According to many scientists, how does increased pollution cause global warming?

How would i answer this for an exam?

[ou.01jthe greatest speed with which any physical object moves is 300,000 km/soundsec. which of the following has a speed of 300,000 km/sec? a.light in water b.light in vacuum c.sound in air. d. sound in water

Both pictures below were taken at the same time of day, but one picture was taken in summer, and the other in winter. how can you tell which is in winter