Earth 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 metres higher than today – even if targets under the Paris climate deal are met
According to the researchers, keeping global warming to within 1.5-2 degrees Celsius may be more difficult than previously assessed.
The study suggests that human-induced global warming of two degrees Celsius may trigger other Earth system processes, often called “feedbacks,” that can drive further warming – even if we stop emitting greenhouse gases .
The feedbacks include loss of permafrost, Arctic summer sea ice and Antarctic ice sheets, as well as dieback of Amazon and boreal forests and increased bacterial respiration in the oceans
What is Hothouse Earth?
A planet that has passed a “tipping point” beyond which its own natural processes trigger uncontrollable warming.
In other words it is a term used to describe a scenario in which human activity causes a higher global temperature than at any time during the past 1.2 million years, due to a breakdown in the feedback loops that regulate the planet’s temperature.
Reasons and Trigger Points
Weakening Carbon Sinks
Forests, oceans and permafrost currently do us a great service by storing carbon. As rising temperatures cause these carbon “sinks” to weaken, some will actually start to emit more greenhouse gases into the atmosphere.
Global warming of 3 ° C could condemn 40% of the Amazon forests to dieback.
Accidental or land-clearing fires — not accounted for in these models — could hasten this destruction.
In Canada, forests that gained CO2-absorbing biomass for most of the 20th century began to lose it around 1970, due mainly to climate-related insect infestations and fires.
Taken together, these forest die-offs would release billions of tonnes of carbon into the air.
Less snow, more heat
Dramatically shrinking polar sea ice, especially in the Arctic, means the deep blue ocean water that takes its place absorbs as much of the sun’s radiative force — about 80% — as was reflected back into space by snow’s mirror-like surface.
The Arctic will likely see its first ice-free summer before mid-century.
Over the last four decades, minimum sea ice extent has dropped by about 40%.
Two-thirds of the world’s megacities are less than 10 metres about sea level, and so is much of the agricultural land that feeds them. Together, West Antarctica’s and Greenland’s frozen reservoirs would lift ocean levels by 13 metres.
Another 12 metres of potential sea level rise is locked in parts of the East Antarctic Ice Sheet that is far more susceptible to climate change than once thought.
All of these processes are interconnected, and the collapse of one could trigger another.
What will happen?
If this happens then there are chances that
- Sea levels increasing by 33 to 300 feet (10 to 60 meters)
- Temperatures increasing by 7 to 9 degrees F (4 to 5 C) worldwide
- Humans, unable to live near the equator, forced to migrate to both the North and South poles to survive.
- Fossil fuels must be replaced with low or zero emissions energy sources.
- There should be more strategies for absorbing carbon emissions such as ending deforestation and planting trees to absorb carbon dioxide.
- Soil management, better farming practices, land and coastal conservation and carbon capture technologies are also on the list of actions.