Enlarge / A reconstruction of temperature in North America and Europe since the end of the last Ice Age, shown in thousands of years before 1950. (credit: Marsicek et al/Nature)
Before the Industrial Revolution (roughly), Earth’s climate had actually been trending slightly cooler.
The sudden reversal toward comparatively rapid warming gave rise to graphs frequently described as “hockey sticks” for their shape.
But that stick only goes back about 2,000 years in climate records based on tree rings.
So what happened between the end of the last “Ice Age” around 11,000 years ago and the beginning of the hockey stick?
Ice core records gave us the general idea decades ago—temperatures were relatively stable.
But to understand what global temperature was doing more precisely, researchers have to compile lots of individual records from around the world. One such effort, published in 2013, showed the slow cooling trend beginning 5,000 years ago, making a super-long hockey stick following a warm plateau that was also about 5,000 years long.
But in 2014, another study showed that this pattern didn’t quite fit climate model simulations.
Instead, the 2014 study showed a very gradual warming of about 0.5 degrees Celsius over the last 11,000 years.
But a new study published this week compiled a separate climate record for the Northern Hemisphere—with slightly different results that look more like that model simulation.
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