Examining a section of the same graph seen in the two previous entries, a graph from the 2001 report of the Intergovernmental Panel on Climate Change, note that humans change the surface of the earth, by planting or harvesting forests, by cultivating land for farming, by building cities, and other activities that change the reflectivity (albedo) of the earth's surface. If man takes a forest and plows it up to create a field of bare dirt, the blackness of the soil will absorb more of the sun's heat, and this creates a warming effect.
According to the scientists represented by the IPCC, however, the net effect of human activity on albedo is actually a cooling effect.
On the other hand, increased solar activity, the item on the right edge of the graph, is a warming influence. This graph was designed to compare the pre-industrial climate and conditions (circa 1750 A.D.) to the current day. Clearly the IPCC believes that increased solar activity is partly responsible for our slightly warmer global temperatures today compared with the climate 250 years ago.