If that is the only way to make the argument (which may be true - this is not simple stuff), then you need to be especially careful about the flip side - the
ad hominum attack.
Furthermore, your reasoning is typical «ad
hominum» logic.
By the way, US, it's «ad hominem», not ad
hominum..
To avoid all the «ad
hominum» vitriol, I now confine my rebuttals to sources within IPCC5 itself.
Both of those arguments are obviously ad
hominum - trust the message because of the messenger.
Of course, sites like this help a lot - but even then, since the average layman can't really follow the physics, it still smells of ad
hominum.