Because of the emission of greenhouse gases such as carbon dioxide associated with human civilization activitiesGlobal WarmingAndClimate changeIt has happened, and the situation is getting worse every year. Reducing the amount of greenhouse gases in the atmosphere is an urgent issue to deal with global warming and climate change. At the international level, the reduction and recovery of greenhouse gases has been stipulated as national policies and laws, and research and development of technologies for this purpose is progressing, but progress has been slow.
A research team led by Mr. Johannes Sutter of the University of Bern designed to reduce the amount of solar radiation as a countermeasure against global warming.Artificially injected aerosols into the stratosphereWe simulated how effective this method is. Results,Outside the unrealistic scenario in which aerosol injection is now being performed, the West Antarctic Ice Sheet (※1) Ultimately can not prevent the collapseI have summarized the results. And even if it were implemented immediately, it would not be a realistic countermeasure because aerosol injection would have to take place for thousands of years and the adverse effects would be unknown.
*1: Among the ice sheets in Antarctica, the one on the western side of the Transantarctic Mountains. Because the bottom of the ice sheet is below sea level, melting due to warming could destabilize the entire West Antarctic ice sheet. Antarctica is sinking under the weight of the ice sheet, but if the West Antarctic ice sheet moves, it is believed that the balance will change from falling to rising, but how unstable is the ice sheet as a whole?
What is SRM (solar patch)?
As a countermeasure against global warming other than a way to reduce greenhouse gas emissions,Insolation correction(SRM; solar radiation modulation)”. SRM is a generic term for technologies that reduce the amount of sunlight that reaches the Earth’s surface. Various methods have been devised, but the most studied is “synthetic aerosol injection into the stratosphere”.
Aerosols are fine particles of solids or liquids dispersed in gases, typical examples of which are smoke and clouds. Aerosols are sometimes released with large-scale volcanic eruptions, have been observed to reflect sunlight to lower the average temperature, and fall from the stratosphere to the surface over time. For this reason, it is assumed that it would be possible to prevent global warming directly by artificially injecting aerosols into the atmosphere to reduce the amount of solar radiation on a global scale.
However, current scientific understanding of atmospheric motion and global climate is insufficient, and there are concerns about potential or unknown negative impacts that may result from the implementation of solar radiation management. There are many concerns. However, countermeasures to climate change have not made much headway, and the possibility of keeping the average global temperature rise below 2°C is rapidly diminishing. (※2) There is a good chance that the implementation of Sunlight Management (SRM) will be seriously considered in the near future.
*2…If the global average temperature increases by more than 2°C compared to pre-industrial levels, the impact of climate change on human society is projected to become very serious. The number has been quoted as a boundary line. For example, the Paris Agreement, adopted in 2015, aims to limit the increase in the global average temperature to less than 2°C, and keep it below 1.5°C.
In addition to the negative impacts, there are many unknowns about whether SRM will be effective enough as a countermeasure to climate change in the first place. Ocean acidification, not least because SRM does not reduce greenhouse gases (※3) This is clearly not a countermeasure to On the other hand, little is known about the effect on melting ice sheets and glaciers, a phenomenon that also has a significant impact on the oceans. Can solar radiation management (SRM) really be an effective measure to combat climate change?
*3: A phenomenon in which carbon dioxide dissolves in sea water and turns into gaseous water, which increases the acidity of sea water. Many organisms that contain calcium carbonate shells, such as oysters, corals, foraminifera, and cocci, live in the ocean. As a result, it is believed that the ecosystem will be severely damaged.
■ Countermeasures to global warming by implementing solar radiation management are unrealistic
Sutter and colleagues simulated how the rate of melting of the West Antarctic ice sheet would change if solar radiation management (SRM) was implemented. In terms of greenhouse gas emissions, three scenarios are used as a basis: “low emissions due to progress in reduction efforts”, “moderate reduction” and “no reduction”. In addition to the scenario in which the aerosol injection is supposed to take place. In the years 2020, 2040, 2060 or 2080, the simulations were also run without SRM. All of these scenarios were analyzed up to 2300 AD, studying changes in the temperatures of the continental surface and sea floor in the Antarctic region, and the rate of melting of the ice sheet in West Antarctica.
As a result, the progression of Antarctic warming and the melting of the West Antarctic ice sheet was confirmed in all scenarios, and the rate of melting was shown to vary according to the scenario. Based on these results, the research team concluded that the scenario in which the collapse of the West Antarctic ice sheet would be prevented and stabilized in the long term would be as follows:Greenhouse gas emissions are almost zeroi lImmediate and long-term implementation of SRM managementI thought there was only one.
Immediate implementation of solar radiation management is not only politically difficult, but also impractical given the unknown negative impacts of solar radiation management. In addition, solar radiation management (SRM) is expected to be implemented for at least hundreds, possibly thousands of years to achieve long-term stabilization of the West Antarctic ice sheet. The effects of injecting aerosols into the stratosphere for such a long period of time is completely unknown territory.
Even under the more realistic scenario of implementing solar radiation management in the middle of this century, the West Antarctic ice sheet would slow its collapse compared to doing nothing but ultimately be unable to stop it. This time it was shown. That is why, if we are going to use solar radiation management to limit global warming, we can only choose the unrealistic scenario of immediate implementation.
Even assuming no negative impacts, implementing sunlight management can delay environmental protection policies such as reducing greenhouse gas emissions. Even if the increase in temperatures is suppressed through solar radiation management, the problem will remain because environmental problems such as ocean acidification will not be solved if carbon dioxide emissions remain high. In addition, the world will be placed in a very dangerous situation, as the suspension of the implementation of solar radiation management will quickly cause temperatures to rise by several degrees Celsius.
from above,The way to keep the global average temperature rise below 2°C is not to manage solar radiation, but to take immediate action to reduce greenhouse gas emissions to net zero.The conclusion of Souter et al.
- J Sutter, and others. “Climate intervention on a high-emissions trajectory could delay, but not prevent, melting of the West Antarctic ice sheet.” (the nature of climate change)
- Johannes Sutter and Thomas F. stalker. “Could artificially dimming the sun prevent ice from melting?”. (University of Bern)
Text: Riri Aye
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