‘Earth at risk of tipping into hellish hothouse conditions’

NEW YORK. — 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 international scientists.

The new study was published in the US Proceedings of the National Academy of Sciences (PNAS) on Monday.

It said it is likely that if a critical threshold is crossed, several tipping points will lead to abrupt change.

Such processes include permafrost thaw; the loss of methane hydrates from the ocean floor; weaker land and ocean carbon sinks; the loss of Arctic summer sea ice and the reduction of Antarctic sea ice and polar ice sheets, said the report.

“These tipping elements can potentially act like a row of dominoes. Once one is pushed over, it pushes Earth towards another,” said Johan Rockstrom, co-author of the report and executive director of the Stockholm Resilience Centre.

“It may be very difficult or impossible to stop the whole row of dominoes from tumbling over. Places on Earth will become uninhabitable if ‘Hothouse Earth’ becomes the reality,” he added.

Some experts said uncontrolled warming is still uncertain, but not implausible [Reuters]

Scientists from the Stockholm Resilience Centre, the University of Copenhagen, Australian National University and the Potsdam Institute for Climate Impact Research worked on the study.

They said that “Hothouse Earth” is likely to be dangerous to many and uncontrollable.

Rivers would flood, storms would wreak havoc on coastal communities and coral reefs would be eliminated - all by century’s end or even earlier.

Global average temperatures would exceed those of any interglacial period — meaning warmer eras that come in between Ice Ages — of the past 1.2m years. Melting polar ice caps would lead to dramatically higher sea levels, flooding coastal land that is home to hundreds of millions of people.

A 2015 Paris climate agreement aimed to keep global warming below 2 degrees Celcius, compared with pre-industrial levels. But according to the report, the risk of tipping cascades could be significant at a 2C temperature rise — and could increase sharply beyond that point.

“This cascade of events may tip the entire Earth system into a new mode of operation,” warned co-author Hans Joachim Schellnhuber, Director of the Potsdam Institute for Climate Impact Research.

The “carrying capacity” of a 4C or 5C degree world, he has said previously, could drop to a billion people. — Al Jazeera.