Creating cloud to reduce warming and wetlands to reduce erosion

2 important stories this week from Science mag. Firstly, they point out that rising concentrations of atmospheric CO2 will have two main impacts, namely those of global warming and acidification of the oceans. That much we understand. Now one solution to the former problem (but not the latter, obviously) is that we "geo-engineer" the world's climate in order to mitigate some of the effects of atmospheric CO2 buildup. Wigley (p. 452, published online by Sciencemag 14 September) explores the option of injecting sulfate aerosol precursors into the stratosphere, which would increase the number of aerosol particles that can function as cloud condensation nuclei and thus increase cloud coverage, replicating the effect of large volcanic eruptions. We know that such cloud cover will reflect more sunlight back into space, but this approach would have no positive influence on ocean acidification. I do wonder if it would lead to local effects such as rainfall. It would also vary according to the height at which the particles are released and localised atmospheric circulation patterns.


The second story is about the effects of hurricanes on erosion. After Hurricanes Katrina and Rita made landfall in 2005 it was painfully obvious that areas where wetlands had been removed were prone to erosion, inundation and sedimentation. Coastal wetlands had been thought to gain and maintain mass through riverine sedimentation during flooding events (think of the Nile valley for a famous example). Turner et al (p. 449, published online 21 September) show that the deposition of sediments by hurricanes is actually the dominant process in the region studied. Yet another reason to put those wetlands back - or don't touch 'em in the first place!!