Any chemists around?

Question

I may be getting hungup on a term, butcould someone explain the difference between geeen house gases, which maybe heating the Earth and the Greenhose effect written about by Carl Sagan, which after nucklar exchange would cool the Earth. Personally pro envirment for health reasons.

I maybe getting hungup on one tern, but could someone explain why greehous gases do not have the same effect as greenhouse effect written by Carl Sagan, but not at the level of a nucelar exchange. Personally pro envirorment because it's healtier.

Answer 1

Did Sagan really use the term "Greenhouse effect"? I've always heard it called "nuclear winter".

Both effects are caused by altering how sunlight interacts with our atmosphere.

In a nuclear winter or catastrophic volcanic eruption, massive quantities of small particles (ash) are dispersed throughout the atmosphere. These particles reflect sunlight back into space, thus cooling the atmosphere. There is geological evidence that this has happened after massive volcanic eruptions in the past. Climatologists have also found that areas with high reflectivity (such as the white polar ice caps) are indeed colder than nearby low-reflectivity areas. Neat.

The classic "greenhouse effect" caused by "greenhouse gases" is almost the exact opposite. Normally, sunlight hits the earth, but some of it reflects back into space as infrared radiation, cooling the earth. Greenhouse gases are opaque to infrared radiation, trapping it in the atmosphere and heating it up. This is less well-documented in the geologic record on Earth (and those who know better will certainly correct me and cite some studies), but Venus is a great example of a runaway greenhouse effect. Radiation gets in, but it can't get out.

So they're both caused by changing the balance of gases and particles in our atmosphere; one cools us down and the other heats us up. I've even heard "conservatives" arguing that if the greenhouse effect ever gets too bad, we can just add sulphur(?) to the upper atmosphere to simulate a massive nuclear winter and cool things down again. Not my idea of fun planetary maintenance, but it's theoretically feasible...

Answer 2

Yea, the greenhouse will absorb infrared, but there are other pollutants in air that can reflect infrared out into space. So warming can occur if the balance tips in one way and may be even exellerated if one type of pollutant is reduced, but other keeps up.