Higher temperatures enhance the chemical reaction, so smog levels can rise even if emissions from vehicle tailpipes or coal - fired power plants remain the same.6, 19 (climatehotmap.org)
If Congress were to not only eliminate EPA's regulatory authority, but take CO2 completely out of the Clean Air Act, it would still be up to the courts to decide whether or not that would eliminate state authority over vehicle tailpipe emissions. (niskanencenter.org)
... total life - cycle energy inputs and greenhouse gas emissions contribute an additional 63 % for onroad, 155 % for rail, and 31 % for air systems over vehicle tailpipe operation. (treehugger.com)