"I think what we were maybe seeing during the first couple of decades was the effect of global warming, and it now seems to be swamped by the effect of regional climate change," he said.
In a few decades Inouye expects the North Pacific Oscillation to flip back to a wetter stage. This will lead to precipitation in the Rocky Mountains and more out-of-sync seasons, as global warming causes high-altitude snows to accumulate.
John Harte is an ecologist at the University of California at Berkeley. For the past 16 years he has used electric heat lamps to warm experimental plots of land at RMBL. The artificial temperature increase matches the small rise of a few degrees that global warming climate models project will occur over the next century.
Harte's study results show snows melting earlier and the soil drying. Drier soils store less carbon. Less carbon in the soil means more carbon in the atmosphere, which will accelerate the pace of warming, he said.
Drier soils are also more suited to sagebrush, the hearty shrub that carpets much of the arid West. In Harte's heated study plots, sagebrush is crowding out wildflowers.
The ecologist said the transition from wildflowers to sagebrush only speeds the trend: Sagebrush is darker than most wildflowers and absorbs heat instead of reflecting it.
He noted that a five-year drought has begun to affect natural areas in the Rocky Mountain meadow in similar ways to the changes he has observed in his artificially heated study plots. "I'm quite persuaded by evidence that snow is melting earlier and the Rockies are drying," he said.
Harte believes the drought of the past five years at RMBL is consistent with global warming projections for the Rocky Mountains. The mountains, he added, are 1,000 miles (1,600 kilometers) inland from the Pacific Oceanprobably too far for ocean cycles to exert a strong influence on RMBL's weather.
"The signal we see in the snow pack and snowmelt is like what is projected from climate models just due to global warming, without any ocean oscillation," he said. "It's not proof of anything. But it says the evidence is consistent with this being a global warming signal."
The ecologist said the current drought could persist for the next 50 to 100 years, transforming RMBL's meadow from a summertime wildflower oasis to sagebrush scrubland.
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