Serendipity

Well, I had a fabulous week at the EGU. I tried to take in many different aspects of climate research, but inevitably ended up at lots of sessions on earth systems informatics (to satisfy my techie streak), and sessions looking at current cutting edge research on earth systems models, such as integrating weather forecast and climate models, model ensembles, and probabilistic predictions. Lots of interesting things going on in this space. 

Here’s what I would regard as the major themes of the conference from my perspective:

• Ocean Acidification. It’s pretty easy to predict because it’s linear in the concentration of CO2 in the atmosphere – i.e. there’s no uncertainty at all. When we kill off life in the seas we also lose a major carbon sink.
• Feedbacks. I learned at least nine different definitions of the word feedback, and also that there are a huge number of feedbacks that we might want to put into an earth system model, so someone’s got to work out which ones are most likely to be important.
• Abrupt Climate Change. I learned that the paleontological record tells us that the earth is quite likely to be twitchy, and we still don’t know anywhere near enough about the triggers. Oh, and lots of climate scientists think we’ve already hit some of those triggers.
• Probabilistic forecasting. I learned a lot about the use of model ensembles (both multi-models, and perturbed physics experiments with single models) to quantify our uncertainties. There’s a strong move in the climate community to replace single predictions of climate change with probabilistic forecasts. The simplest exposition of this idea is MIT’s wheels of fortune.
• Simpler targets for policy makers. I’m very taken with the analysis from Chris Jones and colleagues that show that if we want to stay below the 2°C temperature rise, we have a total budget of One Trillion Tonnes of Carbon to emit, and since the dawn of industrialization, we used up more than half of it. 
• Geo-Engineering. Suddenly it’s okay for climate scientists to start talking about geo-engineering. For years, this has been anathema, on the basis that even just talking about this possibility can undermine the efforts to reduce carbon emissions (which is always the most sensible way to tackle the problem). But now it appears that many scientists have concluded that it’s too late anyway to do the right thing, and now we have to start thinking the unthinkable.

Plus some things that I missed that I wish I’d seen (based on what others told me afterwards):

• Stefan Rahmstorf‘s views on the risks of an abrupt shift in the ocean circulation. Still, I consoled myself with this webcast from one of his talks last year: A greater risk of sea level rise? (Stefan writes great stuff: this primer from 2004 on the risk of abrupt change is fabulous).
• The session on The Cryosphere – for how much longer?, particularly fellow Canadian Luke Copland‘s talk on accelerated collapse of the arctic ice shelves; I’m told this was both spectacular and scary stuff.