Monday, March 14, 2005

First you draw your graph...

Scare tactics - part II.

After posting my previous entry I thought of three other factors that might affect the blooming of flowers in the Northeast. Remember that an environmental organization did a study showing that certain flowers and trees are blooming up to a week earlier than in the 1960s and 1970s. This is being presented as the canary in the coal mine for global warming.

First point - pollution. The skies were pretty dirty in the 1960s. Coal-fired power plants in Ohio, Pennsylvania and New York produced pollution that was carried into New England. There has been substantial cleanup of these emissions in the last 40 years. This would affect the health of plants in New England and healthy plants bloom earlier.

Second point - carbon dioxide. This gas acts as a fertilizer for plants. As the carbon dioxide level increases, plants become healthier and, again, bloom earlier.

Third point - natural weather variations. This study only covers around 40 years. This is important because the US had a period of mild cooling in the 1960s and 1970s. It also had warming in the 1930s. A measure that starts in a known cool period and will show a straight-line temperature increase while a measure that includes known warm periods will show a completely different long-term result - possibly a straight line. Think how different a graph would be showing temperatures from January to July of a single year compared with January to January.

Taken together, do these points account for early blooming without adding in global warming as a factor. Probably. I don't know for sure but neither do the people who did the study. I've only seen news reports about the study, not the study itself so I am only guessing but they probably did not take any other factors into account. They wanted their results to show global warming so the do not want to look too closely at the figures.

Scientific method says that you should plot your data then draw your graph. An old joke among undergraduates is that you draw your graph first then throw out any data that does not match. That constantly happens with global warming. The researchers know that warming is happening so they make the data fit. That's fine when it happens in high school science class but this is being given as proof that we need to re-shape society. We need a higher level of accuracy when the stakes are this high.

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