Cause, Effect And All That

The headline for an article in today's Wall Street Journal reads Climate Changes Are Making Poison Ivy More Potent (sub req).

But when you actually read the story you learn:

New research shows the rash-inducing plant appears to be growing faster and producing more potent oil compared with earlier decades. The reason? Rising ambient carbon-dioxide levels create ideal conditions for the plant, producing bigger leaves, faster growth, hardier plants and oil that's even more irritating.

Although the data on poison ivy come from controlled studies, they suggest the vexing plant is more ubiquitous than ever. And the more-potent oil produced by the plants may result in itchier rashes. "If it's producing a more virulent form of the oil, then even a small or more casual contact will result in a rash," says Lewis Ziska, a plant physiologist for the U.S. Department of Agriculture in Beltsville, Md.

The latest research, led by Dr. Ziska, studied poison ivy plants in Maryland under different levels of carbon-dioxide exposure. One group of plants was exposed to about 300 parts per million of carbon dioxide -- about the same level found in the atmosphere in the 1950s. Another group was exposed to 400 parts per million of CO2 -- about the same level in the atmosphere today.

The commonly accepted climate change narrative is that increased CO2 levels in the atmosphere--primarily created by human activity--have caused global temperatures to rise. There is some historical evidence that raises questions about whether higher C02 levels result in higher temperatures or whether higher temps lead to increased C02 (the data suggests that rising CO2 levels lag rising temps).

But in this case, I'm sure the headline writer was operating under the conventional wisdom of the day. Which means the headline was at best misleading, at worst grossly inaccurate.

The increased prevalence and potency of poison ivy appears to be the result of higher C02 levels. However, it likely has nothing to do with climate change per se. Higher C02 level could very well be impacting both poison ivy and the climate. But there are not dependencies between the two effects.