Dangerous Climate Tipping Points

CLIMATE TIPPING POINTS

Science Magazine - Exceeding 1.5°C global warming could trigger multiple climate tipping points

Around the world, there are alarming reports of catastrophic floods; extreme drought and heat conditions; unprecedentedly ferocious wildfires; and reduced harvests. An article in the 9/9/22 issue of Science magazine provides some insight into the global dynamics that underlie these widespread impacts. Policymakers, insurance companies, and the financial, manufacturing, healthcare and agricultural sectors should understand what is driving these disrupted patterns and accelerate their action to reach Net Zero and significant carbon drawdown well before 2050.

Climate tipping points are conditions beyond which changes in a part of the climate system become self-perpetuating. These changes may lead to abrupt, irreversible, and dangerous impacts with serious implications for humanity.

They occur when change in large parts of the climate system—known as tipping elements—become self-perpetuating beyond a warming threshold. Triggering CTPs leads to significant, policy-relevant impacts, including substantial sea level rise from collapsing ice sheets, dieback of biodiverse biomes such as the Amazon rainforest or warm-water corals, and carbon release from thawing permafrost”. This paper reviews the original analysis from 2008 and updates the understanding of tipping points and their dynamics with improved models, paleo-climate and real-world data.

“Observations have revealed that parts of the West Antarctic ice sheet may have already passed a tipping point. Potential early warning signals of the Greenland ice sheet, Atlantic Meridional Overturning Circulation (critical to maintaining temperate weather in Europe), and Amazon rainforest destabilization have been detected. Multiple abrupt shifts have been found in climate models. Recent work has suggested that up to 15 tipping elements are now active (Lenton et al., 2019).” These tipping points can interact and intensify the speed of change and impacts.

The authors identified nine global “core” tipping elements which contribute substantially to Earth system functioning and seven regional “impact” tipping elements which contribute substantially to human welfare or have great value as unique features of the Earth system (see figure). Their estimated CTP thresholds have significant implications for climate policy: Current global warming of ∼1.1°C above pre-industrial already lies within the lower end of five CTP uncertainty ranges. Six CTPs become likely (with a further four possible) within the Paris Agreement range of 1.5 to <2°C warmings, including the collapse of the Greenland and West Antarctic ice sheets, die-off of low-latitude coral reefs, and widespread abrupt permafrost thaw. An additional CTP becomes likely and another three possible at the ∼2.6°C of warming expected under current policies.

Key Climate Tipping Points

The location of climate tipping elements in the cryosphere (blue), biosphere (green), and ocean/atmosphere (orange), and global warming levels at which their tipping points will likely be 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).

The authors assessment “provides strong scientific evidence for urgent action to mitigate climate change. We show that even the Paris Agreement goal of limiting warming to well below 2°C and preferably 1.5°C is not safe as 1.5°C and above risks crossing multiple tipping points. Crossing these CTPs can generate positive feedbacks that increase the likelihood of crossing other CTPs. Currently the world is heading toward ∼2 to 3°C of global warming; at best, if all net zero pledges and nationally determined contributions are implemented it could reach just below 2°C. This would lower tipping point risks somewhat but would still be dangerous as it could trigger multiple climate tipping points.”

What does this mean for your business, institution, or community? Policymakers will have to deal with more mass migration, conflict, and other interruptions to normal business operating conditions. This paper does not provide detailed predictions of hazards such as rising sea levels and saltwater intrusion that will result from melting glaciers and Antarctic ice.

Article published in Science Magazine 9/9/2022
D. I. Armstrong McKay et al., Science 377, eabn7950 (2022). DOI: 10.1126/science.abn7950

READ THE FULL ARTICLE AT https://doi.org/10.1126/science.abn7950