Judith Curry: Okay. The climate models originated from weather forecast models, and then they added an ocean then land surface biosphere, and then chemical processes, and now ice sheets. They keep adding all these modules and increasing complexity of the models, but the basic dynamics are driven by the same kind of models that model the weather. We’ve learned a lot from climate models, by running experiments, turning things off, turning things on adjusting parameters, taking clouds out, taking sea ice out, holding the sea surface temperature constant in the tropical central Pacific and see what happens, you know, we learn how the climate works by using climate models in that way. However, the most consequential applications of climate models are to tell us what caused the 20th century climate change, how much the climate change is going to change in the 21st century and what’s causing extreme weather events.
I mean, those are the more consequential applications and climate models aren’t fit for any of those purposes. And that’s pretty much acknowledged even in the IPCC report. Well, they, they do claim that they can attribute the global warming, but this can’t be easily separated from the natural variability associated with large-scale ocean circulations. And the way they’ve used climate models to do that involves circular reasoning, where they throw out climate simulations that really don’t match what was observed. So you, you end up, even if you’re not explicitly tuning to the climate record, you’re implicitly tuning. And then the thing with extreme events, weather events is beyond silly because these climate models can’t resolve the extreme events and they can’t simulate the ocean circulation patterns that really determine the locations of these extreme events. And then when you start talking about 21st century, the only thing they’re looking at is the manmade human emissions forcing, they’re not predicting solar variability.
They’re not not predicting volcanic eruptions. They can’t even predict the timing of these multidecadal to millennial ocean oscillation. So all they’re looking at is this one little piece. Okay. So, what are you supposed to do with all that? Not sure we know much more than the sign of the change from more CO2 in the atmosphere, which is more warming. And then there’s another thing. The most recent round of global climate model simulations, the so-called CMIP5 for the IPCC 6th assessment report. All of a sudden the sensitivity to CO2 the range has substantially increased in a lot of the models, way outside the bounds on the high side of what we thought was plausible, even five years ago. So what are we to make of that? And how did that happen? Well, it, it’s a, it’s a rather arcane issue related to how clouds cloud particles interact with aerosol particles.
By adding some extra degrees of freedom into the model related to clouds, then it becomes all of a sudden way more sensitive to increases in CO2. What are we supposed to make of that? I mean, we do not have a convergent situation with these climate models. And this is not mention that the 21st century projections from the climate models, don’t include solar variations. They don’t include volcanoes or the ocean circulation, all of these things that they don’t include. So what are we left with? And then there are these precise targets, such as we will exceed our carbon budget in 2038. This is way too much precision that is derived from these very inadequate climate models.
