I recently asked a group gathered to hear me speak what percentage of the world's energy is provided by these six renewable sources: solar, wind, geothermal, wave, tidal, and ocean energy.
Then came the guesses: To my left, 25 percent; straight ahead, 30 percent; on my right, 20 percent and 15 percent; a pessimist sitting to the far right, 7 percent.
The group was astonished when I related the actual figure: 1.5 percent. The figure comes from the Paris-based International Energy Agency, a consortium of 30 countries that monitors energy developments worldwide. The audience that evening had been under the gravely mistaken impression that human society was much further along in its transition to renewable energy. Even the pessimist in the audience was off by more than a factor of four.
I hadn't included hydroelectricity in my list, I told the group, which would add another 2.5 percent to the renewable energy category. But hydro, I explained, would be growing only very slowly since most of the world's best dam sites have been taken.