In 2005, Emanuel reported that hurricane intensity, which is fed by warmth, had increased some 80 percent during the previous 50 years, a period during which temperatures had increased more dramatically than any time in at least 500 years. Nonetheless, he asserted, that didn’t mean Hurricane Katrina, the sixth strongest Atlantic storm on record, had been brought on by climate change.
Even with a multitude of extreme weather events in recent years — tornadoes in New York City, blizzards in Washington, D.C., 15,000 warm-temperature records shattered across the U.S. in March — each consistent with computer models of a warming world, Emanuel and many other noted scientists have been unwilling to attribute any one event to global warming. There’s just too much variability in the weather, these experts say, and their dedication to data has helped prop open the door for “denialists” to sow doubt about the reality of our warming world.
But Hansen’s shot across the bow this morning indicates that the unwillingness to point fingers may be changing. According to a peer-reviewed paper Hansen has submitted to a leading scientific journal and made available to Time.com prior to publication, scientists can now state “with a high degree of confidence” that some extremely high temperatures are in fact caused by global warming, simply because they occur much more frequently than they used to. (A preliminary draft of the article is available here.) More