October 12, 2004

Much Ado About Nothing

Despite a slew of British press reports to the contrary, the data reveal no unnatural “jump” in atmospheric carbon dioxide levels.

The British press lit up this week with a story about an unprecedented, and surprising “jump” in the levels of atmospheric carbon dioxide. But a check of the data reveals nothing of the kind. Instead, recent fluctuations appear to be just part of natural variability.

That fact didn’t stop the liberal British newspaper The Guardian from starting the buzz about atmospheric carbon dioxide levels. Here’s the first paragraph of its October 11, 2004, article, “Climate fear as carbon levels soar”:

An unexplained and unprecedented rise in carbon dioxide in the atmosphere two years running has raised fears that the world may be on the brink of runaway global warming.

One has to wonder about the article’s timing, given that the data on which it is based was released more than two months ago with nary a peep about it. (Hint: the original timing failed to inject CO2 into the presidential campaigns). We examined the 2003 data when it was first released, as we imagine many researchers and other interested parties did, and saw nothing that struck us as unusual. We reproduce it here so all our readers can have a look.

Figure 1 shows the complete atmospheric carbon dioxide concentration record from atop Hawaii’s Mauna Loa volcano. In Figure 2, we plot the change in the annual average concentration from one year to the next.

CO2 Concentration

Figure 1. Complete monthly record of the atmospheric carbon dioxide concentration (ppm) as measured from Hawaii’s Mauna Loa observatory, 1958-2003.

CO2 Growth Rate

Figure 2. Annual growth rate of the atmospheric carbon dioxide concentration (ppm/year).

Apparently, the Brits are worked up over the last two data points in Figure 2. But to get worked up over two data points near the end of the record shows a lack of understanding of simple statistics. Data points near the end of a period or record have an undue influence on the apparent trend.

For instance, if you put your thumb over the last two data points on Figure 2, then you produce a situation in which there has been no apparent trend in the data since 1977 (the jump in the mid-1970s is likely a result a the Great Pacific Climate Shift, a climatic event of unknown cause that ushered in an era of above normal temperatures in the Pacific Ocean).

If, on the other hand, you put your thumb over the two or three data points preceding the last two, then you create a situation where it appears as if there is a strong upward trend in the annual CO2 growth rate. Which situation is correct? It is impossible to know until we collect more data (i.e., we must wait a few more years). One possible reason for the uptick during 2003 was the hot, dry summer over much of Europe, which led to decreased plant growth (less CO2 uptake) and increased wildfires (more CO2 release).

But, while we await more data, we continue to ponder the timing of The Guardian article. Perhaps this telling passage later in the article provides a clue:

The findings will be discussed tomorrow by the government’s chief scientist, Dr. David King, at the annual Greenpeace business lecture.

As we have discussed previously in these pages, Sir David King is probably England’s biggest proponent of the warming-is-bad attitude and the notion that United States should be made to do something about it. Worse, he has Prime Minister Tony Blair’s ear.

Sir David has been on a veritable crusade this year touring the world to make his point to anyone who would listen, going as far as saying that “In my view climate change is the most severe problem we are facing today—more serious even than the threat of terrorism.”

A more dispassionate look at the sum of all available data and observations should lead to a more rational person to a less sensational conclusion.

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