Tuesday, April 20, 2010
For those of you living in western Washington, you have experienced a typical winter of roughly 2040.
Now how can I say this?
Looking at the average temperatures from November through March at Seattle-Tacoma Airport, the last winter was 1.8F above normal, including the remarkable warmth of January. Examining the temperature predictions using high-resolution models embedded in global climate models, driven by an aggressive increase of greenhouse gases, one find that this corresponds to the expected changes around 2040. (For the hard core climate types, this is based on the MM5 runs forced by the ECHAM-5 GCM, check out:
The April 1 snowpack this year was roughly 70% of normal in the Cascades and this corresponds to the amounts in the models for roughly the same time--2040.
Time travel without traveling!
Now I am not saying this to downplay global warming, but to just add some perspective. Thirty years from now it will be warmer and the snowpack will be less, but here in the Northwest no panic is required. Even our current infrastructure can handle water supplies for such a situation.
This week I had a very interesting meeting with managers from Seattle Public Utilities, who are actively thinking about the implications of global warming on Seattle's water supply. It appears that with some changes in management of the reservoirs (storing more water in the spring and letting the level come down a little farther in the fall) and some modest improvements to the system, Seattle will easily weather climate changes well into mid-century.
In our discussions something came up that should have been obvious to me: the amount of rainfall during the winter and the snowpack at the beginning of summer are both very important, but so is something else--when the winter rains begin in the fall. How will this change under global warming? This is something I am going to investigate in the simulations we are running right now. Several simulations I know of suggest somewhat heavier fall precipitation, which if true, could help mitigate the water situation further.
Another factor this is helping immensely is that even with all the local population growth, water demand has stagnated or even decreased. An amazing accomplishment. Give credit to better plumbing--those water conserving toilets and shower heads--coupled with reduced usage of water during the summer.
Posted by Cliff Mass at 7:36 PM