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Infections and Global Warming

February 26, 2010

From Science-Based Medicine:

Interestingly, infections have probably altered climate for short periods of times. Through history humans burned trees releasing CO2, chopped down forests for agriculture and raised animals, releasing methane. As humans populations increased, both CO2 from burning and methane from animals increased as well. Every now and then large numbers of people have died off. It happen when Columbus et. al. brought infections to the New World and when plague came to the Old. People died. Maybe 90% in the Americas (estimates vary widely) and 2/3’s of Europe died. As a result, burning fuel and agriculture decreased, decreasing emissions and forests grew back, sequestering CO2. And temperature rise slowed or decreased.

“Abrupt reversals of the slow CO2 rise caused by deforestation correlate with bubonic plague and other pandemics near 200-600, 1300-1400 and 1500-1700 A.D. Historical records show that high mortality rates caused by plague led to massive abandonment of farms. Forest re-growth on the untended farms pulled CO2 out of the atmosphere and caused CO2 levels to fall. In time, the plagues abated, the farms were reoccupied, and the newly re-grown forests were cut, returning the CO2 to the atmosphere…Moreover, if plague caused most of the 10-ppm CO2 drops… it must also have been a major factor in the climatic cooling that led from the relative warmth of 1000 years ago to the cooler temperatures of the Little Ice Age.”

Like all good scientists, he notes the problems with his conclusions

“A more complete assessment of the role of plague- driven CO2 changes in climate change during the last millennium would require a narrowing of uncertainties in both the spatial and temporal occurrence of plague and in the amount of farm abandonment (and reforestation), as well as a resolution of the inconsistencies among the CO2 trends from different Antarctic ice cores.”

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