You don't need a scientific argument to believe global warming. Glaciers are melting all around the world. The Arctic ice cap shrinks year by year. Just visit Alaska or Glacier National Park (in the U.S.) and view the old photographs from around the 1950s and 60s. The evidence is clear before our eyes that the Earth is warming. I think many people do not understand or do not want to understand that there will be statistical and environmental fluctuations about a warming trend and that in some years and some places it might actually become colder. But the overall warming trend is clear for all to see.
Even from physics, it should be understood that some degree of anthropogenic global warming MUST be happening. Gases like carbon dioxide are greenhouse gases which trap heat in the atmosphere. Humans are burning fossil fuels, which release greenhouse gases. Ergo, humans are causing global warming. Now I can see people arguing about the
degree of anthropogenic global warming but that it exists
in some amount can not be disputed on scientific grounds. With billions of humans driving cars every day and using electricity from the burning of coal and oil every day, even small effects from an individual perspective add up a lot.
I think quite a few people have a distorted view of how mainstream science works or how scientists think based on the travesty of the parapsychology debate but consider this: surveys have shown that a majority of scientists believe psi is proven or is likely true (one survey showed 56% and the other, 67%). As for climate change, ~95% of climate scientists believe humans are causing global warming. Consider this too: if you're greedy for money and/or power, you don't go into science. The vast majority of scientists do what they do because they want to learn about the world and expand knowledge. Would you rather trust a scientist who does hard work for low pay or an oil company (most funding for global warming opponents comes from Big Oil) whose first loyalty is, by law, to their investors?
Indeed, I would ascribe psi-denialism and global warming denialism to the same phenomenon of denying empirical scientific results because they conflict with deeply held ideological beliefs. In the case of global warming denialism, this is usually libertarianism. Of course, you have heard the accusation that the Left supports action to fight global warming because they believe in controlling other people's lives. But this is a complete misunderstanding of how left-wingers, and people in general, think. What if they support action to prevent global warming because they are concerned about the effects of global warming? What if they are concerned about their children, their grandchildren, and the future of the human race? Is this not much easier to believe than believing that millions of your countrymen are making their and your lives more miserable just because they can?
As for the so-called "Climategate" scandal, what if I followed you around every day for a year, recording everything you said or did during the year and then took the absolutely worst-sounding thing you said, put it out of context, and then claimed that represented you and everyone like you. You would claim this as a libelous attack on character. So too, is the fake "Climategate" scandal.
Video of global temperature increase