Instead of refining the theory, perhaps it should just be scrapped altogether.
In a warming world, scientists have told us to expect more rain and less snow in the Northwest — but not less overall precipitation.
New evidence, however, suggests that both rain and snowfall may decrease across the region during dry years.
Even in the rain-drenched Northwest, the trend could escalate water conflicts if it continues. Farmers, conservationists and city water managers would face severe challenges trying to balance human needs with the survival requirements of endangered salmon that need cold, clean, rushing water.
Researchers with the U.S. Forest Service looked for changes in the amount of water flowing out of mountain basins since 1948 at 43 rivers and streams across Oregon, Washington, Idaho and western Montana.
Few rivers showed significant declines in runoff until researchers isolated the driest 25 percent of years.
Then nearly three-quarters of river basins showed severe decreases in water flow. Runoff fell by 30 percent or greater in most streams, and by nearly 50 percent at some locations during dry years.”
And those are really important years,” says study author Charlie Luce, a Forest Service research hydrologist in Boise.
The pattern found in the new study runs contrary to predictions based on computer simulations of global warming. Those suggest the Northwest should continue to receive about the same amount of precipitation but that runoff will peak earlier and leave rivers emptier in hot summer months.
That’s because rising temperatures are likely to cause more precipitation to fall as rain instead of snow and the mountain snowpack to melt earlier in the spring. In a new forecast for western Washington, for instance, Susan Dickerson and Robert Mitchell at Western Washington University in Bellingham predict increases in winter flows, decreases in summer flows, and a shift toward earlier spring snowmelt as the regional climate warms.
“The biggest hydrologic change is a shift in timing of flow, not a change in total annual flow,” Mote says. Since 1920, snow accumulation in Northwest mountains has fallen about 25 percent, Mote has calculated.
The new findings paint a more complicated picture. Not only will we see more rain and earlier snowmelts, but we also could see significant decreases in overall precipitation during drought years.
The new study doesn’t prove that dry years are getting drier because of less rain and snow, just that rivers run much lower than they did decades ago.
“It is not clear whether precipitation is decreasing, or whether water use is increasing,” says Julia Jones, an associate professor in the department of forest ecosystems and society at Oregon State University.
Because climate models don’t point to decreasing precipitation, says Mote, the OSU climate scientist, rising greenhouse gases may have nothing to do with decreased runoff in dry years. “You can’t conclude based on this study that climate models are missing something.”
Luce agrees that it’s impossible to link greenhouse gases and a warming climate to less precipitation in dry years. But he says the evidence is fairly strong that the decreases in river runoff are the result of less rain and snow and that the shift is contrary to climate models. Luce plans to extend his analysis to precipitation records but says those records aren’t as reliable as the numbers on runoff.
To account for changes in water use, Luce tracked forest water consumption and evaporative losses in one river basin and found that those water losses could not explain the decreases in river flow. Luce and co-author Z.A. Holden with the Forest Service in Missoula, Mont., also noted sharp decreases in flow in two river basins in which large tracts of forest had been lost to fires — which should have increased runoff by allowing more precipitation to reach streams.
Luce speculates that changes in the Pacific Ocean circulation pattern known as the El Nino Southern Oscillation may be the driving force behind his findings. Scientists have linked shifts in the El Nino cycle to droughts in some regions and torrential rains in others. In recent years, some researchers have proposed that global warming may be altering El Nino events and intensifying droughts.
But researchers don’t know enough to predict how the El Nino cycle will respond to future climate warming.
“Climate models embody the theory as we understand it,” Luce says. “Now we’ve got a new set of observations that don’t quite agree with the theory. People can go out and refine the theory.”
These people haven’t got a clue about this, but instead of just admitting that their theory is wrong, they are now busy tweaking their theory so that it still falls in line with “the consensus”, whose validity and conclusions shall never, ever be questioned. Ever.