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@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix gcis: <http://data.globalchange.gov/gcis.owl#> .
@prefix cito: <http://purl.org/spar/cito/> .
@prefix biro: <http://purl.org/spar/biro/> .

<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   dcterms:identifier "key-finding-14-2";
   gcis:findingNumber "14.2"^^xsd:string;
   gcis:findingStatement "Stabilizing global mean temperature to less than 3.6°F (2°C) above preindustrial levels requires substantial reductions in net global CO<sub>2</sub> emissions prior to 2040 relative to present-day values and likely requires net emissions to become zero or possibly negative later in the century. After accounting for the temperature effects of non-CO<sub>2</sub> species, cumulative global CO<sub>2</sub> emissions must stay below about 800 GtC in order to provide a two-thirds likelihood of preventing 3.6°F (2°C) of warming. Given estimated cumulative emissions since 1870, no more than approximately 230 GtC may be emitted in the future to remain under this temperature threshold. Assuming global emissions are equal to or greater than those consistent with the RCP4.5 scenario, this cumulative carbon threshold would be exceeded in approximately two decades. (<em>High confidence</em>)"^^xsd:string;
   gcis:isFindingOf <https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways>;
   gcis:isFindingOf <https://data.globalchange.gov/report/climate-science-special-report>;

## Properties of the finding:
   gcis:findingProcess "Fundamental scientific understanding of the climate system provides a framework for considering potential pathways for achieving a target of preventing 3.6°F (2°C) of warming. There are uncertainties about cumulative CO<sub>2</sub> emissions compatible with this goal, in large part because of uncertainties about the role of non-CO<sub>2</sub> species, but it appears, based on past emissions and future projections, that the cumulative carbon threshold for this goal could be reached or exceeded in about two decades."^^xsd:string;
   
   gcis:descriptionOfEvidenceBase "Key Finding 2 is a case study, focused on a pathway associated with 3.6°F (2°C) of warming, based on the more general concepts described in the chapter. As such, the evidence for the relationship between cumulative CO<sub>2</sub> emissions and global mean temperature response also supports Key Finding 3. <br><br> Numerous studies have provided best estimates of cumulative CO<sub>2</sub> compatible with 3.6°F (2°C) of warming above preindustrial levels, including a synthesis by the IPCC. Sanderson et al. provide further recent evidence to support the statement that net CO<sub>2</sub> emissions would need to approach zero or become negative later in the century in order to avoid this level of warming. Rogelj et al. 2015 and the IPCC demonstrate that the consideration of non-CO<sub>2</sub> species has the effect of further constraining the amount of cumulative CO<sub>2</sub> emissions compatible with 3.6°F (2°C) of warming. <br><br> Table 14.1 shows the IPCC estimates associated with different probabilities (66% [the one highlighted in Key Finding 2], 50%, and 33%) of cumulative CO<sub>2</sub> emissions compatible with warming of 3.6°F (2°C) above preindustrial levels, and the cumulative CO<sub>2</sub> emissions compatible with 2.7°F (1.5°C) are in turn linearly derived from those, based on the understanding that cumulative emissions scale linearly with global mean temperature response. The IPCC estimates take into account the additional radiative forcing effects—past and future—of non-CO<sub>2</sub> species based on the emissions pathways consistent with the RCP scenarios (available here: https://tntcat.iiasa.ac.at/RcpDb/dsd?Action=htmlpage&page=about#descript). <br><br> The authors calculated the dates shown in Table 14.1, which supports the last statement in Key Finding 2, based on Le Quéré et al. and the publicly available RCP database. Le Quéré et al. provide the widely used reference for historical global, annual CO<sub>2</sub> emissions from 1870 to 2015 (land-use change emissions were estimated up to year 2010 so are assumed to be constant between 2010 and 2015). Future CO<sub>2</sub> emissions are based on the lower and higher scenarios (RCP4.5 and RCP8.5, respectively); annual numbers between model-projected years (2020, 2030, 2040, etc.) are linearly interpolated."^^xsd:string;
   
   gcis:assessmentOfConfidenceBasedOnEvidence "There is <em>very high</em> confidence in the first statement of Key Finding 2 because it is based on a number of sources with a high level of agreement. The role of non-CO<sub>2</sub> species in particular introduces uncertainty in the second statement of Key Finding 2 regarding compatible cumulative CO<sub>2</sub> emissions that take into account past and future radiative forcing effects of non-CO<sub>2</sub> species; though this estimate is based on a synthesis of numerous studies by the IPCC. The last statement of Key Finding 2 is straightforward based on the best available estimates of historical emissions in combination with the widely used future projections of the RCP scenarios."^^xsd:string;
   
   gcis:newInformationAndRemainingUncertainties "There are large uncertainties about the course of future CO<sub>2</sub> and non-CO<sub>2</sub> emissions, but the fundamental point that CO<sub>2</sub> emissions need to eventually approach zero or possibly become net negative to stabilize warming below 3.6°F (2°C) holds regardless of future emissions scenario. There are also large uncertainties about the magnitude of past (since 1870 in this case) CO<sub>2</sub> and non-CO<sub>2</sub> emissions, which in turn influence the uncertainty about compatible cumulative emissions from the present day forward. Further uncertainties regarding non-CO<sub>2</sub> species, including aerosols, include their radiative forcing effects. The uncertainty in achieving the temperature targets for a given emissions pathway is, in large part, reflected by the range of probabilities shown in Table 14.1."^^xsd:string;

   a gcis:Finding .

## This finding cites the following entities:


<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   cito:cites <https://data.globalchange.gov/article/10.1088/1748-9326/10/7/075001>;
   biro:references <https://data.globalchange.gov/reference/17451eb2-574e-4bc3-9196-c4ffe4ba23af>.

<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   cito:cites <https://data.globalchange.gov/article/10.1038/nature08019>;
   biro:references <https://data.globalchange.gov/reference/44137105-aa0e-4e33-afc5-0d6c84115504>.

<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   cito:cites <https://data.globalchange.gov/report/nrc-stabilization-targets-2011>;
   biro:references <https://data.globalchange.gov/reference/a8b2d884-2bfb-4a5a-bfa4-a28bd4d68ca9>.

<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   cito:cites <https://data.globalchange.gov/report/ipcc-ar5-wg1/chapter/wg1-ar5-chapter12-final>;
   biro:references <https://data.globalchange.gov/reference/b3bbc7b5-067e-4c23-8d9b-59faee21e58e>.

<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   cito:cites <https://data.globalchange.gov/article/10.1002/2016GL069563>;
   biro:references <https://data.globalchange.gov/reference/bf91f878-c82a-409b-8d96-e21320366a69>.

<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   cito:cites <https://data.globalchange.gov/article/10.5194/essd-8-605-2016>;
   biro:references <https://data.globalchange.gov/reference/e10cd7fc-e821-474a-bbde-74426a52b1d0>.



<https://data.globalchange.gov/report/climate-science-special-report/chapter/mitigation-pathways/finding/key-finding-14-2>
   prov:wasDerivedFrom <https://data.globalchange.gov/report/climate-science-special-report/chapter/front-matter/figure/confidence---likelihood>.