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Rogelj J.,ETH Zurich | Rogelj J.,Potsdam Institute for Climate Impact Research | Hare W.,Potsdam Institute for Climate Impact Research | Hare W.,Climate Analytics GmbH | And 2 more authors.
Environmental Research Letters | Year: 2011

Aggregations of greenhouse gas mitigation pledges by countries are frequently used to indicate whether resulting global emissions in 2020 will be 'on track' to limit global temperature increase to below specific warming levels such as 1.5 or 2 °C. We find that historical emission levels aggregated from data that are officially reported by countries to the UNFCCC are lower than independent global emission estimates, such as the IPCC SRES scenarios. This discrepancy in historical emissions could substantially widen the gap between 2020 pledges and 2020 benchmarks, as the latter tend to be derived from scenarios that share similar historical emission levels to IPCC SRES scenarios. Three methods for resolving this discrepancy, here called 'harmonization', are presented and their influence on 'gap' estimates is discussed. Instead of a 3.4-9.2GtCO2eq shortfall in emission reductions by 2020 compared with the 44GtCO2eq benchmark, the actual gap might be as high as 5.4-12.5GtCO2eq (a 22-88% increase of the gap) if this historical discrepancy is accounted for. Not applying this harmonization step when using 2020 emission benchmarks could lead to an underestimation of the insufficiency of current mitigation pledges. © 2011 IOP Publishing Ltd. Source

Rogelj J.,ETH Zurich | Hare W.,Potsdam Institute for Climate Impact Research | Hare W.,Climate Analytics GmbH | Lowe J.,University of Reading | And 8 more authors.
Nature Climate Change | Year: 2011

In recent years, international climate policy has increasingly focused on limiting temperature rise, as opposed to achieving greenhouse-gas-concentration- related objectives. The agreements reached at the United Nations Framework Convention on Climate Change conference in Cancun in 2010 recognize that countries should take urgent action to limit the increase in global average temperature to less than 2C relative to pre-industrial levels. If this is to be achieved, policymakers need robust information about the amounts of future greenhouse-gas emissions that are consistent with such temperature limits. This, in turn, requires an understanding of both the technical and economic implications of reducing emissions and the processes that link emissions to temperature. Here we consider both of these aspects by reanalysing a large set of published emission scenarios from integrated assessment models in a risk-based climate modelling framework. We find that in the set of scenarios with a 'likely' (greater than 66%) chance of staying below 2C, emissions peak between 2010 and 2020 and fall to a median level of 44 Gt of CO 2 equivalent in 2020 (compared with estimated median emissions across the scenario set of 48 Gt of CO 2 equivalent in 2010). Our analysis confirms that if the mechanisms needed to enable an early peak in global emissions followed by steep reductions are not put in place, there is a significant risk that the 2C target will not be achieved. © 2011 Macmillan Publishers Limited. All rights reserved. Source

Rogelj J.,Potsdam Institute for Climate Impact Research | Rogelj J.,ETH Zurich | Chen C.,Potsdam Institute for Climate Impact Research | Nabel J.,Potsdam Institute for Climate Impact Research | And 10 more authors.
Environmental Research Letters | Year: 2010

This analysis of the Copenhagen Accord evaluates emission reduction pledges by individual countries against the Accord's climate-related objectives. Probabilistic estimates of the climatic consequences for a set of resulting multi-gas scenarios over the 21st century are calculated with a reduced complexity climate model, yielding global temperature increase and atmospheric CO2 and CO2-equivalent concentrations. Provisions for banked surplus emission allowances and credits from land use, land-use change and forestry are assessed and are shown to have the potential to lead to significant deterioration of the ambition levels implied by the pledges in 2020. This analysis demonstrates that the Copenhagen Accord and the pledges made under it represent a set of dissonant ambitions. The ambition level of the current pledges for 2020 and the lack of commonly agreed goals for 2050 place in peril the Accord's own ambition: to limit global warming to below 2 °C, and even more so or 1.5 °C, which is referenced in the Accord in association with potentially strengthening the long-term temperature goal in 2015. Due to the limited level of ambition by 2020, the ability to limit emissions afterwards to pathways consistent with either the 2 or 1 .5 °C goal is likely to become less feasible. © 2010 IOP Publishing Ltd. Source

Chen C.M.,Potsdam Institute for Climate Impact Research | Gutschow J.,Potsdam Institute for Climate Impact Research | Vieweg M.,Climate Analytics GmbH | Macey K.,Climate Analytics GmbH | And 2 more authors.
Climatic Change | Year: 2013

The outcome from the December 2012 climate negotiations in Doha has clarified the rules regarding surplus units for the Kyoto Protocol. We summarize these new rules and estimate the resulting effective emissions during the second commitment period using our unit trade model. Other options to deal with surplus emission allowances are employed as benchmarks to assess the Doha outcome. The effective emissions for developed countries as a group under the Doha outcome could be 10-11 % below 1990 levels or 4-5 % points below business-as-usual levels for the second commitment period if we assume that non-Kyoto Protocol countries domestically achieve their targets. However, if mechanisms exist where non-Kyoto Protocol countries can trade units, their emissions could increase and effective emissions for developed countries could be 7-8 % below 1990 levels. In this low-ambition situation we find the main impact of the Doha surplus rules to be the introduction of the historical cap on emissions allowances. Without the effect of the cap, the Doha outcome allows the Parties to the second commitment period to emit at business-as-usual levels until 2020, while still leaving surplus units at the end of the second commitment period. © 2013 Springer Science+Business Media Dordrecht. Source

Hare W.,Climate Analytics GmbH | Hare W.,Potsdam Institute for Climate Impact Research | Stockwell C.,Climate Analytics GmbH | Flachsland C.,Potsdam Institute for Climate Impact Research | Oberthur S.,Vrije Universiteit Brussel
Climate Policy | Year: 2010

This article argues that a legally binding, multilateral agreement is a necessary condition for achieving the highest levels of greenhouse gas (GHG) emission reductions consistent with limiting warming to below either 2°C or below 1.5°C. Clear legally binding commitments within a multilaterally agreed process with strong legal and institutional characteristics are needed to give countries the confidence that their economic interests are being fairly and equally treated. Common accounting rules are needed for comparability of effort, and in order to protect environmental integrity, to demonstrate transparency, for effective monitoring, reporting and verification (MRV) of emissions and actions, and to facilitate and support a strong international carbon market. Securing full implementation will depend, in part, on the strength of an agreement's compliance mechanism. The Copenhagen Accord, by itself, represents a quintessential 'bottom-up' / 'pledge and review' approach. It is open to interpretation whether the Accord can become a stepping stone on the way to strengthening the legally binding, multilateral framework to fight climate change, building on both the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, or whether it will lead to the unravelling and fragmentation of all that has been built up to date. Legal architecture choices made in 2010 and beyond are likely to be determinative. © 2010 Earthscan. Source

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