The science is clear that there is an increase in the amount of CO2 in the atmosphere. What is not clear from the science is how much of that increase is caused by human activity and what also is not clear is what impact those increases have on the climatic cycle.

Summary

This quote emphasizes that while it is evident from scientific research that there is a rise in atmospheric CO2 levels, the extent to which human activities contribute to this increase remains uncertain. Furthermore, the consequences of these heightened CO2 levels on the Earth's climate are also not fully understood. In essence, the quote points out that while the presence of increased CO2 is scientifically evident, the specific causes and effects of this increase are yet to be fully determined.