Sceptical global warming bloggers tend to rush to take encouragement when anyone with some scientific sounding qualification agrees with them. For example, Dr David Evans' recent article in The Australian made a big splash in sceptic circles, yet it seemed clear from the opening of his article that he was not even claiming to be a scientist with expertise in atmospheric modelling. (His own biography gives his qualifications as being in electrical engineering.) As Deltoid (far from a favourite blog of mine, but he has his moments) pointed out quickly, Evan's "killer" point about troposphere temperatures had been dealt with over at Real Climate half a year ago, and as far as I can tell, is not actually shaking the foundations of the IPCC to the ground in the way software writer David claims.
In a similar vein, Wikipedia notes that of the "30,000 scientists" who have signed the anti global warming Oregon Petition, those in the most relevant category of "atmospheric, environment and earth sciences" apparently number 3,697. There seems to be no easy way of assessing how many of them have actually worked on issues directly relevant to global warming or CO2. Also, as the Wikipedia article explains, it's hard to tell how many signatures are genuine, and indeed many who first signed in 1998 may well have changed their mind since then. The petition certainly has a murky past.
I don't see why I should be convinced by the opinions of your average physicist, doctor and engineer when it comes to questions of assessing global warming issues. After all, just because Edgar Mitchell has a Ph.D and been to the moon does not mean I give any particular credence to his claim that aliens have been here and the US government is hiding the fact. Perhaps a less extreme example to make the same point is the line up of 9/11 conspiracy believers that includes engineers, architects and physicists.
I am aware that there are warming sceptics that have all the specific qualifications and work experience to mean that they are very familiar with the topic. Fine, their opinion is definitely not to be dismissed without examination. However, I still say that the sceptics make their argument much weaker by cheering whenever anyone who can call themselves a scientist says they agree.