How Much of Atmospheric CO2 Increase is Natural?

NOTE: The following post has led to many good comments. The best argument advanced that I am wrong is from a ~1,000 year record of CO2 from the Law Dome ice core (a record I was unaware of) which suggests the recent CO2 increase is almost entirely anthropogenic in origin. I frequently get asked the … Continue reading How Much of Atmospheric CO2 Increase is Natural?