When does weather become climate?

Contributed by
Jul 2, 2012
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When does weather become climate?

It's really starting to feel like the answer is now.

That map shows how much higher than average temperatures have been across the US recently. In Colorado in particular, low amounts of rainfall coupled with dry weather (plus an ever-lengthening warm season allowing pine beetles to flourish and destroy living trees) made the state a match waiting to be lit... and that ignition has happened multiple times in the past few weeks.

And it wasn't just Colorado of course, but also New Mexico, Utah, Wyoming... and not just here in the US, either, as Russia is also on fire.

Is all this due to global warming? Hard to say, exactly. However, these conditions are precisely what you would expect as the Earth warms: weather patterns change, temperature records get broken, conditions go from normally wet to dry, normally dry to wet.

"Weather" is what you look at if you want to know if you need an umbrella or not today. "Climate" is what you expect on average for a given day in a given place. Weather changes on short time scales; climate over long ones. But how long?

Weather + time = climate. It's well past time to start thinking of that "time" as now.

Credit: Jesse Allen, using MODIS data provided by Land Processes Distributed Active Archive Center (LPDAAC)

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