Newsweek has announced its second annual “Green Rankings,” a data-driven environmental assessment of the largest 500 U.S. companies and the 100 biggest global companies. The mag’s goal was “to cut through the green chatter and quantify the actual environmental footprints, policies, and reputations of these big businesses.” The top two spots were the same as last year, but this time Dell edged HP as the #1 ranked company. In fact, the top five companies were exactly the same as last year- IBM, Johnson & Johnson and Intel rounded out the top spots. View Newsweek’s methodology.

Who cares? According to GreenBiz’s Joel Makower, the companies on the list care. As he explains on his blog, he recently asked reps from Fortune 500 firms how many of them actually knew their company’s 2009 Newsweek Green Ranking. “Damn near every one could cite it blindly. The rankings, it seems, have become a major metric in corporate America.”

Makower suggests the “subtleties will be lost on most people, who will view the rankings as Gospel, especially when comparing competitors — e.g., declaring that Dell (#1) is better than HP (#2), Pepsi (#135) is better than Coca-Cola (#141), UPS (#62) is better than Fedex (#105), McDonald’s (#79) is better than Wendy’s (#313), Wells Fargo (#41) is better than Bank of America (#124), and Walmart (#51) is better than Target (#61). There’s great sport in all this, but there can also be both unearned gloating by the winners and needless self-flagellation by the losers, especially when the differences are fairly small.

The biggest difference, Makower says, may be the impact these rankings will have on the field of sustainable business.

[Sources: Newsweek, Joel Makower]