San Francisco Chronicle: Five investigations into the “Climategate” scandal have now cleared a group of scientists accused of twisting data in an effort to prove the world is getting warmer. But many environmentalists and climate researchers fear the damage has already been done. The scandal spawned big headlines and heated blog posts when it erupted last fall after hackers released a stash of unflattering e-mails from a climate research lab in Britain. In one message, a scientist wrote of using a …