This chapter identifies the key pollutants that drive climate change and, importantly, the timescales involved. The three most important man-made greenhouse gases are identified as carbon dioxide, methane and ozone with atmospheric lifetimes of over 100 years, 12 years and 20 days respectively. We predict that since pre-industrial times, these same three gases have raised global warming by 1.04°C, 0.34°C and 0.21°C respectively by 2020. We also demonstrate that aerosols, notably ammonium sulphate and nitrate have contributed to a global cooling of 0.46°C over the same period. Other pollutants are also examined to give a complete overview of global air quality and potential climate change. These results suggest that we have left it too late to meet the global temperature target set by the Paris Agreement of 1.5°C and while air quality will unquestionably improve in the future, climate change will remain a considerable challenge.