Surface temperatures are indeed increasing slightly: They’ve been going up, in fits and starts, for more than 150 years, or since a miserably cold and pestilential period known as the Little Ice Age. Before carbon dioxide from economic activity could have warmed us up, temperatures rose three-quarters of a degree Fahrenheit between 1910 and World War . They then cooled down a bit, only to warm again from the mid-1970s to the late ’90s, about the same amount as earlier in the century.