OK, so maybe a lot of Canadian cities haven’t gotten noticeably warmer since 1919 based on our “1919 or 2019?” quiz and other data. And maybe the Earth itself isn’t getting warmer in response to greenhouse gases the way models say it should. But science marches on undeterred, with a new generation of computer simulations ready to do what the mere planet seems incapable of: get a lot hotter. Yes, the new 6th-generation suite of climate models apparently has some impressive new tweaks and features, such as being able to keep the water in clouds from turning to ice too quickly. Unfortunately the changes in cloud behaviour have resulted in the models’ climate sensitivity to CO2 bumping up a notch. On the plus side, climate scientists who often seem eager to jump on any hint of bad news are giving a cool response to the new models.
The authors of the journal article discussing these new features reported on an experiment in which they quadrupled the amount of CO2 in the atmosphere and sat back to see what would happen. Not surprisingly, the model Earth warmed up. But it went rather substantially past where previous models went in that scenario, so they pried the models open to see why. They noticed that in the new models, clouds behave differently, and in particular as the world warms they thin out over the southern ocean, letting more sunlight hit the surface.
Alas, since these are just models, not real world observations, it isn’t proof that global warming is worse than we thought. On the contrary it’s starting to look like proof that models are worse than we thought. Strange that in a field where the science is supposedly more settled than anything has ever been settled, the computer models get worse over time not better.
The authors express the problem in a very curious sentence: “It is crucial to establish whether the latest models, which presumably represent the climate system better than their predecessors, are also providing a more realistic picture of future climate warming.”
So yes, the new models are better than the old ones. We just don’t know if they work better.