Which cloud data companies have the best environmental practices?

—Adrienne in Austin, Texas

Our understanding of the cloud's environmental performance is slowly coming out of the fog. Our friends at Greenpeace have made a mighty stab at sorting out the cloud's energy demands and sources. Their 2012 report, How Clean Is Your Cloud?, was fairly gloomy, concluding that "most IT companies are rapidly expanding without considering how their choice of energy could impact society." The more recent report, Clicking Clean: How Companies Are Creating the Green Internet, shows that considerable progress has been made. Apple, Box, Facebook, Google, Rackspace, and Salesforce have all committed to powering their data centers with 100 percent clean energy; laggards include Amazon Web Services and Twitter.

The cloud and "end-user devices" like cell phones already account for an estimated 2 percent of the world's global warming emissions, a share comparable to that of global aviation. With hundreds of millions more people lining up to buy electronic devices, the cloud's demand for electricity is expected to increase by more than 60 percent by 2020, so that energy had darn well better be clean.—Bob Schildgen