One of the proposed ways to counter the effects of global warming is by using atmospheric aerosols to reflect heat away from the Earth, and a great deal of research is going into not just how this might work, but whether or not it is a good idea. A new study from MIT has explored some of the potential flow-on effects of such a move and found it would likely trade one set of problems for another, by weakening storms, destabilizing ice sheets and leading to more polluted urban areas.
The research was carried out by MIT’s Department of Earth, Atmospheric and Planetary Sciences, with the team setting out to explore some of the long-lasting effects of solar geoengineering on the climate. These types of schemes vary in their proposed approaches, but generally take inspiration from volcanic eruptions that spew reflective particles into the stratosphere that temporarily bounce the Sun’s energy back into space and temporarily cooling the planet.
For their investigations, the team used a solar geoengineering model in which enough solar radiation is blocked to balance out the warming effects if carbon dioxide concentrations in the atmosphere, which is already at record levels, were to quadruple. Known as the G1 experiment, this model enabled the team to explore the various repercussions of injecting vast amounts of aerosols into the stratosphere, with a strong alteration of extratropical storm tracks the leading consequence.
This refers to the zones in the middle and high latitudes where storms form to create extratropical cyclones, with the strength of the storm tracks directly linked to the severity and frequency of the storms. The team found that under its G1 scenario, storm tracks in both hemispheres would be greatly weakened, which would mean less ferocious winter storms but would bring a host of other climate consequences.
Weaker storms, the scientists note, would also mean more stagnant summertime conditions. This echoes the findings of a similar study at the University of Exeter in 2017, which found that solar geoengineering could reduce the frequency of some cyclones and cause drought in parts of Africa, though the MIT paper goes a little bit further.
“A weakened storm track, in both hemispheres, would mean weaker winter storms but also lead to more stagnant weather, which could affect heat waves,” says Charles Gertler, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences and study author. “Across all seasons, this could affect ventilation of air pollution. It also may contribute to a weakening of the hydrological cycle, with regional reductions in rainfall. These are not good changes, compared to a baseline climate that we are used to.”
Reduced winds to clear away pollution and maintain healthy air quality is just one of the possible outcomes of solar geoeingeering, with the scientists warning it could also alter the circulation of ocean currents, which would have an impact on the stability of ice sheets. This could prove particularly influential down south.
“In the Southern Hemisphere, winds drive ocean circulation, which in turn could affect uptake of carbon dioxide, and the stability of the Antarctic ice sheet,” says co-author Paul O’Gorman. “So how storm tracks change over the Southern Hemisphere is quite important.”
Further, the team found that these weaker storm tracks were closely correlated to changes in temperature and humidity, with the modeling indicating that solar geoengineering could cause the equator to cool while the poles continue warming. This reduced difference in temperature between the poles and equator is what could lead to the weaker storm tracks, according to the team, and kick off a chain reaction of climate consequences that we may not be prepared to grapple with.
“Reflecting sunlight isn’t a perfect counterbalance to the greenhouse effect,” says O’Gorman. “There are multiple reasons to avoid doing this, and instead to favor reducing emissions of CO2 and other greenhouse gases.”
The research was published in the journal Geophysical Research Letters.
Source: MIT