Climate change might turn out to be worse than previously believed thanks to 27 ‘amplifying feedback loops’ that accelerate global warming.
Scientists have warned that this could lead to "tragic" global warming that goes beyond anything humans can control.
Researchers from Oregon State University (OSU) said that some of the feedback loops may not be accounted for in current climate modelling.
One example of an amplifying feedback loop is warming in the Arctic Ocean, leading to melting sea ice that results in further warming because sea water absorbs rather than reflects solar radiation.
The researchers identified dozens of 'loops' where a climate-caused alteration can trigger a process that causes even more warming.
Lead author Christopher Wolf, a postdoctoral scholar at the OSU College of Forestry, said: "Many of the feedback loops we examined significantly increase warming because of their connection to greenhouse gas emissions.
"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 modelling and an accelerated cutback of emissions."
The researchers called for "immediate and massive" emissions reductions, pointing out that "climate disasters" in the form of wildfires, coastal flooding, permafrost thaw, intense storms and other extreme weather are already occurring.
They warned that feedback loops risk driving the global climate towards tipping points – a threshold after which a change in a component of the climate system becomes self-perpetuating.
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.
Even comparatively modest warming is expected to heighten the likelihood that Earth will cross various tipping points, the researchers said, causing big changes in the planet's climate system and potentially strengthening the amplifying feedbacks.
Wolf said: "Climate models may be underestimating the acceleration in global temperature change because they aren't fully considering this large and related set of amplifying feedback loops.
"The accuracy of climate models is crucial as they help guide mitigation efforts by telling policymakers about the expected effects of human-caused greenhouse gas emissions.
"While recent climate models do a much better job of incorporating diverse feedback loops, more progress is needed."
Emissions have risen substantially over the last century, the researchers noted, despite several decades of warnings that they should be significantly curbed.
The scientists said interactions among feedback loops could cause a permanent shift away from the Earth's current climate state to one that threatens the survival of many humans and other life forms.
Professor William Ripple, of OSU, said: "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.
"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."
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