As world warms, multiple ‘climate tipping points’ set to be triggered — and some may already have

The effects of climate change have been progressively getting more aggressive and frequent over the past few decades.

Victims of flooding from monsoon rains carry grasses for their cattle after their flooded home in Sehwan, Sindh province, Pakistan. Scientists worried about consequences of a 1.5 °C temperature rise. | Photo Credit: AP

Floods in Assam, Bangladesh, Pakistan and Australia; drought and wildfire in California, China and southern Europe; tornadoes in the USA. Extreme weather conditions have been constantly in the news from the beginning of the year.

Now, a study published in the Science journal has stated that a rise of 1.5 from pre-industrial levels can trigger multiple climate tipping points. In fact, observations have shown that parts of the West Antarctic ice sheet, an important marker, may have already passed the tipping point. 

Climate tipping points or CTPs are markers of a larger climate system which when triggered beyond a threshold, perpetuate warming on its own. Some CTPs triggers include substantial sea level rise from melting ice sheets, shrinking of Amazon rainforest or corals and warming from carbon release due to melting of permafrost. 

The scientists did a comprehensive review of the previously-identified 9 tipping elements and reassessed suggested CTPs and their corresponding timescale and impacts of tipping. They increased the lists of potential tipping points from 9 to include other possible tipping points we might be facing. 

The study has revealed that human emissions have already pushed the tipping points to dangerous levels. Though the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) had stated that a rise of 2 °C from pre-industrial levels can trigger the tipping points and become irreversible at 2.5-4 °C, even the current 1 °C rise from pre-industrial levels has triggered some tipping points which are now unavoidable.

In an email to The Hindu, the lead author of the study, David Armstrong McKay, said: “What really stood out is just how many tipping points are already looking possible even at today’s warming and could become likely within the Paris Agreement range. That’s really worrying, and underlines just how important striving to keep to the Paris Agreement aim of 1.5 °C is.”

As a result, the goal of UN’s Paris Agreement to limit warming at 1.5-2 °C will not be able to avoid the disastrous effects of climate change and will likely trigger some climate tipping points. “We can’t rule out tipping points being passed even at 1.5 °C, meaning that even this isn’t really a safe level of warming, but it does limit the damage more than closer to 2 °C,” he said. 

With just a few tenths of a degree more, triggering new tipping points could become more plausible. For instance, a major tipping point would be if ocean convection in the Labrador and Irminger Seas in the North Atlantic were to collapse (likely beyond 1.8 °C), which would cause major regional cooling, drive weather extremes in Europe and North America, and also shift subtropical monsoon patterns to new positions, especially in West Africa, said Mr. Mckay.

In case of a dangerous 4 °C rise, the wider Atlantic Meridional Overturning Circulation will collapse which would severely disrupt monsoon systems around the world. There’ll also be significant changes around the Arctic, as declining sea ice and abrupt shifts in the boreal forest position amplify Arctic warming and create very different weather patterns, he added.

According to the scientists, melting ice sheets can take centuries to reshape coastlines, however, sensitive coral reefs have “immediate impacts of human livelihoods”. Poorer sections of the society , especially those who make a living from fishing will be drastically affected.

“Current international policies are projected to result in 2.6 °C of warming by 2100 , which would make multiple damaging climate tipping points likely, which underlines the importance of increasing climate action around the world to make recent net-zero promises a reality,” Mr. McKay said.

While some might see this as ‘game over’ for the climate, Mr. McKay points out that fraction of a degree of warming avoided by emission cuts reduces the likelihood of passing more tipping points. Additionally, the tipping points triggered at 1.5 °C will not prompt ‘some sort of runaway climate change process’.

“The faster we can make greenhouse gas emissions peak and fall, the more likely it is we can avoid triggering multiple climate tipping points and limit future climate damages,” he said.

Published - September 13, 2022 11:03 am IST