User:Abuley34/Tipping points in the climate system

Amazon rainforest dieback ///*** Title probably needs a proper wording***///
See also: Deforestation of the Amazon rainforest and Climate change in Brazil

The Amazon rainforest is the largest tropical rainforest in the world. It is twice the size of India and spans nine countries in South America. It generates around half of its own rainfall by recycling moisture through evaporation and transpiration as air moves across the forest.

Deforestation of the Amazon began in the 1960s. Slash and burn techniques were used to establish farms in order to cultivate crops. However, soils in the Amazon are only productive for a short period after the land is cleared, so farmers would simply move and clear more land. Other colonists cleared land to raise cattle, leading to further deforestation and environmental damage. Heatwaves and drought have now become a factor driving additional tree deaths. This indicates that the Amazon is experiencing climatic conditions beyond its adaptive limits.

In 2021, the first long-term study of greenhouse gases in the Amazon rainforest found that in the 2010s the rainforest released more carbon dioxide than it absorbed. The forest had previously been a carbon sink, but is now emitting a billion tonnes of carbon dioxide a year. Deforestation has led to fewer trees which means more severe droughts and heatwaves develop leading to more tree deaths and more fires. ///***These last two sentences have contradicting purposes in this article, probably focus on how loosing The Amazon forest could take years to get it back or find alternative sinks of the same capacity ***///

Permafrost and methane hydrates
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As the climate warms and the permafrost begins to thaw, carbon dioxide and methane are released into the atmosphere. Research conducted by the US National Oceanic and Atmospheric Administration (NOAA) in 2019 found that thawing permafrost across the Arctic “could be releasing an estimated 300-600m tonnes of net carbon per year to the atmosphere”. ///*** HERE, add sentence that shows this as a percentage of total natural emissions, human emissions, and total emissions to give more context ***/// In a Special Report on the Ocean and Cryosphere in a Changing Climate, the IPCC says there is “high confidence” in projections of “widespread disappearance of Arctic near-surface permafrost this century" which is "projected to release 10s to 100s of billions of tonnes [or gigatonnes, GtC], up to as much as 240 GtC, of permafrost carbon as CO2 and methane into the atmosphere".

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West African monsoon shift
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See also: Monsoon § Africa (West African and Southeast African)

The West African Monsoon (WAM) system brings rainfall to West Africa and is the main source of rainfall in the agriculturally based region of the Sahel, an area of semi-arid grassland between the Sahara desert to the north and tropical rainforests to the south. The monsoon is a complex system in which land, ocean and atmosphere are connected is such a way that the wind direction reverses with the seasons '''///*** This seems suspicious. Someone please verify this last statement. ***///'''.

However, the monsoon is notoriously unreliable. Between the late 1960s and 1980s, the average rainfall declined by more than 30% plunging the region into an extended drought. This led to a famine that killed tens of thousands of people and triggered an international aid effort. Research has shown the drought was largely due to changes in the surface temperatures of the global oceans, in particular, warming of the tropical oceans in response to rising greenhouse gases combined with cooling in the North Atlantic as a result of air pollution from northern hemisphere countries. '''///*** This is attached to a citation. I do not think that this sentence accurately represents the cited information. ***///'''

Arctic sea ice
The IPCC finds that Arctic sea ice loss does not represent a tipping point because “projected losses are potentially reversible”. This depends on the time scale. Arctic sea ice has been melting rapidly for several decades. Some climate scientists describe the Arctic as a tipping element. '''///*** This is poorly written. The sentences do not flow and the information is sparse. Perhaps we add stuff here. ***///'''

Tipping point effects
See also: Effects of climate change

If the climate tips into a state where tipping points begin to cascade, coastal storms will have greater impact, hundreds of millions of people will be displaced by rising sea levels, there will be food and water shortages, and people will die from unhealthy heat levels and generally unlivable conditions. Climatologist Michael E. Mann, believes a global temperature increase of 3 degrees Celsius or more has the potential to trigger collapse of the current societal organization and set the stage for massive unrest and global conflict – bearing in mind the IPCC describes a high probability that tipping points will occur at temperatures above 2 degrees C of global warming. '''///*** This is a 2-sentence paragraph. Make it flow better and break it up. ***///'''

If cascading tipping points lead to climate temperature increases of 4–5 °C, this will make swaths of the planet around the equator uninhabitable, and lead to sea levels up to 60 metres (197 ft) higher than they are today. Humans cannot survive if the air is too moist and hot, and billions of people may die.[citation needed] Hans Joachim Schellnhuber, Director of the Potsdam Institute for Climate Impact Research says if the world warms by this amount, it could only sustain about one billion people. '''///*** That is quite the bold claim. We should either find a citation for that or correct that sentence to something that is probably less drastic but is supported by some scientific finding. ***///'''

A 2021 meta study, conducted by Simon Dietz, James Rising, Thomas Stoerk, and Gernot Wagner, on the potential economic impact of tipping points found that they raise global risk; the medium estimate was that they increase the social cost of carbon (SCC) by about 25%, with a 10% chance of tipping points more than doubling the SCC. Effects like these have been popularized in books like The Uninhabitable Earth and The End of Nature.

Early warning signals
For tipping points that occur because of a bifurcation, it may be possible to detect whether they are getting closer to a tipping point, as the system is getting less resilient to perturbations on approach of the tipping threshold. These systems display critical slowing down, with an increased memory (rising autocorrelation) and variance. Depending on the nature of the tipping system, changes may also be detected in the skewness and kurtosis of time series of relevant variables, with asymmetries in the distributions of anomalies indicating that tipping may be close. Abrupt change is not an early warning signal (EWS) for tipping points, as abrupt change can also occur if the changes are reversible to the control parameter.

These EWSs are often developed and tested using time series from the paleorecord, like sediments, ice caps, and tree rings, where past examples of tipping can be observed. It is not always possible to say whether increased variance and autocorrelation is a precursor to tipping, or caused by internal variability, for instance in the case of the collapse of the AMOC. Quality limitations of paleodata further complicate the development of EWSs. They have been developed for detecting tipping due to drought in forests in California, the Pine Island Glacier in West Antarctica, among other systems. Using early warning signals (increased autocorrelation and variance of the melt rate time series), it has been suggested that the Greenland ice sheet is currently losing resilience, consistent with modelled early warning signals of the ice sheet.

However because the temperature is increasing so quickly there may be no warning.

'''///*** Ack. It hurt my brain to read this. It should be reorganized and rewritten, I think. I am not sure what the point of those paragraphs was. Perhaps I am just dumb. ***///'''

Cascading tipping points
Crossing a threshold in one part of the climate system may trigger another tipping element to tip into a new state. These are called cascading tipping points. Ice loss in West Antarctica and Greenland will significantly alter ocean circulation. Sustained warming of the northern high latitudes as a result of this process could activate tipping elements in that region, such as permafrost degradation, and boreal forest dieback. Thawing permafrost poses a multiplier threat because it holds roughly twice as much carbon as the amount currently circulating in the atmosphere. If this is released into the atmosphere, the world will have to cope with emissions generated by the planet itself as well as those generated by human use of fossil fuels.

A 2021 study with three million computer simulations of a climate model showed that nearly one-third of those simulations resulted in domino effects even when temperature increases were limited to 2 °C – the upper limit set by the Paris Agreement in 2015. The authors of the study said that the science of tipping points is complex such that there is great uncertainty as to how they might unfold, but nevertheless, argue that the possibility of cascading tipping points represents “an existential threat to civilisation”. In July 2021, Nature Geoscience published a review illustrating how cascading interactions in the Earth system have led to abrupt changes in climate, ecological and social systems during the past 30,000 years. The authors point out that "the geological record shows that abrupt changes can occur on timescales short enough to challenge the capacity of human societies to adapt to environmental pressures". ///*** Pretty sure the IPCC report released by working group 2 in February, 2022 backs this statement up ***/// ///*** Correct ***////

[Potential New Section] Sea-level rise and the inhabitability of the island nations
An increase of more than 1.5 degrees C has deep ramifications for the island nations. They might become uninhabitable. This may not fall under the definition of the tipping points though, and we would need to find several citations for this.