Monocle in the sky
One way to reduce temperatures on earth would be to reduce the amount of sunshine reaching us. Hence, a concave lens, 1,000 km in diameter and only a few mm thick, floating in space between the earth and the sun at a distance of about 1.5 million km from the earth. The lens would disperse the rays from the sun reducing sunlight on earth by 0.5 to 1 percent. It’s a bit heavy, though, at 1.57 trillion kg and at $24 quadrillion, a tad expensive.

Cloudy days ahead
Clouds reflect sunlight. Hence, more clouds equals more reflected sunlight equals lessening global temperature. So create more clouds. How? Through cloud seeding using commercial airlines where the exhaust will contain aerosols that enable cloud formation. The other way is to simply increase the reflectivity of the clouds. One plan includes using 1,500 specialised, unmanned sea-faring vessels called Flettner vessels to spray fine mist created from sea water into the air, thickening low-level clouds over the oceans and increasing their reflectivity.

Spinach for the oceans
Phytoplankton has a funny habit of not growing where it should — on ocean areas rich with nutrients. The reason, it turns out, is the deficiency of iron. Iron is a trace element needed for photosynthesis in all plants. So how does this relate to climate change? Pump the ocean surface with iron leading to a bloom of phytoplankton growth. More phytoplankton, more photosynthesis, less CO2 in the atmosphere.

The loggers’ bane
Trees are finally the most ideal way to reduce atmospheric CO2 but it takes a long while to reforest an area — plant the saplings, watch them grow and keep the loggers away. Now there is a way to expedite the whole process: artificial trees. Farms of engineered tree-like installations scrub the air of CO2 by absorbing and storing it into a filter. Apparently, the prototype artificial tree absorbs more CO2 than an equally-sized natural tree.

Keeping it cool
And now something for the polar bear. The loss of Arctic sea ice may be one of the biggest reasons for sleep deprivation among climatologists. For two reasons. It’ll result in the increase of ocean levels and, if we lose enough of that ice, there will come a point where large amounts of methane will be released into the atmosphere (methane is the big daddy of greenhouse gasses currently trapped in the Arctic ice). Both scenarios get Hollywood scriptwriters licking their lips. So preserve the ice. How? Try the simple yet logistical nightmare of spraying fresh water on the ice caps to thicken the ice. Or perhaps build a dam at Bering Strait to prevent the saltier, warmer waters from the Pacific Ocean to melt away the ice.