"During winter, England's Thames River would once freeze solid. This occurred on and off between 1400 and 1800 during a period called the "Little Ice Age" when temperatures dropped by as much as 1.5 degrees Celsius, which came after the medieval warm period around 1000. The anomaly of the Little Ice Age corrected itself, of course, through something called rebounding. The rebounding rate is estimated at 0.5 degrees Celsius per century. Since our present warming rate is roughly 0.6 degrees Celsius per century, the greenhouse effect caused by CO2 may represent only a 0.1 degree Celsius increase in temperature over the course of a century"

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