Complex sentence: Thus the observed increase could be largely due to natural variability; it wasn't until the IPCC's Second Assessment Report (SAR) in 1995 that a "discernible" human influence on global climate was identified.
Split into simpler sentences: Thus the observed increase could be largely due to natural variability. It wasn't until the IPCC's Second Assessment Report (SAR) in 1995 that a "discernible" human influence on global climate was identified.