https://gml.noaa.gov/ccgg/trends/gl_trend.html

This market will resolve once they have updated the daily ppm. Link in comments if I don't notice and I'll resolve asap.

Higher resolves yes if global Co2 is higher on Dec 31 than Dec 30

Flat resolves yes if global Co2 is same on Dec 31 as Dec 30

Lower resolves yes if global Co2 is lower on Dec 31 then Dec 30