ChemCafé

In a former post I mentioned several ideas that had come forth as potential ways to deal with global warming. I had my doubts about some of these propositions, and these doubts were recently confirmed when I read an article in French newspaper Le Figaro. The article relates a meeting of dozens of geoengineering specialists that occured recently in San Francisco, which conclusion was that geoengineering would not be able to provide efficient ways to mitigate global warming in a near future, if at all. Here is a short overview of these methods, and the reasons that may hamper their successful use. They can be classified into two categories: Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM).

Cloud whitening (SRM)

This concept, imagined by Stephan Salter from the University of Edinburgh, consists in spraying seawater in the atmosphere to increase reflectiveness of clouds. The clouds, produced by a fleet of around 1500 unmanned ships, would reflect more radiation from the earth. However, such an operation could have unexpected -and difficult to modelize- effects on oceanic climates and streams.

Covering the deserts with white films (SRM)

According to Alvia Gaskill who proposed this solution, covering a large enough area of the earth (first candidates would be Sahara, arabic and gobi deserts) could be expected to offset some or all of the projected additional radiative forcing and global warming from 2010 to 2070. Together with tremendous costs, ecological consequences such as perturbation of the atmospheric circulation (which could result in sub-saharian monsoon perturbation) must be feared.

Space sunshade (SRM)

Basically, this concept proposed by Roger Angel (University of Arizona), involves the use of trillions of small umbrellas, that would be put in orbit an stop some sunlight from reaching the Earth. If small 1 gram, 60 cm diameter discs were used, 800 000 of them would have to be sent every… minute, for 30 … years, in order to decrease the radiation hitting our planet of 1.8%.

Stratospheric sulfate aerosols (SRM)

Inspired by the eruption of Mount Pinatubo in 1991, which projected tons of particles in the atmosphere, and noticeably cooled the global temperatures of 0.5°C, chemistry Nobel Prize 1995 Paul J. Crutzen suggested the injection of sulfur compounds in the atmosphere. But this project could perturbate water cycles, the stratospheric ozone chemistry and biological life, which make large scale experimentation somewhat unrealistic.

Ocean iron fertilization (CDR)

This method involves the seeding of ocean with iron in order to promote a phytoplankton bloom, which can remove carbon dioxide from the atmosphere. Again, several side-effects are to be expected, as well as an increased water acidification, and the creation of large zones depleted from oxygen (the more the algae ‘breath’, the less oxygen available for the other species).

Although geoengineering is a flourishing field (just try to enter it in wikipedia), many of its promises will probably come true too late (if at all) if one wants to reduce anthropogenic global warming and climate change… scientific creativity will have to find other ways to deal with climate modifications.