Study Finds Climate Feedback Loops Could Add 0.2C to 0.4C by 2100

The paper analyzed four areas: high-latitude permafrost, drying forests and fiercer wildfires, wetlands and lakes, and freshwaters. As the world heats up, permafrost is thawing, wildfires are burning more intensely, and wetlands and lakes are warming. These changes release methane and carbon dioxide locked in trees and soils, worsening the climate crisis. Scientists have long known about such feedback loops that amplify the impact of direct pollution from coal, oil and gas, but the emissions from natural sources are mostly unaccounted for in climate models.

The study, led by Sam Abernethy of Spark Climate Solutions Research and co-authored by Rob Jackson of Stanford University, found that emissions from natural sources will amplify global heating by 20% to 30% by the end of this century. That would add 0.2C to 0.4C to the global average temperature, depending on countries’ overall action to combat the climate crisis. Even small fractions of temperature change can greatly alter the risk of severe heatwaves, floods, drought and other impacts.

“This hidden multiplier is missing from the models guiding climate policy, so those models are likely underestimating how much warming is coming – and overestimating how much carbon we can still afford to emit,” Abernethy said. Jackson said the disruption of the world’s carbon cycles is now being seen in “real time.” “The results are a wake-up call, and it’s imperative that they be included in the next generation of climate policies,” he said. “Failure to do so will make meeting the world’s climate goals less and less likely.”

The United Nations last week conceded that the international pact to constrain global temperature rise to 1.5C above pre-industrial levels will be breached in the next few years. The UN said climate impacts such as this summer’s record heatwaves and wildfires would “strike faster, hit harder and last longer.” Current policies put in place by governments are likely to see global temperature rise to 2.6C above pre-industrial times, according to Climate Action Tracker. That would likely cause severe disruption and hardship for billions of people through sea level rise, crop losses and other consequences.

The paper found that action by countries to cut fossil fuel pollution would still lessen the amount of additional emissions from landscapes. Under the most optimistic climate scenario, with emissions cut quickly, natural sources will add 0.2C of warming. Under a worse case with higher emissions, 0.4C will likely be added.

There has been long-standing concern that if global heating melts enough of the Greenland and Antarctic ice sheets, thaws enough permafrost, warps crucial ocean currents and turns the Amazon rainforest into a savannah, the world will pass a series of catastrophic tipping points. A separate study earlier this year warned that the planet is getting closer to such a “point of no return” where runaway global heating becomes reality.

Bill Ripple, an ecologist at Oregon State University who helped author the earlier study on runaway heating and was not involved in the new paper, called the new research “important.” “One of the most troubling aspects of climate change is that warming can trigger natural processes that cause still more warming,” Ripple said. “This does not mean that a Hothouse Earth trajectory is inevitable, but it provides another warning about the possibility of reinforcing feedbacks that can amplify the warming humans initiate.” He added: “The paper also reminds us why every fraction of a degree matters. The more we warm the planet, the more we risk activating natural processes that add still more greenhouse gases to the atmosphere. This makes rapid reductions in fossil fuel emissions even more urgent.”