I have been teaching advanced high school physics as a substitute teacher recently and enjoying it very much. But I was disturbed by what I saw in the text chapter entitled “Waves, Light and Climate Change.”

First of all, I don’t think a discussion of climate change belongs in an introductory chapter on light and its wave properties. Elementary texts should stick to firmly established science and mention complex, controversial issues as footnotes if at all. The authors thought otherwise – not only did they tack this topic onto the light/wave chapter, they headed the chapter with this alarmist quote:

Quite simply, I think it is no exaggeration to say that climate change is the biggest problem our civilization has ever had to face up to in its 12,000 years, because it requires a collective response.

What does “collective response” mean? Such bland phrases often translate into coercive wealth grabs by politicians. More importantly, the notion that human activity is having or will have a significant deleterious affect on our environment, which is what “climate change” means these days, is not firmly established at all in my view. (I have no expertise in climatology.)

There is a spectrum of viewpoints on global warming, ranging from outright denial at one extreme to hysteria on the other. Neither position is defensible. At one extreme, I was very disappointed to hear Ron Paul, a long-time hero of mine, describe global warming as a massive hoax. It’s not. The other extreme is represented by quotes like this, one of many printed in the margins of the physics text:

We are playing Russian Roulette with our climate … the Earth’s climate system is an angry beast subject to unpredictable responses …

Some facts that are not in dispute:

1. There are “greenhouse gases” in the atmosphere that block some of the re-radiation of solar energy; that is, light that bounces off the earth’s surface and would otherwise escape into space. This blockage increases atmospheric temperature, other things being equal. Without any greenhouse gases, so much solar energy would be re-radiated that we would freeze to death.
2. The primary greenhouse gases, in order of their importance are H₂O (water vapor), CO₂ (carbon dioxide), CH₄ (methane) and N₂O (nitrous oxide).  Water vapor is self limiting – when its concentration reaches saturation, it rains. So there is no point in to trying to reduce atmospheric water vapor concentration. So if global warming is significant and we want to do something about atmospheric greenhouse gas concentrations, we have to concentrate on CO_2.
3. It is a fact that concentrations of CO₂ have increased substantially, from about 280 parts per million in pre-industrial times to about 380 at present. Most of this increase can be attributed to burning of fuels.
4. The arctic ice sheet has exhibited marked melting in recent years. But some reports have ice increasing in the antarctic.
5. Solar flares are a major driver of climate change on earth.

Now it gets murky. To begin with, it is very difficult to generate a meaningful average temperature for the entire earth. Temperatures vary widely from place to place and from time to time. Therefore extreme care must be taken in aggregating and interpreting temperature data.

Secondly, computer modeling is a very tricky business. I know; for many years I did computer modeling of systems far simpler that the entire earth’s atmosphere, and there are lots of pitfalls, notwithstanding the sophistication of contemporary methods. In finite element analysis or computational fluid dynamics the analyst lays an imaginary gridwork over the system in question, with independent variables like temperature and pressure at each node point. He makes simplifying assumptions about the behavior of variables between grid points and may end up with hundreds of thousands of simultaneous equations to be solved repeatedly as the virtual clock is stepped forward in time. If the grid is too coarse or the time steps are too large or the assumptions too gross or the starting conditions are inaccurate or the integration algorithms are not robust or the software has bugs – the whole undertaking can go haywire.

Third, increases in temperatures or sea levels must be put in perspective. A small amount of warming – one or two degrees C – would be a benign outcome for almost all of us – perhaps reduced heating costs or shifts in agricultural production. A one foot increase in sea level would be trivial almost everywhere.

But what about the strange weather we’ve been having? Given the media propensity for focusing on disasters, it’s no wonder it seems that way but hurricane intensity, for example, compares with that of past seasons. Recent weather isn’t particularly strange.

We need to think through all sorts of approaches, including geo-engineering, and conduct cost/benefit analyses for each. The end goal – human welfare – must always be kept in sight. I highly recommend Bjørn Lomborg’s thoughtful book, “The Skeptical Environmentalist.” Lomborg is a careful scientist who acknowledges the reality of global warming and pleads for careful examination of all plausible approaches.

Lastly, we must realize that this is a global problem. Anything the U.S. might do to reduce CO₂ emissions would be dwarfed by increased CO₂ emissions in China, where automobile ownership is surging and new coal-fired power plants are being built. Certainly California’s program, which went into effect this year, will have no noticeable effect on global concentrations, unless it sets an example that the Chinese decide to follow. Even if they do, cap-and-trade schemes such as California’s may not work out as theory says they should. Such has been the record in Europe.