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Study: Global warming causes more global warming

Steam rises from cooling towers at the Jaenschwalde coal-fired power plant in Germany, in this file photo from 2010. The Jaenschwalde power plant is one of the biggest single producers of CO2 gas in Europe.

Sean Gallup, Getty Images

It is bad enough that warming temperatures are being blamed for the drought in California or melting sea ice in the Arctic.

Now, a new study finds a warmer world could actually be causing an increase in emissions of greenhouse gases like carbon dioxide (CO2) and methane from ecosystems on land. Using data from ice cores dating back nearly 1 million years, researchers uncovered what is called positive feedback in climate, where effects of one factor serve to amplify another and thus worsen the cycle of climate change.

Taking 800,000 years of ice core data and putting it into a mathematical model, the researchers, writing in the journal Nature Climate Change on Monday, were able to demonstrate a correlation between the rising temperatures and a spike in greenhouse gas emissions across several ice ages.

"This gives a direct deduction from this past data that there is a strong effect of the temperature on concentrations on carbon dioxide and methane, in other words two major greenhouse gases," Tim Lenton, a co-author on the paper from the University of Exeter, told CBS News. "That gives us a direct confirmation purely from the data that there is this positive feedback loop."

The study also suggests alterations of the Earth's orbit of the sun - a key theory known as the Milankovitch cycles - didn't have nearly as much impact on the severity of ice ages as previously believed. Serbian mathematician Milutin Milankovitch had suggested the Earth's orbit - essentially is proximity to the sun - could explain why there were ice ages every 100,000 years.

But Lenton and is colleagues said the true drivers were temperature and greenhouse gases, with the Earth's orbit playing more of a bit role.

"So the orbit might begin to trigger a change or pace change but the internal feedbacks kind of take over and are responsible for great majority of the change we see," Lenton said.

That echoes a study out earlier this month in the journal Geology, which found that glacier movement in the Southern Hemisphere is influenced primarily by sea surface temperature and atmospheric carbon dioxide rather than changes in the Earth's orbit.

Even though this temperature and greenhouse gas data is from past ice ages, Lenton said there are lessons for the Earth moving forward. The world saw record high temperatures in 2014 and the models suggest rising emissions in the coming decades will result in significantly higher temperatures as well as other impacts such as worsening floods and the disappearance of glaciers.

"The interesting thing is that we are going to world with less ice cover, so we wouldn't expect the same feedback from changing ice and snow cover because we are melting that away," he said. "But this study is focused on temperature and greenhouse gases and they should still be there now and into the future."

"It is giving us confirmation that as we are driving the global temperature, we should expect the Earth to respond with further increases in carbon dioxide and methane," he said.

Previous studies have found there were higher levels of greenhouse gas emissions during the ice ages than in modern times. But until now, scientists struggled to discern the drivers for this trend from the analysis of gas bubbles contained in the ice cores.

Some scientists had pointed to Antarctic temperatures increasing ahead of CO2 variations as proof that temperature was a driver of CO2 changes. But more recent studies have cast doubt on there being a significant time lag between CO2 and temperature.

George Sugihara, another co-author on the study who is with the Scripps Institution of Oceanography, turned to his dynamical systems theory to provide the strongest proof of a connection. First proposed in 2012, the theory looks at two things that are affecting one another over time to prove causality. Sugihara also used the theory earlier this month to prove cosmic rays were having some effect on year-to-year variations in temperature but couldn't explain 20th century warming trend.

"I think this is a pretty heavy piece of evidence, a pretty compelling piece of evidence," Sugihara told CBS News of the link between temperatures and emissions. "It basically reinforces our mechanistic understand of the processes at work."

  • Michael Casey

    Michael Casey covers the environment, science and technology for CBSNews.com