Deniers don't use science
The environmental movement calls for political change and individual responsibility to preserve our enviroment. The environmental movement is not science, it is in response to science. The scientists in all the major fields related to global warming agree that it is caused by man and that it will have a major effect on our climate. You are correct in saying that the strictest form of the scientific method is not applied, but that is because we have only one planet to experiment on. The modeling and testing of the models, backed up by verification and by physical properties of matter (eg we know co2 causes atmospheric greenhouse effect, we can demonstrate that) are valid scientific approaches, and they are all we have. To demand pure experimental science is to demand that we ignore anything happening to the climate and any possiblity that man might be damaging it's ability to sustain life. Some members of the environmental movement may not know their science, but that doesn't negate the fact that the vast majority of true scientists have come to the conclusion that agw is a looming disaster that can be averted or at least mitigated if we act.
