July 14, 2011
Whenever we get an especially cold winter or very bad snowstorm, climate change deniers fill our TV screens with their claims that the day’s weather proves that global warming is a joke. But we don’t see the opposite. There’s a severe drought in the southern United States and heat waves are hitting various parts of the country, but no one is screaming “climate change is real” because of them. Why?
Cold spells, snowstorms, droughts, heat waves—these are all examples of weather, not climate. And weather and climate are not the same thing. “No climate scientist will tell you that a dry year is a result of climate change,” Barry Nelson, a senior policy analyst for the National Resource Defense Council’s water program recently told Salon. “What they will say is that the decade-long drought in the Southwest that we’ve seen is consistent with the patterns we’re likely to see in the future. The basic weather patterns are what climate change predicts.”
Here’s how I explained it a couple years ago:
In short, weather is a data point. Climate is a collection of data.
You can think of it like the economy. I can tell you that the Dow is up 112.61 as I write this, at 9,284.22. This is the weather (partly sunny, 84 F). But it doesn’t tell you anything useful about the economy as the whole (like the weather conditions don’t tell you anything useful about climate). A graph of the Dow over the last year, showing a terrifying decline followed by a steady rise, begins to tell the story of the last year. But to get a true picture of the economy, we’ll need to look at lots of other bits of data, like consumer confidence, unemployment rates and durable goods orders. It’s complicated, messy and hard to understand. That’s climate.
Now, if you make changes to the country’s economic situation, for example, by raising taxes, that is going to have some effect on the economy as a whole. Economists will crunch the numbers and come out with predictions. They won’t all be the same, but they will probably trend toward some particular end.
Adding carbon dioxide to the atmosphere is akin to raising taxes. We’ve changed the climate situation. And while these climate models—which are far simpler than economic models and more certain—may not agree on the specifics, the general trend is that temperatures are going to rise.
What responsible climate scientists will tell you is that extreme weather events—not only droughts and heat waves but also floods, severe snowstorms and other events one might not associate with something called “global warming”—are likely to become more and more common as we continue to pump carbon dioxide and other greenhouse gases into the atmosphere. And like tomorrow’s Dow, we can’t predict exactly which one will happen, where and when. But as long as we continue to debate a science that is largely settled, all we can do is prepare for the inevitable disasters.
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