California Dreamin' Of Wetter Times

California, the state that raises 30% of US fresh produce, is in the grip of a severe drought. Billed as the driest period in the state's recorded rainfall history, climate change alarmists have hastened to blame the parched conditions on anthropogenic global warming (AGW). Paleoclimate history tells a different story, however, and highlights the amazingly short attention span of AGW advocates. Going beyond the 163-year historical period, science shows that there have been other, longer lasting and more severe droughts than the current dry spell. Today's drought is minor when compared with ancient Megadroughts, which occurred between 850 to 1090 and 1140 to 1320. In fact, the worst droughts suffered by the American Southwest all happened so long ago that human memory fails us.

As bad as people think conditions are in the Golden State, they may get much dryer before the current drought ends. According to Bill Patzert, a research scientist and oceanographer at NASA's Jet Propulsion Laboratory in Pasadena, the West is in a 20-year drought that began in 2000. He attributes the persistent drought conditions to a phenomenon known as the Pacific Decadal Oscillation (PDO). The PDO negative phase, which is linked to extreme high-pressure ridges that block storms, is currently underway. This may mean another 10 parched years for the Southwest.

California, the US's most populous state with 38 million residents, has built a massive economy—Hollywood, Silicon Valley, and millions of acres of incredibly productive farmland—all in a semiarid coastal region that has its share of natural hazards. In an article in the San Jose Mercury News, environmental reporter Paul Rogers describes the potential impacts of such a prolonged drought:

Farmers would fallow millions of acres, letting row crops die first. They'd pump massive amounts of groundwater to keep orchards alive, but eventually those wells would go dry. And although deeper wells could be dug, the costs could exceed the value of their crops. Banks would refuse to loan the farmers money...

In urban areas, most cities would eventually see water rationing at 50 percent of current levels. Golf courses would shut down. Cities would pass laws banning watering or installing lawns, which use half of most homes' water. Across the state, rivers and streams would dry up, wiping out salmon runs. Cities would race to build new water supply projects, similar to the $50 million wastewater recycling plant that the Santa Clara Valley Water District is now constructing in Alviso.

Noting that agriculture is only 3% of the state's economy, a megadrought would still impact food prices across the nation. Undoubtedly the federal government would step in with billions of dollars of aid for the 38 million residents who send the largest delegation to the US Congress in Washington, DC, and wield the largest block of votes in the Electoral College in presidential elections.

Hailed as possibly the worst drought California has seen in 500 years, Gov. Jerry Brown has declared a state of emergency. Some rural areas may run out of water entirely in coming months if conditions don't improve. California's State Water Project, an agency that redistributes water from the snowy mountains in the north to the drier south, has announced it will not be able to deliver water to many communities in the coming months. Those towns will be on their own for water resources.

“Cities would be inconvenienced greatly and suffer some. Smaller cities would get it worse, but farmers would take the biggest hit,” said Maurice Roos, chief hydrologist at the state Department of Water Resources. “Cities can always afford to spend a lot of money to buy what water is left.”

Though the current drought is undoubtedly a bad one, it really is not anything special. The longest droughts of the 20th century occurred from 1987 to 1992 and from 1928 to 1934. According to Scott Stine, professor of geography and environmental studies at Cal State East Bay, both were minor compared to the ancient droughts of 850 to 1090 and 1140 to 1320.

Californians may be dreaming of a wetter climate but not that long ago the state was beset by heavy rains and disastrous mud slides. This is also nothing unusual from a historical perspective. Between the two medieval megadroughts, for example, the long-term record shows decades of above-normal rainfall—the kind that would cause devastating floods today.

“We continue to run California as if the longest drought we are ever going to encounter is about seven years,” Stine said. “We're living in a dream world.”

What causes this extreme variability? In a paper appearing in Nature Geoscience, Staryl McCabe-Glynn et al. identify some possible linkages while stressing the uncertain nature of climate variation. Note that they make the obligatory mention of possible human influence due to rising greenhouse gas (GHG) emissions at the end.

Precipitation in southwestern North America has exhibited significant natural variability over the past few thousand years. This variability has been attributed to sea surface temperature regimes in the Pacific and Atlantic oceans, and to the attendant shifts in atmospheric circulation patterns. In particular, decadal variability in the North Pacific has influenced precipitation in this region during the twentieth century, but links to earlier droughts and pluvials are unclear. Here we assess these links using δ18O data from a speleothem from southern California that spans AD 854–2007. We show that variations in the oxygen isotopes of the speleothem correlate to sea surface temperatures in the Kuroshio Extension region of the North Pacific, which affect the atmospheric trajectory and isotopic composition of moisture reaching the study site. Interpreting our speleothem data as a record of sea surface temperatures in the Kuroshio Extension, we find a strong 22-year periodicity, suggesting a persistent solar influence on North Pacific decadal variability. A comparison with tree-ring records of precipitation during the past millennium shows that some droughts occurred during periods of warmth in the Kuroshio Extension, similar to the instrumental record. However, other droughts did not and instead must have been influenced by other factors. Finally, we find a significant increase in sea surface temperature variability over the past 150 years, which may reflect an influence of greenhouse gas concentrations on variability in the North Pacific.

In “Variable North Pacific influence on drought in southwestern North America since AD 854,” they provide a history of sea surface temperatures (SST) from a region of the pacific Ocean known as the Kuroshio Extension that is in good, but not perfect agreement with California's history of drought, at least for the ancient megadroughts.

According to the authors, high SSTs in the Kuroshio Extension provide heat fluxes that generate an atmospheric wave, shifting the jet stream north over the western Pacific and south over the eastern Pacific. “The same wave pattern is visible lower in the atmosphere where moisture is transported (~ 850 hPa) as a ridge over the western Pacific and a trough over the eastern Pacific,” the authors explain. These are the same shifts that moderate or unleash the dreaded Arctic Vortex on the continental US.

A previous comparison with drought records from western North America showed that although most droughts occurred during periods of cool EEP SSTs, certain droughts were synchronous with warm EEP SSTs (El Niño-like) and thus required other explanations. The Kuroshio Extension SST reconstruction further supports this interpretation. For instance, the record shows predominantly warm Kuroshio Extension SSTs during MCA droughts from AD~ 854–1080 when EEP SSTs were warm, suggesting that some droughts could be driven more by NPDV than ENSO. Interestingly, the warmest Kuroshio Extension SSTs occurred during the LIA, from ~ 1,700 to 1,800, and the coolest occurred during the early twentieth century, a time in which SWNA was wetter than any other period of the past ~ 1,000 years.

So the PDO and El Niño/La Niña cycles, known as the ENSO, seem to have an impact on such goings on. These are most probably linked to the 11 year solar variability cycle. But with nature things are never so straight forward. People undoubtedly have some impact on climate, at least on a regional basis, as do other creatures. Consider the impact of one of the smaller creatures in nature—the mountain pine beetle.

It is well known that forest have a marked impact on climate: they modify energy and moisture exchange between the land and the atmosphere; absorb a high fraction of the incoming solar radiation, which leads to warming at the surface; evaporation from soil and foliage lowers surface temperatures and sustains a moist atmospheric boundary layer; and potentially alters cloud physics and precipitation. In these and other ways, forests modify climate. Enter the pine beetle.

The mountain pine beetle, Dendroctonus ponderosae, is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia. Pine beetles lay their eggs under the bark of pine trees, leading to tree mortality. During the early phase of the infestation, lifeless needles turn red. As reported in Nature Geoscience, H. Maness et al. demonstrated that a large-scale ecological disturbance—forest dieback resulting from mountain pine beetle infestation in British Columbia—has altered the energy balance and temperature of the local land surface. Using satellite data, they show that pine beetle disturbance in the forests of British Columbia has raised regional summer-time surface temperatures by 1°C.

Though some dim bulbs have tried to blame the beetle infestation on climate change, the reverse is true. The pine beetle has had as much impact on North America's regional climate as the IPCC claims humans have had through CO2 emissions. It also points out how complex and interrelated the factors that control climate are. Do any climate models take into account the spread of pine beetle infestations? How many other factors exist that can have nontrivial impact on large areas of the globe, impacts on a par with the supposed changes that warmists froth at the mouth over?

The take home message here is that there are far too many people making pronouncements about climate change without understanding what has gone before. How many news readers have declared a storm “the storm of the century,” a year “the hottest in history,” or a drought “the worst ever?” Even over excited science types fall victim to the moment when applying superlatives to natural events. The world would be better off with fewer myopic climate scientists.

Sorry, California, but your drought is nothing special, even if it lasts another 10 years. Just because you have never seen such a thing before doesn't make it unprecedented or even unusual in the grand scheme of things. It may cause you some discomfort, and cramp that California life style we hear so much about, but you will just have to do what we humans do best. That means exercising the trait that took us to the top of the evolutionary heap on planet Earth—adaptability.

Be safe, enjoy the interglacial and stay skeptical.

From NASA Science News

California is experiencing an extreme drought--by some measures the deepest in more than a century. NASA researchers are investigating the underlying causes as satellites, aircraft, and high-altitude balloons collect sobering images of the desiccating landscape.