Even if we are able to limit future warming, we will still have to deal with triggering four climate-tipping points if we can’t keep that global temperature below 1.5 degrees Celsius.
A new study published in Science on September 9, 2022, is the latest and most comprehensive evidence indicating that countries must enact policies to meet the temperature targets set by the 2015 Paris Climate agreement if humanity hopes to avoid potentially catastrophic sea level rise and other worldwide harms.
So what is a climate-tipping point? A climate-tipping point is a critical threshold that, when crossed, leads to large and often irreversible changes in the climate system.
An international team of scientists looked at 16 climate tipping points — when a warming side effect is irreversible, self-perpetuating, and major — and calculated rough temperature thresholds at which they are triggered.
Pins are colored according to our central global warming threshold estimate being below 2°C, i.e., within the Paris Agreement range (light orange, circles); between 2 and 4°C, i.e., accessible with current policies (orange, diamonds); and 4°C and above (red, triangles). Study published in Science on September 9, 2022,
None of them are considered likely at current temperatures, though a few are possible. But with only a few more tenths of a degree of warming from now, at 1.5 degrees Celsius (2.7 degrees Fahrenheit) warming since pre-industrial times, four move into the likely range, according to the study.
Besides the Greenland and West Antarctic Ice sheets – a more immediate loss of tropical coral reefs around the globe and thawing of Arctic permafrost that releases massive amounts of greenhouse gases trapped in now frozen land are four significant tipping points that could be triggered at 1.5 degrees Celsius of warming, which is three-tenths of a degree (half a degree Fahrenheit) warmer than now.
The new study makes it clear that every tenth of a degree of warming that is avoided will have huge, long-term benefits. For example, the enormous ice sheets in Greenland and Antarctica are already melting rapidly, adding enormous amounts of fresh water to the ocean and driving global sea level rise.
This means that the tipping point falls somewhere around 1.5 degrees Celsius of warming. The hotter the Earth gets, the more likely it is to trigger runaway ice loss. But keeping average global temperatures from rising less than 1.5 degrees Celsius reduces the risk of such loss.
Of course, if the Greenland and Antarctica ice sheets both melted – the sea level would rise at least 30 feet, but that will take several hundred years. But climate scientists who study the ice sheets warn that dangerous sea level rise will occur even sooner, and potentially before it’s clear that ice sheets have reached a tipping point.
“Let’s hope we’re not right,” said study co-author Tim Lenton, an Earth systems scientist at the University of Exeter in the United Kingdom. “There’s a distinct chance some of these tipping points are going to be unavoidable. And therefore it’s really important we do some more thinking about how we’re going to adapt to the consequences.”
