We do not know if we are a small or large part of the present global warming. It is not possible through science to determine an exact answer to this question. Certainly the natural factors, and there are many, that have acted to change the climate many times through the history of the Earth, are still operating today. They have not gone away. But human emissions of  is a new (natural) factor. So it is very unlikely that we are the only factor causing the present global warming but we may be one of the factors,