Anthony Watts opens mouth, places foot firmly - in the weakening Walker Circulation

As if one foot in mouth wasn't enough for the day, Anthony Watts does it again (archived here, cached here). Maybe he wanted to give both his clodhoppers a turn. Whatever - he posted one of his "claim" articles, which was about a new paper published in Geophysical Research Letters. The paper, by Katinka Bellomo and Amy C. Clement from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, was describing evidence of the expected slowdown in the Walker Circulation. Beneath his "claim" headline Anthony wrote:

From the UNIVERSITY OF MIAMI ROSENSTIEL SCHOOL OF MARINE & ATMOSPHERIC SCIENCE and the “correlation is not causation department” comes this paper that suggests GHG’s decrease the Walker Circulation. Only one problem. They don’t give a clear cut mechanism, only tenuous linkage. I suspect Willis will have a thing or two to say about this paper.

Only one problem, the scientists did give a clear cut mechanism. (Actually, they referred to more than one mechanism, although they emphasised the one proposed by Isaac Held and Brian Soden.) As the authors explained right at the very beginning of their paper:

About El Niño

With the Australian Bureau of Meteorology declaring an El Niño, and for anyone who is not familiar with the phenomenon, here is a short version of what happens. I wrote a longer article last year. There are more references down below as well.

About ENSO and El Niño

El Niño is one of the phases of the El Niño Southern Oscillation, or ENSO. There are three distinct phases, plus an in-betweener. These are known as:

• El Niño - the phase where the ocean releases warm air to the surface, usually resulting in an increase in global surface temperature
• La Niña - the phase where the ocean cools the surface, usually resulting in a decrease in global surface temperature - though with climate change it usually means a lesser increase, not a decrease
• Neutral - when there is neither an El Niño or a La Niña
• Modoki - which is a part way El Niño. It doesn't affect as much of the Pacific Ocean, and has different teleconnections (ocean-atmosphere links over a distance). You could think of it as an in-betweener that can't make up its mind whether to turn into a full blown event or not. (Don't tell a climate scientist that I said that - they'd correct me.)