Answer to Question 1
The average U.S. temperature has risen, we have seen an increase in precipitation, we are seeing changes in the ways that snow melts through the winter seasons, and we are having heat waves with associated droughts.
Answer to Question 2
In IPCC AR5, researchers investigated scenarios representing four different sets of assumptions about the level of anthropogenic emissions. These scenarios, called representative concentration pathways (RPCs), projected significantly different levels of radiative forcing by the year 2100. See Figure 18-17 for a comparison of +2.6 and +8.5 +2.6 represents what would happen if we curb greenhouse gas emissions immediately and +8.5 assumes that we continue with our current population growth rate and do not change our use of technology.