Back to climate change

I've given readers a bit of a  break from climate change posts, but this item from a couple of weeks ago is important.

Real Climate noted some new research indicating the (possibly) very strong regional differences in a warming world.   It's all to do with how atmospheric flow changes.  Here's a couple of key paragraphs:

I think there were some surprising aspects in Deser et al.‘s results. Not that I didn’t expect natural multi-annual variations to be important (on shorter time scales, they are very pronounced), but what strikes me is the strong contrast (on a 50-year time scale) between the global mean temperature (lower graph), which was not very sensitive to the regional atmospheric circulation, and the regional temperatures which were strongly influenced.

It has long been recognized that local and regional climate would warm at different rates than the global mean, but not with such large differences as presented by Deser et al. at the time scales of 50 years and for continental scales. Their results imply that while some regions could experience almost zero warming over 50 years, this will be compensated by substantially stronger in other regions (because they also find that the global mean temperatures to be largely insensitive to the different model initial conditions).

These results also imply a surprisingly long persistence of weather regimes in different parts of the world. Usually, one tends to associate these with inter-annual to decadal scales. However, Deser et al observe:

Such intrinsic climate fluctuations occur not only on interannual-to-decadal timescales but also over periods as long as 50 years… even trends over 50 years are subject to considerable uncertainty owing to natural variability.

These findings were in particular important for the winter season at mid-to-high latitudes. Hence, they could be entirely attributed to chaotic dynamics. On the other hand, the two simulations that they highlighted in their study represented extreme cases, and most of the simulations suggested that the future outcome may be somewhere in between.

My interpretation of Deser et al.‘s results is that the range of possible future temperatures gets broader at the same time as the most likely outcome follows a warming curve. This means that the most likely scenario is warming for the future while there still is a small possibility that the temperature for a particular location hardly changes (or even cools) over a 50-year period.

What strikes me as important about this is it surely means that those economists or advocates who argue for money to be spent more on adaptation to climate change rather than limiting emissions are barking up the wrong tree.

It has long been acknowledged that regional effects of climate change are harder to predict that the bigger picture - this research seems to go further in demonstrating this.   So if you are a politician, how can you reliably predict what adaptation projects are most appropriate to your particular region?