See: IPCC Warnings
EMISSIONS REDUCTION
Emissions reduction is the basis for all international agreements to mitigate climate change. However, net-zero carbon treaties can only slow global warming – not cool the planet. Emissions reduction is essential but will almost certainly fail to limit global warming to 1.5º or even 2º C.
CLIMATE COOLING STRATEGIES
NB: Planet cooling has the potential to reduce extreme weather events and avoid climate tipping points – and reverse climate change. However, most cooling strategies do nothing to alleviate ocean acidification.
- Carbon capture and storage (CCS), removal of CO2 from the atmosphere, has the potential to cool the planet. It is the subject of active research, including a $100M XPRIZE. Both Post-Combustion CO2 Capture and Direct Air CO2 Capture may work. Current CCS technologies are not ready for large-scale deployment.
- Iron fertilization of the ocean—drawing down carbon dioxide from the atmosphere and sequestering carbon in the deep sea—is a very controversial concept. Ocean fertilization can stimulate algal blooms, capturing CO2 and increasing the biome food supply. In a bid to boost salmon stocks and sequester carbon, 100 tons of iron and rock dust was dumped into the ocean off the coast of British Columbia in July 2012. The results were ambiguous.
- Stratospheric Aerosol Injection (SAI) – spraying SO2 droplets into the stratosphere – offers potential for near-term climate cooling. Altering the chemistry of the atmosphere is controversial – some fear that stratospheric sulphates may damage the ozone layer.
- Space Shaders at Lagrange 1 (L1) can produce a diffuse penumbra shadow on the surface of the Earth. If implemented, sunshades at L1 could provide safe and flexible long-term climate cooling.
ATMOSPHERIC VS SPACE-BASED GEOENGINEERING
Atmospheric Geoengineering Space-Based Geoengineering
• Rapid, polluting, hard to control • Slow, expensive, clean
• Modest costs – low tech • Expensive – high tech & risky
• Works only in daylight regions • Works for entire planet
• Short-term, needs replenishment • Long lifetime
• Alters atmospheric chemistry • No effect on atmospheric chemistry
• Threat to the ozone layer • No threat to the ozone layer
• Cannot rapidly modulate sunlight • Can tune sunlight
• Little regional climate control • Some regional climate control
• No increase of habitable land • Can double arable/habitable land**
• Will not save ocean ecosystems • Will not save ocean ecosystems
** Space-based geoengineering is not limited to the L1 point. Other orbits for solar sails may allow regional heating or cooling – to extend the growing season or reverse desertification.
L1 SUNSHADE PROPOSALS
Various proposals to use L1 to shade and cool the Earth include releasing dust clouds in space. Additional loads of dust particles would renew the sun shield, as needed.
In 2006, Roger Angel published "Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)” Angel proposed placing trillions of small “flyers” at L1 made of transparent material that would deflect the sunlight, rather than to absorb it, to minimize the shift from L1 caused by radiation pressure. Angel’s flyers would also use active station-keeping to maintain position at L1.
Currently, MIT has re-engineered Angel’s concept, proposing Space Bubbles (thin bubbles of silicon manufactured in space) to deflect sunlight at L1. MIT has not revealed how large rafts of space bubbles will maintain position at L1 (station-keeping).
See: IPCC Warnings