Thursday, April 2, 2009

Correlation does not imply causation

Megan McArdle has a hilarious example, showing that more Mexican lemons imported into the US reduces auto accident fatalities. Srlsy.

So while lemon imports are indeed correlated with reduced traffic deaths, any causal links is, ahem, hard to envision. Even a drooling idiot can suspect that lemons might not have a lot to do with auto fatalities. So let's order up some studies. Science!

It's interesting when this happens, and when it doesn't. A global temperature rise over the last 400 years is correlated with increased atmospheric Carbon Dioxide released by industrial activity.

Correlated. Causal links are increasingly controversial. So how about some statistical studies of the data? Science!

Well, there is some interesting research being published in, you know, scientific journals and stuff*.

BECAUSE the increase in the concentration of atmospheric carbon dioxide has correlated with an increase in the use of fossil fuels, causation has been assumed.

Tom Quirk has tested this assumption including through an analysis of the time delay between northern and southern hemisphere variations in carbon dioxide.

The paper's abstract reads (my emphasis):
THE conventional representation of the impact on the atmosphere of the use of fossil fuels is to state that the annual increases in concentration of CO2 come from fossil fuels and the balance of some 50% of fossil fuel CO2 is absorbed in the oceans or on land by physical and chemical processes. An examination of the data from: i) measurements of the fractionation of CO2 by way of Carbon-12 and Carbon-13 isotopes; ii) the seasonal variations of the concentration of CO2 in the Northern Hemisphere; and iii) the time delay between Northern and Southern Hemisphere variations in CO2, raises questions about the conventional explanation of the source of increased atmospheric CO2. The results suggest that El Nino and the Southern Oscillation events produce major changes in the carbon isotope ratio in the atmosphere. This does not favour the continuous increase of CO2 from the use of fossil fuels as the source of isotope ratio changes. The constancy of seasonal variations in CO2 and the lack of time delays between the hemispheres suggest that fossil fuel derived CO2 is almost totally absorbed locally in the year it is emitted. This implies that natural variability of the climate is the prime cause of increasing CO2, not the emissions of CO2 from the use of fossil fuels.
Dang it all, Mr. Dr. Quirk, how are we supposed to take over the world economy for Make Benefit Glorious Nation of Kazakhstan Environment Revolution if you and your denier friends keep peeing in the cereal bowl here? The science is settled, darn it! SETTLED, I SAY!

Hey you deniers! Get the heck off my lawn!

I'm sure that this just slipped by the media because they're wicked busy and everything, and they'll all publish stories about it when someone points out the oversight. Any Obama's unicorn that pees high test into the tank will show up any day now.

* ‘Sources and Sinks of Carbon Dioxide’, by Tom Quirk, Energy and Environment, Volume 20, pages 103-119. ISBN 0958-305X

1 comment:

DirtCrashr said...

It's all because of the patriotic revolutionalry zeal of the Lemonistas that your automobile accident rate has declined, you gringo dog!