There are many parts of the climate system (referred to as “tipping elements“) that potentially have tipping points that scientists are worried about, which could affect hundreds of millions of people. Here’s some of them:
West Antarctic ice sheet collapse
Some ice sheets, including in West Antarctica and some basins in East Antarctica, are grounded at sea on prominent underwater ridges. Once warming seas melt the ice past these ridges these ice sheets can be melted from underneath as well as from the top and sides. This could cause a tipping point in ice sheet melting, and lock in substantial future sea level rise
Arctic sea ice loss
As described in ‘What are Climate Tipping Points?‘, less sea ice due to warming results in a darker sea surface overall, which reflects less heat, raises local temperatures, and leads to yet more sea ice loss and warming. This would cause warming to happen far faster in the Arctic than anywhere else, and it’s been suggested that this could cause stranger weather elsewhere by affecting the jet stream. The loss of Arctic summer sea ice was previously thought to be a key climate tipping point, but more recent research suggests only Arctic winter sea ice might tip. The loss of Arctic summer sea ice won’t imminently trigger catastrophic warming either – check out our in-depth Fact-Check on the impacts of Arctic sea ice loss for more information
Permafrost / clathrate thawing
A lot of carbon is trapped frozen in seafloor sediments and in permafrost on land. Global warming could cause these deposits to thaw, and beyond a tipping point this could become self-perpetuating and release large volumes of greenhouse gases that would further add to global carbon emissions. However, it is estimated that a lot more warming is needed to trigger this tipping point, and in the meantime it will act more as a gradual positive feedback
Amazon rainforest dieback
Decreasing rainfall could push the Amazon rainforest past a tipping point beyond which the rainforest ecosystem can no longer be maintained and a rapid dieback to a savannah-like state could occur. This would also lead to a large release of carbon that used to be locked up in the rainforest and so worsen global climate change. But this won’t happen at exactly 3°C and trigger catastrophic warming – see the “Forests Under Fire” section of this Fact-Check for more information
North Atlantic circulation slowdown
Ocean circulation in the North Atlantic (known as the Atlantic Meridional Overturning Circulation, to which the Gulf Stream is linked) is gradually slowing down as surface water warming and meltwater from Greenland makes seawater less dense, and it could pass a tipping point beyond which circulation here collapses. This would mean less warmth for Europe, disrupted weather around the North Atlantic and for tropical monsoons, and higher sea levels in eastern US as water ‘builds up’ there instead of moving north
Changing albedo (how much light and heat is reflected by the Earth’s surface) due to air pollution in South Asia could cause a rapid weakening of the Indian Summer Monsoon that could could cause severe droughts across South Asia. However, climate change might actually strengthen the monsoon, making this tipping point complicated
Some scientists have also hypothesised that some of these tipping points could trigger each other in a cascading domino effect, leading to a global warming being amplified towards a ‘Hothouse Earth’ state, This is uncertain though, and is now the subject of ongoing research to see if this could actually happen.
It is critical to try and predict when we might reach these tipping points so that we can try and avoid them – visit ‘Can we predict Climate Tipping Points?‘ to find out how scientists are trying to do this.
Updated on: 17/4/2019 and thereafter with new links to Fact-Check articles exploring these tipping elements in more depth; 8/8/19 with extra maps and Hothouse Earth mention; 3/11/22 starting update with more information and tipping points.