Earth's temperature changes over time depending on a number of factors including variations of the suns energy reaching the earth and changes in greenhouse effect. The degree to how much humanity has contributed to this rise in temperate vs naturally occurring processes such as volcanic eruptions and comet activity is debatable. I've heard some pretty good arguments on both sides and remain open minded however that's not the point. As a believer of limited government I am opposed to turning an environmental matter into a political matter. The concept that we are considering more taxes in order to take action towards environmental responsibility I find to be completely ludicrous.
I'm a firm believer of setting up scalable systems for long term success and therefore believe that the ground work for attaining a clean environment should be a grassroots movement rather then a political movement. I oppose the carbon tax, if we take this path we run into the risk of further expanding government power creating more and more taxes, and having less power to shape our society and the direction of our planets future.
Its important to fight for justice, but be carful you don't fall into a mock fight and taken advantage of by disguised special interests rather then taking part in a true grassroots movement. In a free society government remains limited so that the only thing expanding is human innovation and freedom.