{"id":8586,"date":"2016-04-27T04:21:59","date_gmt":"2016-04-27T04:21:59","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=8586"},"modified":"2016-04-27T06:09:00","modified_gmt":"2016-04-27T06:09:00","slug":"1-5c-vs-2c-global-warming-new-study-shows-why-half-a-degree-matters","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/1-5c-vs-2c-global-warming-new-study-shows-why-half-a-degree-matters\/","title":{"rendered":"1.5\u00b0C vs 2\u00b0C global warming \u2013 new study shows why half a degree matters"},"content":{"rendered":"
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The warming difference between 1.5\u00b0C and 2\u00b0C could be decisive for the future survival of tropical coral reefs (Credit: Paul via Flickr)<\/span><\/figcaption><\/figure>\n

European researchers have found substantially different climate change impacts for a global warming of 1.5\u00b0C and 2\u00b0C by 2100, the two temperature limits included in the Paris climate agreement. The additional 0.5\u00b0C would mean a 10-cm-higher global sea-level rise by 2100, longer heat waves, and would result in virtually all tropical coral reefs being at risk. The research is published on 21 April, in\u00a0Earth System Dynamics<\/span><\/a>, an open access journal of the European Geosciences Union (EGU<\/span>), and is presented at the\u00a0EGU<\/span>\u00a0General Assembly.<\/span><\/p>\n

\u201cWe found significant differences for all the impacts we considered,\u201d says the study\u2019s lead author Carl Schleussner, a scientific advisor at Climate Analytics in Germany. \u201cWe analysed the climate models used in the [Intergovernmental Panel on Climate Change (IPCC<\/span>)] Fifth Assessment Report, focusing on the projected impacts at 1.5\u00b0C and 2\u00b0C warming at the regional level. We considered 11 different indicators including extreme weather events, water availability, crop yields, coral reef degradation and sea-level rise.\u201d<\/span><\/p>\n

The team, with researchers from Germany, Switzerland, Austria and the Netherlands, identified a number of hotspots around the globe where projected climate impacts at 2\u00b0C are significantly more severe than at 1.5\u00b0C. One of these is the Mediterranean region, which is already suffering from climate change-induced drying. With a global temperature increase of 1.5\u00b0C, the availability of fresh water in the region would be about 10% lower than in the late 20th\u00a0century. In a 2\u00b0C world, the researchers project this reduction to double to about 20%.<\/span><\/p>\n

In tropical regions, the half-a-degree difference in global temperature could have detrimental consequences for crop yields, particularly in Central America and West Africa. On average, local tropical maize and wheat yields would reduce twice as much at 2\u00b0C compared to a 1.5\u00b0C temperature increase.<\/span><\/p>\n

Tropical regions would bear the brunt of the impacts of an additional 0.5\u00b0C of global warming by the end of the century, with warm spells lasting up to 50% longer in a 2\u00b0C world than at 1.5\u00b0C. \u201cFor heat-related extremes, the additional 0.5\u00b0C increase marks the difference between events at the upper limit of present-day natural variability and a new climate regime, particularly in tropical regions,\u201d explains Schleussner.<\/span><\/p>\n

The additional warming would also affect tropical coral reefs. Limiting warming to 1.5\u00b0C would provide a window of opportunity for some tropical coral reefs to adapt to climate change. In contrast, a 2\u00b0C temperature increase by 2100 would put virtually all of these ecosystems at risk of severe degradation due to coral bleaching.<\/span><\/p>\n

On a global scale, the researchers anticipate sea level to rise about 50 cm by 2100 in a 2\u00b0C warmer world, 10 cm more than for 1.5\u00b0C warming. \u201cSea level rise will slow down during the 21st\u00a0century only under a 1.5\u00b0C scenario,\u201d explains Schleussner.<\/span><\/p>\n

Co-author Jacob Schewe, of the Potsdam Institute for Climate Impact Research in Germany, says: \u201cSome researchers have argued that there is little difference in climate change impacts between 1.5\u00b0C and 2\u00b0C. Indeed, it is necessary to account for natural variability, model uncertainties, and other factors that can obscure the picture. We did that in our study, and by focusing on key indicators at the regional level, we clearly show that there are significant differences in impacts between 1.5\u00b0C and 2\u00b0C.\u201d<\/span><\/p>\n

William Hare, a senior scientist and\u00a0CEO<\/span>\u00a0at Climate Analytics who also took part in the\u00a0Earth System Dynamics research<\/span><\/a>, adds: \u201cOur study shows that tropical regions \u2013 mostly developing countries that are already highly vulnerable to climate change \u2013 face the biggest rise in impacts between 1.5\u00b0C and 2\u00b0C.\u201d<\/span><\/p>\n

\u201cOur results add to a growing body of evidence showing that climate risks occur at lower levels than previously thought. It provides scientific evidence to support the call by vulnerable countries, such as the Least Developed Countries and Small Island Developing States, that a 1.5\u00b0C warming limit would substantially reduce the impacts of climate change,\u201d says Hare.<\/span><\/p>\n

More information<\/span><\/h4>\n

This research is presented in the paper \u2018Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 \u00b0C and 2 \u00b0C\u2019 published in the\u00a0EGU<\/span>\u00a0open access journal Earth System Dynamics on 21 April 2016. The study co-author Michiel Schaeffer\u00a0has also presented the results<\/span><\/a>\u00a0at a press conference at the\u00a0EGU<\/span>\u00a0General Assembly in Vienna.<\/span><\/p>\n

Citation: Schleussner, C.-F., Lissner, T. K., Fischer, E. M., Wohland, J., Perrette, M., Golly, A., Rogelj, J., Childers, K., Schewe, J., Frieler, K., Mengel, M., Hare, W., and Schaeffer, M.:\u00a0Differential climate impacts for policy-relevant limits to global warming: the case of 1.5\u202f\u00b0C and 2\u202f\u00b0C<\/span><\/a>, Earth Syst. Dynam., 7, 327-351, doi:10.5194\/esd-7-327-2016, 2016.<\/strong><\/span><\/p>\n

The team is composed of Carl-Friedrich Schleussner (Climate Analytics, Berlin, Germany [CA] and Potsdam Institute for Climate Impact Research, Potsdam, Germany [PIK]), Tabea K. Lissner (CA and\u00a0PIK<\/span>), Erich M. Fischer (Institute for Atmospheric and Climate Science,\u00a0ETH<\/span>\u00a0Zurich, Switzerland [ETH]), Jan Wohland (PIK<\/span>), Mah\u00e9 Perrette (PIK<\/span>), Antonius Golly (GFZ<\/span>\u00a0German Research Centre for Geosciences, Potsdam, Germany and University of Potsdam), Joeri Rogelj (ETH<\/span>\u00a0and International Institute for Applied Systems Analysis, Laxenburg, Austria), Katelin Childers (PIK<\/span>), Jacob Schewe (PIK<\/span>), Katja Frieler (PIK<\/span>), Matthias Mengel (CA and\u00a0PIK<\/span>), William Hare (CA and\u00a0PIK<\/span>), and Michiel Schaeffer (CA and Wageningen University and Research Centre, Wageningen, The Netherlands).<\/span><\/p>\n

The\u00a0European Geosciences Union (EGU<\/span><\/a>)<\/strong>\u00a0is Europe\u2019s premier geosciences union, dedicated to the pursuit of excellence in the Earth, planetary, and space sciences for the benefit of humanity, worldwide. It is a non-profit interdisciplinary learned association of scientists founded in 2002. The\u00a0EGU<\/span>\u00a0has a current portfolio of 17 diverse scientific journals, which use an innovative open access format, and organises a number of topical meetings, and education and outreach activities. Its annual General Assembly is the largest and most prominent European geosciences event, attracting over 11,000 scientists from all over the world. The meeting\u2019s sessions cover a wide range of topics, including volcanology, planetary exploration, the Earth\u2019s internal structure and atmosphere, climate, energy, and resources. The\u00a0EGU<\/span>\u00a02016 General Assembly is taking place in Vienna, Austria, from 17 to 22 April 2016. For information about meeting and press registration, please check\u00a0http:\/\/media.egu.eu<\/span><\/a>, or follow the\u00a0EGU<\/span>\u00a0on\u00a0Twitter<\/span><\/a>\u00a0and\u00a0Facebook<\/span><\/a>.<\/span><\/p>\n

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Earth System Dynamics (ESD<\/span><\/a>)<\/strong>\u00a0is an international scientific journal dedicated to the publication and public discussion of studies that take an interdisciplinary perspective of the functioning of the whole Earth system and global change. The overall behaviour of the Earth system is strongly shaped by the interactions among its various component systems, such as the atmosphere, cryosphere, hydrosphere, oceans, pedosphere, lithosphere, and the inner Earth, but also by life and human activity.\u00a0ESD<\/span>\u00a0solicits contributions that investigate these various interactions and the underlying mechanisms, ways how these can be conceptualized, modelled, and quantified, predictions of the overall system behaviour to global changes, and the impacts for its habitability, humanity, and future Earth system management by human decision making.<\/span><\/p>\n

Links<\/span><\/h4>\n