(note: this is part 2 in a series from an essay by noted ozone expert, P.J. Crutzen, on using a 'stop-gap' solution to stop runaway global warming. for part 1 click here. For part 3, click here. Once again, the text has been loosely 'translated' into non-scientific terms where necessary for those of us who are not familiar with scientific terminology. The opinions expressed in the translation are of the Editor's and not necessarily of Dr. Crutzen's)
ALBEDO ENHANCEMENT BY STRATOSPHERIC SULFUR INJECTIONS: A CONTRIBUTION TO RESOLVE A POLICY DILEMMA Pt. 2
An Editorial Essay
By far the preferred way to resolve the policy makers’ dilemma is to lower the emissions of the greenhouse gases. However, so far, attempts in that direction have been grossly unsuccessful.
(translation: "Of course the government would prefer to pass laws lowering fossil fuel emissions, but so far lawmakers have largely avoided passing such bills.")
While stabilization of CO2 would require a 60–80% reduction in current anthropogenic CO2 emissions, worldwide they actually increased by 2% from 2001 to 2002, a trend, which probably will not change at least for the remaining 6-year term of the Kyoto protocol, further increasing the required emission restrictions.
(translation: " In order to stop the greenhouse effect there would need to be approximately 3/4 of all emissions stopped immediately, but instead emissions worldwide are up by 2% and don't appear to be declining anytime soon.")
Therefore, although by far not the best solution, the usefulness of artificially enhancing earth’s albedo and thereby cooling climate by adding sunlight reflecting aerosol in the stratosphere might again be explored and debated as a way to defuse the Catch-22 situation just presented and additionally counteract the climate forcing of growing CO2 emissions.
(translation: " One way to solve the problem would be to once again consider my plan of 'sprinkling' tiny reflective particles in the higher atmosphere, which would also help with the weather.")
This can be achieved by burning S2 or H2S, carried into the stratosphere on balloons and by artillery guns to produce SO2.
To enhance the residence time of the material in the stratosphere and minimize the required mass, the reactants might be released, distributed over time, near the tropical upward branch of the stratospheric circulation system.
(translation: "To keep the particles up in the air for a while, we could spray them upwards at the tropics where we can tap into an invisible circulation system high above.")
In the stratosphere, chemical and micro-physical processes convert SO2 into sub-micrometer sulfate particles. This has been observed in volcanic eruptions e.g., Mount Pinatubo in June, 1991, which injected some 10 Tg S, initially as SO2, into the tropical stratosphere. In this case enhanced reflection of solar radiation to space by the particles cooled the earth’s surface on average by 0.5 ◦C in the year following the eruption.
("translation: When pollution rises, it's chemistry changes into very small particles. We learned that when Mount Pinatubo erupted, a large amount of similar type smoke blasted into the upper atmosphere above the volcano and the tiny particles ended up cooling the Earth's surface for a year.")
Although climate cooling by sulfate aerosols also occurs in the troposphere, the great advantage of placing reflective particles in the stratosphere is their long residence time of about 1–2 years, compared to a week in the troposphere.
Thus, much less sulfur, only a few percent, would be required in the stratosphere to achieve similar cooling as the tropospheric sulfate aerosol.
This would make it possible to reduce air pollution near the ground,improve ecological conditions and reduce the concomitant climate warming.
(translation: " Although lower atmosphere pollution also cools Earth's surface, putting reflective particles up in the higher atmosphere lasts much longer. Plus less sulfur has to be used high up, so the ground area would be cooler and less polluted ")
The main issue with the albedo modification method is whether it is environmentally safe, without significant side effects.