Climate change 2014 : IPCC fifth assessment synthesis report (AR5 SYR)

IPCC Fifth Assessment Synthesis Report Introduction The Synthesis Report (SYR) of the IPCC Fifth Assessment Report (AR5) provides an overview of the state of knowledge concerning the science of climate change, emphasizing new results since the publication of the IPCC Fourth Assessment Report in 2007 (AR4). [...] The rate of warming of the observed global mean surface temperature over the period from 1998 to 2012 is estimated to be around one-third to one-half of the trend over the period from 1951 to 2012 (Box 1.1, Figures 1a and 1c). [...] The difference between models and observations may also contain contributions from inadequacies in the solar, volcanic, and aerosol forcings used by the models and, in some models, from an overestimate of the response to increasing greenhouse gas and other anthropogenic forcing (the latter dominated by the effects of aerosols). [...] The record of observed climate change has thus allowed characterisation of the basic properties of the climate system that have implications for future warming, including the equilibrium climate sensitivity and the transient climate response (see topic 2). [...] Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, and in global mean sea-level rise; and it is extremely likely to have been the dominant cause of the observed warming since the mid-20th century.