Positive Feedback Causes Greenhouse Gases to Accelerate Warming

New research has found evidence of a positive feedback mechanism brought on by climate change in which global warming itself may intensify a rise in greenhouse gases, resulting in additional warming.

It is well known that greenhouse gases cause the Earth's global temperatures to increase. But now a study, published in the journal Nature Climate Change, shows that the global temperature itself has a profound effect on atmospheric greenhouse gas concentrations. This means that as the Earth's temperature rises, the positive feedback in the system results in additional warming.

While previous research has indicated that historically, the Earth has had higher levels of greenhouse gases during warm periods than during ice ages, ice-core data has made it difficult to determine the cause and effect.

"It can be highly misleading to use simple correlation to infer causality in complex systems," researcher George Sugihara, from Scripps Institution of Oceanography, explained in a statement. "Correlations can come and go as mirages, and cause and effect can go both ways as in a kind of chicken and egg problem, and this requires a fundamentally different way to look at the data."

So an international team of researchers, led by Egbert van Nes from Wageningen University in the Netherlands, used a novel mathematical model to have a fresh look at the data.

The analysis revealed that the glacial cycles experienced by the planet over the past 400,000 years are driven by strong internal feedbacks in the Earth system. Slight variations in the Earth's orbit - known as Milankovitch cycles - function as subtle pacemakers for the process.

Direct evidence of this positive feedback mechanism has been difficult to achieve, but through Earth system models scientists can at least gain a better understanding of the complex processes at play that lead to a warmer world, and what we can expect in the future due to climate change.

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