No, the Cold Doesn't Mean No Global Warming

Jan. 8, 2010 — -- No, the cold snap in some parts of the northern hemisphere (New York, Florida, Beijing, Northern India, Europe) does not mean that manmade global warming is not happening, or even that it's happening just a little less.

This is, of course, an old story...and more and more 5th graders are bringing it home from their science classes to get their parents up to date on the latest climate science.

Bottom line -- fast and simple? Three points:

1. Weather is not climate.

2. Manmade global warming means less frequent cold snaps (not none at all) and more frequent heat waves -- just as we've been having.

3. You know (don't you?) about the record high temperatures this week in Washington State, Alaska and Bulgaria in the Northern Hemisphere -- plus, down south, the record-breaking high temperatures in New Zealand, and the second hottest year on record (after 2005) in Australia?

Take a look at a piece, "Weather Is Not Climate," that my ABC News colleague Clayton Sandell and I filed on the same question three years ago.

In it, we spoke to Mark Serreze, a research scientist at the National Snow and Ice Data Center.

"The fact that we had a couple of cool months doesn't say anything at all about long-term trends," said Serreze. "It's just a clear example of natural variability on the climate system. The long-term averages are decidedly toward a warming planet.

"We have a gradual warming of Earth's system, but that is interspersed with a strong natural variability in the system," he said. "This is just the way the system works."

Kevin Trenberth, a scientist at the National Center for Atmospheric Research, agreed.

"Weather is chaotic. It has an infinite amount of variability, and that's just the nature of weather," he said. "Weather dominates on a day-to-day basis, and there will be warmer periods and cooler periods. But it's the overall pattern that gives you the climate."

'It's Not Actually That Cold'

There is also a new piece by Malcolm Ritter, a science writer at The Associated Press. You can find it by clicking HERE.

Weather vs. Climate

Or take a look at a blog post by Eoin O'Carroll at the Christian Science Monitor.

In it, he writes, "It's not actually that cold.

"Yes, it takes chutzpah to say this amid reports of seniors in Britain burning books to stay warm, but it's true. It was actually colder in London this week last year....

"It's the same story all over the Northern Hemisphere. Yes, it's colder than what we're used to in January, but we're not breaking very many new temperature records."

Ten Days vs. 20 Years

Weather is short-term and local -- say, the next five or 10 days in the Tri-State Area.

Climate is long-term and regional (or bigger) -- say, the average over the next 20 years in the American Northeast.

If you look at this graph of the past 130 years from the National Climate Data Center, you will see that from year to year there have been sharp spikes and valleys.

But the "decadal average" (over ten years) has been rising, is now the hottest since modern records were kept, and accelerating, the scientists tell us.

In Boulder, Colo., the National Center for Atmospheric Research recently reported that, while the ratio of record hot to record cold days in the 1950s was very roughly 1-to-1, by the 2000s, there were more record hot days by a ratio of 2-to-1.

A Note on the 'Proximate Causes' of the Cold Snap

The weather systems of the planet are highly complex.

This is the reason it's so hard to predict weather -- which is short-term and local -- but easier to predict climate, which is long-term and regional.

It's like the surface of a pot of boiling water. You can't predict whether a bubble will or won't appear at a precise tiny point on the surface exactly five minutes after you turn on the heat, but you can predict what the overall surface will look like overall -- it will be bubbling.

However, modern meteorologists are getting better all the time, and among the partial explanations they now give of the immediate ("proximate") causes of the cold snap are a) that the "rivers of air" -- like the jet stream that flows east to west in the northern hemisphere -- have developed some big dips to the south, which pull down Arctic air into lower latitudes, and b) that something called the AO -- short for Arctic Oscillation -- is relatively weak at the moment.

Since the AO's winds tend to swirl around the north pole and, when they are stronger, keep the cold Arctic air penned in up there, when they are weaker, it can let more frigid air spill down toward the south.

Scientists often advise that, when thinking about weather, or climate -- or anything, really -- it's always important to remember that nothing ever happens for any one reason.