What is the scientific basis for AGW (anthropogenic global warming)?

Anthropogenic is defined as follows:
of, relating to, or resulting from the influence of human beings on nature.

Source: http://www.merriam-webster.com/dictionary/anthropogenic

Due to sunlight hitting the earth, infrared radiation is emitted by the earth. Greenhouse gases in the atmosphere absorb this radiation, which results in a warming of the earth. The greenhouse effect is normal when balanced and keeps the earths surface from being frozen all the time.

Since the industrial revolution, CO2 in the atmosphere has been increasing due primarily to the burning of fossil fuels and to deforestation. This causes an enhanced greenhouse effect which can lead to global warming.

There is a concensous among scientists that when the CO2 in the atmosphere reaches twice the pre-industrial level, the enhanced greenhouse effect alone will warm the earth by 1.2 to 1.3 degrees celsius.

Industrial age increases greenhouse effect

Industry took off in the mid-1700s, and people started emitting large amounts of greenhouse gases. Fossil fuels were burned more and more to run our cars, trucks, factories, planes and power plants, adding to the natural supply of greenhouse gases. The gases—which can stay in the atmosphere for centuries—are building up in the Earth’s atmosphere and, in effect, creating an extra-thick heat blanket around the Earth.

The result is that the globe has heated up by about one degree Fahrenheit over the past century—and it has heated up more intensely over the past two decades.

Source: http://www.edf.org/climate/basics-global-warming?gclid=CLLJhMb9iasCFUeFQAodj0lBsw

Source: http://www.edf.org/sites/default/files/climate/graph-world-global-temp-datasets_1.jpg

http://www.edf.org/sites/default/files/climate/csiro-global-mean-sealevel-400w.jpg

During the 20th century, sea level rose an average of 7 inches after 2,000 years of relatively little change.

The trends show an increase of global temperature and sea levels since the industrial revolution, which doesn't argue with the theory of AGW (anthropogenic global warming).

Using proxy records (ice cores, tree rings, and coral reefs) scientists have reconstructed the past 2,000 years of global surface temperatures, which shows a sharp uptick in temperature over the last few decades.

Source: http://www.edf.org/sites/default/files/climate/national-academies-proxy-temp-record-400w.jpg

Based on the graph, global temperatures have clearly spiked more than normal since the industrial revolution.