There are four possible positions on the issue:
(1) The globe is not warming.
(2) The globe is warming, but its primary cause is not man-made. Sunspot fluctuations, variations in the Earth's orbit, etc. are the culprit.
(3) The globe is warming, but there has not been enough data yet collected to reach a decisive conclusion either way as to its primary cause.
(4) The globe is warming, and its primary cause is man-made.
I hold the fourth position, but there are many who do not. The (1) position is almost more understandable than the (2) position, if only from a psychological perspective. If you agree the globe is warming, then you have already demonstrated an ability to trust scientists at all -- why would the next logical step, of agreeing to humanity's involvement, cause you to suddenly decry as bureaucrats suffocated by institutional orthodoxy the very same scientists you already listened to? At least (1) is consistent in its rejection of scientific consensus. It's more honest in its devotion to dishonesty.
Less honest in its devotion to dishonesty is (3), which almost sounds like a reasonable thing to say. The existence of (3) as an option in the first place is due to a rhetorical masterstroke on the part of global warming skeptics: by intertwining the issue with its debate about itself, skeptics have replaced a scientific decisionmaking process with a political decisionmaking process. "We don't trust the scientists to make such a declaration at this time." So when exactly do you plan to start trusting the scientists? The unstated answer is "Only when the scientists start agreeing with us," which rejects the scientifically required possibility that further data will only confirm what the scientists are already saying. Hence, the debate has been sequestered into a place beyond the reach of science. Genius.
What positions (1) through (3) all share, though, is a response to the question "So if global warming's primary cause isn't man-made, how come the vast majority of respectable scientists say it is?"
Global warming skeptics sieze on our use of the word "respectable" to shape their answer. This is where the depictions of scientists as bureaucrats suffocated by institutional orthodoxy come in. Science, we are told, is nothing but an extension of academia, where concerns over gaining tenure or finding a thesis advisor or having a friend on the grant allocation committee at the National Science Foundation exert at least as much influence over how science is done as does the desire to pursue knowledge.
Basically, the global warming skeptics are saying that there is a conspiracy in the scientific community to convince the public that position (4) is true.
I'm certainly not one to automatically reject conspiracy theories out of hand, but I do subject them to a few rudimentary plausibility tests. The first of these is to ask, "Qui bono?" Who would such a conspiracy benefit?
I don't see how it could benefit the scientists. Even universal public acceptance of position (4) would not significantly increase their material wealth, certainly not like lobbying for, say, an oil company. I suppose it might boost public opinion of scientists -- the extreme form of this would be for the public to venerate scientists as "the saviors of humanity," although that's a very generous exercise of imagination.
The next rudimentary plausibility test would be to ask, what would the costs be to the organization perpetrating the conspiracy if its true conduct were to become known? We've seen that political scandals involving conspiracy rarely have any lasting fallout: if they did, Watergate alone would have ensured the demise of the Republican party. Scandals can end the careers of individuals, but they never do more than temporarily disrupt the organizations to which the involved individuals belong.
But that's in politics, where scandal is to forever be expected. Science is the only area of human endeavor when the number-one concern is to make sure that one really knows what one thinks one really knows. Its only goal is to be honest. A concerted effort to distort the truth within the scientific community would spell the absolute suicide of science in the world, and I don't think any scientist would be willing to risk that for the remote prospect of being regarded as humanity's savior.
Bottom line, the reward is too paltry, and the risk too enormous, for scientists to be involved in such a conspiracy. If individual members of the scientific community find themselves shunned and ostracized because of their statements on global warming, it's because their thought processes are somehow flawed, not because they're heroic whistle-blowers.
I have yet to hear a convincing argument in favor of a scientific conspiracy to promote position (4). I hereby invite anyone from positions (1) - (3) to advance such a case in the comments section. I guarantee I will issue some sort of reply.