Global warming is an urgent issue of increasing concern to scientists, policy makers and the public. Global warming refers to the long-term increase in the average temperature of the Earth's climate system, caused primarily by the accumulation of greenhouse gases (GHGs) in the atmosphere. This phenomenon is exacerbated by human activities such as fossil fuel burning, deforestation and industrial processes that release large amounts of carbon dioxide (CO2), methane (CH4) and other heattrapping gases.