The blue plume in panel a) shows the response to faster CO2 emissions reductions (blue line in panel b), reaching net zero in 2040, reducing cumulative CO2 emissions (panel c).
The grey plume on the right of panel a shows the likely range of warming responses, computed with a simple climate model, to a stylized pathway (hypothetical future) in which net CO2 emissions (grey line in panels b and c) decline in a straight line from 2020 to reach net zero in 2055 and net non-CO2 radiative forcing (grey line in panel d) increases to 2030 and then declines. Orange dashed arrow and horizontal orange error bar show respectively the central estimate and likely range of the time at which 1.5☌ is reached if the current rate of warming continues. Panel a: Observed monthly global mean surface temperature (GMST, grey line up to 2017, from the HadCRUT4, GISTEMP, Cowtan–Way, and NOAA datasets) change and estimated anthropogenic global warming (solid orange line up to 2017, with orange shading indicating assessed likely range). Global warming is likely to reach 1.5☌ between 20 if it continues to increase at the current rate. Human activities are estimated to have caused approximately 1.0☌ of global warming 5 above pre-industrial levels, with a likely range of 0.8☌ to 1.2☌. *Box SPM.1 Core Concepts Central to this reportĪ.1. In the SPM, knowledge gaps are identified associated with the underlying chapters of the Report.Ĭhanges to the Underlying Scientific-Technical Assessment to ensure consistency with the approved Summary for Policymakers
The level of confidence associated with each key finding is reported using the IPCC calibrated language 3. The underlying scientific basis of each key finding is indicated by references provided to chapter elements. This Summary for Policymakers (SPM) presents the key findings of the Special Report, based on the assessment of the available scientific, technical and socio-economic literature 2 relevant to global warming of 1.5☌ and for the comparison between global warming of 1.5☌ and 2☌ above pre-industrial levels. The IPCC accepted the invitation in April 2016, deciding to prepare this Special Report on the impacts of global warming of 1.5☌ above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. This Report responds to the invitation for IPCC ‘… to provide a Special Report in 2018 on the impacts of global warming of 1.5☌ above pre-industrial levels and related global greenhouse gas emission pathways’ contained in the Decision of the 21st Conference of Parties of the United Nations Framework Convention on Climate Change to adopt the Paris Agreement 1.
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