Thought progression: 

1) Summer is the season of glacier melt. It stands to reason that colder summers would lead to less melting. 
2) Colder winter seasons in high latitudes would lead to drier storm systems that produce less snowfall since the amount of water vapor in the air would be lower.

Thought progression:

Colder summers would occur when
a) the obliquity (tilt) is at its minimum value of 22˚ since it would minimize insolation during summer.
b) perihelion (sun farthest from Earth) is during summer. 
c) the Earth’s orbit is at it most elliptical point since perihelion would be at its maximum distance.

Thought progression:

a) CO2 levels increased by approximately 11 ppm from 1 Jan 2013 to 1 Jan 2017, which gives an average of 2.75 ppm per year. (Note that the annual rate of CO2 increase is accelerating.)
b) May, the beginning of the spring growing season.
c) September, the last month of the growing season.
d) The annual cycle of vegetation over the northern hemisphere continents is responsible. As the continents green and photosynthesis increases during the growing season (spring and summer), uptake of CO2 increases and atmospheric levels fall. When plants become dormant in the fall and winter, uptake CO2 decreases and atmospheric levels increase. 

Thought progression:

The summer-early fall climate of the L.A. Basin is characterized by
1) Clear, sunny days.
2) Warm daytime temperatures, and warm temperatures enhance ozone production.
3) Weak winds that prevent dispersion of pollutants.
4) Daily sea-breezes and strong high-pressure aloft that form a strong low-level inversion that prevents vertical mixing of pollutants.

Thought progression: 

1) The five hottest months of the year are May through September.
2) The number of daylight hours is longest during the months of May to August.