Slide 1 of 15
Geoengineering our planet
Humans may have changed the Earth's climate ever since they began using "slash and burn" tactics to clear forests for growing crops. But today's civilizations must deal with the industrial revolution's contribution to a warming planet and the choice of trying to reverse or balance out such climate change with new geoengineering tactics.
Geoengineering ideas typically aim to stop the warming of the Earth's climate by removing the greenhouse gas carbon dioxide (CO2) or by reflecting more sunlight back into space. Many mimic natural processes such as the cooling effect of volcanic eruptions or boosting the CO2-absorbing effect of forests. But the idea of humans intentionally engineering the Earth's climate on a grand scale still attracts plenty of controversy as well.
Here you can take a look at ratings for some of wildest geoengineering ideas described in a 2009 report by the UK's Royal Society. The British study has been cited in later U.S. reports by the U.S. National Academy of Sciences (2010) Washington-based Bipartisan Policy Center (2011).
Cloud seedingSlide 2 of 15
White clouds based on small micro-droplets of moisture could reflect more sunlight to slow down the heating of the planet. Many proposals have suggested using ships or aircraft to seed clouds with a spray of salty ocean water, or perhaps dropping a special hydrophilic (water-attracting) powder from aircraft.
Impact: Low to Medium. There is uncertainty about producing enough of the cloud seeding effect, and the method is largely limited to areas over oceans.
Affordability: Medium. The cost of ocean water is low, but the cloud seeding must continue almost constantly for a long period of time.
Timeliness: Medium. The effect on lowering temperatures would begin within one year. Deployment could start within years or a few decades.
Safety: Low. The cloud seeding may end up affecting weather patterns and ocean currents. There is also the possibility of pollution of the cloud seeding uses chemicals or materials other than sea-salt.Slide 3 of 15
Air capture of CO2Slide 4 of 15
Air capture of CO2
Humans could capture CO2 directly from the ambient air similar technologies already capture carbon from power plants. The CO2 would be absorbed by solids or alkaline liquids before being moved to long-term deep storage underground.
Impact: High. This idea is both doable and has no limits on the size of its possible effect. It also tackles a main cause of climate change and ocean acidification by removing CO2.
Affordability: Low. The carbon capture methods would have potentially high material and energy costs.
Timeliness: Low. Humans still need to do more work to find cost-effective air capture methods, and would need time to build the infrastructure to do the job. It would also be slow to reduce global temperatures.
Safety: Very high. There are few side effects.Slide 5 of 15
Aerosols in the atmosphereSlide 6 of 15
Aerosols in the atmosphere
Humans could release a wide range of tiny particles into the stratosphere to reflect sunlight back into space. That mimics the natural cooling effect of huge volcanic eruptions that toss similarly small particles high into the atmosphere. Fleets of aircraft, rockets, balloons or even huge artillery guns could do the job of delivery.
Impact: High. This is already doable and possibly very effective. There is also no limit to its effect on global temperatures.
Affordability: High. This only requires small quantities of materials at relatively low cost.
Timeliness: High. The effect would start to reduce temperatures within one year. Deployment would only require years or possibly a few decades.
Safety: Low. Many possible side effects include damage to the stratospheric ozone layer, effects on high-altitude clouds, and impact on the biological productivity of plants and animals.Slide 7 of 15
Space sun shieldsSlide 8 of 15