Posting this here for lack of a better thread. Most of you are probably not aware that I'm a dropout from graduate school, where I was studying climatology in the atmospheric science department at UC Davis. I honestly wasn't a very good researcher, and I finally hit the level that being a good student isn't enough. Well, my one research idea, that I never really got around to figuring out how to do, was to try to get a better handle on the influence of marine stratocumulus (a.k.a. the marine layer, alias June Gloom) on climate change. The effects of clouds have always been very difficult to model in climate models, because of the difficulty in connecting small-scale phenomena to the global circulation models that need to run for a long time.
Well, anyway, some researchers finally published a few studies on the topic, and there's an article with the someone scary title:
A World without Clouds
The good: They say that they basically couldn't do this kind of study 10 years ago, so maybe I would have been spinning my wheels waiting for better computing time, even if I had been a good researcher. They did some neat stuff binding a high-resolution cloud physics model into a general circulation model for climate, replacing a lot of the parameterizations (read: guesswork) with something more physical. The "future work" idea of doing samples of cloud physics at multiple sites in the GCM sounds great.
The bad: I had hypothesized a slight negative feedback on marine stratocumulus, maybe out of hope. They show a slight positive feedback on climate change, which is fairly intuitive: a warmer atmosphere is more turbulent, and therefore the clouds "burn off" faster. Less clouds mean less white things (high albedo) to reflect light back to space. As always, positive feedback is bad for you, because it means global warming happens faster.
The ugly: Oh gosh, how do I even begin. So one of the things about climate change is that there's bound to be something in the paleoclimate data where we've seen it before. Four billion years of Earth had some pretty wild swings, and if you add in Venus and Mars too, it's just about everything possible. The direct causes are different -- like asteroids and microbes and volcanoes, but the gases produced are the same.
Anyway, they seem to have linked the disappearance of stratocumuli to the Paleocene-Eocene Thermal Maximum. So if their research is correct, we have something of a hard ceiling at 1200ppm of CO2. If we exceed that value, then all of the stratocumulus clouds disappear. And at that point, we get an additional 4°C of warming just from the missing clouds, for a total of +8°C. To get the clouds back, CO2 would have to go all the way down to 2010 levels or so, because of the hysteresis. So this is a fucking nightmare, right? It probably happened before, with the PETM and it's +8° temperature rise, and it was a disaster then, too.
This is also a feasible level of carbon dioxide. We're at 411ppm now, but under the "business as usual" scenarios, we hit 1200ppm by 2100. It's ugh, my intuition was right that this was important, but I didn't deliver. And I find out that there's a plausible doomsday scenario lurking behind it. At least we now have an "avoid utter disaster" target.