New research suggests that it may be more difficult to stall the impact of global warming than previously thought and that a simple greenhouse gas emissions reduction may not be enough.
An international team of researchers now believes that it will be difficult to keep global warming to within 1.5-and-2 degrees Celsius, even if the carbon emission reductions mapped out in the Paris Agreement are met.
Scientists warn that the new conclusions show that the planet is at risk to enter “Hothouse Earth” conditions, where the global average temperature in the long-term will stabilize at 4-to-5 degrees Celsius higher than pre-industrial temperatures with sea levels 10-to-60 meters higher than they currently are.
“Human emissions of greenhouse gas are not the sole determinant of temperature on Earth,” lead author Will Steffen from the Australian National University and Stockholm Resilience Centre said in a statement. “Our study suggests that human-induced global warming of 2 degrees Celsius may trigger other Earth system processes, often called ‘feedbacks,’ that can drive further warming—even if we stop emitting greenhouse gases. Avoiding this scenario requires a redirection of human actions from exploitation to stewardship of the Earth system.”
The global average temperatures are currently just over 1 degree Celsius above the pre-industrial levels. Recent studies indicated that temperatures are rising about 0.17 degrees Celsius per decade.
The researchers considered 10 natural feedback processes in the study, including permafrost thaw, the loss of methane hydrates from the ocean floor, the weakening of land and ocean carbon sinks, increasing bacterial respiration in the oceans, Amazon rainforest dieback, boreal forest dieback, a reduction of northern hemisphere snow cover, the loss of Arctic summer sea ice and a reduction of Antarctic sea ice and polar ice sheets.
Some of the feedbacks are considered tipping elements that lead to abrupt change if a critical threshold is ultimately crossed, meaning the feedbacks could go from storing carbon to emitting carbon uncontrollably in warmer climates.
“These tipping elements can potentially act like a row of dominoes,” co-author Johan Rockström, Executive Director of the Stockholm Resilience Centre and incoming co-Director of the Potsdam Institute for Climate Impact Research, said in a statement. “Once one is pushed over, it pushes Earth towards another.
“It may be very difficult or impossible to stop the whole row of dominoes from tumbling over,” he added. “Places on Earth will become uninhabitable if ‘Hothouse Earth’ becomes the reality.”
While the report paints a dire picture, the researchers do suggest a way to reverse course that goes beyond reducing carbon dioxide and other greenhouse gas emissions.
The team suggests the enhancement and creation of new biological carbon stores including improved forest, agricultural and soil management, biodiversity conversation and technologies that remove carbon dioxide from the atmosphere and store it underground in an effort to combat rising temperatures.
The study was published in the Proceedings of the National Academy of Sciences of the United States of America.