This first one shows the precipitation anomalies over the past 30 years versus the longterm average. Really shows the recent droughts in the southeast and how they've been building over time. Also vividly shows the drying out of the Pacific Northwest and the surplus of moisture along the northern third of the country. This is probably directly tied to global warming (man-made or not). Jet stream lifts north, drying out the south and the Pacific Northwest, while bringing in warmer air to the northern areas, and thus more moisture as well.
The second one just re-iterates that the United States has definitely warmed nation-wide.
The third composite is of the winters of the past 30 years. They have also definitely warmed, especially over the upper midwest and central plains. So chances are, there is a greater likelihood of any random winter being warmer than average rather than cooler.
And the fourth and last is precipitation over the winter. The past 30 years have shown a drying of the winters along the east coast.
