It’s with some trepidation I dip my toes into this subject. But this recent report from the Earth System Science Center at The University of Alabama in Huntsville, using data from NASA’s Terra satellite, shows why keeping a minimum of skepticism about anything you hear about what conditions on Earth will be like in 20, or 50, or 100 years is probably warranted.
The problem is that predictions about future temperatures on Earth are all based on models. And as anyone who has ever worked with models (whether financial — can you say “subprime”? — or scientific) knows, models are only as good as assumptions that go into them. Small tweaks to those assumptions can result in big differences in model outcomes.
One assumption in climate change models has to do with how much heat energy is released back into space during hot spells. The reported study suggests that climate models may be at least partially based on a bad assumption:
In research published this week in the journal Remote Sensing, Spencer and UA Huntsville’s Dr. Danny Braswell compared what a half dozen climate models say the atmosphere should do to satellite data showing what the atmosphere actually did during the 18 months before and after warming events between 2000 and 2011.
“The satellite observations suggest there is much more energy lost to space during and after warming than the climate models show,” Spencer said. “There is a huge discrepancy between the data and the forecasts that is especially big over the oceans.”
The other inherent problem with models is that they must by definition be based upon either existing conditions, or predictions about how existing conditions will change in the future (which are, of course, themselves based upon trends existing within current conditions). Models about the future can’t incorporate unexpected, unanticipated changes in conditions. With a system as complex as Earth’s climate, affected, as it is, by a huge number of factors, a skeptic can wonder whether or not unanticipated changes in assumptions will occur and, if they do, whether they will affect model results. A small sort of example of this seems to be at work in this study:
Not only does the atmosphere release more energy than previously thought, it starts releasing it earlier in a warming cycle. The models forecast that the climate should continue to absorb solar energy until a warming event peaks.
Instead, the satellite data shows the climate system starting to shed energy more than three months before the typical warming event reaches its peak.
“At the peak, satellites show energy being lost while climate models show energy still being gained,” Spencer said.
The ScienceDaily web site’s report concludes:
Applied to long-term climate change, the research might indicate that the climate is less sensitive to warming due to increased carbon dioxide concentrations in the atmosphere than climate modelers have theorized. A major underpinning of global warming theory is that the slight warming caused by enhanced greenhouse gases should change cloud cover in ways that cause additional warming, which would be a positive feedback cycle.
Instead, the natural ebb and flow of clouds, solar radiation, heat rising from the oceans and a myriad of other factors added to the different time lags in which they impact the atmosphere might make it impossible to isolate or accurately identify which piece of Earth’s changing climate is feedback from human-made greenhouse gases.
Now, a caveat: I am not an expert in climate change studies, and have no independent way to evaluate this particular study, or to evaluate the impact on the viability of climate change models even if the study is accurate. My personal view is that yes, human activity is increasing concentrations of carbon dioxide and other “greenhouse gases” in the atmosphere, and yes, that increase probably will have long-term impacts on Earth’s climate, but just what that impact will be is uncertain. Probably warmer, maybe by a lot, maybe by a little, with negative effects most places and positive effects in others. But models being imperfect, this is an area in which the answer to the question will only really be known over time.
Categories: Science