Complex sentence: The authors argued that after what they regard as the failure of the 2009 Copenhagen Climate Summit, the Kyoto Protocol crashed and they claimed that it "" has failed to produce any discernable real world reductions in emissions of greenhouse gases in fifteen years.
Split into simpler sentences: The authors argued that, after what they regard as the failure of the 2009 Copenhagen Climate Summit, the Kyoto Protocol crashed. They claimed that Kyoto had "" failed to produce any discernable real world reductions in emissions of greenhouse gases in fifteen years.