Thank you, global warming purveyors:
Tahoe City — Global warming seems to have reached the lowest depths of Lake Tahoe, scientists warned Monday, potentially complicating plans to preserve the lake’s fabled water clarity and biological health.
A new study by researchers at UC Davis suggests the lake has heated by nearly 1 degree Fahrenheit since the early 1970s, when readings began. The warming may be significantly altering the dynamics of Lake Tahoe’s cold-water upwellings and seasonal mixing of sediments and nutrients, the scientists said.
It’s the latest sign that a changing climate may be showing up in the Sierra Nevada, one of many mountain ranges around the world in which scientists are looking for the subtle impacts of global warming. No one can be certain if any given change is due to human activity, but the widely held assumption is that emissions of carbon dioxide and other heat-trapping greenhouse gases are involved.
[A] warming signal is emerging in the lake’s temperature data at virtually all depths, down to as deep as 1, 300 feet.
“The lake has warmed from top to bottom over the past 30 years,” Schladow said. He said there are no local or regional factors big enough to explain the warming, even with all the development that has occurred in the Tahoe Basin in recent years.
Schladow and others said the changes are consistent with emerging data worldwide that point to an increase in temperature taking place far more rapidly than any previous change in the geologic record.
There is no reliable way to gauge Lake Tahoe’s water temperature before the 1930s. But air temperature data in the Tahoe City region go back about 90 years and show about a 3.6-degree Fahrenheit increase, enough to account for the increase in average water temperature and consistent with the emerging global data on climate shifts.
The data show that relatively wide swings in Lake Tahoe water temperatures are common from one year to the next, at least during the past 30- plus years of regular monitoring and some 7,300 individual measurements.
But after smoothing out the peaks and troughs, scientists said there is a clear upward tilt in the numbers, with temperatures increasing by an average of about 0.027 degree Fahrenheit a year from 1970 to 2002.