What is global warming ? how did they find out this was happening? ?

Question

What is global warming ? how did they find out this was happening? ?

Answer 1

Global warming is a term used to imply that significant human caused warming is and/or will be occurring.  It is largely a political phenomena created to push a left wing agenda.  CO2 has not driven temperature fluctuations in the past and there is very little indication that it is having significant or any influence now.  

Answer 2

Global warming is the gradual increase in mean global temperature due to anthropogenic emissions of greenhouse gases.  The more accurate term is Global Climate Change because it will have more dramatic impacts than just warming the earth slightly.

It was discovered thanks to years of monitoring CO2 levels in atmosphere in Hawaii.  The 2nd link I attached has a good synopsis of of anthropogenic sources of CO2 are altering the global C biogeochemical cycle (starts on page 3 of the article).