North Carolina Tentmaker
New Member
Good questions Brother James. This is something I studied in graduate school and will try to explain.
First let me say I have no problem with a young earth. That is not a matter of science it is a matter of faith. If you believe in an all powerful God, and I do, then he could have made the earth yesterday if he wanted to, complete with tall trees that have rings if you cut them down and fully grown men and women with memories. IF he wanted to. Ultimately we have a choice of believing what he has revealed to us in the Bible or not. But as we look at the earth there is an apparent age we can measure through many sources.
With all of these sources the systematic error increases with time and there are assumptions that must be made. Carbon Dating, as many know, is problematic because it assumes a constant background radiation.
So how do we measure what the climate may have looked like hundreds of thousands of years ago? Obviously we were not there to take measurements. Climate scientists use many sources to estimate past conditions, or at least the record of past conditions that God has created for us. Two of these sources are marine sedimentation and ice cores.
Back in high school chemistry class you studied the Periodic Table of Elements. From that table you learned that Oxygen has an atomic weight of 16 (15.999 but who is counting). But the truth is that all Oxygen atoms are not O16. There are stable Oxygen isotopes that exist as O18 and O17. O17 is extremely rare, but O18 fairly common. Studies of sea water show that 1 out of every 499 molecules of water contains an O18 or deuterium atom instead of a regular 016 oxygen atom. Furthermore, as we heat water up or cool it down we can see that the ration of O16 to O18 follows a linear correlation to the temperature. As the average temperature of the oceans increases, for every degree C the amount of O18 increases about 0.7 parts per thousand. Using this ratio we can look at ice cores drilled in Antarctica and by measuring the O16 to O18 ratio in the water of each layer we can estimate the average temperature of the sea water that formed it. Remember, the ice was not formed from sea water, it was formed from rain or snow that fell on the surface of Antarctica. The water molecule first evaporated from the surface of the oceans so we can use the ratio to calculate the average temperature of the oceans.
Of course this does not happen with just the oxygen, it happens with the hydrogen also. Most of the Hydrogen atoms are normal H1 atoms, but a few are H2 or deuterium atoms. About 1 in every 6422 hydrogen atoms is a deuterium atom. As we raise the temperature of our sea water that ration increases just like the oxygen did (more heat, more energy, more different isotopes). As the average sea temperature raises the amount of H2 increases about 6 parts per million.
Going back to our ice core sample, we can measure the ration of H1 and H2 and use that to also calculate the average mean temperature of the oceans.
Then comes the exciting part. When we put our graphs of hydrogen and oxygen isotopes together, it matches!
Now ice core samples can take us back in history about 400,000 years. Prior to that we have to shift to ocean sediment cores. These can go back about twice as far as the ice cores, about 800,000 years. This gets a little more complex. Within the sediment layers we can find the calcite shells of micro organisms. Like shellfish, but tiny. Primarily we use singe cell eukaryotes that have shells and live deep in the ocean. Because these shells are formed in sea water, we can look at the H1/H2 and O16/O18 ratios inside those shells and can use that to estimate the average temperature of the sea water. Using the ocean sediment cores is not as reliable as the ice cores because there might be localized temperature changes, but the top 400,000 years of the ocean cores match the ice cores.
Of course as we move further and further back up the sediment record the reliability and variability increase so we cannot be as precise.
So that gives us the temperature record, so how do we correlate that to the CO2 level? Another great question. We can do it the same way, but instead of oxygen or hydrogen isotopes we have to look at carbon and strontium isotopes found in carbon deposits (old dead stuff). Because these isotopes are sensitive to the amount of CO2 in the atmosphere we can develop a history of CO2 levels.
Again, the really interesting part comes when we put these two graphs together and we look at the CO2 level vs the Temperature and see the correlation.
I am not a global warming alarmist. But Crabby is correct when he states there is a correlation between global average temperatures and CO2 levels in our atmosphere. It is also true that the CO2 level in our atmosphere has gone up in the last 200 years and is at a historic high. As of January 9, 2014 it stands at 396.81 ppm. This is an increase from about 315 ppm in the late 1950s.
