Temperatures across 98 percent of Earth’s surface were hotter at the end of the 20th century than at any time in the previous 2,000 years.
Such nearly universal warming, occurring in lockstep across the planet, is unique to this current era, scientists say. By contrast, other well-known cold and warm snaps of the past, such as the Little Ice Age or the Medieval Warm Period, were, in fact, regional rather than worldwide.
What’s more, the rate at which temperatures are increasing now far exceeds any previous temperature fluctuations measured in the last two millennia. Those are the conclusions of a trio of new papers examining temperature trends over the last 2,000 years, published online July 24 in Nature and Nature Geoscience. Those previous climate fluctuations were primarily driven by natural causes, including powerful volcanic eruptions, rather than human-caused greenhouse gas emissions.