Im not sure if someone needs proof that CO2 is a greenhouse gas.. pretty basic physics with lots of references if needed.
A very interesting question is: Does a temperature increase cause an increase in CO2 or does an increase in CO2 cause a temperature increase?
You have to understand a little about feedback and forcing functions. Per the rules hopefully we can follow, here is a reference on the subject
https://www.yaleclimateconnections....a-feedback-and-forcing-in-the-climate-system/
CO2 is a feedback mechanism because as temperature rises, the ocean temperature also rises releasing CO2 into the atmosphere. Since CO2 is a greenhouse gas, this is positive feedback because the initial temperature rise caused more greenhouse gas which in turn causes more temperature rise. For CO2 as feedback, the concentration of CO2 will have a time delay compared to the driving temperature change. Ie, CO2 concentration will lag temperature change when its acting as positive feedback.
CO2 can also be a forcing function. If you simply add CO2 to the atmosphere so that its concentration increases, it will cause temperature to rise because it is a greenhouse and traps more energy. When CO2 is a forcing function, the concentration of CO2 will precede the rise in temperature. Ie, as a forcing function, CO2 concentrations leads temperature rise.
Note.. CO2 as a forcing functions seems like a very simple basic concept and I can find many references on this. But you will find conservative blogs that deny this. PLEASE provide a reference if someone does not agree with the simple idea that if you add CO2 to the atmosphere, it will increase the greenhouse effect and cause an increase in temperature. Pretty much the basic definition of what a greenhouse gas does.
Before we came along, CO2 mainly acted as a feedback mechanism and reacted to and amplified temperature change. There is ice core data going back about 800 thousand years that shows a series of glacier and interglacier periods. caused by Milancovitch cycles (reference
http://clivebest.com/blog/?p=8656 ). We are currently in a interglacier warm period (a good thing, ice sheets cover a lot of the planet in the cold periods). The ice core data provides both temperature and CO2 concentrations and the temperature always rises first and then the CO2 concentration rises. Temperature falls, then the CO2 concentration falls. CO2 in this case is acting as feedback and it tends to amplify the response to the solar input changes.
But.. something completely different happened when we came along. Unlike in the past where CO2 concentrations were governed by plants and temperature, we started burning fossil fuel which by itself, increased the CO2 concentration in the atmosphere. This is the forcing function of CO2 (do I need more references on this - easy to find) . Very simple green house gas concept. If you increase the green house gas concentration, it will trap energy resulting in a temperature increase. In this case CO2 concentration will LEAD temperature rise.
Greenland ice cores do, or do not, support pre-industrial episodes of climate change?
