Human and natural drivers of climate change Annual fossil CO 2 emissions increased from an average of 6.4 GtCper year in the 1990s, to 7.2 GtC per year in CO 2 radiative forcing increased by 20%from 1995 to 2005, the largest in any decade in at least the last 200 years Changes in solar irradiance since 1750 are exstimated to have caused a radiative forcing of [+0.06 to +0.30] Wm -2
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