A small number of scientists disagree that global climate change is caused by human activity. However, scientific consensus supports the idea that human activity is affecting climate. This is possible because

This is possible because the data which we have for global warming can be interpreted in multiple possible ways. While the most often interpretation - which also seems to be true given the changes in the environment that have been happening and general observations that can be made - is also the correct one. The people who disagree with this view, most likely interpret the data in a wrong way.