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24 2Efforts to limit climate change below a given temperature level require that global emissions 1 of CO 2 cumulated over time remain below a limited quota. This quota varies depending on 2 the temperature level, the desired probability of keeping below this level, and the 3 contributions of other gases. In spite of the limited quota, global emissions of CO 2 from fossil 4 fuel combustion and cement production have continued to grow by 2.5% per year on average 5 over the past decade. Two thirds of the CO 2 emission quota consistent with a 2°C 6 temperature limit has been used, and the total quota will likely be exhausted in a further 30 7 years at the 2014 emissions rates. We show that CO 2 emissions track the high end of the latest 8 generation of emissions scenarios, due to lower than anticipated carbon intensity 9 improvements of emerging economies and higher global GDP growth. In the absence of more 10 stringent mitigation, these trends are set to continue and further decline the remaining quota 11 until the onset of a potential new climate agreement in 2020. Breaking current emission 12 trends in the short term is key to retain credible climate targets within a rapidly diminishing 13 emission quota. 14 15 Recent studies have identified a near-linear relationship between global mean temperature change 16 and total CO 2 emissions cumulated over time [1][2][3][4][5][6][7][8][9] . This relationship leads to an intuitive and 17 appealing application in climate policy. A global "quota" on cumulative CO 2 emissions from all 18 sources (fossil fuel combustion, industrial processes and land-use change) can be directly linked to 19 a nominated temperature threshold with a specified probability of success. It can be used regardless 20 of where or, to a large degree, when the emissions occur 10 . 21 22Despite the many reservoirs and timescales that affect the response of the climate and carbon 23 cycle 11 , the proportionality between temperature and cumulative CO 2 emissions is remarkably 24 robust across models. The relationship has been called the Transient Climate Response to 25 3 cumulative carbon Emissions (TCRE) and was highlighted in the fifth assessment report (AR5) of 1 the Intergovernmental Panel on Climate Change (IPCC) 12 . The near-linear relationship has strong 2 theoretical support: radiative forcing per emitted tonne of CO 2 decreases with higher CO 2 3 concentrations, an effect which is compensated by the weakening of the ocean and biosphere 4 carbon sinks leading to a larger fraction of emitted CO 2 remaining in the atmosphere [13][14][15] . The 5 uncertainty in the TCRE, accounted for here in the given probability 12,16 , thus comes from the 6 climate response to CO 2 and the carbon cycle feedbacks 14,[17][18][19] . The near-linear relationship holds 7 for cumulative CO 2 emissions less than about 7500 GtCO 2 and until temperatures peak 16 . 8 9 Although CO 2 is the dominant anthropogenic forcing of the climate system 20 , non-CO 2 greenhouse 10 gases and aerosols also contribute to climate c...

Abstract. The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVE-CLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation), the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasigeostrophic model. The ocean component is CLIO3, which consists of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is of 3 • by 3 • , and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetation model that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as desert. VECODE also simulates the evolution of the carbon cycle over land while the ocean carbon cycle is represented by LOCH, a comprehensive model that takes into acCorrespondence to: H. Goosse (hugues.goosse@uclouvain.be) count both the solubility and biological pumps. The ice sheet component AGISM is made up of a three-dimensional thermomechanical model of the ice sheet flow, a visco-elastic bedrock model and a model of the mass balance at the iceatmosphere and ice-ocean interfaces. For both the Greenland and Antarctic ice sheets, calculations are made on a 10 km by 10 km resolution grid with 31 sigma levels. LOVECLIM1.2 reproduces well the major characteristics of the observed climate both for present-day conditions and for key past periods such as the last millennium, the mid-Holocene and the Last Glacial Maximum. However, despite some improvements compared to earlier versions, some biases are still present in the model. The most serious ones are mainly located at low latitudes with an overestimation of the temperature there, a too symmetric distribution of precipitation between the two hemispheres, and an overestimation of precipitation and vegetation cover in the subtropics. In addition, the atmospheric circulation is too weak. The model also tends to underestimate the surface temperature changes (mainly at low latitudes) and to overestimate the ocean heat uptake observed over the last decades.

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