Saturday, December 1, 2007

Teaching: thinking globally, observing locally

Yesterday morning, the National Weather Service issued a blizzard warning for my local mountains. It was the perfect set-up for a winter storm: a storm off the coast of Baja California, a jet stream that looped way down to Baja, and then up across central Arizona and straight for our mountains. I was on my next-to-last day discussing weather in my intro class, and it made for a perfect discussion. We could talk about winds, about low and high pressure, about the role of the mountains in controlling the weather in Durango and Denver.

The students were attentive and engaged, in the way that’s only possible when the professor is discussing the possibility of a powder day with a class full of skiers.

And then it fizzled.

It’s been raining. Raining hard. The temperature has stayed in the mid-30’s (F), even through last night. If it had been just a few degrees colder, there would be more than a foot of snow on the ground. But even though it has cooled a bit this afternoon, and there are now some big, fluffy flakes in the air, the snow isn’t sticking. I can see where the snow line probably is: there’s a layer of low clouds around 8000 feet, and that’s where the NWS is currently predicting the snow accumulation stops.

I only live at the edge of the mountains, and the ski area reportedly has two feet of fresh snow, and expects at least another foot. So the students won’t be disappointed.

But the lack of snow down here is important. Snow stays on the ground for months, and a lot of the water soaks into the ground. Rain runs off. And the cold and the snow help the pinyons and the Ponderosas fight off the bark beetles that have been killing the trees and making the summer fire hazards that much worse.

One storm doesn’t mean much. But changes in the snow level are one of the predictions of climate scientists like Jonathan Overpeck (who spoke here a couple years ago). And on Monday I’m talking about climate. So: do I use this storm as an example?

In some ways, that would be a very dangerous thing to do. Many people confuse climate with weather, and assume that if a winter is snowy, or a summer is cool, or a hurricane season is less active than expected, then global warming has turned out to be wrong. But weather and climate are not the same thing: weather is local and short-term; climate is regional or global, and deals with longer-term trends.

On the other hand, global climate can seem distant and irrelevant. Even with CNN and the internet and Google Earth exercises, it’s easier to care about things in one’s own backyard. One of the successes of An Inconvenient Truth, in my opinion, was the way it took a global scientific issue and made it personal, made it worth caring about.

So. Should I use the local weather as an example, and risk students walking out of class convinced that a single storm is what confirms or denies the existence of global warming? Or should I stick with discussing evidence that has been peer-reviewed by specialists, and remember that I’m professionally a structural geologist, not a meteorologist, and I am probably missing some crucial explanation for why this storm appears to be fizzling out, at least at my elevation?

(As I write, of course, the snow has begun to stick. Maybe we’ll get something out of this one after all.)


Ron Schott said...

Interestingly, the same storm fizzled out here in Kansas (all rain).

Nonetheless, my recommendation is to use the example - with the proper caveats - because it, unlike the snow, is likely to stick at your elevation.

Maybe they'll forget the caveats and blur the weather-climate distinction, but maybe it'll catch someone's imagination and they'll be inspired to learn more, and if they are so inspired they'll probably relearn the caveats on their own.

John Fleck said...

I agree with Ron - a potentially great example. Global warming is a matter of a few degrees. In this case, a few degrees was the difference between rain and snow at your house. A few degrees in general pushes the snow line around a lot.

Mel said...

Can you discuss what the climate change prediction is for your area? If global warming, will lead to a loss in snow ppt (due to warmer temperatures) you could say by watching the weather pattern over years, (not just one storm) you will see these predictions play out. I do think your local storm's snow line and it's potential impact on fires and infestations is a great way to discuss small temperature changes that will have a large impact to local economy/ecology/etc.