Researchers have solved a climate change mystery, demonstrating in a Rutgers-led study that the modern global temperature is the warmest in approximately 12,000 years and affirming the role of greenhouse gases in global warming, according to a press release.
The mystery in question was the Holocene temperature conundrum, which concerns approximately 12,000 years of Earth’s history up to now, said lead author Samantha Bova, a postdoctoral research associate in the Department of Marine and Coastal Sciences.
Proxy data, or physical indicators in the environment of past climate conditions, indicated the Earth was warmer approximately 6,000 to 10,000 years ago than it is now before a global cooling period, she said. This was contrasted by climate models, which indicated a steady warming across the Holocene era.
“This mismatch between what the proxies were showing and what the models were showing is something that was termed the Holocene temperature conundrum,” Bova said. “It suggested that maybe our climate models were not doing a great job of simulating climate over the last 12,000 years.”
This led some people to believe the current modern average global temperature is cooler than past average global temperatures, said co-author Yair Rosenthal, distinguished professor in the Department of Marine and Coastal Sciences.
He said the study disproves this idea by demonstrating that previous proxy data reflected the progression of seasonal temperatures, not annual temperatures. The researchers developed a method of converting the seasonal temperature from a proxy to a mean annual temperature, according to the study.
“It will enable you to remove the seasonal component in that record, and you can actually calculate what the mean annual temperature was from the seasonal data,” Bova said. “I think having a robust method like that is something new, and it gave us a new vantage point on what the evolution of global temperature has been for the last 12,000 years.”
Potential directions for this research in the future include using the method on other previously published data or modifying the process for use on other proxies often used by climate researchers, she said.
Bova said determining the cause of the conundrum was an interdisciplinary effort and that this publication was the culmination of a decade’s long collaboration that spanned several research institutions, which worked together to standardize how climate models are compared to observable evidence.
By confirming the credibility of climate models, Rosenthal said the study has confirmed the role of greenhouse gases such as carbon dioxide in global warming and given a response to skeptics of climate change.
“This is real,” he said. “We just, I think, put a punch in the belly of some of the deniers.”