There are many parts of the climate system that potentially have tipping points (sometimes called “tipping elements“) that scientists are worried about, many of which could affect a lot of people. Here’s some of them:
- Ice sheet collapse
- Many ice sheets (especially in West 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, which could cause a tipping point in ice sheet melting. This could cause a similarly rapid jump in sea levels
- Arctic summer 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. But the loss of Arctic summer sea ice won’t imminently trigger a catastrophic warming – check out our in-depth Fact-Check on the impacts of Arctic sea ice loss for more information
- Gulf Stream slowdown
- Ocean circulation in the North Atlantic (known as the Atlantic Meridional Overturning Circulation, of which the Gulf Stream forms a part) is gradually slowing down as meltwater from Greenland enters the Ocean, and it could pass a tipping point beyond which it slows down even more rapidly. This would mean less warmth for northern Europe as well as higher sea levels in eastern US as water ‘builds up’ there instead of moving north
- Amazon 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 switch to savanna could occur. This would also lead to a large release of carbon that used to be locked up in the rainforest and so could worsen global climate change. But this won’t happen at exactly 3°C and trigger catastrophic warming – it’ll act as a slow feedback making climate change gradually worse. See the “Forests Under Fire” section of this Fact-Check for more information
- Monsoon weakening
- Changing albedo (how much light and heat is reflected by the Earth’s surface) in South Asia could cause a rapid weakening of the Indian Summer Monsoon that could could cause severe droughts across South Asia
- Permafrost / clathrate thawing
- A lot of methane is trapped frozen in seafloor sediments and in permafrosts on land. Global warming could cause these deposits to melt, and beyond a melting tipping point this could become self-perpetuating and release large volumes of greenhouse gases that would further add to global carbon emissions (and then trigger more greenhouse gas release). 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
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.