We analyzed climatological and geographical variables in 90 countries from the Northern Hemisphere to determine the significant variability of plant species richness as it relates to broad-scale levels of global warming. This variability was quantified by the parameters of temperature and precipitation. Of the 27 temperature variables and 13 precipitation variables, 6 variables had negative influences on species richness while 5 variables had positive impacts. When we estimated the effect of higher temperatures, we found that a 1 or $2^{circ}C$ rise in global warming produced an increase in species richness of 1.6 or 3.2%, respectively.