"The always excellent Future Pundit site poses an interesting question. Will it be possible for us to engineer inexpensive climate control? And if so, should we?"

What period of time in human history was there an ideal climate? What would be the target- do we want the climate of early 1900's? !950? 1800? What do we have idea of what was, that we would want?

But if we wanted to cool the planet, it probably a better idea to focus on the oceans instead of the sky. And generally speaking instead being concerned about temperature, we should be more concerned with controlling where and how much it rains.

71 % of Earth surface is ocean. The Oceans beyond the continental shelves is very clear water. If you interfered with vast areas in the ocean region at or near tropics you would have a profound affect upon global temperature.

Now one of the biggest vocanic event in modern history was KRAKATAU, INDONESIA (1883):

"The amount of tephra [[Solid matter that is ejected into the air by an erupting volcano]] generated is thought to be about 20 cubic kilometers, or twenty times that of the destructive Mt. St. Helens eruption in 1980. Near Sumatra, the Sunda Straits were clogged with so much debris that it looked like solid ground. Relief ships were unable to reach coastal communities like Telok Betong for weeks. Over the ensuing months, storms and high-tides would disperse thick banks of floating pumice beyond the Straits, into the Java Sea and Indian Ocean. Ships thousands of kilometers from Krakatau would report huge fields of this floating debris for months after the eruption. One such accumulation floated 8,170 km, until it reached Durban, South Africa in September, 1884. "

Now much is said about the fine dust in the atmosphere that spread throughout the world creating gory blood-like sunsets. But what affect did it have on the oceans? Particularly the oceans nearest the event (Indian and south Pacific). Ash of course provides nutrients for ocean algae.