Slow climate feedbacks could amplify global warming
Future warming from fossil fuel burning could be more intense and longer-lasting than previously thought. This prediction emerges from a new study by University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology oceanographer Richard Zeebe published in the Proceedings of the National Academy of Sciences on August 5.
“When we talk about climate sensitivity, we’re referring to how much the planet’s global surface temperature rises for a given amount of CO2 in the atmosphere,” Zeebe said.
According to Zeebe, climate sensitivity could change over time. He uses past climate episodes as analogs for the future, which suggest that so-called slow climate ‘feedbacks’ can boost climate sensitivity and amplify warming.
An example of a feedback is the familiar audio feedback experienced when a microphone interacts with a speaker. If the audio output from the speaker is received again by the microphone, the initial audio signal is strongly amplified in a positive feedback loop.
A variety of feedbacks also operate in Earth’s climate system. For example, a positive feedback loop exists between temperature, snow cover and absorption of sunlight. When snow melts in response to warming, more sunlight can be absorbed at Earth’s surface because most surfaces have a lower reflectivity than snow. In turn, the additional absorption of sunlight leads to further warming, which leads to more snow melt.
Climate change may be a longer intense process
Previous studies have usually only included fast climate feedbacks (snow cover, clouds, etc.). Using information from pre-historic climate archives, Zeebe calculated how slow climate feedbacks (land ice, vegetation, etc.) and climate sensitivity may evolve over time. Armed with these tools, Zeebe was able to make new predictions about long-term future climate change.
“The calculations showed that man-made climate change could be more severe and take even longer than we thought before,” says Zeebe. Although we will not see immediate effects by tomorrow—some of the slow processes will only respond over centuries to millennia—the consequences for long-term ice melt and sea level rise could be substantial. “Politicians may think in four-year terms but we, as scientists, can and should think in much longer terms. We need to put the impact that humans have on this planet into a historic and geologic context.
“By continuing to put these huge amounts of carbon dioxide in the atmosphere, we’re gambling with climate and the outcome is still uncertain. The legacy of our fossil fuel burning today is a hangover that could last for tens of thousands of years, if not hundreds of thousands of years to come.”
Read the UH news release for more.