04-17-2016, 11:48 AM
(04-17-2016, 10:55 AM)Belsnickel Wrote: After all, don't we get most of our historic atmospheric data from ice cores? And since there is no ice outside of the ice ages, we would have nothing to work with for the hundreds of millions of years not included in the information we do have.
First, it has been repeatedly shown, both on Earth and other planets, that temperatures closely follow CO2 levels. So you can make the correlation with a high degree of certainty that when CO2 levels are high, temps are high, and vice versa. And there has been ice on the planet outside of ice ages. The polar caps have been around for the majority of Earth's history, ice age or not. Lastly, there are other methods of determining CO2 levels besides ice cores. Not all those methods result in statistical numbers, but give a pretty clea picture of CO2 levels throughout history.
One method is looking at the number of stomata on fossilized leaves. Those are the holes on the bottoms of leaves that take in CO2. Since the plant loses water when the holes are open to take in CO2, it is an evolutionary advantage to be able to survive with the least amount of stomata possible. When CO2 levels are high, plants have fewer stomata. When CO2 levels are low, the plants require more stomata to take in enough CO2 to conduct photosynthesis. Scientists can compare the number of stomata on fossilized leaves to modern day plants and plants fossilized during the times that we do have actual CO2 numbers and extrapolate the approximate CO2 levels at the time.
The graph I posted was obviously a very simple representation of CO2 levels. But it was not meant to be the definitive say. It was simply posted to refute the most common climate change denier assertion that we are simply in a normal cycle of temps....when the levels of CO2 are clearly not within those normal cycle boundaries. You can find cyclic graphs that go back farther and have better data, but that one was fine to illustrate a point for most people.
