Models

Introduction

The Coupled Model Intercomparison Project (CMIP) is a framework for coordinated climate simulations conducted with Earth System Models (ESMs) and General Circulation Models (GCMs). The most recently completed phase of the project (2010-2014) is CMIP5, which promotes a standard set of model simulations in order to understand the response of the climate system to changes in the external forcing. To this overarching purpose, CMIP5 allows scientists to

• evaluate how realistically the models simulate the recent past (1861-2005)
• analyze projections of future climate change on two time scales, near term (out to about 2035) and long term (out to 2100 and beyond)
• understand some of the factors that cause differences in model projections, including quantifying some key feedbacks such as those involving clouds and the carbon cycle.

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Description

This page collects the output of 34 climate models, providing projections of sea ice concentration in the Arctic and Antarctic regions for the period 2010-2100. In particular, the sea ice concentration has been averaged over three time slices of 30 years each: 2010-2039, 2040-2069 and 2070-2099. The maps are available for the months of February, when sea ice extent and area are near its maximum in the Arctic and minimum in the Antarctic, and September, when sea ice extent and area are minimum in the Arctic and maximum in the Antarctic. This selection is performed in accordance with IPCC 2013 ^[1].

The projections are formulated for three different RCP (Representative Concentration Pathways) scenarios. These are three greenhouse gas concentration trajectories adopted in the fifth IPCC Assessment Report (AR5), in 2013^[2]. The three RCPs, RCP2.6, RCP4.5 and RCP8.5, are named according to the increase of radiative forcing from anthropogenic emissions of well-mixed greenhouse gases in the year 2100 relative to pre-industrial values (+2.6, +4.5, and +8.5 W/m2, respectively)^[3].

For each map, the sea ice extent and area are included. Furthermore, the observed reference climatological sea ice extent line (15%) is mapped for the period 1981-2010 (NSIDC). This allows an immediate visual comparison of the modelled state with the current sea ice condition. The 15% contour line of the modelled sea-ice concentration field is also drawn in the maps.

The models differ both, in their complexity and in their spatial resolution. For this reason, the model results differ sometimes substantially. However, a transition towards a September ice-free Arctic for the highest-emission scenario RCP 8.5 occurs across all the models ^[4]. Most of the maps show a sea ice concentration which is the average of different model runs (ensemble members), for the same RCP scenario. The number of the ensemble members is reported underneath the color bar, together with the model name.

Documentation

A complete documentation for the models can be found at the es-doc (Earth System Documentation), including references.Specifically, use the following search criteria Project/MIP Era: CMIP5, Document Type: Model.

Technical aspects

Some technical aspects concerning the maps are reported in the following points:

• The models ACCESS1.0, ACCESS1.3, BNU-ESM, GFDL-CM3 and GFDL-ESM2M are interpolated to a regular lon/lat grid, for visualization purposes.
• The land masks for the models CanESM2, CSIRO-MK3.6.0 and EC-EARTH are not perfectly matching the sea ice concentration variable. However, these were the best land masks available for these models.
• The maps related to the models CSIRO-MK3.6.0, GISS-E2-H, GISS-E2-H-CC, GISS-E2-R and GISS-E2-R-CC do not include the 15% contour line of the model.

Bibliography

1. IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp, doi:10.1017/CBO9781107415324, 1087-1093
2. R. Moss, M. Babiker, S. Brinkman, E. Calvo, T. Carter, J. Edmonds, I. Elgizouli, S. Emori, L. Erda, K. Hibbard, R. Jones, M. Kainuma, J. Kelleher, J. F. Lamarque, M. Manning, B. Matthews, J. Meehl, L. Meyer, J. Mitchell, N. Nakicenovic, B. O’Neill, R. Pichs, K. Riahi, S. Rose, P. Runci, R. Stouffer, D. van Vuuren, J. Weyant, T. Wilbanks, J. P. van Ypersele and M. Zurek (2008). Towards New Scenarios for Analysis of Emissions, Climate Change, Impacts, and Response Strategies (PDF). Geneva: Intergovernmental Panel on Climate Change. p. 132.
3. J. Weyant, C. Azar, M. Kainuma, J. Kejun, N. Nakicenovic, P.R. Shukla, E. La Rovere and Gary Yohe (2009). Report of 2.6 Versus 2.9 Watts/m2 RCPP Evaluation Panel (PDF). Geneva, Switzerland: IPCC Secretariat.
4. F. Massonnet, T. Fichefet, H. Goosse, C. M. Bitz, G. Philippon-Berthier, M. M. Holland, and P.-Y. Barriat (2012). Constraining projections of summer Arctic sea ice. The Cryosphere, 6, 1383–1394. doi:10.5194/tc-6-1383-2012

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