Strategies for Technologic Fixes
A Turn-of-the-Century Example
Rainmaking was last tried in San Diego in 1916 when a drought had lasted too long for comfort. The city council decided to hire a Charles M. Hatfield, who came and did his work. Soon after, in a succession of downpours, San Diego received more than seven inches of rain near the coast. Farther inland, one recording station is reported to have received 44 inches within a month. A dam broke on Otay River, and 50 people were drowned. Despite his apparent success, Hatfield was not paid. Presumably, this would have implied that rainmaking works, and then the city could have been held accountable for the damages wrought by flooding.
Whether people can make rain is in doubt. However, human activity arguably has influenced climate since about 1950, and has done so quite probably since 1975. As discussed, the statistics for the last two decades leave practically no room for doubt about a strong human factor over this time span. Given a choice we would prefer not to change the climate. The unpalatable truth is that wishful human desires are utterly irrelevant to geophysics. Can we do something to set things straight?
Warming results from the pile-up of greenhouse gases, and the positive feedback comes from the response of the system (darkening of surfaces on Earth, by removal of snow and sea ice, mainly). Warming is retarded by (1) uptake of heat by the ocean, and (2) an increased amount of dust in the atmosphere, presumably mainly from soot caused by both internal combustion and open fires. So, how can we stop the warming and attempt to enhance the cooling processes? The most obvious action is to decrease the release of carbon dioxide and other greenhouse gases. This has been done successfully with respect for the CFCs, which are also powerful greenhouse gases (although this was not the reason for the action). It could be done for carbon dioxide, by moving away from coal to other less carbon-intensive energy sources. However, this seems to be economically and politically unpalatable, for reasons insufficiently studied and publicized. (Much of what is published on the subject is not convincing.)
We can also attempt to remove the carbon dioxide from the effluent of carbon-driven power stations. This is possible, but expensive. One could make carbon dioxide clathrates, that is, water ice with room in its structure to accommodate the gas (similar to the methane hydrates discussed previously). But low temperature and high pressure are necessary for this to happen, and the waste clathrate would then have to be moved to where it is stable, or where the release of carbon dioxide would do but little damage. The deep ocean floor has been discussed as one possible place for disposal.
Also, carbon dioxide (and effluent in general) can be pumped deep into the ground under high pressure, into the very places where methane has been removed by oil companies . But dissolving carbon dioxide in petroleum might actually result in recovery of more oil because of increased mobility.
In addition, carbon dioxide can be removed from the atmosphere by planting trees and letting them grow to maturity. This is entirely feasible (at least for awhile) and has engendered much interest and discussion. A somewhat analogous uptake, through the green plankton of the ocean, has been proposed. The idea is to fertilize the ocean in places where iron is limiting to plankton growth and let the resulting phytoplankton sink to below the surface, where the carbon would be hidden from exchange with the atmosphere. This scheme has received much criticism, since much of the carbon is trapped right below the surface layer from where it becomes available for upward mixing, by storms.
We can also, conceivably, darken the sky artificially, to simulate the cooling effects from volcanic eruptions. If we do so in space, particles could stay aloft for a long time before returning to Earth. They could provide shading. Many people may be uncomfortable with the idea of putting a ring belt of dust around the Earth. We might, as a final item on this list, seed tropical clouds to make them more abundant and more reflective.
All this being said, as a matter of basic principles, technological fixes are likely to be expensive and will have to rely on continuing efforts and concerted management. They also would need international agreement to work.