It would take a global effort to make a demonstrable change. The leading nations that contribute to/exacerbate the climate change trend either are developing countries (China, Indonesia/SE Asia) or have their head-in-the-sand attitude (USA). This is a collective problem that the deniers have and will drag everyone else down with them.

Because man is too insignificant to have any effect on the climate. In the last 100 years, co2 levels have increased a scant 0.02%

For much the same reason a single person will not significantly affect the import/export balance of their home country. A problem caused by the actions of a lot of people is unlikely to be solved by the actions of a single person, unless the person is in a position to change the actions of a lot of people (eg by passing a law)

One person changing all their lightbulbs to CFL's won't help.

If everyone that used mains electricity did so, you could mothball or remove from use a very polluting power station or two burning coal or oil.

Dude I can change the climate in my house. but global warming that's a big one.You will just need to adjust to it and get over it.

Because after the Americas were colonized and the indigenous cultures were destroyed, we unfortunately lost the technique to perform effective rain dances.