The climate conversation

July 16, 2012
With early summer unusually hot in much of the US, speculation about climate change has risen along with the temperature. Quality of the conversation about global warming, however, seems never to rise.

With early summer unusually hot in much of the US, speculation about climate change has risen along with the temperature. Quality of the conversation about global warming, however, seems never to rise.

News reports imply that extraordinary warmth confirms the climate change nightmare—that human activity, especially the use of fossil energy, intensifies the greenhouse effect and portends overheating. The main culprit in this scenario is carbon dioxide, which absorbs radiated infrared energy that otherwise would escape into space, warming Earth's surface and lower atmosphere. Because the atmospheric concentration of CO2 is increasing, people are thought to be causing observed warming, and a hot US summer is taken as evidence of the relationship.

This is the normal conversation about global warming. It has lapses.

Weather and climate

Weather in the US, which occupies less than 2% of Earth's surface, is not the same as global climate. Hot weather in one region can be offset by cold weather elsewhere. Reports linking the US heat wave to climate change must, if they're to be taken seriously, also tell what's happening elsewhere in the climate.

In fact, broader views subdue the drama. According to researchers at the University of Alabama-Huntsville, satellite measurements of the global lower troposphere in June were only 0.37º C. above the 1981-2010 average and not part of a clear uptrend. For the US, writes Roy Spencer, one of the researchers, in a blog entry, average temperatures in June "were not that remarkable."

Weather extremes nevertheless are predicted by the computer models predicting dangerous warming. So when they occur, the tendency is strong to flaunt them as evidence that global warming is "real" and that people must do something about it.

The reality of global warming isn't at issue. The mechanism is essential to life. That the temperature record over a century and a half of industrialization trends upward also needs no validation from weather. What's at issue is the extent to which activity related to industrialization caused the observed warming, which bears on whether and how activity changes might mitigate it.

Some observed warming probably can be attributed to people and fossil energy. But periods of cooling have occurred during periods of rapid growth in CO2 emissions, indicating that human influence—and therefore the amount of warming likely to result from further CO2 loading of the atmosphere—may be weaker than what computer models suggest. Fulfillment of dire warming predictions requires amplification of CO2 effects by associated increases in the most important greenhouse gas: water vapor. Whether water vapor increases or decreases as a result of CO2-induced warming is a question awaiting an answer.

If a hot summer in parts of one country is to become a political issue, then, two questions deserve more attention than they receive in the popular conversation: What, if anything, is happening in the global climate that makes warmth appear to be anything more than weather? And how might people respond with reasonable hope that their costly exertions will lower global average temperature?

What's interesting in the summer of 2012 is the absence of appeals for urgent political response. Part of the reason for this is that the Environmental Protection Agency has undertaken to cut CO2 emissions through regulation. It's also a general election year. In times past, at least some candidates would be warning about "tipping points" and calling for drastic precaution. The issue governing the current election, though, is a stubbornly sluggish economy.

More questions

So two other questions should shape conversation about global warming this steamy summer: Where might the economy be now if the US 2 years ago had enacted cap-and-trade legislation certain to have raised energy costs painfully enough to lower consumption and CO2 emissions meaningfully? And if benefits are doubtful, why does the EPA work so hard to produce the same result autonomously?

Outside the framework of questions such as these, conversation about uncomfortable temperatures is just grousing about the weather.

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