Humans, as a species, are control freaks; we seek to establish complete dominion over our environment. In our selfish arrogance, we often fail to anticipate the consequences of our actions. Denial that there even are problems is common; assumptions of human mastery over all is a given. This attitude is apparent in our approach to dealing with both weather issues and climate change.
For instance, we see this whenever a drought occurs. The cries arise for cloud seeding, a vain attempt at producing or enhancing precipitation. Despite being pursued for well over half a century, whether it actually produces the desired results in still unclear. It does leave measurable, physical effects on the cloud, but it is not clear that it enhances precipitation. If so, it is on an inconsistent basis.
Even knowing this, we persist in the belief that we can coerce nature to our bidding when and where we please through cloud seeding. The Chinese want to force rain to clear the air before the Olympics. The government of the Philippines, currently in an extended dry spell, are attempting cloud seeding to break the drought. At the request of farmers in Queensland and New South Wales, Australia, cloud seeding is again being pursued. I wish them luck, but whatever success they may have will likely be down to random chance.
While cloud seeding is not especially effective, at least it is relatively harmless, wasting only time and resources. More risky are larger-scale, geo-engineering projects offered up as solutions to anthropogenic warming or as ways to sequester carbon dioxide.
Dumping iron in the ocean to promote plankton growth is bound to have some sort of unexpected outcome. For example, in certain water conditions a plankton bloom can lead to a chain reaction resulting in further oxygen depletion of the water. This places further stress on the already overstressed ocean biosphere, creating a 'dead zone' in the ocean such as those observed off the Oregon coast the last several years. The consequences are potentially large, in theory impacting the food supply.
Proposals to create a 'sunshade' for the planet are potentially even worse. The idea that we can mimic a volcanic eruption and actually control the consequences is madness. Maybe, as an absolute last resort we could think about it, as Climate Progress noted. New Scientist reports that such a screen, incorrectly applied, 'could result in sudden warming – which would be worse than the long-term warming that had been avoided because of its swiftness'. They also report a later study which claimed that 'even if correctly deployed – a sulphur sunshade could have deleterious effects on the environment by reducing rainfall'.
None of this is meant to say that we humans cannot alter our environment. We just cannot control the outcomes or minimize the blowback, especially on regional and planetary scales. And it is the height of hubris to think we can. I would like to believe that we could learn something from the experiment we already have running – the 35% (and rising!) increase of CO2 in the last 100 years. Just look at how well that's turning out!
Here's an idea. Instead of trying to bend Nature to our will, let's cooperate with her. Instead, let's fix our behaviour -- something we can more reliably control-- and reduce our emissions of CO2 to slow the forcing and minimize the damage. It's only human.