Serious sceptics

Tomorrow 25,000 delegates descend on Durban for the next UN climate change conference, following on from Kyoto, Bali, Copenhagen, Cancun and many others.  The original Kyoto protocol expires next year and not much agreement is expected this time.  You wonder why the delegates don’t save energy by changing to conference call.

Not everyone who is sceptical about international agreements to counteract global warming is a climate change denier. There’s much more to the argument than that. Let’s review some of them.

1. Are we really experiencing unprecedented warming?
2. Is it man made?
3. How much damage will it cause?
4. How much will it cost to prevent?
5. Is it worth paying the costs of mitigation now to prevent damage costs in the future?
6. Who should pay?

Is the warming unprecedented?   Here is one reputable record, taken from the Stern report. (Unless otherwise specified the evidence in these posts is from that source.  Access the full report here.)

This is an example of the famous hockey stick graph.  It certainly shows a big recent rise.   There are many reasons why skeptics dispute it.

They say the time scale is selected to maximise the apparent recent rise.  Here’s a graph going back to the last ice age.

The recent uptick hardly features. But so what? Something unprecedented for a thousand years is unprecedented for modern man, whatever may have happened in the distant past. The alarmists win that point.

Another source of dispute is the habit of some alarmists of joining inferred climate measures based on glacial ice cores and tree rings with actual temperature measurements, which have only been available from the mid 19^th century.  You can see the problem at the right end of the first graph. The rise is pretty much dependent on the black line, real measurements, while the inferred measurements show no such rise.  This suggests to some that one or other is unreliable and therefore that the whole graph is misleading.   In the graph above the different series are shown correctly, but in popular alarmist articles time series collected in different ways are sometimes joined together as if they were a single series.  Such “unacknowledged splices” drive sceptic bloggers mad.

Nevertheless, open minded people need to make a judgment.  These are the only data we have, and there does appear to have been an unprecedented recent rise in global temperatures.

Tomorrow.  Is it man made?

Jim Thornton