'''Global Warming''' is any increase in average air temperature at the [[Earth]]'s surface over a period of decades or more. Since 1989, advocates have clashed on the issue of whether human beings are more responsible than nature for modern periods of global warming; see [[global warming theory]]. | '''Global Warming''' is any increase in average air temperature at the [[Earth]]'s surface over a period of decades or more. Since 1989, advocates have clashed on the issue of whether human beings are more responsible than nature for modern periods of global warming; see [[global warming theory]]. |