The effects of climate change on air quality are difficult to model due to the large number of unpredictable variables. Hotter temperatures favor ozone production. Higher atmospheric water content may blunt this effect in some regions. Higher levels of natural volatile organic compounds (VOCs), such as terpenes from plants, are likely to act synergistically with anthropogenic VOCs to favor ozone production. Droughts increase wildfire risks that produce particulate pollution and carbon monoxide, a VOC involved in ozone production. Some models predict increased ozone concentrations in many urban settings. Future revisions of National Ambient Air Quality Standards, a process driven by politics and science, should consider these effects.