... period, the earthbegan to cool slightly over the next 25 years or so. In the late 1960s and 1 970 s, the cooling trend ended over mostof the Northern Hemisphere. During the 1 970 s and into the 1980s, ... downwind.Either these particles and gases slowly settle to the ground in dry form (dry deposition) or they are re-moved from the air during the formation of cloud particles and then carried to the ... climatic region includesmost of the Great Plains, the southern coastal sections ofCalifornia, and the northern valleys of the Great Basin. Asin the arid region, northern areas experience lower...