TCS Daily


Year of the Rat

By Sallie Baliunas - September 16, 2002 12:00 AM

LOS ANGELES - The rat strutted on the velvet covering of the chain supporting the grand crystal chandelier that once resided in a cathedral in France but now illuminates the circular stairwell of my dear friends' home in Holmby Hills, Los Angeles. This summer is the invasion of the rats, Los Angeles style, meaning even the most elegant homes are affected. In this era of global warming panic, news stories blame invading rats on fossil fuel burning. Can a threat of bubonic plague be far behind in the propaganda that human-made global warming causes every harmful change to the ecosystem?

But the uptick in the city's rat population just cannot be blamed on human use of energy.

One might have thought that the rats had left Holmby Hills when Bugsy Siegel moved away in the 1940s. No, the Norway rat (Rattus norvegicus) has been in Los Angeles for decades. Blaming human-made global warming for this or any other phenomena related to ever-changing weather is as fashionable as nearby Rodeo Drive.

The rats have moved into the city in increasing numbers this summer owing to the current, severe drought. Records at nearby Mount Wilson Observatory in the San Gabriel Mountains show that this year is the driest since 1904, when the Observatory was founded. Dry, barren forests forced the canny rats to seek human habitats, where food and lawn sprinklers provide sustenance.

Residential Los Angeles hosts a thriving population of rats, lurking in old drafty structures with small entryways, or in the iconic palm trees and ground cover of the manicured gardens of Holmby Hills. But this year more rats have been attracted to human environments out of desperate survival, and people, sensitized by global-warming media hype, have noticed.

While some find domesticated rats suitable as pets (not I; I am very fond of terriers, who enforce a zone of rat avoidance), wild and feral rats can carry pathogens, including the fleas that harbor the bacterium Yersinia pestis that causes deadly bubonic and the rarer but highly lethal pneumonic plague. In the nearby San Gabriel Mountains, bubonic plague is reported occasionally in rock squirrels. And guess where the last rat-borne urban epidemic of bubonic and pneumonic plague occurred in the U.S.? In Los Angeles, in 1924 - 1925, where 33 pneumonic infections left 31 fatalities.

Bubonic plague was tested as a germ warfare agent by the vicious Japanese Unit 731 during World War II. Chinese prisoners (whom the experimenters callously designated as "loglike pieces of wood") and civilians were exposed to rats infected with bubonic plague-carrying fleas, and many died.

The great epidemics in Europe and China in the 14th century (a period of unusual cold) were effective because of rat and flea infestations, which we moderns tend to quench, thereby reducing the spread of plague. Furthermore the disease is a bacterial one, and is muted by simple and widely available antibiotics. According to the Centers for Disease Control and Prevention, in 1984 a veterinarian in Southern California survived the plague, transferred to him from a cat. But the plague went no further, owing to vigilance and diligence.

Although half of untreated victims of bubonic plague succumb to death, bubonic plague would not make an effective bioterror weapon if the rodents carrying the fleas were controlled, and antibiotics were available.

The Los Angeles rats also spell trouble for reasons other than plague. They might transmit other diseases, like murine typhus, rickettsialpox and rat-bite fever. Beyond spreading pathogens, the rats are destructive as they chew electrical wiring, insulation and even wood foundations.

As for global warming causing the rat increase - first remember that the local, not global conditions matter. Local temperatures at the L.A. Civic Center ranked below average (computed from 1921 to 2001) in 1999, 2000 and 2001. The temperature in 2002 has not so far been unduly warm. It is the drought that has caused the influx of rats to the city, not temperature. Periodic droughts in the Southwestern U.S. are a natural feature of the area's climate, and no evidence links their frequency or severity to fossil fuel use.

The increase in rat population is real; the drought in southern California is real. But the two are not linked to fossil fuel burning. Public confusion arises from a common series of logical errors made by promoters of the idea of human-made global climate change.

Here's how the promotion goes. First, confuse a local ecosystem response (rats seeking new habitats during a drought) or an event like drought with local temperature. Next, incorrectly associate local temperature (which in L.A. is not unusually warm) with globally-averaged warmth. Next, invoke the widespread myth that scientists agree that recent surface warming is definitely linked to fossil fuel use, through the use of sophisticated but unproved computer simulations of climate.

Finally, avoid mentioning two important facts. First, all the computer simulations say that for the global surface warming trend to be human-made, it must be preceded by warming in the layer of air from just above the surface to a few miles in altitude. Second, precise measurements made by NASA and NOAA instruments show that this low layer of air does not display the strong warming trend forecast by the computer simulations. The NASA and NOAA measurements going back as far as forty years find no confirmatory human-made warming trend in that air layer. Hence, the widespread surface warming cannot have been caused by fossil fuel use, and the surface warming trend is predominantly natural.

The scientific conclusion is that human-made global warming cannot be stretched to cover the increase in the Los Angeles rat population, except in the superstitious world of urban myths. Relieved of that worry, residents can go to the real work of controlling sanitation and access to potential rat harborage. Until the drought abates, the rats may wander noticeably through the city. Rats might be seen perusing the Gucci shoes, Cartier sunglasses and edgy fashions on Rodeo Drive, then retiring to their glamorous homes in Holmby Hills. But when the rain returns and the forest blooms, the rats will head home to the forests.

Notes: Holmby Hills has been home to moguls of industry and movie stars like the Bogarts and Lana Turner. Breathtaking gardens frame architectural diamonds, some of which were designed by African-American Paul Revere Williams (1894 - 1980). Williams drafted plans for over 2,000 homes, besides working on Los Angeles International Airport's arched landmark building, the Shrine Auditorium and expansion of the Beverly Hills Hotel, whose pink and green color scheme owes to Williams.
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