Drought May Be ‘New Normal’

Studies predict warming trend will make recent drought look like a wet period by century’s end


Lightning strikes sparked five wildfires in Gila County, but damp conditions from recent monsoon activity kept the fires from spreading.

Lightning strikes sparked five wildfires in Gila County, but damp conditions from recent monsoon activity kept the fires from spreading.

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A month of monsoon has done wonders for Rim Country forests despite small fires sparked by lightning strikes, but those blessed months of near-normal rain may become a fond memory, according to a just-published study.

This week, thunderstorms started five wildfires in Gila County, but the damp conditions kept the fires from spreading.

Those fires included a three-acre fire in the Hellsgate Wilderness area, a 15-acre fire in the Tonto Basin and a 200-acre fire in the Superstition Mountains, as well as a 5-acre fire near Pleasant Valley and a 2-acre fire near Globe.

Those fires would have posed a big threat a month ago, but the steady succession of monsoon rains has dramatically changed fire behavior.

Forecasters expect a normal monsoon season and a wetter-than-normal winter, thanks to the El Niño warming of surface waters in the Pacific. Payson has received about 5.5 inches so far this year, compared to a normal total of 14.1 inches at this point. Normally, Payson gets about 3.3 inches of rain in August.

Meanwhile, July ranked as the hottest month on record for the continental United States, according to the National Oceanic and Atmospheric Administration — a full 3.3 degrees above the average for the 20th Century. That made the first seven months of 2012 the hottest stretch since forecasters started keeping records in 1895. Drought conditions now affect two-thirds of the states. That includes all of Arizona, with Gila County facing “severe” drought conditions.

Unfortunately, the region may find such conditions will become the “new normal,” according to an accumulation of studies.

The bone-dry stretch from 2000 to 2004 ranked as the worst drought in 800 years — but may offer just a taste of future conditions as the planet inexorably warms, concluded a study published in the July 29 issue of the journal Nature Geoscience. The lead author was Christopher Schwalm from Northern Arizona University.

That drought reduced by half the amount of carbon dioxide Arizona forests removed from the atmosphere, as trees died and soils dried. Moreover, projections suggest that by the end of this century such conditions may actually qualify as the wet end of the cycle — a shift that would dramatically impact vegetation, water supply and fire patterns through the western United States.

“To our surprise, the drought, which was severe with respect to recent and past conditions, is forecasted to become the wetter end of a new climatology,” said Schwalm. “And it would make the 21st Century climate akin to the mega-droughts of the last millennium.”

If those predictions prove accurate, Payson’s coup in winning the rights to 3,000 acre-feet annually from the Blue Ridge Reservoir may prove a just-in-time lifeline, making Payson one of the few rural Arizona communities with enough water to supply projected future needs.

The four-year period the researchers studied came amidst a 10-year dry period, interrupted by several near-normal winters. The drought has clamped down again this year, with Roosevelt Lake drained below 50 percent of its capacity.

The researchers concluded that the drought helps drive itself by reducing the absorption of carbon dioxide on a global scale, as plants die and decay. This releases carbon dioxide. By contrast, the long-lived plants like ponderosa pines killed or stunted by the drought actually remove carbon dioxide from the atmosphere and lock it away for centuries.

The recent drought proved much more severe than several earlier episodes revealed in the tree ring data and other measurements. For instance, the researchers documented two less serious droughts — one from 977 to 981 and the other from 1146-1151.

Normally, the plants and chemically reactive rocks in North America can absorb about a third of the carbon dioxide released into the atmosphere by the use of fossil fuels. However, the researchers predicted that the drought-stressed plants would lose that ability on a large scale, if the 2000-2004 period becomes the “new normal.”

During that period, runoff into the Colorado River dropped by half, crop productivity fell by 5 percent and evapotranspiration in forests decreased by a third.

The study in Nature Geoscience adds to a growing weight of evidence suggesting that the American Southwest may face increasingly hot, dry conditions in coming decades.

Studies have documented a dramatic increase in extreme weather, from droughts, to floods to high temperatures, all consistent with climate model analysis of the likely effect of the gradual rise in temperatures in the past century.

One study published in the journal Nature Climate Change noted that in 2011 the U.S. experienced 14 extreme weather events, causing $1 billion in damages. Similar extreme conditions hit all across the globe.

Moreover, the rise in atmospheric carbon dioxide most likely accounts for the average temperature increase of 1.5 degrees centigrade in the past 250 years, according to another study by researchers from the University of California at Berkeley available online at BerkeleyEarth.org.

The study used both direct temperature measurements and other indirect measures, like carbon dioxide ratios in air bubbles trapped in arctic ice, tree rings and other measures.

The study linked several global temperature drops to particles injected into the atmosphere by volcanoes.

However, a direct link between atmospheric carbon dioxide and temperature provided the best explanation for warming periods, especially in the past 50 years when temperatures rose 1 degree centigrade.

The link between atmospheric carbon dioxide and temperature proved far stronger than any other explanation tested, including variations in solar radiation, shifts in human population, sunspot frequency or climate shifts like El Niño and La Niña patterns.

Another study offered dire warnings for the future of the pinyon pine and juniper tree forests that dominate the landscape around Payson.

The combination of drought and beetles have killed 2.5 million acres of pinyon-juniper in the Southwest in the past 15 years, concluded researchers from NASA and Oregon State University in a study published in the journal Echohydrology.

The death of millions of acres of the hardy, drought-resistant trees will cause a serious increase in soil erosion and blowing dust. That dust, in turn, will settle on top of the snow pack and spur earlier melting, exchanging the gradual release of water into the water table and streams for quick, early spring flooding.

In some areas, the drought and insects have killed 90 percent of the trees. The most-hard hit areas are generally lower in elevation than Payson, with significantly less rainfall.

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