The micro climate around urban areas is definitely subject to impact by humans and our love of concrete, asphalt, and air conditioning (heat exchange) in the summer time, but the planetary climate? The idea that we, who amount to less than a thin dusting of bacteria on a basketball, can affect a climate powered by a star one million times the mass of our home world should be ludicrous to anyone other than a raving imbecile like Albert Gore, Jr.
They believe that a butterfly in asia affects the desert winds in the Sahara.
They likewise would have to conjecture that a moth darting in front of a candle can cause the candle to grow brighter.