Academic studies released Monday disagreed that California's record drought was linked to climate change, with two finding against such a link and a third — from Stanford University — finding a connection.
The studies were contained in a special edition of the Bulletin of the American Meteorological Society, organized by the U.S. National Oceanic and Atmospheric Administration, which on Monday published 22 studies on 2013 climate extremes and their connection to global climate change, the Associated Press reported.
The report seeks to find how much and how man-made warming has influenced the weather, NOAA research meteorologist Martin Hoerling, an editor of the report, told the AP.
Meanwhile, an early snow storm — the first of the season — dumped up to 3 inches along the Lake Tahoe Basin, the Los Angeles Times reported. While a welcome harbinger of winter, the snowfall wasn't expected to dent the ongoing drought:
The first snow of the season dumped up to 3 inches along the Lake Tahoe Basin, forcing authorities to shut down California 108 at Sonora Pass, which remained closed Monday, said Tom Dang, a meteorologist for the National Weather Service in Sacramento.
It was the first time in several years that a storm had dropped so much snow on the Sierra this early in the year, he added.
Drought and climate
The National Oceanic and Atmospheric Administration released the report Monday looking at 16 different global weather events from last year to determine if they were caused by human-induced climate change.
Three different studies included in the report examined the ongoing drought in California, but NOAA insists the evidence was not strong enough to point to a link between human activities and a lack of rain in the west.
"Drought is a highly complex meteorological phenomenon, and in general a combination of factors come together to determine the severity and length of a drought" said Stephanie Herring of NOAA during a conference call.
One study from Stanford University found that the chances of high atmospheric pressure patterns in the northern Pacific associated with California's drought seem to have increased due to human activity.
Such a high pressure system, like the so-called ridiculously resilient ridge currently parked over California, can divert rain-bearing storms from the West Coast.
"Our paper found a clear influence of the observed global warming on the probability of the atmospheric conditions," Stanford researcher Noah Diffenbaugh told KPCC.
But NOAA's Hoerling argued in an interview with KPCC that the Stanford study did not look at other factors, such as how climate change might affect pressure systems in the subtropical Pacific.
If pressure raised there as well, it would essentially cancel out the high pressure of the north. In fact, Hoerling said, some research suggests that pressure in the subtropics might increase under climate change more than it would in the north, resulting in more rain in California.
"[The Stanford team] didn't do the second leg of analysis that you would really need to do to pin climate change to California [precipitation]," he said.
Hoerling also argued that, while California's current drought is three years old, the Southwest as a whole has been parched in various parts since 1998.
"This is of greater concern in some sense because of its sustained and regionally consistent effect," Hoerling said.
Weird weather around the world
In addition to the drought, the NOAA study looked at several other noteworthy weather events from 2013.
The list includes the extreme rains and flooding in parts of Colorado, the freak blizzard that struck South Dakota last October, the unusually cold spring in the United Kingdom and the heat waves in Australia, Japan, South Korea and China.
The dramatic heat in Australia in particular was examined by five independent groups of researchers.
All of them found evidence that human activities are influencing temperatures in that region.
Similarly, scientists looking at the extreme summers in Japan, South Korea and China also concluded that human-caused climate change made such heat spells more likely.
As for Colorado, researcher think the chances of another extreme rain event, like the one that flooded Boulder last year, will actually be less likely in the future due to climate change.
This study, dubbed "Explaining Extreme Events of 2013 from a Climate Perspective," is the third such report released in as many years.
Researchers involved used computer models to simulate weather patterns in order to explain and predict the impacts of climate change.
NOAA said this is still a new and developing field of study and more research is needed to refine the use of these tools.
In the meantime, the federal agency hopes world leaders will use the data gathered so far to improve their planning for weather events in the future.