Michael E. Mann, Stefan Rahmstorf, Kai Kornhuber, Byron A. Steinman, Sonya K. Miller & Dim Coumou
"Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events" http://www.nature.com/articles/srep45242
The idea of climate change has been around for decades. So, you might
wonder, what do climate scientists work on nowadays? Answer: Rather
than studying global climate change, they study /regional/ climate
change. The models have become much more detailed. That's important,
because climate change affects different regions differently, even for
locations in the same latitude band.
In recent years we have seen a series of persistent, extreme summer
weather events, including the 2003 European heatwave, the 2010 Pakistan
flood, the 2010 Russian heatwave, the 2011 Texas drought, and the ongoing
California drought.
More-or-less everybody assumed these regional events were related to
global climate change somehow, but there wasn't a straight-line mechanistic
explanation. Until now.
The paper by Mann et al. doesn't present much in the way of new data;
instead it offers an explanation for the existing data. This is how
physics works in the real world: Sometimes progress hinges on new
data, and sometimes it hinges on new theories and new simulations.
Their explanation is pretty much the opposite of what I was expecting.
The usual naïve mental model goes like this: If you heat a beaker of
coffee from the bottom, it goes unstable, Rayleigh-Bénard convection,
stability is good, instability is bad, yadda-yadda.
What's really going on is more like heating the coffee from above:
It becomes more stable.
You may think it's unpleasant if a storm front comes through during the
spring or summer; it makes for bad weather for a day or two. But it's
much much worse if the front doesn't move! Somebody to your west gets
persistent mild weather, which is nice for them, but you get persistent
stormy weather and perhaps flooding, while somebody to your east gets
persistent heat and drought.
If the Rossby wave stalls, the resulting changes in the regional climate
are disproportionate to the changes in the global average temperature.
This explains persistent events; it does not explain isolated events such
as Katrina, Sandy, et cetera.
-- To repeat, heretofore I thought the nightmare scenario was that something
that used to be stable would go unstable; for instance, if you destabilize
the Gulf Stream then western Europe becomes almost uninhabitable.
-- As of today I realize that the opposite is just as scary: Something that
was heretofore unstable can become stable.
-- There are other nightmare scenarios, including positive feedback from
arctic methane releases; see e.g. http://imgur.com/gallery/Xe9wS
-- Or all of the above. And more besides.
I don't know /exactly/ what will happen, in the sense that if you play
Russian roulette with bullets in five of the six chambers I don't know
/exactly/ what will happen ... but I know it's not a good game to be
playing.