We Are Unbelievably Screwed

It appears that anthropogenic climate cghange driven temperatures in the Pacific Ocean that may create a permanent draught in the US Southwest

You know, the sort of things that decimated Anasazi society in pre-Columbian times.

Waters in the northern Pacific Ocean naturally cycle between patterns of cool and warm temperatures every few decades. But hundreds of simulations from climate models suggest human-caused warming may have locked this cycle into a pattern that is driving a megadrought in the western US – and could extend this dynamic for decades.

“We expect that as long as greenhouse gas forcing continues to increase, there will be continued meteorological drought in the western United States,” says Jeremy Klavans at the University of Colorado, Boulder.

Since the 1850s, sea surface temperatures in the northern Pacific Ocean have regularly cycled between a positive phase, with temperatures above average in key parts of the ocean, and a negative one, characterised by cooler-than-average temperatures there. This slow cycle, which takes place over the course of decades, is called the Pacific Decadal Oscillation (PDO).

However, since the late 1980s, this cycle has undergone an extended negative trend. The ocean’s surface has maintained a horseshoe shape of cooler-than-average water surrounding a warmer interior. Last month, this negative phase saw its cooler-than-average temperature anomaly hit a new record. 

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The finding also suggests climate models could have a bias towards underestimating human influence on major temperature cycles in the ocean and atmosphere, says [Syracuse University climate scientist Tripti] Bhattacharya. “We know that the Earth system models have persistent biases in certain regions, and the north Pacific is one of them.”

So, things are going to hell in a handbasket, and existing models are almost certainly underestimate the severity of the climate change.