Much of climate science is settled and doesn't need repeating. We know that injecting increasing amounts of greenhouse gases to the atmosphere leads to warming, for instance.
But how that warming will play out in atmospheric and oceanic circulation patterns, although often discussed, remains to be seen.
Several past studies suggested warming could lead to a weakening of trade winds over the Pacific, but, as Richard Allan of the University of Reading discusses in a fascinating new post on a major new study from Nature Climate Change, that might be all wrong. Maybe warming will lead to a strengthening of these trade winds, as the new study argues, which could feed into exisitng ocean circulation patterns.
Other studies have suggested that the warming expected in the atmosphere has been diverted into the ocean: this study posits a mechanism to explain that.
It's complicated as this — no doubt simplified — diagram shows:
But especially fascinating for us on the West Coast are the implications, which Allan discusses in an offhand style near the end of his post:
The implications or these changes could be substantial. It would be surprising if these large changes in atmospheric and ocean circulation over the last 2 decades (including also apotentially long-term decline in the Atlantic ocean circulation), have not already disrupted our weather patterns. The map shows this seasons sea surface temperature departures from normal (from NOAA), with a cool East Pacific and unusual patterns over the north Pacific and north Atlantic that are associated with this seasons extreme weather, including drought in California, intense cold in eastern north America and flooding in the UK and Europe.
"Including drought in California." Hmmm.
Update: Michael Mann on HuffPost updates with the $64,000 question for California:
Such conditions are basically equivalent to the flip-side of El Niño, known as La Niña. In other words, the slowing of global warming may relate, at least in part, to the tendency for more frequent La Niña-like conditions in recent years. That gives us stronger trade winds in the eastern tropical Pacific, more burial of heat below the ocean surface, colder tropical Pacific sea surface temperatures, and slightly cooler global average temperatures than we might otherwise have seen.
The $64,000 question, then, is whether this increased tendency for La Niña-like conditions over the past decade is entirely natural in origin, or whether it might instead in some way be tied to climate change itself.
For California, especially Southern California, the 64k question is whether we will be seeing more La Nina conditions, or if this apparent tendency will pass. (As opposed to the question of global temps.) More on this and the Pacific Decadal Oscillation as the news comes in.