It is well known that greenhouse gases emitted as pollution warm the earth by trapping heat. What is not so well known is that some gases, notably sulfur, and black carbon, also are responsible for cooling the planet. The science can be complex, and in need of much more investigation, but there are certainly known incidents wherein sulfur contributes greatly to cooling.
The best known example is the year without a summer, which was in 1816. In that year, and in 1815, the eruption of Mt. Tambora in Indonesia sent a record amount of cloudy ash and gas into the atmosphere, causing cooling around the world. Solar activity during that time, the Dalton minimum, is also thought to have contributed to the cooling, as solar activity was particularly low.
Industrial pollution also gives rise to some gases known for cooling effects. More often, however, the results are mixed, and the earth atmosphere is found to be affected by both heating and cooling in alternating ways. This is true and demonstrable just as having insulation installed in a home is likely to trap both heat and coolness, depending upon the season and location.
Global warming theory should not always be associated directly then, with all pollution. Pollution does affect, and even harm plant, human and animal life certainly, but it does not always produce only heat. Snow and precipitation by rain are affected by heavy cloud cover in those places where the Atmospheric Brown Cloud reduces some of the natural radiation of heat in those regions. The Atmospheric Brown cloud was originally called the Asian Brown Cloud for its concentrated smog over vast Asian regions.
The type of pollution that becomes ozone, is known as photochemical smog. Ozone is of great value high in the stratosphere but it is problematic at lower levels where people and other organisms need breathable air and less contamination. Decreases in phytoplankton for example are a direct result of depleted upper stratosphere ozone is a bad thing for earth, just as increased cancers are due to the increased UV radiation. But, closer to earth, trapped ozone wreaks havoc by way of inhibiting respiration, damaging crops and plants both with short term and long term ill health effects. One might think of the ozone, then, much the same as a rocket propellant like hydrazine. It is desirable to have way up there, but having it in the baby bottle, or at the family barbecue, it is going to do some damage.
Photochemical smog (low ozone) can even be responsible for freezing rain and ice storms. For this reason, it should not be confused with those factors that are associated with global warming.
Global warming is a very real issue to be confronted, but weather and climate are very different things, and should be considered as related, but not synonymous.
