Tipping - 232

 If you put a brick or a domino on end you can play with it.  You can push it and sometimes it rocks back and stands upright. Or, if you go a bit too far it will fall over. Or, it may fall onto another brick or domino and you’ve made a mess.

Two hundred columns ago I wrote about, “self-perpetuating feedback loops” which is a fancy way of talking about climate tipping points. If a feedback loop is pushed too far, in our case warms too far, it will continue to warm and disintegrate without our help.

Scientists tell us we have warmed the earth about 1.1 degree C since the beginning of the industrial revolution. The earth has responded to this. Heat waves are more common, droughts more severe, and forest fires start earlier and last longer. Since water expands as it warms the oceans have risen half a foot and some coral reefs have suffered extensive bleaching, (death).  The once thick multiyear year arctic ice has lost 95% of its mass. In one-decade, extreme rainfall events have surged by 50%. These are troubling indicators but these events do not mean the climate is lost.

At what point and in what way to do we measure when we will pass the point of no return.  In other words what are the critical temperature thresholds.

Ten scientists examined 312 research papers, and identified 16 tipping points calculating when global ecosystems will flop and not get up. Currently we have warmed about 1.1 C above preindustrial levels.

Some thresholds are expected to pass the point of no return at 1.5C above preindustrial temperatures or a further warming of .4C.  Some will reach their tipping point at 2 degrees C or a further warming of .9C.  The scientists set the last category of ecosystem tipping points at 4C above preindustrial temperatures. These temperature targets have error bars which means the tipping points may be at a warmer threshold and later, or conversely, could trigger at a lower temperature thus sooner than they set.

Here are the 16 ecosystem tipping points as grouped. Those vulnerable at 1.5 C are the Greenland Ice Sheet. It is expected to collapse irreversibly at 1.5C. The Labrador Sea/Subpolar Gyre will also collapse, and the Low Latitude Coral Reefs will die-off too if we warm .4C more.

At 2 degrees C these ecosystems will reach their threshold from which they will not return: The Amazon Rainforest, most mountain glaciers, the subglacial basins of the East Antarctica.

If we warm to 4C the arctic winter sea ice will be no more, the permafrost below the Northern Boreal Forest will melt. The southern boreal forest will die while the northern fringes will press north. The world’s largest ice sheet, the East Antarctic Ice Sheet, will collapse.

Here is a portion of the scientists’ conclusions:

“A significant likelihood of passing multiple climate tipping points exists above ~1.5°C, particularly in major ice sheets. The tipping point likelihood increases further in the Paris range of 1.5 to <2°C warming. Current policies leading to ~2 to 3°C warming are unsafe because they would likely trigger multiple climate tipping points. Our updated assessment of climate tipping points provides strong scientific support for the Paris Agreement and associated efforts to limit global warming to 1.5°C.”

While we can take satisfaction the current American administration is countering the greenhouse effect with the Whitehouse effect, it is obvious we must be vigilant. In fact, we must double our efforts nationally and internationally.

If humanity misses a tipping point because we haven’t run hard and diligently enough, we do not get to rerun the race. Each tipping point, when passed, is irreversible.

AAAS Science Magazine 9Sep 2022 “Exceeding 1.5C global warming could trigger multiple climate tipping points”

https://doi.org/10.1126/science.abn7950