In its new report on the risks from human-caused climate change, the American Association for the Advancement of Science (AAAS) sets climate science back rather than “advancing” it. The report, counterfactually titled “What We Know,” is more an account of what the scientific community thought it knew about a decade ago than an up-to-date telling of current understanding.
Not surprisingly, the group ignores the fact that climate science is moving in a direction that increasingly suggests that the risk of extreme climate change is lower than has been previously assessed. Instead, the AAAS continues to play up the chance of extreme outcomes with the intent of scaring us into taking action — action that would have little impact on either future climate change or the risks therefrom.
The AAAS largely appeals to its own authority in trying to persuade us to believe its conclusions and yet informs its authority with old and obsolete science.
The new report asserts:
Below are some of the high-side projections and tail risks we incur by following the current path for CO2 and other greenhouse gas emissions. Most of these projections derive from computer simulations of Earth and its climate system. These models apply the best understanding science has to offer about how our climate works and how it will change in the future. There are many such models and all of them have been validated, to varying degrees, by their ability to replicate past climate changes.
However, the best and most recent science shows the AAAS assessment to be outdated and badly misplaced. In fact, climate models have done remarkably poorly in replicating the evolution of global temperature during the past several decades, and high-end climate-change scenarios from the models are largely unsupported by observations.
For example, in January, researchers John Fyfe and Nathan Gillett published an article in the prominent journal Nature Climate Change that found that “global warming over the past 20 years is significantly less than that calculated from 117 simulations of the climate by 37 models.” And last year, scientists Peter Stott and colleagues published a paper in the journal Environmental Research Letters that concluded that “the upper end of climate model temperature projections is inconsistent with past warming.”
A host of other prominent papers that have examined the sensitivity of the climate to greenhouse-gas emissions collectively suggest that not only is future global warming likely to be less than previously expected, but, and perhaps more important, the outside chance that it will be extremely large has shrunk dramatically. This position is further supported by new research that downplays the threat of abrupt climate change from Arctic methane release, a shutdown of the Gulf Stream, and rapid sea-level rise.
Instead of an informed report by the esteemed group focused on presenting what today’s best science tells us regarding the risks from extreme climate change and our ability to mitigate them, what we got from the AAAS was a textbook example of climate alarmism: link human-caused greenhouse-gas emissions to climate change, raise the possibility that climate change will be disastrous, and then tell us we have to act now to save ourselves.
The first part of the AAAS guide to climate alarm is certainly true: Human-caused greenhouse-gas emissions do put pressure on the climate to warm. But the most important details — to what degree and of what character — are still uncertain and are being intensely studied and debated.
The second part has been relegated to the realm of climate fantasy. Today’s leading science suggests that coming human-caused climate change is going to be less than expected, with a much-diminished associated risk of abrupt changes with catastrophic outcomes.
Which means that the third part — that immediate action is required to reduce the risk of extreme change — is largely inapplicable (and such action is likely to be ineffective to boot).
The new AAAS report runs up climate alarm but runs down climate science. The result is a misleading document that is aimed at influencing public policy. This is the situation that should be raising alarm.
— Paul C. Knappenberger is assistant director of the Center for the Study of Science at the Cato Institute.