Is there less oxygen in the air in winter?

Well no, it really doesn't have much to do with the season as it does with barometric pressure, though temperature is an important factor. As you may know, air is a combination of multiple gases and water vapor. read more

A single 500 milliliter breath of cold air at 0 degrees C will contain more molecules of oxygen than the same volume of air at 40 degrees C. So, to simply answer your question; given the same pressure, cold winter air will have more oxygen than hot summer air per volume. read more

Significant variation in the uptake of CO2 (about 8 ppm) implies that there is a commensurate variation in the production of oxygen (albeit in only ppm). read more

1. Photoplankton contributes far more oxygen than terrestrial plants. It does just fine in the winter. 2. Terrestrial plants in the tropics contribute far more oxygen than those in temperate zones. 3. The amount of oxygen in the atmosphere is so large that a few months worth of plant production have very little effect. read more