Greenpeace International revisited their rankings of industry leaders in cloud computing to adjust Apple’s score, due in part to Apple’s promise to make its data centers “coal-free” by 2013 and its increasing ambition to power its growing iCloud through 100 percent renewable energy.

In a report released Thursday, the environmental organization upgraded Apple in three of four categories reflecting the company’s commitment to clean energy in its cloud computing facilities. Even with its upgrades, Apple remains near the bottom of the pack, which includes Microsoft, Google, Facebook, IBM, Oracle and others.

In May, Apple CFO Peter Oppenheimer announced plans for implementing renewable energy at the company’s three current data centers by 2013, and Apple’s new data center in Reno, Nevada, will have access to many renewable energy options, according to the Greenpeace report.

However, the Cupertino-based maker of the iPhone and iPad has not instituted an infrastructure siting policy, like that of Facebook, that would express a commitment to building data centers in areas with an established clean energy grid, said David Pomerantz, a spokesman for Greenpeace International.

Pomerantz also said Apple struggles in the category of transparency because it is “famously tight-lipped” about information about its practices. Beyond the company’s goals, Apple releases little detail on the specifics of its renewable energy practices, he said.