National Geographic : 2009 Dec
50 450 parts per million 350 250 150 2008 AVERAGE PREINDUSTRIAL LEVEL 299 271 385 HIGHEST ICE CORE READING (333,000 YEARS AGO) *PERCENTAGES DO NOT ADD UP TO 100 BECAUSE OF ROUNDING. GRAPHIC: NIGEL HOLMES. SOURCES: JOHN STERMAN, MIT; DAVID ARCHER, UNIVERSITY OF CHICAGO; GLOBAL CARBON PROJECT A fundamental human flaw, says John Sterman, impedes action on global warming. Sterman is not talking about greed, selfishness, or some other vice. He's talking about a cognitive limita- tion, "an important and pervasive problem in human reasoning" that he has documented by testing graduate students at the MIT Sloan School of Management. Sterman teaches system dynamics, and he says his students, though very bright and schooled in calculus, lack an intuitive grasp of a simple, crucial system: a bathtub. In particular, a tub with the tap running and the drain open. The water level can stand for many quantities in the modern world. The level of carbon dioxide in Earth's atmosphere is one. A person's waistline or credit card debt---both of which have also become spreading problems of late---are two more. In all (Continued on next page) It absorbs some of the heat radiation coming off Earth's sunbaked surface and reradiates it back downward. Not for at least 800,000 years, say the oldest air bubbles found in Antarctic ice cores---and probably not for millions of years. How does CO cause warming? Hasn't CO been this high before?