I think that human activities are contributing to the speed of change, but I agree that the earth's natural cycles are playing a big part in what we are witnessing.
I don't think we will have to worry about what we put into the atmosphere too much longer as our way of life is going to change drastically during the next 5 to 10 years, as are ability to use the oil we once could, will be severely curtailed. That change will severely limit what we put into the atmosphere.