>>10737566>Why would people spend millions drilling in Greenland at all of it's as tainted and unreliable as you say?
CO2 is just one among many tracers you can measure in ice core. In gas phase you can also measure
1. CH4, CH4 isotopes (dD, d13C, C14), 2nd most important GHG
2. N2O, N2O isotopes, N2O position dependent isotopes. 3rd most important GHG
3. Noble gases. d15N of N2, important for calculating gravitational fractionation. d18O of O2 proxy of oxygenation region on earth. Xe/Kr, proxy of mean ocean temperature.
4.. clumped isotopes of O2 proxy of tropospheric ozone and oxidative capacity of the atm.
5. Ethane, propane, acetylene (proxy of biomass burning)
On ice phase you can also measure water isotopes (the classic) for T proxy, dust (and different dust isotopes), organics biomarkers, Lead (also the classic, you can actually date the rise and fall or roman empire from greenland lead content), and others (you might notice I know more about gases than ice chemistry because I'm an ice bubble person).
Finally after drilling is done you can measure borehole temperature and do temperature reconstruction. Ice core is not only for CO2 measurements, there's a whole field and analytical technique for a whole lot of things