Monday, December 3, 2012

The Coming Storm(s)

This is how Reno looked yesterday. Yikes. Now that's wet!

Heavy wind and rain whipped the Reno-Tahoe region over the weekend...

But fortunately, there was no severe flooding.

“So far, so good,” Gov. Brian Sandoval said during a 2:30 p.m. tour beside a swiftly flowing river near Vista Boulevard in Sparks. Sandoval spoke of a welcome change in the weather that helped avoid a serious flood and lauded officials from Sparks, Reno and Washoe County for an effective joint effort in preparing for expected flooding.

“You prepare for the worst and hope for the best and that’s exactly what happened,” Sandoval said. “You can never take anything for granted. We were ready for whatever was going to take place.”

“We were very lucky,” agreed Steve Driscoll, assistant city manager for the city of Sparks. Businesses across the Sparks industrial area were ringed with sandbags in advance of the expected flooding while crews also built an earthen berm to hold back floodwaters near the North Truckee Drain. Whipped by strong wind, heavy rain fell in the Truckee River watershed throughout the night, with significant flooding still expected well into the morning hours.

Mainly because the storm arrived colder than expected and moved much faster than expected, much of the precipitation ended up falling as snow and the system started leaving the region this morning. Reno and Sparks are indeed very lucky today. Throughout last week, an atmospheric river (a band carrying huge flows of vapor, causing heavy rainfall) brutally dumped torrential levels of rain throughout Northern California. Over 315,000 people lost power in the Bay Area last weekend as urban areas were subjected to well over 3 inches of rain and 60+ mile per hour winds. Northern Nevada pretty much just experienced the tail end of this mega-storm. So what happened? Is it just the occasional bout of bad weather? Or is there more to this? A recent blog at Scientific American detailed what may be frightening news ahead.

Because atmospheric rivers play such terrible roles in floods and such vital roles in water supply, it is natural to wonder what might happen with them as climate change takes firmer hold. Recall that Zhu and Newell first coined the term “atmospheric river” to describe features they observed in computer models of weather. Those models are closely related to models used to project the future consequences of rising greenhouse gas concentrations. Scientists do not program atmospheric rivers into weather and climate models; the rivers emerge as natural consequences of the way that the atmosphere and the atmospheric water cycle work, when the models are let loose to simulate the past, present or future. Thus, the rivers also appear in climate projection models used in Intergovernmental Panel on Climate Change assessments.

A recent review by one of us (Dettinger) of seven different climate models from around the world has indicated that atmospheric rivers will likely continue to arrive in California throughout the 21st century. In the projections, air temperatures get warmer by about four degrees Fahrenheit on average because of increasing greenhouse gas concentrations. Because a warmer atmosphere holds more water vapor, atmospheric rivers could carry more moisture. [...]

All seven models project that the number of atmospheric rivers arriving at the California coast each year will rise as well, from a historical average of about nine to 11. And all seven climate models predict that occasional atmospheric rivers will develop that are bigger than any of the historic megastorms. Given the remarkable role that atmospheric rivers have played in California flooding, even these modest increases are a cause for concern and need to be investigated further to see if the projections are reliable.

So yes, yet again climate change is leading to erratic and more severe weather. On one hand, this storm did provide some much needed rain as most of Northern Nevada has been suffering from extended drought. But as mentioned above, anything more intense could have caused massive flooding and damage. Sadly, extreme is becoming "the new normal" when it comes to our weather. And unless we take action on climate change very soon, what we've seen this year will be considered a cake walk compared to the kind of severe weather we will see in the future.

The world is now on track for temperatures to rise at least 2 degrees Celsius (but possibly as high as 4) by the end of the century. This will mean even more catastrophic weather in our future. Climate change is now here, and it's already delivering more extreme weather. There's now little time left to act before the weather becomes too much for us to handle.

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