1. Climate Forecasting Unit Attributing the global warming slowdown of the last decade and the 2012 Arctic sea ice minimum V. Guemas (1,2), F. J. Doblas-Reyes (1,3), I. Andreu-Burillo (1), M. Asif (1), David Salas y Mélia (3), Matthieu Chevallier (3), A. Germe (3) (1)CFU, IC3, Barcelona, Spain (2)CNRM-GAME, Météo-France, Toulouse, France (3)ICREA, Barcelona, Spain

2. Climate Forecasting Unit Part I : The global warming slowdown

3. Climate Forecasting Unit Initializing allows to the SST evolution along the predictions Successful Ec-Earth2.3 climate prediction of the 2000-2010 global temperature plateau Global mean Sea Surface Temperature (60°S-60°N) Init NoInit Ensemble- mean smoothed with 1-year running mean ERSST Guemas et al, Nature Climate Change, 2013

4. Climate Forecasting Unit Initializing allows to the SST evolution along the predictions Successful Ec-Earth2.3 climate prediction of the 2000-2010 global temperature plateau Global mean Sea Surface Temperature (60°S-60°N) Init NoInit ERSST Ensemble- mean smoothed with 1-year running mean Guemas et al, Nature Climate Change, 2013

5. Climate Forecasting Unit ORAS4 Ocean heat uptake (0-800m excluding the mixed layer) at the onset of the plateau The plateau seems due to increased ocean heat absorption Analysis of these predictions to attribute the 2000-2010 global temperature plateau Guemas et al, Nature Climate Change, 2013

6. Climate Forecasting Unit Increased ocean heat uptake in the Pacific captured by Init Analysis of these predictions to attribute the 2000-2010 global temperature plateau ORAS4Init

7. Climate Forecasting Unit Weak signals after ensemble-mean operator on NoInit Analysis of these predictions to attribute the 2000-2010 global temperature plateau ORAS4NoInit

8. Climate Forecasting Unit Part II : The 2012 Arctic sea ice minimum

9. Climate Forecasting Unit The 2012 Arctic sea ice minimum into context Extent (Million km 2 ) ±2 standard deviation mean 1979-2000 Spain + Portugal + France + Italy + Switzerland + Germany + Netherlands + Belgium + Poland + Austria + Czech Republic + England + Scotland 3.41 million km 2 7 million km 2 NSIDC

10. Climate Forecasting Unit 2012 Sea Ice Outlook : July report Forecast systems Why 2012 record-low missed by all the forecast systems ? Observed Median 1979- 2007 average

11. Climate Forecasting Unit An extreme summer storm NASA 1 of the 8 most extreme summer storm over the 1979-2012 period 2012 record-low due to climate change or natural variability ?

12. Climate Forecasting Unit Guemas et al, BAMS, 2013 Attributing the September 2012 Arctic ice minimum Millions km 2 Our sea ice model overestimates the 2012 excess sea ice loss relative to the 2000-2011 average CTRL = NEMO3.2 ocean model + LIM2 sea ice model initialized on 1 June 2012 from a 5-member sea ice reconstruction and forced with ERAinterim. Sea ice Loss relative to the average of the September minima over the 2000-2011 period

13. Climate Forecasting Unit Attributing the September 2012 Arctic ice minimum Millions km 2 New record low seems primarily due to sea ice memory and warm conditions Guemas et al, BAMS, 2013

14. Climate Forecasting Unit Conclusions 1.The global warming slowdown seems to be associated with an increased ocean heat uptake below the mixed layer, mainly in the tropical Pacific 2.The 2012 Arctic sea ice minimum seems to have been mainly caused by the memory of the sea ice history and the warm 2012 atmospheric conditions