Friday, February 01, 2008

CO2 Signals From The Past

Earlier this week, I posted a discussion that disputed the basis for anthropogenic global warming, primarily on the basis that the correlation between temperature changes and atmospheric levels of carbon dioxide is so tenuous. Today I want to highlight two papers that further challenge that correlation, both in the immediate, short term and throughout the geological time period of the past 500 million years.

In many ways, the short term is insufficient for a meaningful trend and the tectonic scale reflects planetary conditions no longer present or relevant. So what of the interim scale of the past 2,000 years or so? Most would agree pre-industrial carbon dioxide levels were in the order of 200-280ppm and current levels are in the 360-380ppm range. When I ask people why this relatively minor increase is a concern, the answer I am always given is because of the supposed link to temperature and global warming. But are levels of carbon dioxide of any concern if there is no link to present temperature levels as AGW suggests?

Co2science has made this review available of a paper by Loehle that produced a useful graph for temperature changes for the past 2,000 yrs.:

Loehle's temperature reconstruction clearly shows the marked medieval warm period and the Little ice Age and the fact that today's temperatures are not unusual in the context of natural temperature variation over the past two millenia. His graph does show the increase in temperature for the past 200 years but does so in a context that is not alarming.

Neither the temperature, nor the rate at which it is changing, are unprecedented or a cause for alarm.

Follow Up:
Moreover, the data indicate that there has been no global warming since 1998 despite the continued increase in carbon dioxide levels.