Climate Change: Global Warming

Context:

  • 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.