We had dinner with some friends recently. It would not be polite to name names, but it was a really excellent meal. The conversation turned to climate change and I was interested to know why their son and his girlfriend, both very bright people finishing engineering and science degrees at a prestigious university, believed that a rising CO2 level is to blame.
I asked why when CO2 levels have been so much higher in the past is today’s relatively low level such a cause for concern. Surprisingly, the physics major assured me that today’s level is the highest it has ever been. Rather than argue the point, when I got home I dug out the following graph:
The key points are obvious. Not only have CO2 levels been much higher over geological timescales, but temperature and CO2 levels are not correlated, at least not in the simplistic way that the IPCC and media would have us believe.
I have emailed them a link to the following paper (which discusses this graph in more detail) and it will be interesting to see whether one or both of them is able to overcome the painful cognitive dissonance that I remember well on first encountering inconvenient data like this.