“Green swan” is a relatively recent term as such things go—coined by a group of academicians in their January 2020 report for the Bank of International Settlements (BIS). It’s derived from the term “Black Swan”, coined and made popular by writer and risk analyst Nassim Nicholas Taleb in his 2007 book The Black Swan: The Impact of the Highly Improbable . (View Highlight)
Green swans, or “climate black swans”, present many features of typical black swans. Climate-related risks typically fit fat-tailed distributions: both physical and transition risks are characterised by deep uncertainty and nonlinearity, their chances of occurrence are not reflected in past data, and the possibility of extreme values cannot be ruled out. In this context, traditional approaches to risk management consisting in extrapolating historical data and on assumptions of normal distributions are largely irrelevant to assess future climate- related risks. That is, assessing climate-related risks requires an “epistemological break” with regard to risk management…
However, green swans are different from black swans in three regards. First, although the impacts of climate change are highly uncertain, “there is a high degree of certainty that some combination of physical and transition risks will materialize in the future”. That is, there is certainty about the need for ambitious actions despite prevailing uncertainty regarding the timing and nature of impacts of climate change. Second, climate catastrophes are even more serious than most systemic financial crises: they could pose an existential threat to humanity, as increasingly emphasized by climate scientists. Third, the complexity related to climate change is of a higher order than for black swans… (View Highlight)
That’s the name of a startup that is attempting to reflect sunlight back into space. As Technology Review first reported last week, the startup claims to have launched balloons to release sulphur into the stratosphere, potentially taking the first step toward serious geoengineering—which refers to manipulating the climate through carbon dioxide removal or solar radiation management. (View Highlight)
For decades, researchers have toyed with the idea of cooling the environment by such methods, inspired by the aftereffects of large volcanic eruptions. Particularly the 1991 eruption of Mount Pinatubo in the Philippines, which cooled the entire planet by about half a degree Celsius on average for many months. (View Highlight)
The ocean already blunts the effects of climate change, naturally absorbing 30% of annual carbon emissions. But as it dissolves in the water, the CO2 combines with calcium and other ions, depleting them. As a result, the pH of the waters drops, harming marine life, and CO2 uptake slows. “Alkaline enhancement” aims to reset the water chemistry.
Liming is one approach. The added calcium hydroxide, or lime, raises the water’s pH and enables it to sequester more CO2 in the form of calcium bicarbonate or as carbonate deposited in the shells of sea creatures. In effect, the liming enhances the way the ocean naturally removes CO2, says Harald Mumma, an environmental engineering graduate student at Notre Dame. “We just speed up natural processes and make it happen not on geological time scales, but on human time scales.” (View Highlight)
In April last year, teams from the Centre for Climate Repair at the University of Cambridge and India’s Institute of Maritime Studies spread iron-coated rice husks across the Arabian Sea. Since iron is scarce in much of the ocean, it’s believed—and proven in academic experiments over the years—that adding iron would fertilise a bloom of photosynthetic algae. Which would then soak up carbon and sequester it when the algae die and sink. (Algae are microscopic aquatic organisms that convert water and carbon dioxide into sugar and release oxygen through photosynthesis.) (View Highlight)
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