Normalized CH4-O3 relation from Fiore et al (2008)
ch4_htap_pert
An object of class numeric
of length 1.
Fiore, A.M., West, J.J., Horowitz, L.W., Naik, V. and Schwarzkopf, M.D., 2008. Characterizing the tropospheric ozone response to methane emission controls and the benefits to climate and air quality. Journal of Geophysical Research: Atmospheres, 113(D8).