As the term implies, global warming is the gradual increase in the average temperature of the atmosphere and ocean due to human influences. (hubpages.com)
It occurs due to rise in global warming which occurs due to increase in temperature of atmosphere by burning of fossil fuels and release of harmful gases by industries. (hubpages.com)
Global warming Increase in average global temperatures of the atmosphere and oceans over the past 100 years. (slideplayer.com)