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No. 2219:
Progress Report on Warming

Today, a global warming progress report. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

When I face questions about global warming, it's usually a struggle to point out that the problem must be kept in the scientific domain and out of politics. Any of us can fall into the trap of naming whatever political figure we like least, and taking the position opposite to his or hers.

With that in mind, let's look a a helpful summary article in this week's Science magazine. It's by a group of climate experts from NASA, the Scripps Institute, and institutes in Germany, Australia, and France. 

What they've done is straightforward. First, they graph the increase of CO2 concentration, temperature, and sea level, since 1975. Each increases a bit more strongly than a simple linear rise.  Maybe they're rising exponentially, maybe not.

The changes might not seem extreme. In thirty years, CO2concentrations are up fifteen percent, Earth's temperature has risen just under a degree Fahrenheit, and sea level has risen three inches. 

The authors also display the most important predictions made back in 1990. It turns out that CO2 concentration has risen pretty much exactly as it was predicted. Global temperature has risen in accordance with the worst case predictions. And sea level is up 25 percent beyond the worst case predicted. While some other doomsday predictions were far too high, the climate ones were not. 

So climatologists in 1990 were not Chicken Little, telling us the sky was falling. None of them overestimated what was happening. In fact, it'd be easy to look at this and let ourselves become Chicken Little. One could curve-fit an exponential extrapolation to the data. But extrapolation is no more trustworthy than blindly opposing the hated-politician-du-jour.

We need good analytical predictions. They, in turn, must be built upon a thorough knowledge of weather, chemistry, fluid mechanics, and global economics. The 1990 predictions were pretty good, although somewhat conservative. Predictions are better now. 

To gain just an inkling of the complexity, let's look again at rising sea levels. The overall rise reflects the ice-cap melting that we're all seeing (although part of the rise comes from thermal expansion of warming oceans). But that net value is an average of larger local sea level variations. The tectonic plates, upon which we live, rise and fall relative to one another. Since Louisiana and Texas are dropping, we see the sea level rising sharply. But Alaska is rising, so Alaskans see their sea level dropping. New Orleans might go under while Anchorage remains dry, or rising sea levels might catch up with tectonic subsidence and flood both. 

In any case, we are faced with climate change and it's hard to doubt that we play a significant role in that change. Nor can one reasonably doubt the importance of reducing consumption, waste, and emissions, while we look for better information -- while we focus, not on the people we like or dislike, but on the data. 

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

S. Rhamstorf, A. Cazenave, J. A. Church, J. E. Hansen, R. F. Keeling, D. E. Parker, R. C. J. Somerville, Recent Climate Observations Compared to Projections. Science, Vol. 316, 4 May, 2007, pg. 709. 

For more on sea level variation, see:



(photo by JHL)