I believe the climate is changing because of many factors, however the main factors that I think are responsible are the following.
I am not a greenie however, The amazon rain forrest is being decimated every day by big corporations cutting down the old growth trees to use as tooth picks or somthing. This forrest is the largest oxygen factory on the planet and in particular the old growth trees. As a consequence of the reduction of these trees the Co2 levels are rising. Even though people are planting more and more trees everyday, it will take at least one hundred years before these new trees are able to filter out large amounts of Co2 from the atmosphere.
The other important contributing factor is the continued use of fossil fuels. And more importantly, the extremely inefficient way in which we are forced to use them. Cars are puposely designed to burn fuel inefficienty so that we have to purchase more fuel on a more regular basis, and any attemp to increase the efficiency of a car is met with resistance from petrol station owners and major corporations due to there fear of losing profits.
These two factors put together are IMO the fastest way to affect the climate of this planet, and the resulting weather anomalies and other unusual events are a direct result.