Tuesday, April 20, 2010

Its 2040!


Congratulations!

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:
http://www.atmos.washington.edu/~salathe/reg_climate_mod/ECHAM-MM5/seadiffs)

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.

14 comments:

Big Wave said...

I don't think any of us water our lawns in summer anymore - brown has become the normal color by August...(I never did like pushing the lawnmower)...

MarkM said...

Cliff,
So this past winter was a warm winter for 2010. It would be an average winter for 2040. What will the warm winters be like in 2040? No snowfall at all?

Matt said...

Cliff, your post makes me wonder about the accuracy of the long term forecasts, specifically, maybe a typical 2040 winter will be worse than we thouht, maybe this winter suggests things have changed sooner than we thought?

Matt

Rob said...

Anecdotally - fall precip/snow & resulting runoff events west of the Cascades tend to be more of a challenge for reservoir operations vs spring snowmelt. I'm wondering if this will become even more of an issue in 2040 (rainier, more rain/snow events, maybe more rain/snow events throughout the year...?). From an operational standpoint, Seattle might want to consider how best to optimize their storage in the context of changing hydrology with particular focus on fall/early winter operations.

Michael said...

Very fun Cliff

I think this type of potential future climate mapping to our past winter is a great way for people to develop a tangible understanding of how our climate can evolve.

Yorik said...

I like the comparison, gives me a good idea of what the numbers will feel like! However, I didn't really expect water to stop coming out of my tap due to lower snowpack. What about minimum fish flows and high water temps in this kind of a climate regime?

garyLambda said...

It's not 2040 I worry about, it's 2100. ie. if we melt the perafrost and release tons of methane gas, the models I've seen show that this gas overwhelms any contributions from C02. That is to say, no amount of carbon reduction on our part will affect the climate trend. And instead of being masters of our fate, we'll just go along for the ride. And that ride will NOT be nice.

Why? Because the warming that occurs in the central USA will make much of the land less able to sustain crops. We'll just farm farther North? well the soil in Canada is not the same as that in the Central and Southern US.

If you have any information on this feedback loop, I'd be glad for you to do a posting on it.

KeithL said...

Of course, integrate 30 years of this kind of deficit into the equation, and 2040 might be a little different, no?

32.5 East said...

Cliff says "Seattle will easily weather climate changes well into mid-century." and "Thirty years from now it will be warmer and the snowpack will be less, but here in the Northwest no panic is required.".

Sure global warming may cause problems elsewhere in 30 to 40 years but things will be peachy here. Thank god the hole is in the other end of the boat.

Christopher said...

A few posts ago you suggested that meteorologists consider that summer in the PNW really starts about July 12.

I'm wondering, then, when you see the start of the other seasons, and their durations. Forgetting the solstices and equinoxes, what do you consider the natural seasons of our local climate?

Dan McShane said...

One thing that will be interesting will be the impact to hydrology on river flooding. Intense warm fall rains with no snow pack may alter how flood events take place. We have seen flood already from October storms. While rain on snow with wind has caused bad floods in the past, we may see more flashy type floods in the fall. This will present an interesting problem for reservoir managers. It is one of the challenges faced in California such as the reservoir systems on the Russian River.

Bruc said...

I say let's not just depend upon changes in water management, the PUD needs to actively promote begin rain water harvesting in Seattle not just detain peak storm flows that over-follow combined sewer treatment facilitates, but to water our gardens in the summer. Let's make Seattle Resilient in 2040.

SteveM said...

I realize this focus of the “don’t worry” message in this post was directed toward Seattle’s water supply for consumptive use, but there’s much more even to the water supply picture to consider if this winter represents what will be “typical” by the 2040s. For example, salmon and steelhead in the Columbia and Snake Rivers face very tough conditions in 2010 because of this winter’s below-average snowpack. Low snow pack means low stream flows and higher water temperatures this summer – a double whammy if you’re a cold-water fish. More rain in November-December (or even in April) isn’t going to help fish who need water in July. For salmon, it’s snowpack that counts (as opposed to precipitation totals). While those of us west of the Cascades can rightly take some comfort in knowing we’ll still have adequate drinking water supplies even in such dry and warm conditions, there are a host of other problems that crop up when the dry year that’s currently the exception becomes the rule.

mig said...

Big Wave and SteveM make excellent points. And, as other areas of the nation and world are hit (even) harder, the Puget Sound area could see an influx of climate refugees. Not good for our water supply, environment, or our quality of life. It's not alarmist to ring the alarm about something alarming!