If one takes the MBH98 / 99 reconstruction as base, the variation in the pre-industrial period was ~ 0.2 K, of which
less than 0.1 K (in average) from volcanic eruptions, the
rest mostly from solar (I doubt that land use changes had much
influence on global temperatures).
You may wonder why the government finds the need to pursue such action since 1) U.S. carbon dioxide emissions have already topped out and have generally been on the decline for the past 7 - 8 years or so (from technological advances in natural gas extraction and a slow economy more so than from already - enacted government regulations and subsidies); 2) greenhouse gases from the
rest of the world (primarily driven by China) have been sky - rocketing over the same period, which lessens any impacts that our emissions reduction have); and 3) even in their totality, U.S. carbon dioxide emissions have a negligible
influence on local / regional / global climate change (even a immediate and permanent cessation of all our carbon dioxide emissions would likely result in a mitigation of global temperature rise of
less than one - quarter of a degree C by the end of the century).