Paris, 9 February 2012
The IPCC was formed for the purpose of gathering and summarizing all the available scientific information on climate change, its impact and solutions for countering or adapting to it. The first section of its fifth report, to be published in mid-September 2013, will give an update on the new findings compiled in recent years. Just as for the 2007 edition, the international scientific community has joined forces, in particular through the WCRP (World Climate Research Programme), to define and carry out an exercise to simulate past and future climate conditions, called the CMIP-5 (Coupled Model Intercomparison Project).
This ongoing research effort, which requires vast resources in terms of manpower, computing power and data storage capacity, involves more than 20 climatology centers around the world and the development of some 50 numerical models. In France, many organizations are contributing to the project, in particular through the CNRM, in association with CERFACS and IPSL.
The CMIP-5 project introduces a number of innovations in relation to the previous exercises:
Findings of the French simulations
In keeping with the IPCC's conclusions of 2007, all scenarios predict a trend toward higher temperatures between now and 2100. The severity of the rise varies depending on the scenario under consideration, reaching 3.5 to 5°C for the most unfavorable but only 2°C for the most optimistic — a scenario that depends on the successful implementation of policies to reduce greenhouse gas emissions. In addition, it seems that natural factors alone cannot explain the average global warming observed since the second half of the 20th century.
The new simulations confirm an intensification of the hydrological cycle5 and the rapid melting of the Arctic sea ice. According to the most pessimistic scenario, the Arctic Sea will be totally ice-free in the summer by 2040 or 2060, depending on the model.
Some new responses are offered by the simulations coupling climate to the carbon cycle. In particular, they make it clear that anthropogenic emissions must be rapidly reduced in order to reach “negative” emissions (i.e. a level of anthropogenic activity that makes it possible to draw CO2 directly from the atmosphere) by the end of the 21st century.
The analyses of this set of simulations, in combination with simulations by other international research groups, will shed new light on the link between human activity and climate change, both in the past several decades and, more importantly, in the decades and centuries to come.
© Patrick Brockmann (LSCE/IPSL, CEA/CNRS/UVSQ)
Changes in the Earth's surface temperature for the period 2071-2100 compared with the period 1971-2000, calculated using the CNRM-CERFACS and IPSL models for scenario RCP4.5 (moderate).
1 - Institut Pierre-Simon Laplace, uniting six environmental science laboratories, four of which participate in climate modeling projects: LATMOS (CNRS / UPMC / UVSQ), LMD (CNRS / ENS / UPMC / Ecole Polytechnique), LOCEAN (CNRS / UPMC / MNHN / IRD) and LSCE (CNRS / CEA / UVSQ).
2 - CNRM-GAME, Météo-France / CNRS.
3 - Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique, European Center for Research and Advanced Training in Scientific Computing (CNRS / CERFACS / Total SA / Safran / EDF/ EADS / CNES / Météo-France / ONERA).
4 - Intergovernmental Panel on Climate Change.
5 - Involving precipitation and evaporation on a planetary scale.
CNRS press officer
Priscilla Dacher l Tel +33 (0)1 44 96 46 06 l firstname.lastname@example.org
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