Human activity has impacts
Global climate is an extremely complex phenomenon of interplay between a great many factors, some well understood, others not. That local drought cannot be directly attributed to human-caused increases in greenhouse gases does not mean that such play no role.
What is known with very high confidence is that human activity continues to change earth's atmosphere and that carbon dioxide, methane and nitrous oxide are major man-made drivers of climate change.
According to the Intergovernmental Panel on Climate Change, referred to by Patrick Ryan's Jan. 30 letter critiquing Don Gaede's Jan. 24 letter of concern about rising carbon dioxide levels, it is virtually certain that human influence continues to negatively impact global climate systems.The IPCC report was produced by some 1,000 scientists from over 30 countries. The summary alone is some 100 very technical pages. It is inconceivable that Mr. Ryan has read the report and even more unbelievable that he is expert on the highly complex systems reported on. To dismiss the crucial issues as "model-driven political agendas" is absurd.
As Mr. Ryan himself writes, the correct path to understanding climate change is adherence to scientific fact. And some modesty in critiquing that which one does not know much about in the first place.