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Saturday, November 26, 2005
Better facts on greenhouse gases
The European Project for Ice Coring in Antarctica has released information on a study of Antarctic ice cores going back two-thirds of a million years. The findings indicate present greenhouse gas levels are higher than at any time during the past 650,000 years.
While this is the factoid the New York Times chooses to trumpet, it is not really the most important discovery by the scientists checking the gas contents of ice bubbles in the deep glaciers.
More important will be the relationship between fluxuations in greenhouse gases and global temperatures.
The greatest weakness of the argument that temperature increases documented in the past century-plus are caused by human release of greenhouse gases is a lack of any historical evidence of causality. Sure, we have some good measurements of climate variations over thousands and even hundreds of thousands of years. And with the newly reported findings, we have good measurements of greenhouse gases over the same time period. Yet the evidence of causality - that gases build up, then temps rise or gases decrease, then temps fall - continues to be muddled. In the Times story, geologist James White of the University of Colorado fudges the issue:
"CO2 and climate are like two people handcuffed to each other," he said. "Where one goes, the other must follow. Leadership may change, or they may march in step, but they are never far from each other. Our current CO2 levels appear to be far out of balance with climate when viewed through these results, reinforcing the idea that we have significant modern warming to go."
Note the "leadership may change" part. In other words, sometimes the evidence shows temps rising before there is an increase in greenhouse gases. That alone breaks any certainty present greenhouse gas levels are causing temperature increases. What's more, the data itself is inconclusive enough scientists don't even claim increased gas concentrations "usually" preceed global temperature increases. They just seem to be found in close chronological proximity. Thus greenhouse gas levels as a "cause" of global warming is not any more likely than ketchup being a "cause" of mustard.
Finally, even if gas buildups clearly preceed warming, it doesn't necessarily follow they "cause" it. Take this example: You clearly need a stockpile of bread before you can make a sandwich, but does this mean sliced bread is the "cause" of sandwiches?
The media often take up scientific theories which predict disaster and promote them like some social justice campaign. The question of evidence and proof are tossed aside as frightening, gloom-and-doom prophecies get top billing. The European group's work greatly expands our understanding of prehistoric atmospheric gas concentrations, but it fails to provide the "proof" of a causal relationship - or even a consistently preceeding relationship - between those gas levels and global warming. By looking at this issue through the tunnel vision of environmental activist groups and Third World economic concerns, the media undercuts the wide ranging exploration still very necessary to understand climate change, atmospheric dynamics and earth history.
Perhaps there is an underlying cause of global warming which also results in increased atmospheric greenhouse gas levels. Yet if that cause is not "human induced," an entire world political movement will become obsolete. Are scientists willing and able to challenge such powerful forces in their search for understanding?
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