I was recently sent a link to part of a Martin Bashir documentary about Global Warming. While the documentary doesn't try to disprove that Global Warming is happening (as some other "investigative" reporters claim), it does raise questions about the causes of Global Warming.

The overall message of his documentary is that carbon dioxide (CO2) is not the primary contributor to Global Warming. In An Inconvenient Truth, Al Gore uses ice core samples dating back thousands of years to show that there is, in fact, a correlation between temperature and the amount of CO2 in the atmosphere. He doesn't give the level of correlation, but even an amateur can spot that the graph lines are mostly aligned.

In Freakonomics, the authors explain the difference between correlation and causation. Just because two things are correlated (they move together) doesn't mean that one is the cause of the other or vice-versa. Obviously, the movie is implying that the CO2 is the cause of Global Warming, but it can't be proved just from the data shown in the movie.

Martin Bashir's report, however, claims that the CO2-Temperature correlation is simply that, just a correlation. His documentary claims there is no causation there. He may or may not be right. This documentary claims that the true cause of Global Warming is an increase in activity on the Sun. The explanation is as follows. The Earth is normally bombarded by cosmic rays which combine with rising water vapor to form clouds. With the Sun's activity currently in a heightened state, the Solar Wind is "blowing" away many of the cosmic rays. This leads to less cloud coverage and higher temperatures.

The data presented in the YouTube clip show a negative correlation between cosmic rays and temperature (when cosmic rays go down, temps go up), and a positive correlation between sun activity and temperatures. This all sounds very reasonable, but unfortunately, I don't think it gets us any closer to a proven cause than Al Gore's CO2 stance. They both have correlations, but we haven't necessarily proven causality.

Either way, you can't argue that reducing our CO2 emissions is a bad thing. Even if it has very little effect on Global Warming, reducing emissions means that we are driving more efficient standards, and thus will be promoting cleaner living all around. Additionally, it will reduce our dependence on fossil fuels, of which price will become a deterrent as extraction becomes more difficult.

So, don't watch this Martin Bashir documentary and think "CO2 isn't causing Global Warming, so I can continue on doing whatever I please without being responsible." Regardless of who is right about the cause of Global Warming, we still need to try to be more energy efficient.