Global climate change, therefore, refers to the changes in all the interconnected weather elements of the Earth. Global warming simply refers to an increase in average global temperature that may have occurred at any time in the Earth's history. The term is now often used to describe the increase in global temperatures caused by human activity since the beginning of the industrial age about 200 years ago. Most greenhouse gases occur naturally in the atmosphere. GHGs produced by human activities in largest amounts are carbon dioxide, methane and nitrous oxide.
Greenhouse gases act as the glass in a greenhouse.
Small changes in the concentration of these gases can consequently have significant effects. Sulfate particles in the atmosphere, because they reflect heat outside of the Earth's atmosphere, sometimes mask the effect of greenhouse gases locally. Causes of Global Warming The Earth's orbital movements around the sun and the expansion and retreat of polar ice caps are two factors that have a slow impact on global climate. Atmospheric dust, changes in ocean circulation, vapour, clouds, snow and greenhouse gases influence global climate as well, but at a faster rate. Because of natural climate variability, it has been difficult to attribute climate change to a specific cause.