The study, published Monday in the journal Nature, constructs a 2-million-year-long temperature record to predict future rises in heat. Using 61 sea surface temperature proxies taken from ocean sediment cores from around the world, Carolyn Snyder, who works as a climate policy official at the Environmental Protection Agency, looked at average temperatures over periods of 5,000 years, finding that changes in temperature coincided with carbon dioxide levels.
Temperatures averaged out over the most recent 5,000 years — which includes the last 125 years or so of industrial emissions of heat-trapping gases — are generally warmer than they have been since about 120,000 years ago or so, Snyder found.
If factors are similar to what can be seen in the past, “stabilization at today’s greenhouse gas levels may already commit Earth to an eventual total warming of 5 degrees Celsius (range 3 to 7 degrees Celsius, 95 per cent credible interval) over the next few millennia,” as she wrote in her study.
Synder said, “This is based on what happened in the past. In the past it wasn’t humans messing with the atmosphere.”
Some Experts Challenge The Findings
Gavin Schmidt, chief of NASA’s Goddard Institute for Space Studies called the research findings “simply wrong.”
“The actual committed warming is only 0.5 to perhaps 1 [degree Celsius] – and nothing in the study changes that. You have this chicken and egg situation, where ice changes, which causes CO2 to change, which causes ice to change, and so on and so forth.”
When researchers look back far enough, the effects of the relationship become blurry. “You’re mixing the impact of CO2 on climate, and climate on CO2,” he said.