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Alan J. Hewitt, Ben B. B. Booth, Chris D. Jones, Eddy S. Robertson, Andy J. Wiltshire, Philip G. Sansom, David B. Stephenson, and Stan Yip

plots ( Hawkins and Sutton 2009 ). The fractional variances are based on the posterior medians of the superpopulation variances , , , and . a. Variability in CO 2 emissions Four CO 2 -concentration-driven scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5) were used, from which the decadal rate of change ΔCO 2 was determined. Compatible fossil fuel emissions can be determined as follows (shown in Fig. 2a ): Note that Emission( t ) is to the atmosphere. When we consider variability in CO 2

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A. Anav, P. Friedlingstein, M. Kidston, L. Bopp, P. Ciais, P. Cox, C. Jones, M. Jung, R. Myneni, and Z. Zhu

-LR having the largest cold bias (1°C). All models except IPSL-CM5A-LR, IPSL-CM5A-MR, MPI-ESM-LR, and BCC-CSM1.1 show a lower trend than observations, with the lowest trend being in HadGEM2-ES, which has an increase of 0.4°C decade −1 (less than is seen in observations). The interannual variability is fairly well simulated by CMIP5 models, with a MVI lower than 1.5 in most of the subdomains and for most of the models; however, severe problems reproducing the IAV are found in the high-latitude Northern

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Nathan P. Gillett, Vivek K. Arora, Damon Matthews, and Myles R. Allen

by estimating using a detection and attribution analysis. Figure 3 shows global-mean temperature anomalies in the simulations used for this analysis. While the responses to each forcing are broadly similar across models, there are some differences and not only in the magnitude of response. In particular, the OTH response differs considerably between models. We regress observed decadal-mean temperature anomalies taken from the gridded observational temperature dataset Hadley Centre

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ChuanLi Jiang, Sarah T. Gille, Janet Sprintall, and Colm Sweeney

-driven current ( Speer et al. 2000 ; Iudicone et al. 2011 ). The deep water upwells DIC-rich water to the surface ocean south of the PF. North and south of the PF, the ocean takes up CO 2 from the overlying atmosphere, as indicated from the shipboard measurements. Also shown are the Subantarctic Front (SAF) and Subtropical Front (STF). As a choke point of the ACC system, the Drake Passage has become a key location for investigating the Southern Ocean and its role in global climate. The decade-long (2002

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Spencer Liddicoat, Chris Jones, and Eddy Robertson

reduction in E FF over the course of the twenty-first century. The smoothed E FF plot ( Fig. 2b ) does not indicate the need for negative emissions until very close to 2100, though variability in the unsmoothed version ( Fig. 2a ) results in occasional years of negative emissions during the last two decades of the twenty-first century. However, from 2100 onward negative emissions are required for much of the time ( Fig. 2b ), at an average rate of −0.45 GtC yr −1 from 2150 to 2300. This is caused

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Chris Jones, Eddy Robertson, Vivek Arora, Pierre Friedlingstein, Elena Shevliakova, Laurent Bopp, Victor Brovkin, Tomohiro Hajima, Etsushi Kato, Michio Kawamiya, Spencer Liddicoat, Keith Lindsay, Christian H. Reick, Caroline Roelandt, Joachim Segschneider, and Jerry Tjiputra

.g., Denman et al. 2007 ; Le Quéré et al. 2009 ). The observed AF has been relatively constant apart from interannual variability for several decades since direct CO 2 observations began in the late 1950s ( Keeling et al. 1995 ; Denman et al. 2007 ). Recent studies have claimed a small but measurable upward trend is now detectable in the observations ( Canadell et al. 2007 ; Le Quéré et al. 2009 ), although uncertainty in land-use emissions makes this detection difficult ( Knorr 2009 ). AF is not

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Jörg Schwinger, Jerry F. Tjiputra, Christoph Heinze, Laurent Bopp, James R. Christian, Marion Gehlen, Tatiana Ilyina, Chris D. Jones, David Salas-Mélia, Joachim Segschneider, Roland Séférian, and Ian Totterdell

years of the experiments) regionally. These relatively large regional discrepancies are caused by modes of interannual- to decadal-scale variability, which evolve slightly differently in BGC compared to COU–RAD (not shown). Since the SST responses over the 140 years are smaller than the amplitude of variability, we conclude that they are not significantly different for the purpose of this study. The northern Atlantic and Nordic seas (defined here as the region between 47° and 80°N, 60°W and 20°E

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Pierre Friedlingstein, Malte Meinshausen, Vivek K. Arora, Chris D. Jones, Alessandro Anav, Spencer K. Liddicoat, and Reto Knutti

the terrestrial biosphere ( Le Quéré et al. 2009 ; Denman et al. 2007 ). Processes controlling these uptakes as well as their response to change in atmospheric composition (mainly CO 2 ) and climate are far from being well understood. For about two decades now, land and ocean carbon cycle models have been attempting to simulate the historical and/or future evolution of the carbon cycle with very modest improvement in terms of uncertainty reduction (e.g., VEMAP 1995 ; Cramer et al. 2001 ; Orr

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V. Brovkin, L. Boysen, V. K. Arora, J. P. Boisier, P. Cadule, L. Chini, M. Claussen, P. Friedlingstein, V. Gayler, B. J. J. M. van den Hurk, G. C. Hurtt, C. D. Jones, E. Kato, N. de Noblet-Ducoudré, F. Pacifico, J. Pongratz, and M. Weiss

sea ice, putting emphasis on land–atmosphere interactions. This approach allows isolation of the direct effects of LULCC on the atmosphere from the indirect effects caused by interactions with the other components of climate system (e.g., sea ice). However, neglecting these feedbacks may reduce the magnitude of effects of LULCC on climate (e.g., Davin and de Noblet-Ducoudré 2010 ). On decadal to centennial time scales, the feedbacks through interactive SSTs and sea ice have the potential to

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Pu Shao, Xubin Zeng, Koichi Sakaguchi, Russell K. Monson, and Xiaodong Zeng

. 2005 ; Friedlingstein et al. 2006 ; Denman et al. 2007 ; Booth and Jones 2011 ). The importance of the terrestrial component of the carbon cycle to future model projections is widely recognized, in large part because the terrestrial component is so greatly influenced by anthropogenic activities such as restoration from past disturbances and changes in land use or management ( Houghton 2007 ). The interannual and interdecadal variability in the growth rate of atmospheric CO 2 concentration is

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