Stomata data show higher readings and variability than the excessively smoothed ice core record. (drtimball.com)
Thus sorry, while stomata data give a rough idea of (local!) (wattsupwiththat.com)
I have repeatedly pointed out (in several places including WUWT) that (1) ice core data are useful because they indicate CO2 concentration and isotope - derived temperature data from the same trapped gas bubbles but (2) ice core data are NOT a direct indication of anything because (2a) different ice cores provide different indications and (2b) other proxies (e.g. stomata data) provide different indications to those of the ice cores and to each other. (wattsupwiththat.com)