164 research outputs found

    Reply to Comment on 'Unintentional unfairness when applying new greenhouse gas emissions metrics at country level'

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    This is a companion article to 2021 Environ. Res. Lett. 16 068001 This is a companion article to 2019 Environ. Res. Lett. 14 114039H2020 Societal Challengeshttp://dx.doi.org/10.13039/100010676Peer Reviewe

    Natural Climate Solutions must embrace multiple perspectives to ensure synergy with sustainable development

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    To limit global warming to well below 2°C, immediate emissions reductions must be coupled with active removal of greenhouse gases from the atmosphere. “Natural Climate Solutions” (NCS) achieve atmospheric CO2 reduction through the conservation, restoration, or altered management of natural ecosystems, with enormous potential to deliver “win-win-win” outcomes for climate, nature and society. Yet the supply of high-quality NCS projects does not meet market demand, and projects already underway often fail to deliver their promised benefits, due to a complex set of interacting ecological, social, and financial constraints. How can these cross-sectoral challenges be surmounted? Here we draw from expert elicitation surveys and workshops with professionals across the ecological, sociological, and economic sciences, evaluating differing perspectives on NCS, and suggesting how these might be integrated to address urgent environmental challenges. We demonstrate that funders” perceptions of operational, political, and regulatory risk strongly shape the kinds of NCS projects that are implemented, and the locations where they occur. Because of this, greenhouse gas removal through NCS may fall far short of technical potential. Moreover, socioecological co-benefits of NCS are unlikely to be realized unless the local communities engaged with these projects are granted ownership over implementation and outcomes

    Understanding the carbon dioxide removal range in 1.5 °C compatible and high overshoot pathways

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    Carbon dioxide removal (CDR) features prominently in the 1.5 °C compatible and high overshoot pathways in the IPCC’s Sixth Assessment Report (AR6, WGIII). However, the amount of CDR varies considerably among scenarios. We analyze the range in CDR volumes in AR6 WGIII pathways by exploring relationships between variables as potential driving forces, focusing on CDR in 2050 and scenario properties linked to reaching net-zero CO2. It is also shown how the relative and absolute contribution of CDR to total mitigation up until reaching net-zero CO2 substantially differs across scenarios. The volumes of CDR in 2050 and 2100 and the cumulative amount throughout the 21st century were most strongly correlated to the degree to which CO2 emissions are reduced as a means of reaching net-zero CO2. CDR in 2050 is also substantially correlated to the timing of net-zero CO2. The robustness of the analyzed relationships was evaluated by comparing different scenario filtering and data-cleaning approaches. Beyond filtering and cleaning, additional factors that influence CDR deployment in scenarios, such as discount rates, carbon price trajectories, and scenario design choices, were discussed.Peer Reviewe

    Path independence of carbon budgets when meeting a stringent global mean temperature target after an overshoot

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    Emission pathways that are consistent with meeting the Paris Agreement goal of holding global mean temperature rise well below 2 °C often assume a temperature overshoot. In such overshoot scenarios, a given temperature limit is first exceeded and later returned to, under the assumption of large‐scale deliberate carbon dioxide removal from the atmosphere. Here we show that although such strategy might result in a reversal of global mean temperature, the carbon cycle exhibits path dependence. After an overshoot, more carbon is stored in the ocean and less on land compared to a scenario with the same cumulative CO2 emissions but no overshoot. The near‐path independence of surface air temperature arises despite the path dependence in the carbon cycle, as it is offset by path dependence in the thermal response of the ocean. Such behavior has important implications for carbon budgets (i.e. the total amount of CO2 emissions consistent with holding warming to a given level), which do not differ much among scenarios that entail different levels of overshoot. Therefore, the concept of a carbon budget remains robust for scenarios with low levels of overshoot (up to 300 Pg C overshoot considered here) but should be used with caution for higher levels of overshoot, particularly for limiting the environmental change in dimensions other than global mean temperature rise

    Geosciences after Paris

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    The adoption of the Paris Agreement is a historic milestone for the global response to the threat of climate change. Scientists are now being challenged to investigate a 1.5 degrees C world - which will require an accelerated effort from the geoscience community
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