# Understanding climate in 100 year intervals

I find it hard to find information about how the Earth's past climates have been deduced. I know there are archaeological ways of seeing CO2 levels from the past, but to what range can the CO2 levels be understood and at what range can the actual temperature of the area be deduced. How is it definitely known that there were not fast shifts upward and downward in temperatures and CO2 levels in 100 year times spans. I say this understanding that man-made climate change is real, but I want to understand better how to explain it to others and if there are any resources that go in depth into this concept.

• You want to read up on Paleoclimatology. Your questions as currently phrased (there are several) are probably too broad (and possibly unclear) for the community to answer in a satisfactory way. – gerrit Apr 21 '17 at 16:32
• to what range can the CO2 levels be understood, do you mean resolution or accuracy, on the CO₂ levels or on the time axis? Same question for temperature. When you say *in 100 year time spans", do you mean within a single 100 time span? – gerrit Apr 21 '17 at 16:36
• I know it's not clear, but I'm referencing when people say the climate is heating up much faster than previous climate changes in Earth's history. 100 years was just an arbitrary small value. How is it known the temperature did not oscillate quickly up for 50 years, then go back down and the average of both is seen in evidence? – Biomed Boy Apr 21 '17 at 17:16
• Are you asking whether there are any instances in the record in which the climate heated us as fast as it does today? Or are you asking specifically for the methodology on how we try to answer such a question? – gerrit Apr 21 '17 at 19:35
• @BiomedBoy I think the two key words you are looking for are resolution and accuracy. You want to know the resolution (which is properly measuring the time of a CO$_2$ sample) and accuracy (properly measuring the level of a sample) of various means of measuring ancient CO$_2$ levels. If you want to know about the various methods, you should edit that into your question to narrow it down. – kingledion Apr 22 '17 at 0:02