There are some scientists among the critics of the theory that global warming is caused by human activity. As they have sought funding from the very industries that face regulation, thier bias is real and thier conclusions should be suspect. For example, Dr. Fred Singer observed that "CO<sub>2</sub> changes have lagged about 800 years behind the temperature changes. Global warming has produced more CO<sub>2</sub>, rather than more CO<sub>2</sub> producing global warming."<ref>S. Fred Singer and Dennis T. | There are some scientists among the critics of the theory that global warming is caused by human activity. As they have sought funding from the very industries that face regulation, thier bias is real and thier conclusions should be suspect. For example, Dr. Fred Singer observed that "CO<sub>2</sub> changes have lagged about 800 years behind the temperature changes. Global warming has produced more CO<sub>2</sub>, rather than more CO<sub>2</sub> producing global warming."<ref>S. Fred Singer and Dennis T. |