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Dangerous climate feedback loops have been underestimated

New research led by scientists from the Oregon State University suggests that current climate models may underestimate some of the effects of global warming because they fail to take full account of the role of amplifying feedback loops. Their report, published in the journal One Earth, calls for urgent action to bring greenhouse gas emissions under control and to provide a roadmap for policymakers aiming to avert the most devastating consequences of climate change. 

The researchers considered the roles of 41 climate feedback loops that could either amplify or reduce the effects of climate change. Among these, 27 were amplifying feedback loops that involve a climate-caused alteration which triggers a process that further accentuates the initial alteration. For example, rising temperature leads to the melting of sea ice in the Arctic which, in turn reduces the area of ice able to reflect incident radiation. This leads to further warming because the solar radiation is then absorbed by the dark ocean waters rather than being reflected by the white ice. 

Another example involves the effects of wildfires which are becoming more common due to the warm, dry conditions. Combustion of the vegetation introduces a lot of carbon dioxide into the atmosphere, which then contributes to the greenhouse effect and leads to even higher temperatures.

OSU College of Forestry postdoctoral scholar Christopher Wolf and Professor William Ripple led the study, and were joined by scientists from the University of Exeter, the Potsdam Institute for Climate Impact Research, the Woodwell Climate Research Center, and Terrestrial Ecosystems Research Associates. The researchers considered the role of both biological and physical feedbacks in climate change processes. Biological feedbacks include forest dieback, soil carbon loss and wildfire; physical feedbacks involve changes such as reduced snow cover, increased Antarctic rainfall and shrinking Arctic sea ice.

“Many of the feedback loops we examined significantly increase warming because of their connection to greenhouse gas emissions,” Wolf said. “To the best of our knowledge, this is the most extensive list available of climate feedback loops, and not all of them are fully considered in climate models. What’s urgently needed is more research and modeling and an accelerated cutback of emissions.”

The levels of greenhouse gas emissions have risen substantially over the last century, despite several decades of warnings by climate scientists that these levels need to be drastically reduced. The scientists say the amplifying effect of feedback loops, as well as interactions between different loops could cause Earth systems to cross tipping points and lead to permanent shifts away from the current climate state to one that threatens the survival of many humans and other life forms.

“In the worst case, if amplifying feedbacks are strong enough, the result is likely tragic climate change that’s moved beyond anything humans can control,” Ripple said. “We need a rapid transition toward integrated Earth system science because the climate can only be fully understood by considering the functioning and state of all Earth systems together. This will require large-scale collaboration, and the result would provide better information for policymakers.”

The authors call for urgent and massive reductions in greenhouse gas emissions to mitigate the possible major threats looming from climate tipping points that are drawing ever-closer due to the activation of many amplifying feedback loops. They say that even comparatively modest warming is expected to heighten the likelihood that the Earth will cross various tipping points, causing big changes in the planet’s climate system and potentially strengthening the amplifying feedbacks even further.

“Transformative, socially just changes in global energy and transportation, short-lived air pollution, food production, nature preservation and the international economy, together with population policies based on education and equality, are needed to meet these challenges in both the short and long term,” Ripple said. 

“It’s too late to fully prevent the pain of climate change, but if we take meaningful steps soon while prioritizing human basic needs and social justice, it could still be possible to limit the harm,” he added.

The paper in One Earth has a corresponding website that features more about climate feedback loops, including infographics and interactive animations.

By Alison Bosman, Staff Writer

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