Much of the analysis regarding climate security has been focused on either impacts which are already being felt or those which are in line with conservative estimates of climate change. The concept of tipping points in the global climate which would cause irreversible changes has often been dismissed as being of low probability or ill understood. However, new research shows that these tipping points may be closer than we think and are perhaps already unfolding. This solidifies the sense of climate emergency.
The Intergovernmental Panel on Climate Change (IPCC) first introduced the concept of tipping points two decades ago with the belief that these phenomena would only be likely if global warming exceeded 5°C above preindustrial levels. Now, the IPCC suggests that these tipping points could be exceeded between 1-2°C of warming. If current government pledges to reduce emissions are put into practice this will result in 3°C of warming, the world is already 1.2°C warmer than pre-industrial times. Scientists suggest that it is imperative to limit warming to 1.5°C if we are to stand a decent chance of not triggering climate runaway effects.
So, what are these tipping points? In a comment piece in Nature, scientists identify the three most important ones as ice collapse, biosphere destruction and the oceanic currents.
Ice Collapse
The West-Antarctic ice sheet may already have reached a tipping point. Rising ocean temperatures mean that the “grounding line” where ice, ocean and bedrock meet is retreating rapidly in the West-Amundsen embayment. For example, the Thwaites glacier, which contains enough freshwater in it to raise world sea levels by half a metre, is especially at risk. Global warming has already increased the so called “ice pump” process of melting by up to 100 times, meaning the Thwaites glacier is already responsible for 4% of global sea level rise. The real risk of a tipping point lies in the fact that Thwaites, and most of the West-Antarctic ice sheet, is only supported by the grounding line and extends far out to sea. If the grounding line retreats far enough the overhanging ice sheet could collapse and force sea levels up. If the whole ice sheet collapses, the global sea level could rise by more than 3 metres. Although this process could take centuries, the possibility exists for sea rises of 1-2 metres by the end of the century. This would not only displace millions of people living in low lying areas but also hugely increase the damaging effect of storm surges. Quite apart from the devastating impact on human security, climate security would undoubtedly be threatened in manifold ways as a result. Worryingly, the Wilkes Basin in East Antarctica and the Greenland ice sheet could be threatened by similar effects, together holding the potential for over 10 metres of sea level rise.
Biosphere Collapse
The Amazon is the world’s largest rainforest, holding 10% of all known species. As a rainforest, it generates its own rainfall by a process known as evapotranspiration where water exhaled from the leaves forms clouds which then create rain. This self-sustaining system is at risk from wide-scale deforestation and human caused fires. Already, NASA satellites are picking up a decrease in the moisture over the Amazon, causing an increased drought risk. The tipping point here is the level of forest loss which will result in the death of this self-sustaining system and the die back of the Amazon rainforest to be replaced with a dry savanna. Scientists estimate this level at between 20-40% of forest loss. Since 1970, 17% of the rainforest has already been lost, meaning we may be close already. Indeed, recent studies show that areas of the Amazon are already dying off. If the Amazon is lost, 100 billion tons of sequestered carbon will be released into the atmosphere, three times the amount of carbon released each year by burning fossil fuels. Boreal forest in the arctic is also dying as a result of large-scale fires and insect infestations. Permafrost in the Arctic is already thawing and causing the release of methane, which is 30 times more potent a greenhouse gas than carbon dioxide. Scientists have calculated that for a 50/50 chance at keeping warming at 1.5°C, we can only release 500 Gigatonnes (Gt) more of carbon into the atmosphere. Together, the Amazon rainforest’s dieback, boreal forest death and permafrost melt emissions could release 300 Gt of carbon dioxide. This means we could have far less time than we think to reach this temperature increase.
Oceanic Currents
The Gulf Stream is common parlance for an Atlantic Ocean current which carries hot water from the tropics to the Poles and so balances out unequal heating from the Sun. This vital process is now at risk from the ice melt, especially in Greenland, which is now 6 times faster than it was in the early 1990s. This causes havoc with the vertical motion of the current which drives its movement, as the freshwater from ice melt prevents the cold water from sinking. In fact, one study estimates that it could already slowed 15% since the 1950s already. The disintegration of the Greenland ice sheet and the changes in the current are happening far more quickly than expected, leading some to fear that a collapse of the current may be possible. If this happened, then weather patterns would be disrupted, and the negative impacta of extreme weather would increase. For example, the West African monsoon would be disrupted, potentially causing severe drought in the Sahel.
Cascading Effects
Unfortunately, many of these tipping points could spark a cascade of other tipping points. Research has analysed the risk and found possible links between 45% of interactions between system tipping points. Although much of the work around tipping points is limited due to problems with data and understanding it is clear that even a slight risk of these points being reached is worth a response. Lenton and his team emphasize that the past way to do this is by keeping global warming at or below 1.5°C from pre-industrial levels. Research also shows that some tipping points can be exceeded for a short time before becoming irreversible, giving more hope for the goal of eventually stabilising below 1.5°C of warming.
Climate Security
A few of the implications of these tipping points for climate security have already been mentioned above. A collapse of the ice sheets could cause a sea level rise that sparked migration in the tens to hundreds of millions, causing a risk of conflict in many areas of the world. The fast change of oceanic currents, which regulate weather systems, could be disastrous for those areas of the world which already face conflict as a result of drought or livelihood stress (e.g. the Sahel). A yet more frightening prospect is the possibility of a cascade of tipping points which overwhelms adaptive capacity in large parts of the world. Some already forecast displacement as high as 1 billion people by 2050. A cascade like this could potentially even impact those areas of the world were adaptive capacity is high, like Europe. The impact on climate security of tipping points is likely to be catastrophic, but the exact details depend on too many factors to speculate at length.
This article was mainly based off this Nature and this CBS article, along with the other references linked
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