Planet at risk of heading towards irreversible 'hothouse' conditions, new report says

Christopher Davidson
August 7, 2018

If polar ice continues to melt, forests are slashed and greenhouse gases rise to new highs - as they now do each year - the Earth will pass a tipping point.

Feedback mechanisms acting "like a row of dominoes" will then spin the world into a "Hothouse Earth" state of uncontrollable climate change.

"If such a threshold is crossed, the study warns, global average temperatures could climb as much as 8 degrees Fahrenheit above current temperatures and sea levels could rise 30 to 200 feet".

The world is at risk of entering "hothouse" conditions where global average temperatures will be four to five degrees Celcius higher even if emissions reduction targets under a global climate deal are met, according to a new report by top worldwide scientists.

". Many parts of the planet could become uninhabitable for humans", Professor Steffen said.

"A Hothouse Earth trajectory would nearly certainly flood deltaic environments, increase the risk of damage from coastal storms, and eliminate coral the end of this century or earlier", the study says.

Where is the tipping point?

The Earth's global temperature is 1C away from a climatic tipping point that threatens the future of humanity, scientists have warned.

The planet has already warmed 1 C over pre-industrial times, and is heating up at a rate of 0.17 C per decade.

However, it is not clear whether the world's climate can be safely "parked" near 2 C above pre-industrial levels or whether this might trigger other processes which drive further warming even if the world stops emitting greenhouse gases, the research said.

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Scientists from the Stockholm Resilience Center, the University of Copenhagen, Australian National University and the Potsdam Institute for Climate Impact Research have laid bare the consequences of breaching the 2C mark.

Experts also worry about phenomena like wildfires, which will spread as the planet gets hotter and drier and have the potential to accelerate carbon dioxide buildup and global warming.

To state that 2 C is a no-return threshold "is new", said Martin Siegert, co-director of the Grantham Institute at Imperial College London, who was not involved in the study.

The study authors "collated previously published ideas and theories to present a narrative on how the threshold change would work", he said.

"It's rather selective, but not outlandish".

Maximising the chances of avoiding such a hothouse state requires more than just reducing greenhouse gas emissions, the report said.

The tipping point dangers were identified as thawing permafrost, the release of methane trapped on the ocean floor, weakening land and ocean carbon sinks, increased carbon dioxide production by ocean bacteria, Amazon rainforest die-back, coniferous forest die-back, reduced northern hemisphere snow cover, loss of Arctic summer sea ice, reduced Antarctic sea ice and melting polar ice sheets.

Commenting on the findings, Chris Rapley, Professor of Climate Science at University College London said: "Previous research has shown that an increase in the mean global temperature of 11-12C would make more than half of the land area now occupied by humans uninhabitable".

Even if every country that signed on to the Paris climate agreement meets its obligations under the pact and limits the global temperature increase to 3.6 degrees Fahrenheit, runaway global warming could still be a threat, the newspaper reports.

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