A new paper, out on Wednesday, August 24, in the journal Nature, challenges our current notions on how sensitive the planet is to human-generated greenhouse gas emissions, and how long they’ve been at work.
Using paleoclimate records from the past 500 years, researchers show that sustained warming began to occur in the tropical oceans and the Northern Hemisphere land masses as far back as the 1830s.
Given that organized, global temperature records enter the scene only around the 1880s, previous estimations of man-made climate change are fairly limited and lacking in scope.
The new research involved 25 scientists from around the world, including more than a dozen researchers from the PAGES (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.
Relying on special analyses of coral, tree rings and ice cores, the research team created several reconstructions of the climate for the past few hundred years, and found that sustained warming in tropical oceans and continental land masses in the Northern Hemisphere began around the 1830s, with roughly a 50 year lag in the Southern Hemisphere.
The simulations also suggest that the major catalysts of these changes are greenhouse gases emitted around the Industrial Revolution, which began around the mid-18th century.
While some researchers remain skeptical, claiming that warming in the 1830s could be more easily explained by the significant cooling effect of the powerful volcanic eruptions in 1815 that took place in Indonesia and might have set the scene for a rebound effect, the study authors say that they had started out with the same assumption, but as they continued to “test the data and our methods it became clear that you don’t need these big eruptions in the early 1800s to explain the early warming”.
According to the study lead author Nerilie Abram, an expert in paleoclimatology at the Australian National University, the study indicates that we’ve been warming the Earth far longer than previously thought, and might be closer to the kind of dangerous climate consequences many experts have predicted the planet could see if we blow past the limit of 2-degrees Celsius over pre-industrial levels.
“Actually finding that humans had a measureable impact on the climate in the mid-19th century was somewhat of a surprise,” Abram said. “It’s a finding that, no matter which way we tested, we kept coming up with that same answer.”