In a world where climate change has always been the norm, climate change is now taken as punishment for sinful levels of consumption. We treat changes of a few tenths of a degree in some statistical residue, known as the global mean temperature anomaly, as portents of disaster.
Ice ages have occurred in a 100,000-year cycle for the last 700,000 years, and there have been previous interglacials that appear to have been warmer than the present despite lower carbon-dioxide levels.
The Earth is never exactly in equilibrium. The motions of the massive oceans where heat is moved between deep layers and the surface provides variability on time scales from years to centuries. Examples include El Nino, the Pacific Decadal Oscillation, the Atlantic Multi-decadal Oscillation, etc. Recent work suggests that this variability is enough to account for all change in the globally averaged temperature anomaly since the 19th century. To be sure, man’s emissions of carbon dioxide must have some impact. The question of importance, however, is how much.
A generally accepted answer is that a doubling of carbon dioxide in the atmosphere would perturb the energy balance of the Earth about 2 percent and this would produce about 2 degrees Fahrenheit warming in the absence of feedbacks. The observed warming over the past century, even if it were all due to increases in carbon dioxide, would not imply any greater warming.
The fact that some models suggest changes in alarming phenomena will accompany global warming does not logically imply that changes in these phenomena imply global warming. This is not to say that disasters will not occur; they always have occurred and this will not change in the future. Fighting global warming with symbolic gestures will certainly not change this. However, history tells us that greater wealth and development can profoundly increase our resilience.
The need to courageously resist hysteria is clear. Wasting resources on symbolically fighting ever-present climate change is no substitute for prudence.
Richard S. Lindzen is a professor of atmospheric science at MIT. He wrote this for The Free Lance-Star in Fredericksburg, Va.
