanging on for now. But no scientist is sure how much more they can endure.

A recent study published in Nature Climate Change analyzed the rings of thousands of living trees and architectural wooden beams from around the Southwest to reconstruct a 12-centuries-long timeline of climate extremes. The authors concluded that there was probably not a drought as severe as today’s in the past 1,200 years.

○

NowThis - NASA (gif) / Lake Mead 2000 & 2022

• https://twitter.com/nowthisnews/status/1550514064421445632

○