The first system, still under computer testing, uses simple buoys, placed in the seasonally warm ocean waters that breed hurricanes, powered by wave action, to slowly pump the warm water down about 100 feet to the much colder water. The resulting very-slightly cooler surface water would reduce the intensity of hurricanes (eliminating them is equally possible, but not desired). At $1 billion the system would cost far less than the damage caused by a single hurricane season.
The second system offers to cool the planet for only $250 million. The world output of sulfur dioxide (volcanoes, humans, sea spray, other sources) is 200 million tons, but it's all in the troposphere. In 1991, the heavily studied Mt. Pinatubo eruption sent some sulfur dioxide into the stratosphere and cooled the world. Modeling shows a mere 100,000 tons per year of SO2, which is a garden-hose-like 34 gallons per minute, and one twentieth of one percent of the world troposphere emissions, would reverse arctic warming and reduce northern hemisphere warming. If the system is shut off the stratosphere would return to normal in a couple of years, just as it did after the Pinatubo eruption, so the whatcouldpossiblygowrong argument is weak. Several delivery systems could work such as a long chain of hoses, pumps and balloons, or a tall lightweight chimney held by weather balloons.
The book also brings to light two interesting facts about global warming:
1) Eating locally grown food over mass produced food actually increases greenhouse emissions, because only 11 percent of of food emissions are transportation related (and delivery from producer to retailer is only 4%). A full 80% of food related emissions are from production, and big farms are far more efficient than small farms.
2) The world's cows, sheep and other cud-chewers are responsible for 50% more greenhouse gas than the entire transportation sector, due to methane being 25 times more potent than CO2. Forgoing beef for one day a week is better than switching to a hybrid vehicle.