Climate domino effects risk pushing Earth into ‘hothouse’ state

The Earth could enter ‘hothouse’ conditions due to climate issues including Amazon rainforest dieback, reduction of northern hemisphere snow cover and loss of polar ice sheets – even if carbon emission reductions are met. 

Even if the carbon emission reductions called for in the Paris Agreement are met, there is a risk of the planet entering what scientists call ‘hothouse Earth’ conditions.

Under these conditions, the Earth’s climate will in the long term stabilize at a global average of 4 to 5 degrees Celsius higher than pre-industrial temperatures, with the sea level 10 to 60 metres higher than today.

These are the findings of a paper published by an international team of scientists working with the Stockholm Resilience Centre, which concluded it is “now urgent to greatly accelerate the transition towards an emission-free world economy”.

“Human emissions of greenhouse gas are not the sole determinant of temperature on Earth. Our study suggests that human-induced global warming of 2°C may trigger other Earth system processes, often called ‘feedbacks’ that can drive further warming – even if we stop emitting greenhouse gases,” explained lead author Will Steffen in a statement.

The study considers 10 natural feedback processes, some of which are “tipping elements” that lead to abrupt change if a critical threshold is crossed and could turn from storing carbon to emitting it uncontrollably.

Among them are permafrost thaw, weakening land and ocean carbon sinks, increasing bacterial respiration in the oceans, Amazon rainforest dieback, reduction of northern hemisphere snow cover and reduction of Antarctic sea ice and polar ice sheets.

“These tipping elements can potentially act like a row of dominoes. Once one is pushed over, it pushes Earth towards another. Places on Earth will become uninhabitable if ‘Hothouse Earth’ becomes the reality,” added co-author Johan Rockström.

Maximizing the chances of avoiding a “Hothouse Earth” requires not only reduction of carbon dioxide and other greenhouse gas emissions but also the enhancement or creation of new biological carbon stores, concluded the statement.

Photo credit: Liam Moloney/ CC BY-SA 2.0

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