Good investments

If I had only one wish for the next 50 years," said Bill Gates, "it would be to invent the thing that halves the cost of carbon dioxide." The founder of Microsoft went on: "We must innovate our way to zero CO2 emissions."

Gates is thinking like an entrepreneur: he knows there are profits to be made from developing an energy technology that is half as expensive as drilling for carbon-based fuels. But he is also thinking like an environmentalist: he knows the globe can't bear the ecological cost of spewing more and more carbon dioxide into the atmosphere.

And more spewing is on the schedule. World energy consumption is likely to grow by more than 50 percent over the next 25 years, largely due to rapid development in China and India, where energy use is expected to double. It's estimated that 80 percent of energy consumption in 2035 will come from an old familiar source: fossil fuels. The use of clean energy sources is growing, but unless those sources become cheaper and more efficient, they won't put a dent in the rise in carbon emissions. The energy industry will keep investing in fossil fuels (like the ones buried in the Alberta tar pits, which Bill McKibben writes about in "Pipeline to disaster").