Nine tipping points now 'active' in cascade of changes sparked by global warming, say experts

In a commentary published this week, a group of scientists has issued a stark warning that over half the tipping points identified a decade ago to mark climate change progression are now "active". Under threat from these changes are the Amazon rainforest, and large sheets of ice in Greenland and Antarctica — ecosystems that are already seeing massive, unprecedented changes sooner than experts predicted.

These now-active tipping points, in their observation, are:

Arctic sea ice
Greenland ice sheet
Boreal forests
Permafrost
Atlantic Meridional Overturning Circulation
Amazon rainforest
Warm-water corals
West Antarctic Ice Sheet
Parts of East Antarctica

The ongoing "cascade" of changes sparked by global warming could threaten the existence of human civilizations, as per the study, which was published in Nature on 27 November. In their collective view, the evidence is mounting that these events are more likely and more interconnected than experts previously thought, which could create a potential domino effect.

"We must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming," Johan Rockström from the Potsdam Institute for Climate Impact Research, according to SciTechDaily. The comment's authors have called for urgent action, specifically, a dramatic reduction in greenhouse gas emissions to avoid any more tipping points or warnings of a "hothouse"-like worst-case scenario — a less habitable planet.

"A decade ago we identified a suite of potential tipping points in the Earth system, now we see evidence that over half of them have been activated," lead author Professor Tim Lenton, director of the Global Systems Institute at the University of Exeter, said. "The growing threat of rapid, irreversible changes means it is no longer responsible to wait and see. The situation is urgent and we need an emergency response."

The comment doesn't just dwell on anthropogenic emissions or human causes of warming. Instead, it assesses the tipping points

"...as science advances, we must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming. This is what we now start seeing, already at 1 degree Celcius warming," Rockström said. Many of these changes are apparent already, the study adds, with the current one-degree Celcius of warming.

The authors also cite tipping points to draw attention to the mounting evidence that a state of 'planetary emergency' needs to be declared. This, so that world accelerates down the path towards a stable planet, and a sustainable emissions profile, the comment suggests. The authors also reckon that the data they reviewed for the comment is strong enough evidence to declare a planetary emergency today.

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