A team of researchers has published a list of possible "tipping points" indicating when climate changes could pass a "critical threshold at which a small change in human activity can have a large, long-term consequence for the Earth's climate system."
As opposed the gradual, long-term warming trend, such a tipping point could accelerate or change the effects already being perceived due to global warming: More intense storms, more flooding, more intense drought, more heat waves, a longer growing season, etc.
The researchers identified nine possible tipping points, the worst-case timeframe in which they might "tip," and the degree to which they are sensitive to Seven could occur this century. While some of the tipping points identified are widely discussed, the timeframe suggested by these researchers may be more quick than other scientists believe, and they acknowledge high degrees of uncertainty.
Here are the nine potential tipping points:
The Indian summer monsoon, which is needed to sustain crops, could collapse anytime as land-to-ocean pressure gradients change with pollution and warming patterns. That could lead to an "erratic" fluctuation that would "chaotically change between an active and a weak phase." This is considered an "intermediately sensitive" tipping point with large uncertainty.
Arctic sea ice, which reached its lowest known extent in the summer of 2007, could disappear completely in summer within a decade or so, as the open water absorbs more heat from the sun than is reflected by white ice. This is considered a "highly sensitive" tipping point with low uncertainty.
The Sahara and Sahel in Africa could change dramatically, becoming either far more dry or far more wet, as ocean temperature and vegetation-climate feedbacks change within a decade or so. This is considered an "intermediately sensitive" tipping point with large uncertainty.
The Amazon rainforest could dieback significantly within 50 years due to a combination of deforestation and global warming, which could trigger a 30% decrease in rainfall. This is considered an "intermediately sensitive" tipping point with large uncertainty.
The Boreal Forest, which rings the northern latitudes and provides habitat for migratory bird species and other wildlife, could die back within 50 years as trees succumb to summer heat stress, increased diseases and other threats. This is considered an "intermediately sensitive" tipping point with large uncertainty.
the Atlantic thermohaline circulation, which ensures the Gulf Stream warmth reaches Europe, could collapse within 100 years as warming of the oceans alters water density and disrupts the global circulation of the seas. This is considered a "lowly sensitive" tipping point, with intermediate uncertainty.
The El Nino Southern Oscillation, which refers to patterns of warming and cooling in the Pacific Ocean that affect weather worldwide, could within 100 years change to a persistent warm or cool pattern, or change so that warm El Nino patterns are more intense, leading to more intense droughts in some area, and likelihood of flooding elsewhere. This is considered an "intermediately sensitive" tipping point with large uncertainty.
The Greenland ice sheet could decay within 300 years as cycles of degradation and regrowth tip toward melting within 300 years or more. This could lead to a rise in sea levels of more than 20 feet. This is considered a "highly sensitive" tipping point with low uncertainty.
The West Antarctic ice sheet could collapse within 300 years, leading to a sea level rise of as much as 15 feet worldwide. This is considered an "intermediately sensitive" tipping point with large uncertainty.
Society must not be lulled into a false sense of security by smooth projections of global change, said Tim Lenton of the University of East Anglia, the lead author of the research, published in the Proceedings of the National Academy of Science. Our findings suggest that a variety of tipping elements could reach their critical point within this century under human-induced climate change. The greatest threats are tipping of the Arctic sea-ice and the Greenland ice sheet, and at least five other elements could surprise us by exhibiting a nearby tipping point.
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