On this morning's edition of NBC's Today Show, new host Meredith Vieira and veteran weather reporter Willard Scott demonstrated that neither one of them understands what "global warming" means.
SCOTT: Well, listen are you a globing -- a global-warming fan? Do you believe in global warming?
VIEIRA: I'm not a fan. No. No, sir.
SCOTT: Well --
VIEIRA: But I -- something's going on, 'cause it's warm here.
SCOTT: Well, now, wait a minute -- that's it; it's warm here. From Savannah [Georgia] all the way up to Boston, we're having unheard-of warm weather, but ask the folks out in Denver and Colorado --
VIEIRA: That's so.
SCOTT: -- the coldest winter they've had in years. So it all depends on which side of the Mississippi you're hanging your hat.
This is a perfect example of the problem with the phrase "global warming." People expect the world to get warmer. They expect every day in every place to be little warmer than the same day in the same place last year. That's not how it works.
Weather and climate are very complex systems that accomplish a very simple task: they redistribute air and moisture around the globe. Some moisture evaporates off the ocean and moves inland to create wind and precipitation. Everything else is details.
The power to keep this system going comes from two sources: the rotation of the Earth and energy from the Sun*. The rotation of the Earth doesn't change enough from year to year to matter much and nether does the amount of energy coming from the Sun. But the amount of energy (heat) from the Sun that we keep does change. We do this two ways: by changing the color of the Earth's surface and by changing the composition of the atmosphere. We change the color of the Earth by cutting down forests and building or paving over soil. By making the Earth darker or lighter we change the amount of energy that is absorbed or reflected away. We change the composition of the atmosphere by causing certain gasses to be emitted into the air from power plants, automobiles, and cow butts. Finally, those forests we cut down played an important role in maintaining the composition of the atmosphere; by cutting them down we change that composition. The sum total of all of these changes is that the Earth is keeping more of the energy from the sun than it used to.
While most of this energy is converted into heat, its effect isn't to simply make every spot on the Earth a little warmer than that spot used to be. Remember, weather and climate are nothing more than the redistribution of air and moisture around the globe. If you feed more energy to a car's drive train, it will go faster. If you pack more energy into a stick of explosive, it will explode bigger. If you store more energy in a battery, your pink bunny will play its drum longer. Faster, bigger, longer lasting: that's what all of that extra energy does to our weather.
A system with more energy in it will operate differently than one with less energy. In systems as big and complicated as our weather and climate, the changes could show a great deal of variety. In one place it might be colder. In another place, there might be bigger or more frequent storms. Still other places might become drier, cloudier, or even hotter. The weather might do one thing this year and something completely different next year. We don't know.
The important point is not that we're making the weather warmer; the important point is that we are making it unstable. We don't know what direction it will change for any given point. Over the last 150 years, in historical terms, the weather was unusually stable. During that time, our numbers grew six-fold and we developed a global agricultural system based on a few crops specially bred for high productivity. Those crops can only be grown in very narrowly defined environments. As long as the weather stays within predictable bounds, we can feed the world**. If it changes too quickly, we run the risk of our food supply failing***.
Last August, Pat Robertson announced that the "blistering summer" had overcome his greenhouse skepticism and made a convert out of him. What happens if he gets a little chilly this winter? Will he change his mind back? Vieira and Scott showed that they think global warming is entirely a matter of how warm they are right now. If they're hot; it's real. If they're cold; it's bogus.
This why we need to wean people off the phrase "global warming." It was a useful phrase to get people's attention and to simplify a hard concept, but it was short-sighted. It has become a liability to the ongoing project of educating the public. "Climate change" or "weather instability" are less graphic but more realistic. They're also fairly boring. Any suggestions?
* There's also a tiny bit of heat from inside the Earth and that chaos theory butterfly in Brazil that causes hurricanes, but they fall into the detail category. I'm dealing with the big picture here.
** Global hunger is not caused by a shortage of food; it is caused by poverty and interruptions to the distribution system.
*** There are a lot of things we can do to alleviate that risk, but that's a post for another day.