Natural cycles had little to do with 20th-century temperature trends

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Reconstructing crime scenes is more or less what most geoscientists do for a living. Sometimes the “whodunnit” revolves around a mass extinction event 66 million years ago, and sometimes it’s about an extreme weather pattern just last week. But as with a homicide investigation, geologists also have to consider natural causes.

A new study led by the University of Oxford’s Karsten Haustein takes a look at the influence of natural causes on the temperatures of the last century. While natural variability inherent to the climate system was thought to play a role in some features of our temperature record, the new results suggest that the record is dominated by external forces—though some of those are natural, too.

Explaining wiggles

It’s well-established that human activities are the dominant cause of recent climate change. But looking at the instrumental temperature record, which goes back to the late 1800s, there are significant wiggles that look curious. Why, for example, did global temperatures drop for a time after World War II before resuming their upward ascent in the late 1970s?