Excellent work! Extra credit worthy.


1) Focus question
Obliquity minimum. Smaller tilt => smaller seasonal variation => cooler summer.
Aphelion in summer. Farthest distance => less intense solar radiation => cooler summer.
Eccentricity large. Most elliptical orbit => maximizes the Earth-Sun distance at aphelion => cooler summer.

2) Focus question
Warmer summers => more melting.
Colder winters => lower SVP => less snow => less ice build up.
Surprisingly, cool summers (less melt) and relatively warm winters (higher SVP, more snowfall) would be most conducive to ice ages.

3) Focus question (If the LA question)
Lots of sunshine.
Warm temperatures. Ozone production increases with temperature.
Gentle winds to transport pollutant away from source region.
Persistent inversion to trap pollutants near ground.


3) Focus question (If the PHX question)
Lots of sunshine.
Hot temperatures.
Dip in AQI in mid-summer: An uptick in cloudiness during peak of summer thunderstorm season.

4) Focus question
a) about 2.2 ppm/year
b) 8-9 ppm increase; 6-7 ppm decrease
c) April/May; September
d) Seasonal cycle of photosynthesis over Northern Hemisphere land masses. 
Increase photosynthesis in growing season => increase CO2 uptake by plants => decrease CO2 in air.