Okay, perhaps that's a bit of an overstatement, but it has its basis in fact.
See, most Global Warming/Climate Change enthusiasts base their opinion that Anthropogenic Global Warming (AGW or "man-made global warming") on computer models. These are computer models that use complex equations developed from the limited amount of data in an attempt to model the behavior of the Earth's atmosphere. These complex models are then used to predict future behaviors of the planet. The outcomes of these models are where the headlines come from that say the Earth will be some temperature hotter than today.
Similarly, an astronomer named Frank Drake developed an equation to predict how many civilizations exists throughout the Milky Way Galaxy. Widely accepted by the scientific community, the Drake Equation had very imperfect information upon which it was based, just as our climate models do today. The inputs have changed in favor of increased outcomes in some ways and in favor of decreased outcomes in others. Drake used his equation to predict that there might be 1,000,000 civilizations in the Milky Way.
Today, we believe there may be 200 billion stars, double the number from then 1960s when Drake made his equation. This changes the model in favor of alien life. However, we have discovered that other solar systems are not built the way we thought they were, and that there are dangers in the galaxy that can destroy hundreds of earth-like biospheres in a single stroke, changing the outcome in favor of fewer civilizations. So while Drake predicted 1,000,000 civilizations, the answer may actually be much more or less.
By changing the inputs in the Drake equation, the outcome changes radically. Setting all values to 1 (1 unit or 1%, depending on the input) and setting the Milky Way at 200 billion stars produces a result of 20 communicating civilizations. Change just one thing, say the fraction of life-sustaining planets where life evolves, to 2%, doubles the outcome. The equation is very simple, but it is used and quoted on television, in newspaper articles and even in reports to Congress time and time again. Ask most scientists if they believe that there is alien life somewhere in the galaxy, and you'll probably get a "yes." As Carl Sagan might say, any other outcome would be an awful waste of space.
There is no way to test the Drake Equation except to go out into the universe and find out how many alien civilizations there are. Almost everyone recognizes that this is too expensive based upon existing technology and economies.
Similarly, the only way to test climate change models is to test the outcome in real life. However, Warmers want us to make changes in our lifestyles, economies and politics based solely upon their computer models.
There is no empirical evidence of alien life, only supposition, mathematical modeling, and the hope of Star Trek, Star Wars and Halo fans everywhere. Right now, the only physical evidence is the videography of UFOs (which may or may not be alien space ships) and the occasional mutated cow fetus hung upside down in a clear tank (thank you Joss Whedon).
The only empirical evidence of AGW is similarly flawed: Random samplings of glaciers, estimates of animal populations, imperfect and unequivalent temperature and climate obersvations mostly in industrialized nations, all feeding computer models stating that warming must be happening. This isn't evidence, it's sorcery! One might as well be reading tea leaves or runes. To the knowlege of this author (and I admit I might be wrong), no model has ever been built that has stood the test of time. No model has been given inputs of the climate in 1970s, the inputs of that decade, and then accurately show what the Earth's climate was in 1980, 1990, or 2000. The climate models are just as much a guess as Mr. Drake's model for alien civilizaitons.
So when I meet Warmers, I tend to have one question on my mind: "Do you believe in alien civilizations, and why?" The answers, when asked, are always entertaining. Many quote the Drake equation, which as we have seen has no basis in fact.
Oh, you might be asking, do I believe there is alien life?
The answer is yes. It's based on no more than my faith in God and his love for diversity. Similarly, the belief in Anthropogenic Global Warming is based on nothing more than faith: Faith in imperfect computer models and imperfect scientists, not scientific reality.