The failure of the climate models

 Steven Hayward:

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One big problem is the resolution of the models, described thus:

Even the simplest diagnostic test is challenging. The model divides Earth into a virtual grid of 64,800 cubes, each 100 kilometers on a side, stacked in 72 layers. For each projection, the computer must calculate 4.6 million data points every 30 minutes. To test an upgrade or correction, researchers typically let the model run for 300 years of simulated computer time. . .

But as algorithms and the computer they run on become more powerful—able to crunch far more data and do better simulations—that very complexity has left climate scientists grappling with mismatches among competing computer models.

The problem is that the 100 km resolution of the models simply isn’t high enough to predict the climate accurately. Steven Koonin’s recent book Unsettled: What Climate Science Tells Us, What It Doesn’t, and Why It Matters, which contains one of the best discussions for the layperson of how climate models work that I’ve ever seen, gilds this point: “Many important [climate] phenomena occur on scales smaller than the 100 km (60 mile) grid size (such as mountains, clouds, and thunderstorms).” In other words, the accuracy of the models is highly limited. Why can’t we scale down the model resolution? Koonin, who taught computational physics at CalTech, explains: “A simulation that takes two months to run with 100 km grid squares would take more than a century if it instead used 10 km grid squares. The run time would remain at two months if we had a supercomputer one thousand times faster than today’s—a capability probably two or three decades in the future.” (I’ll have a long review of Koonin’s book in the next edition of the Claremont Review of Books.)

The Wall Street Journal reports that the newest models kept spitting out even more dire predictions of future warming than many previous models—but that the climate modelers don’t believe the projections:

The scientists soon concluded their new calculations had been thrown off kilter by the physics of clouds in a warming world, which may amplify or damp climate change. “The old way is just wrong, we know that,” said Andrew Gettelman, a physicist at NCAR who specializes in clouds and helped develop the CESM2 model. “I think our higher sensitivity is wrong too. It’s probably a consequence of other things we did by making clouds better and more realistic. You solve one problem and create another.” . . .

Since then the CESM2 scientists have been reworking their climate-change algorithms using a deluge of new information about the effects of rising temperatures to better understand the physics at work. They have abandoned their most extreme calculations of climate sensitivity, but their more recent projections of future global warming are still dire—and still in flux.

Kudos also for the Journal reporting that the latest IPCC report last summer draw back from some of the previous extreme predictions of future doom, something not widely reported, if at all, in the media: “In its guidance to governments last year, the U.N. climate-change panel for the first time played down the most extreme forecasts.”

This passage is also a big problem for the climatistas:

In the process, the NCAR-consortium scientists checked whether the advanced models could reproduce the climate during the last Ice Age, 21,000 years ago, when carbon-dioxide levels and temperatures were much lower than today. CESM2 and other new models projected temperatures much colder than the geologic evidence indicated. University of Michigan scientists then tested the new models against the climate 50 million years ago when greenhouse-gas levels and temperatures were much higher than today. The new models projected higher temperatures than evidence suggested.

Watch for the climatistas to say, “Move along, nothing to see here.”

One big reason the 100 sq km resolution of climate models is inadequate is that the behavior of clouds and water vapor can’t be adequately modeled—something the IPCC reports usually admit in the technical sections the media never read. The WSJ story is similarly revealing on this point....

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This probably explains why most of their past projections have been wrong.  For the last 50 years, they have been predicting doom and gloom while the climate as a whole has remained pretty nice.   As I often note, the poles are still not ice-free, nor are coastal cities underwater both of which were projected by some in the climate crowd.