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Guivarch C.,Center International Of Recherche Sur Lenvironnement Et Le Developpement | Hallegatte S.,Center International Of Recherche Sur Lenvironnement Et Le Developpement | Hallegatte S.,National School of Meteorological Studies
Global Environmental Change | Year: 2013

Political attention has increasingly focused on limiting warming to 2 °C. However, there is no consensus on both questions "Is the 2 °C target achievable?" and "What should be done with this target that becomes increasingly difficult to achieve?" This paper aims at disentangling the points of deep uncertainty underlying this absence on consensus. It first gives simple visualizations of the challenge posed by the 2 °C target and shows how key assumptions (on the points of deep uncertainty) influence the answer to the target achievability question. It then proposes an "uncertainties and decisions tree", linking different beliefs on climate change, the achievability of different policies, and current international policy dynamics to various options to move forward on climate change. © 2012 Elsevier Ltd. Source

Kriegler E.,Potsdam Institute for Climate Impact Research | O'Neill B.C.,U.S. National Center for Atmospheric Research | Hallegatte S.,National School of Meteorological Studies | Kram T.,PBL Netherlands Environmental Assessment Agency | And 3 more authors.
Global Environmental Change | Year: 2012

Socio-economic scenarios constitute an important tool for exploring the long-term consequences of anthropogenic climate change and available response options. A more consistent use of socio-economic scenarios that would allow an integrated perspective on mitigation, adaptation and residual climate impacts remains a major challenge. We assert that the identification of a set of global narratives and socio-economic pathways offering scalability to different regional contexts, a reasonable coverage of key socio-economic dimensions and relevant futures, and a sophisticated approach to separating climate policy from counter-factual " no policy" scenarios would be an important step toward meeting this challenge. To this end, we introduce the concept of " shared socio-economic (reference) pathways" Sufficient coverage of the relevant socio-economic dimensions may be achieved by locating the pathways along the dimensions of challenges to mitigation and to adaptation. The pathways should be specified in an iterative manner and with close collaboration between integrated assessment modelers and impact, adaptation and vulnerability researchers to assure coverage of key dimensions, sufficient scalability and widespread adoption. They can be used not only as inputs to analyses, but also to collect the results of different climate change analyses in a matrix defined by two dimensions: climate exposure as characterized by a radiative forcing or temperature level and socio-economic development as classified by the pathways. For some applications, socio-economic pathways may have to be augmented by " shared climate policy assumptions" capturing global components of climate policies that some studies may require as inputs. We conclude that the development of shared socio-economic (reference) pathways, and integrated socio-economic scenarios more broadly, is a useful focal point for collaborative efforts between integrated assessment and impact, adaptation and vulnerability researchers. © 2012 Elsevier Ltd. Source

Notaro M.,University of Wisconsin - Madison | Mauss A.,National School of Meteorological Studies | Williams J.W.,University of Wisconsin - Madison
Ecological Applications | Year: 2012

This study focuses on potential impacts of 21st century climate change on vegetation in the Southwest United States, based on debiased and interpolated climate projections from 17 global climate models used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Among these models a warming trend is universal, but projected changes in precipitation vary in sign and magnitude. Two independent methods are applied: a dynamic global vegetation model to assess changes in plant functional types and bioclimatic envelope modeling to assess changes in individual tree and shrub species and biodiversity. The former approach investigates broad responses of plant functional types to climate change, while considering competition, disturbances, and carbon fertilization, while the latter approach focuses on the response of individual plant species, and net biodiversity, to climate change. The dynamic model simulates a region-wide reduction in vegetation cover during the 21st century, with a partial replacement of evergreen trees with grasses in the mountains of Colorado and Utah, except at the highest elevations, where tree cover increases. Across southern Arizona, central New Mexico, and eastern Colorado, grass cover declines, in some cases abruptly. Due to the prevalent warming trend among all 17 climate models, vegetation cover declines in the 21st century, with the greatest vegetation losses associated with models that project a drying trend. The inclusion of the carbon fertilization effect largely ameliorates the projected vegetation loss. Based on bioclimatic envelope modeling for the 21st century, the number of tree and shrub species that are expected to experience robust declines in range likely outweighs the number of species that are expected to expand in range. Dramatic shifts in plant species richness are projected, with declines in the high-elevation evergreen forests, increases in the eastern New Mexico prairies, and a northward shift of the Sonoran Desert biodiversity maximum. © 2012 by the Ecological Society of America. Source

Pre-monsoon is a very challenging period for regional duty-forecasters and those involved in mitigation of severe weather consequences. Indeed, violent thunderstorms producing high winds, large hail and even tornados are common features from March to May in East India and Bangladesh. Taking advantage of SAARC (South Asian Association for Regional Cooperation) research publications, as well as knowledge and practical methodology developed by NOAA's National Weather Service in the Tornado Alley, a methodology is proposed that might help IMD forecasters make the best use of their new workstation SYNERGIE. The case study of the 13 April 2010 severe storm has been chosen for this purpose. More than 140 reported deaths and nearly 500,000 people were left homeless or otherwise affected by the storm. A good comprehension of both synoptic and mesoscale conceptual models is needed; then, aided by appropriate numerical model fields, drawing proper weather symbols on surface analysis charts is an important step towards the building and sharing of local expertise with regional or local forecasters. A graphical analysis is proposed and discussed. Source

Guivarch C.,Center International Of Recherche Sur Lenvironnement Et Le Developpement | Hallegatte S.,Center International Of Recherche Sur Lenvironnement Et Le Developpement | Hallegatte S.,National School of Meteorological Studies
Climatic Change | Year: 2011

To clarify the link between existing infrastructure legacy and the 2°C target, we extend the work of Davis et al. (Science 329:1330-1333, 2010) by introducing non-CO2 greenhouse gases and the inertia in transportation-needs drivers. We conclude that climate policies able to maintain climate change below 2°C cannot disregard existing infrastructure. © 2011 Springer Science+Business Media B.V. Source

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