Ten-minute trainer: a case against the establishment case for alarm over CO2

For teachers with 30 minutes to spare, and a suitable class (perhaps one whose important exams in this area have been completed successfully), here is a brief YouTube clip which does a cool, calm, and collected job of undermining the case for alarm over CO2 - a case which may be taken for granted in your curricula.  He is particularly critical of the 'positive feedbacks' which are a crucial part of the case for alarm:


This is a short video of about 13 minutes (no 10-minute trainer takes exactly 10 minutes!) linked to at the NoTricksZone which notes it was linked to in a tweet by Tallbloke.

The video is the work of David Evans in Australia. More details of his case can be found here:

http://joannenova.com.au/2012/01/dr-david-evans-the-skeptics-case/

and he has also produced some very good, but longer videos here: http://joannenova.com.au/2012/04/david-evans-explains-the-skeptics-case-youtube/

Some minor points. 

(1)   The claim that positive water-vapour driven feedback is ‘assumed’ in the models is not quite correct.  What they assume is that global relative humidity stays constant as temperature rises.  This necessarily means water vapour levels will increase in the models, and this is what is believed to lead to the positive feedback that appears in them.  In practice, there is some evidence that relative humidity has been decreasing in recent decades. 

 Source: http://www.climate4you.com/ 

(2)    The first graphic in the short video shows ‘observed temperature increase’ as the output of models.  If it was in fact the observed temperature increase, then the models would be doing a perfect job on them.  Actually the output of models is ‘expected temperatures’, or 'predicted temperatures'.  When these are compared with observed temperatures, the discrepancies are obvious.