Our planet is at the risk of entering an irreversible ‘hothouse’ condition – where the global temperatures will rise by four to five degrees and sea levels may surge by up to 60 meters higher than today – even if targets under the Paris climate deal are met, a study warns.
According to the researchers, keeping global warming to within 1.5-2 degrees Celsius may be more difficult than previously assessed.
A team of scientists showed that even if the carbon emission reductions called for in the Paris Agreement are met, there is a risk of Earth entering what the scientists call “Hothouse Earth” conditions. A “Hothouse Earth” climate will in the long-term stabilize at a global average of 4-5 degrees Celsius higher than pre-industrial temperatures with sea level 10-60 meters higher than today, according to the study. Currently, global average temperatures are just over 1 degree Celsius above pre-industrial and rising at 0.17 degree Celsius per decade.
The study considers ten natural feedback processes, some of which are “tipping elements” that lead to abrupt change if a critical threshold is crossed. These feedbacks could turn from being a “friend” that stores carbon into a “foe” that emits it uncontrollably in a warmer world. These feedbacks include permafrost thaw, loss of methane hydrates from the ocean floor, weakening land and ocean carbon sinks, increasing bacterial respiration in the oceans, Amazon rainforest dieback, boreal forest dieback, reduction of northern hemisphere snow cover, loss of Arctic summer sea ice, and reduction of Antarctic sea ice and polar ice sheets.
Maximising the chances of avoiding a “Hothouse Earth” requires not only reduction of carbon dioxide and other greenhouse gas emissions but also enhancement and creation of new biological carbon stores through an improved forest, agricultural and soil management, and technologies that remove carbon dioxide from the atmosphere and store it underground, researchers said.