It's wrong to blame our warming climate on human pollution alone, says a major analysis by U. S. climate scientists who say North America's warming and drying trend also has important natural causes.
Natural shifts in ocean currents have caused much of the warming in recent decades, and almost all of the droughts, says the U. S. National Oceanic and Atmospheric Administration (NOAA).
Most climate researchers today deal exclusively with man-made "greenhouse" gases, and often dismiss suggestions of naturally caused warming as unscientific.
Yet NOAA says Western Canada has warmed by two degrees and Eastern Canada hasn't warmed at all because flows of air from naturally shifting Pacific currents have affected the West most.
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The lengthy re-analysis of climate data doesn't dispute that greenhouse gases from fossil fuels cause a warmer climate. But it raises questions about the details: How much warming? How many causes? And why isn't it the same every-where?
It also stresses that we don't understand climate as well as we like to think, because scientists only have good data from about 1948 onward.
