10:05 AM Thu, Jan 22, 2009 | Permalink
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Interesting presentation this morning here at the Weather Summit in Steamboat CO, from Stu Ostro of the Weather Channel. He's been looking at odd and extreme weather events over the last 5 to 10 years and wondering if they can be correlated to global warming. During our snowy December in Portland, I received a lot of comments along the lines of "so much for global warming". To that I continue to reply, Portland isn't the globe. Ostro has looked at record highs v. record lows around the country and the world, and the record highs outweigh the record lows. Can that be directly attributed to climate change? Not sure about that, but these are the kind of questions that need to be asked. What I can tell you is I've seen a few things recently in the Northwest that I don't ever remember seeing before. Such as:
January 2008 Vancouver, WA tornado. Definitely a rare and odd event.
The massive wind field of the Dec 2007 windstorm. The Pacific Northwest has seen lots of big windstorms over the years, but the size of that storm was unlike anything I remember seeing in the last 23 years of forecasting in Oregon.
Very warm temperatures in the mid-atmosphere. In meteorology we use constant pressure surfaces to analyze the atmosphere. One that is commonly used is the 500 millibar (mb) level, which varies in elevation, or height, but is roughly centered around 18,000 ft. The height of that pressure surface correlates well with the temperature of the air at that level. Over the last few summers I've seen values of the 500 mb surface that I don't remember seeing except maybe once or twice, since I've been looking at such maps since 1980. Even now, the anomalies of the 500 mb heights in western Canada are huge.
Am I ready to definitively say all these things are a direct cause of humans pumping greenhouse gasses into the atmosphere? No, I'm not. My examples above are anecdotal and not scientifically robust. But these are the things that need to be looked at as we continue to probe the question of what human-caused climate change will look like. And cold extremes may part of the picture, ironically enough. More frequent extremes are theoretically consistent with a warmer atmosphere. We may already be seeing some early examples of those extremes, but much work and research needs to be done to show a conclusive connection to human-caused climate change.
Matt Zaffino
Ajanders, thanks for the comments. I agree, science is about facts and challenging hypotheses. Climate and weather are anything but simplistic. And I don't believe I made any political references. Also true, Portland is part of the globe, but it is not the entire globe. The point I was making is you have to look at temperature extremes around the planet, and that simplistic comments like "it's cold here where I live therefore human caused climate change isn't happening" misses the point. Another thing to remember: there is still going to be a lot of natural variability. A warmer atmosphere doesn't eliminate that. That means there will still be cold snaps. But my earlier point stands: two weeks of cold weather in Portland doesn't mean humans are not warming the atmosphere. Just as a hot spell in August isn't conclusive proof of a warmer climate. What we need to look more closely at is the nature, frequency and extent of the extremes across the globe. And from that, we may be able to see some meaningful trends.
Matt Zaffino
Portland is part of the globe as is the Southeast
portion of the US. Look at the temps in the Carolinas, also in the Northeast. Please don't be simplistic. Be factual. Science is to be objectively viewed not politically triggered.