"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia."[12] "Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years."[13] Human influence on the climate system is clear.[14] It is extremely likely (95-100% probability)[15] that human influence was the dominant cause of global warming between 1951-2010.[14] "Increasing magnitudes of [global] warming increase the likelihood of severe, pervasive, and irreversible impacts."[16] "A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability."[17] "The overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change"[16] Without new policies to mitigate climate change, projections suggest an increase in global mean temperature in 2100 of 3.7 to 4.8 °C, relative to pre-industrial levels (median values; the range is 2.5 to 7.8 °C including climate uncertainty).[18] The current trajectory of global greenhouse gas emissions is not consistent with limiting global warming to below 1.5 or 2°C, relative to pre-industrial levels.[19] Pledges made as part of the Cancún Agreements are broadly consistent with cost-effective scenarios that give a "likely" chance (66–100% probability) of limiting global warming (in 2100) to below 3 °C, relative to pre-industrial levels.[20]