There is a substantial amount of evidence that points to human-caused climate change. Yes, there are natural fluctuations in global climate over time, but nothing of this scale has been observed in the timescale that the current change has taken place. Humans spill extremely large concentrations of CO2 (as well as far more potent greenhouse gasses) into the atmosphere. Moreover, deforestation in areas like the boreal forest, and fires in the tundra, have turned these carbon sinks into carbon sources. With CO2 concentrations rising, sea and land temperatures will continue to rise on average.