You just inadvertently demonstrated precisely why E-mail is interesting, but not good to try and base any conclusions on.
To take your example, that statement could mean, "Tweak your algorithm to arrive at our predetermined conclusion.", as you seem to imply.
It may also mean: "Your algorithm does not arrive at the anticipated conclusion. Could you check to make sure that the inputs were correct, and that it's functioning properly?"
It might also mean "Your algorithm didn't produce the level of warming we expected. We need you to re-work it to account for [some factor]"
Out of context, "the level of warming we expected" produced by the algorithm might be way too high or way too low. So anyone can derive whatever "expectation" you want from it. If you want to take an email like that and make it into proof that the science is cooked, go ahead. Of course, that's not very scientific.