Human-caused climate change has been happening for a lot longer than we thought, scientists say

Aug 24, 2016 at 12:00pm

Chelsea Harvey, The Washington Post

The new study, just out on Wednesday in the journal Nature, suggests human-caused, or anthropogenic,  climate change has been going on for decades longer than existing temperature records indicate. Using paleoclimate records from the past 500 years, the researchers show that sustained warming began to occur in both the tropical oceans and the Northern Hemisphere land masses as far back as the 1830s — and they’re saying industrial-era greenhouse gas emissions were the cause, even back then.  

“I don’t think it changes what we know about how the climate has warmed during the 20th century, but it definitely adds to the story,” said Nerilie Abram, an expert in paleoclimatology at Australian National University and the new study’s lead author.  

People first started keeping organized, global temperature records starting around the 1880s, and these are the records that many scientists reference when looking back on how the climate has changed over the last century. And it’s clear that it’s been warming — and that human activities are the primary cause. But just looking at records from the 1880s on doesn’t tell the whole story, according to Abram.  

“We can see that by only looking from the 1880s on, we don’t have the full picture of how we’ve been changing the climate,” she said.   

The new research involved 25 scientists from around the world, including more than a dozen researchers from the PAGES 2k (or Past Global Change 2000 year) Consortium, a group supporting research into Earth’s past in order to gain a better understanding of its climate future. The PAGES team has been involved with creating paleoclimate reconstructions of temperatures over both land and sea. These reconstructions have relied on special analyses of coral, tree rings and ice cores, all of which contain chemical fingerprints that can give scientists insights into what the climate was like hundreds or even thousands of years ago.

The research team used these paleoclimate records to look back at the progression of industrial-era warming across the Earth over the past few hundred years. The industrial era is a period of time loosely beginning around the mid-18th century, when industrial growth around the world led to a sharp increase in the burning of fossil fuels and the emission of greenhouse gases, which contributed to the onset of anthropogenic climate change on Earth.  

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