Record-breaking California drought enhanced, not caused, by climate change
Thursday, December 11, 2014, 2:36 PM - Has climate change been exonerated in the case of the state of California vs. the worst drought to affect the area in 1,200 years? Don't count on it.
In a new report that surfaced on Monday, NOAA - the National Oceanic and Atmospheric Administration - announced that "natural oceanic and atmospheric patterns are the primary drivers behind California's ongoing drought."
Firstly, even in the report itself, the scientists involved do not completely rule out climate change as a factor. They simply state that natural factors were the dominant ones in this case. As they summed up in the report FAQ:
The current California drought ... has been accompanied by extreme high surface temperatures, which have exacerbated the stresses on water resources. The magnitude of the warmth during this drought is considerably greater than during previous California droughts, and cannot be reconciled with natural variability alone but is partly a consequence of climate change.
Secondly, and perhaps more importantly, buried in these headlines is an implication that climate change has ever been claimed as a cause of the drought. It has not.
Simply put, that's not how climate change works.
Global warming and the resulting changes to Earth's climate system do not specifically cause weather events to form. In fact, the effects of climate change appear to stifle storm formation, resulting in fewer storms overall. At the same time, though, the increased heat energy and moisture content in the atmosphere - directly due to climate change - pushes a greater number of those storms that do form into becoming extreme events.
Thirdly, climate scientists are already pointing out issues with the study.
In an article on the environmental news site EcoWatch, Michael E. Mann, Director of the Penn State Earth System Science Center, brought up some important points:
First of all, there is the role of Pacific sea surface temperature (SST). Despite what the authors claim, the Pacific SST patterns underlying the ongoing drought-favorable conditions may be partly forced, and not simply a result of natural climate variability.
Secondly, the approach taken in this latest study doesn't account for the potential influence of decreasing Arctic Sea Ice.
Most inexplicable of all, though, is the fact that the authors pay only the slightest lip service to the role of surface temperature in drought, focusing almost entirely on precipitation alone. That neglects the fact that California experienced record heat over the past year, and this anomalous heat certainly contributed to the unprecedented nature of the current drought.
And most ironic of all, just days ago, another article in [the journal Geophysical Research Letters] concluded that the record heat played a role in making the current California drought the worst such drought in at least 1200 years!
For Mann's full explanation of these points, click here to access the article.
Mann goes on to state that he does not doubt the intentions of the authors, and that he is sure the study was done in good faith. However, what he finds troubling is the fact that the study has apparently not gone through the peer-review process to check its methodology, and that there was such attention brought to the report's conclusions despite that fact.
As for what actually caused the California drought, that's a sticky question.
The researchers who penned the report may be right when they point the finger at the 2011/2012 La Nina weather pattern in the equatorial Pacific Ocean, and the persistent 'blocking' high pressure over the eastern Pacific that set up in its wake. If we accept that, however, it raises at least two other questions: What factors made that La Nina event unfold the way it did, and what exactly went into forming the persistent ridge of high pressure over the eastern Pacific Ocean?
The effects of climate change on the El Niño-La Niña pattern is still uncertain. It may be that it has the same effect on this pattern as it does on the formation of extreme weather - resulting in fewer, but more extreme events. That's still being studied.
As for the persistent 'blocking' pattern, research has already shown a link to climate change. Stanford climate scientists refer to this pattern as the Ridiculously-Resilient Ridge (or Triple-R), and point out how this pattern has had a strong influence on keeping storms from bringing moisture to California, and their research shows how the formation of these Triple-R's is far more likely now than it was before human activity began pumping massive amounts of greenhouse gases into the atmosphere.
So, there is a link to climate change just in the weather pattern that formed, which resulted in three years of rainy seasons that just didn't deliver the rain to California.
Also, as pointed out by the study scientists (and Dr. Mann), the extreme temperatures California has experienced throughout the drought, which also have links to climate change, made the situation much worse.
Thus, overall, the cause of the drought is very likely a mixture of different factors, but the severity of the drought - the fact that it is the worst drought the region has suffered in around 1,200 years - was certainly enhanced by climate change.
What's ahead for California?
One final issue the report addresses is what scientists expect from the drought in the months ahead.
With the developing El Niño in the Pacific Ocean this year, the researchers say that this reduces the risk of the drought continuing at its current intensity. However, they also point out that it does not eliminate the risk, and the development of an El Niño alone is not necessarily a remedy to the crisis.
Even if the drought does end, California's water deficit is extreme and it will take years of 'normal' precipitation for the state to recover. According to the University of California Center for Hydrologic Modeling (UCCHM) drought update website, just to make a dent in the drought emergency, it would take having a strong rain storm sweep through every week for three months. Furthermore, this once-a-week pattern would have to persist for a total of 5 years for there to be a long-term recovery from the drought.
Let's hope that this year's El Niño does break down the Triple-R pattern, so that California can at least start this long road to recovery as soon as possible.