No supercomputer is powerful enough to predict cloud cover decades into the future, so Fasullo and colleague Kevin Trenberth struck on another method to test which of the many climate simulations most accurately predicted clouds: They looked at relative humidity. When humidity rises, clouds form; drier air produces fewer clouds. That makes humidity a good proxy for cloud cover." “The models at the higher end of temperature predictions uniformly did a better job,” Fasullo said. The simulations that fared worse — the ones predicting smaller temperature rises — “should be outright discounted,” he said. " The models that predict less severe outcomes fared worse when tested against historical data. Just like Arctic ice cover is procceeding much more rapidly than expected.
Looking back at 10 years of atmospheric humidity data from NASA satellites, the pair examined two dozen of the world’s most sophisticated climate simulations. They found the simulations that most closely matched humidity measurements were also the ones that predicted the most extreme global warming.
In other words, by using real data, the scientists picked simulation winners and losers.
“The models at the higher end of temperature predictions uniformly did a better job,” Fasullo said. The simulations that fared worse — the ones predicting smaller temperature rises — “should be outright discounted,” he said.
The IPCC report that set off panic in the boasrdrooms of the world's biggest corporations was not a worst case scenario report. Everything in it had to be vetted and approved by the governments involved, not just the scientists who wrote it. This meant that the report was closer to a best case rather than a wost case. Turns out that the worst case is the one that seems more likely. And just a reminder: atmospheric carbon has to stay below 350 ppm for the world to maintain the climate we've grown to depend on. Current levels are watching 390 ppm disappearing behind them.