Hey, I just found this thread, and had to put in my two cents, I hope you read it all as there is a lot of important information here that I have learned over the years.
Global warming and ice ages are cyclical, and they are simply a function of a few factors.
There are three orbital factors. The first is the elliptical orbit of the earth. In a more elliptical orbit, mean temperatures are higher as the earth is further away at the poles of the ellipse compared to a more circular orbit. Next, how the earth is tilted in relation to the placement of the continents affects reflectivity (more on that later) which can affect global temperature. And lastly for orbital factors is the wobble of the earth about its axis which causes sporatic temperature fluctuations (ice sheets never fully melt, or develop depending if you are in an ice age or a warming period). You can look up Milankovitch cycles to find out more about these cycles.
Next factor is the albedo or reflectivity of the earth. UV rays are absorbed by the earth from the sun. However land masses reflect a majority of this UV radiation, and ice sheets even more. In fact if it wasn’t for the shallow water (which absorbs the greatest percentage of the UV radiation from the sun) there wouldn’t be that much UV energy absorbed at all. This is why supercontinents trigger ice ages as you have large refelctive land masses, and only a small percentage of shallow water bodies around these land masses that absorb UV radiation. Sea levels that are low means more land mass is exposed, so sea level rise is actually a good thing (more shallow seas) from a climactic and survival perspective.
The position of the land masses can also affect global temperature. Having deep oceans at the equator (where most of the UV radiation is focused) and land masses at the poles will result in the least possible amount of UV radiation being absorbed as whatever little UV arrives at the poles is mostly reflected away.
Next is global water circulation, the short and sweet version is basically how the absorbed UV radiation is circulated. Poor circulation means global cooling. A good example of circulation would be the Gulf Stream that sends warm water up as far north as Scandinavia from equatorial waters.
There are more factors, however they are dwarfed by these factors, and can be considered irrelevant.
The largest greenhouse gas is water vapour. So that push for Hydrogen cars is ludicrous for two reasons. One, the exhaust is water vapour (yeah let’s put more of that up there to reduce global warming, duh). The second is that Hydrogen has to be extracted from water, and that process requires more energy than the hydrogen provides, so more coal power plants are fired up to make less energy (pretty stupid eh).
CO2 is actually still being absorbed by the Ocean (yes it does this, something no one seems to mention) and trees (more CO2 = larger trees) and there are more trees today than 50 years ago (believe it or not). Even with the pollution over the years, the earth is still adapting to the point where CO2 levels are a lot less than what they should be.
Now the important part. Currently we are in an interglacial period, where ice ages and global warming periods cylce back and forth every few thousand years. You can take a look at ice cores and they will record this cycle. The last ice age being about 20 000 years ago, so we are due for another one. So why is this worse than global warming? Well an ice age means ice cover over much of the land mass that is currently inhabited by us. That means mass starvation and chaos, not to mention mass extinctions of other animal species, the comfortable life as we know it today will cease, becoming much more harsh, but that’s a cake walk compared to what can and has happened.
We have been very lucky over geological time in that none of the conditions mentioned earlier have been at there worst, so there was always some possibility of the earth coming out of those ice ages, except for one time where we were almost locked in a permanent ice age “Snow Ball Earth” as it’s called. At the end of the Vendian age, life almost became extinct on earth before it took off. The albedo was very high and there weren’t many shallow seas, and there was a super continent at the antarctic pole. These factors locked the earth in an ice age that only ended because of very active plate tectonics that broke up the super continent, we almost never existed.
Now this is unlikely to occur soon if ever, but contrast that or an ice age in general with the opposite, global warming. Well, the earth has been MUCH warmer in the past such as in the Cretaceous, where crocodiles lived in the arctic, large inland seas were found on all the continents, and much of the world was a lush tropical to sub-tropical environment. The diversity of organisms was also very high.
So from a survival point of view we should warm the earth if anything (pollution is still bad, I am against it in every way, but maybe hydrogen cars have a purpose after all).
So which would you prefer, certain death of millions possibly billions of people and mass extinctions of organisms, or a SWEET Cretaceous climate, waking up in a paridise every morning. Imagine that, warming the earth can be an awesome thing. I can deal with a little less coast and no polar bears.
I you have any more questions or comments let me know, as I am an Earth Sciences Student.
