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New synthesis shows what a wasted decade means for the climate pact made in Paris. New synthesis shows what a wasted decade means for the climate pact made in Paris., Author(s): Niklas Höhne, Michel den Elzen, Joeri Rogelj, Bert Metz, Taryn Fransen, Takeshi Kuramochi, Anne Olhoff, Joseph Alcamo, Harald Winkler, Sha Fu, Michiel Schaeffer, Roberto Schaeffer, Glen P. Peters, Simon [...]

The Paris climate agreement aims at holding global warming to well below 2 degrees Celsius and to 'pursue efforts' to limit it to 1.5 degrees Celsius. To accomplish this, countries have submitted Intended Nationally Determined Contributions (INDCs) outlining their post-2020 climate action. Here we assess the effect of current INDCs on reducing aggregate greenhouse gas emissions, its implications for achieving the temperature objective of the Paris climate agreement, and potential options for overachievement. The INDCs collectively lower greenhouse gas emissions compared to where current policies stand, but still imply a median warming of 2.6-3.1 degrees Celsius by 2100. More can be achieved, because the agreement stipulates that targets for reducing greenhouse gas emissions are strengthened over time, both in ambition and scope. Substantial enhancement or over-delivery on current INDCs by additional national, sub-national and non-state actions is required to maintain a reasonable chance of meeting the target of keeping warming well below 2 degrees Celsius. The objective of the Paris climate agreement is to limit global-average temperature increase to well below 2 degrees Celsius above pre-industrial levels and to further pursue limiting it to 1.5 degrees Celsius; here, the adequacy of the national plans submitted in preparation for this agreement is assessed, and it is concluded that substantial enhancement or over-delivery on these plans is required to have a reasonable chance of achieving the Paris climate objective. Paris climate action plans assessed The principal climate goal of the Paris Agreement of December 2015 is to hold the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 degrees above pre-industrial levels. This Perspective assesses the national plans submitted to the Paris meeting for post-2020 action to reduce global greenhouse gas emission by 2030. It also provides projections for global mean temperature increase over the twenty-first century that would be consistent with the present national plans and discusses options that may help to reduce greenhouse gas emissions to levels that are more consistent with maintaining a reasonable chance of meeting the well below 2 degrees Celsius climate target., Author(s): Joeri Rogelj [sup.1] [sup.2] , Michel den Elzen [sup.3] , Niklas Höhne [sup.4] [sup.5] , Taryn Fransen [sup.6] , Hanna Fekete [sup.4] , Harald Winkler [sup.7] , Roberto Schaeffer [...]

The Paris climate agreement aims at holding global warming to well below 2 degrees Celsius and to 'pursue efforts' to limit it to 1.5 degrees Celsius. To accomplish this, countries have submitted Intended Nationally Determined Contributions (INDCs) outlining their post-2020 climate action. Here we assess the effect of current INDCs on reducing aggregate greenhouse gas emissions, its implications for achieving the temperature objective of the Paris climate agreement, and potential options for overachievement. The INDCs collectively lower greenhouse gas emissions compared to where current policies stand, but still imply a median warming of 2.6-3.1 degrees Celsius by 2100. More can be achieved, because the agreement stipulates that targets for reducing greenhouse gas emissions are strengthened over time, both in ambition and scope. Substantial enhancement or over-delivery on current INDCs by additional national, sub-national and non-state actions is required to maintain a reasonable chance of meeting the target of keeping warming well below 2 degrees Celsius., In December 2015, the Paris Agreement (1)--a new global agreement to combat climate change--was adopted under the United Nations Framework Convention on Climate Change (UNFCCC). In preparation of this agreement, [...]

Byline: Michel den Elzen (1), Niklas Hohne (2) Abstract: The IPCC Fourth Assessment Report, Working Group III, summarises in Box 13.7 the required emission reduction ranges in Annex I and non-Annex I countries as a group, to achieve greenhouse gas concentration stabilisation levels between 450 and 650 ppm CO.sub.2-eq. The box summarises the results of the IPCC authors' analysis of the literature on the regional allocation of the emission reductions. The box states that Annex I countries as a group would need to reduce their emissions to below 1990 levels in 2020 by 25% to 40% for 450 ppm, 10% to 30% for 550 ppm and 0% to 25% for 650 ppm CO.sub.2-eq, even if emissions in developing countries deviate substantially from baseline for the low concentration target. In this paper, the IPCC authors of Box 13.7 provide background information and analyse whether new information, obtained after completion of the IPCC report, influences these ranges. The authors concluded that there is no argument for updating the ranges in Box 13.7. The allocation studies, which were published after the writing of the IPCC report, show reductions in line with the reduction ranges in the box. From the studies analysed, this paper specifies the 'substantial deviation' or 'deviation from baseline' in the box: emissions of non-Annex I countries as a group have to be below the baseline roughly between 15% to 30% for 450 ppm CO.sub.2-eq, 0% to 20% for 550 ppm CO.sub.2-eq and from 10% above to 10% below the baseline for 650 ppm CO.sub.2-eq, in 2020. These ranges apply to the whole group of non-Annex I countries and may differ substantially per country. The most important factor influencing these ranges above, for non-Annex I countries, and in the box, for Annex I countries, is new information on higher baseline emissions (e.g. that of Sheehan, Climatic Change, 2008, this issue). Other factors are the assumed global emission level in 2020 and assumptions on land-use change and forestry emissions. The current, slow pace in climate policy and the steady increase in global emissions, make it almost unfeasible to reach relatively low global emission levels in 2020 needed to meet 450 ppm CO.sub.2-eq, as was first assumed feasible by some studies, 5 years ago. Author Affiliation: (1) Netherlands Environmental Assessment Agency, P.O. Box 303, 3720 AH, Bilthoven, The Netherlands (2) Ecofys Germany GmbH, Cologne, Germany Article History: Registration Date: 22/07/2008 Received Date: 20/05/2008 Accepted Date: 27/06/2008 Online Date: 11/09/2008

How can dangerous interference with the climate system be avoided? Science can help decision-makers answer this political question. Earlier publications have focused on the probability of keeping global mean temperature change below certain thresholds by stabilizing greenhouse gas concentrations at particular levels. We compare the results of such 'stabilization profiles' with a set of 'peaking profiles' that reduce emissions further after stabilization and thus result in a concentration peak. Given the inertia in the climate system, stabilization profiles lead to ongoing warming beyond 2100 until the temperature reaches equilibrium. This warming partly can be prevented for peaking profiles, in this way, these profiles can increase the likelihood of achieving temperature thresholds by 10-20% compared with the likelihood for the associated stabilization profiles. Because the additional mitigation efforts and thus costs for peaking profiles lie mainly beyond 2100, peaking profiles achieving temperature thresholds with the same likelihood as the original stabilization profile, but at considerably lower cost (up to 40%), can be identified. The magnitude of the cost reductions depends on the assumptions on discounting. Peaking profiles and overshoot profiles with a limited overshoot may, in particular, play an important role in making more ambitious climate targets feasible. abatement costs | concentration stabilization | climate change | integrated assessment model | multigas emission pathway

So far, climate change mitigation pathways focus mostly on C[O.sub.2] and a limited number of climate targets. Comprehensive studies of emission implications have been hindered by the absence of a flexible method to generate multi-gas emissions pathways, user-definable in shape and the climate target. The presented method 'Equal Quantile Walk' (EQW) is intended to fill this gap, building upon and complementing existing multi-gas emission scenarios. The EQW method generates new mitigation pathways by 'walking along equal quantile paths' of the emission distributions derived from existing multi-gas IPCC baseline and stabilization scenarios. Considered emissions include those of C[O.sub.2] and all other major radiative forcing agents (greenhouse gases, ozone precursors and sulphur aerosols). Sample EQW pathways are derived for stabilization at 350 ppm to 750 ppm C[O.sub.2] concentrations and compared to WRE profiles. Furthermore, the ability of the method to analyze emission implications in a probabilistic multi-gas framework is demonstrated. The probability of overshooting a 2[degrees]C climate target is derived by using different sets of EQW radiative forcing peaking pathways. If the probability shall not be increased above 30%, it seems necessary to peak C[O.sub.2] equivalence concentrations around 475 ppm and return to lower levels after peaking (below 400 ppm). EQW emissions pathways can be applied in studies relating to Article 2 of the UNFCCC, for the analysis of climate impacts, adaptation and emission control implications associated with certain climate targets. See www.simcap.org for EQW-software and data.

During the negotiations on the Kyoto Protocol, Brazil proposed a methodology to link the relative contribution of Annex I Parties to emission reductions with the relative contributions of Parties to the global-mean temperature increase. The proposal was not adopted during the negotiations but referred to the Subsidiary Body for Scientific and Technological Advice for consideration of its methodological aspects. In this context we analyze the impact of model uncertainties and methodological choices on the regionally attributed global-mean temperature increase. A climate assessment model has been developed to calculate changes in greenhouse gas concentrations, global-mean temperature and sea-level rise attributable to individual regions. The analysis shows the impact of the different choices in methodological aspects to be as important as the impact of model uncertainties on a region's contribution to present and future global temperature increases. Choices may be the inclusion of the anthropogenic non-C[O.sub.2] greenhouse gas emissions and/or the C[O.sub.2] emissions associated with land-use changes. When responsibility to global temperature change is attributed to all emitting Parties, the impacts of modeling uncertainties and methodological choices on contributions of individual Parties are considerable. However, if relative contributions are calculated only within the group of Annex I countries, the results are less sensitive to the uncertainty aspects considered here.