According to recent study, earth is at the risk of entering an irreversible hothouse condition – where the global temperatures will rise by four to five degrees even if targets under 2015 Paris climate deal are met. Hothouse Earth climate will in long-term stabilise at global average of 4-5 degrees Celsius higher than pre-industrial temperatures with sea level 10-60 metres higher than today.
Key Highlights of Study
Currently, global average temperatures are just over 1 degree Celsius above pre-industrial and rising at 0.17 degree Celsius per decade. Keeping global warming to within 1.5-2 degrees Celsius as agreed in 2015 Paris climate agreement by around 200 countries may be more difficult than previously assessed.
Human-induced global warming of two degrees Celsius may trigger other Earth system processes often called feedbacks that can drive further warming even if greenhouse gases emissions are stopped. Avoiding this scenario will require redirection of human actions from exploitation to stewardship of Earth system.
The study consider ten natural feedback processes, some of which are tipping elements that lead to abrupt change if critical threshold is crossed. These feedbacks can turn from being friend that stores carbon to foe that emits it uncontrollably in warmer world.
These feedbacks include permafrost thaw, weakening land and ocean carbon sinks, loss of methane hydrates from ocean floor, increasing bacterial respiration in oceans, boreal forest dieback, Amazon rainforest dieback, reduction of northern hemisphere snow cover, loss of Arctic summer sea ice and reduction of Antarctic sea ice and polar ice sheets. These feedbacks tipping elements can potentially act like row of dominoes. Once one is pushed over, it pushes Earth towards another.