Answer to Question 1
Answers will vary, but may include decreases in global snowfall, but increases in blizzards. Increases in lake-effect snowfall; higher intensity and frequency of tropical cyclones; more tornadoes, etc.
Answer to Question 2
Several examples may include solar variability (sun spot activity), changes in Earth-Sun relationships (Milankovitch Cycles), plate tectonics and orogenies, and changes in concentrations of atmospheric gases and aerosols.