Reuters: Trees in the western United States and Canada are dying twice as quickly as they did just 30 years ago, with rising average temperatures almost certainly to blame, researchers reported on Thursday. These thinner and weaker forests will become more vulnerable to wildfires and may soak up less carbon dioxide, in turn speeding up global warming, they said. The U.S. and Canadian researchers from a variety of agencies and universities studied trees in old-growth forests for more …