evidence: In its 2013 fifth assessment report, the IPCC stated in its summary for policymakers that it is "extremely likely that more than half of the observed increase in global average surface temperature" from 1951 to 2010 was caused by human activity. By "extremely likely", it meant that there was between a 95% and 100% probability that more than half of modern warming was due to humans. [...] There is a wide range of future warming possible from different RCP scenarios and different values for the sensitivity of the climate system, but all show a similar pattern of declining future aerosol emissions and a larger role for greenhouse gas forcing in future temperatures. [...] Some uncertainty remains due to the role of natural variability, but researchers suggest that ocean fluctuations and similar factors are unlikely to be the cause of more than a small fraction of modern global warming.