SEATTLE - This week Al Gore released an updated version of his original climate change movie “An Inconvenient Truth.” It’s called The Climate Reality Project.
If you check out the website an ad pops up that sounds a little bit like a suspense movie trailer, and in a way it is. Gore’s goal this time around is to sound the alarm about the potential connection between global climate change and extreme weather events like flooding and hurricanes.
The connection there is pretty strong. A warming atmosphere leads to more moisture and that means more extreme precipitation events, even in dry places – on the global level.
But things get fuzzier when you zoom in from that 30,000-foot viewpoint, closer to home.
Cliff Mass, a professor of atmospheric sciences at the University of Washington, gave a talk at a conference on climate change this week in Seattle and said that the global science may not be directly applicable on the local level. “Simplistic talk about warming temperatures causing more extreme precip over the NW is completely bogus.”
Mass went on to explain that jet streams, or the westerly winds, play a big role in the weather in the Northwest. These fast flowing air currents in the atmosphere move east over the Pacific Ocean to the U.S. coast. Mass says that some models show that with climate change, those air currents might weaken and move north. “If the jet stream moves northward the flow, the storms could move northward and we could end up in a dryer situation with less extreme precipitation.”
It’s not certain that the jet stream will move northwards and if it doesn’t, things could be a lot wetter in the Northwest.
Scientists may not know how much precipitation we’ll have in the future around here, but they’re pretty sure it’s going to be warmer, and that’s a problem for a different reason.
In the Northwest up to 85 percent of our precipitation comes in the winter, much of that as snow. Now turn the thermostat up a degree or two and that snow is going to come as rain – flowing directly into rivers. Alan Hamlet, a researcher with the Climate Impacts Group at the University of Washington, explains that as it gets warmer the very make up of our precipitation will change.
“Let’s imagine that I have ten inches of precipitation that falls on a river basin and over half the area I get it coming as snow, then half of the water that would come out at the bottom of the river doesn’t come out. Why?” he asks. “Because it’s collecting as snow at high elevations.”
That means that, as it gets warmer, a normal precipitation event –- where it might be raining in Seattle or Portland but snowing in the mountains — could just mean rain all over, and that means flooding.
Hamlet says he thinks the global predictions for more extreme precipitation events can be applied here in the northwest, and that we should be preparing for the worst. “Our management strategies may be inadequate for dealing with the risks that are actually going to be experienced in the future. When things are changing rapidly it requires a different way of looking at things, and particularly looking forward in time.”
The Army Corps of Engineers is charged with managing many of our levies and reservoirs. For them, the word of the day from the scientific community is uncertainty. Larry Schick handles water management for the Army Corps of Engineers in Seattle. “It’s that uncertainty that’s difficult to plan with. It’s a huge challenge and when you’re engineering something there’s always uncertainty. Every bridge will fail under the right conditions. and quite frankly it’s not clear how we’ll deal with that.”
Schick says planning major flooding infrastructure without a firm handle on climate predictions for the reason is really tough, but the corps is getting ready for the fall flooding season, nevertheless. We’re entering a la nina year, which could mean colder temperatures with lots of precipitation.
A recent report by the U.S. Climate Change Science program found that across the U.S. and North America there have been increases in extreme climate events. All these trends are expected to continue in the future with the buildup of greenhouse gases in the atmosphere.
So, get your ski passes and your rain gear. The weather in the Northwest in the coming years will be interesting.