# **1. Introduction**

There is now compelling evidence that the climate is changing globally at a pace unprecedented in human history and that this change is directly related to anthropogenic greenhouse gas (GHG) emissions (IPCC, 2013). Impacts of these changes will be felt in many domains, but few appear as exposed and critical to human basic needs as agriculture. Agricultural development has indeed formed the basis for the emergence of civilizations and sustainable provision of food and revenues for poor farmers is still today a concern in many low‐ and middle‐income countries. As the world is still comprised of close to one billion undernourished people, climate disturbances in regions already facing significant weather variability represent a critical challenge. At the same time, agriculture, forestry and other land use (AFOLU) are responsible for a quarter of all anthropogenic GHG emissions (Smith _et al._ , 2014). By 2030, land related mitigation strategies including reduction of direct emissions from agriculture and deforestation, increased carbon sequestration through afforestation, and most importantly, substitution of fossil energy sources by biomass feedstocks, could account for 20‐60% of the mitigation effort necessary to slow climate change (Rose _et al._ , 2012). A considerable share of biomass for energy use is projected to originate in developing countries, and the potential for emissions reductions and sink enhancement from other sources is largest there. As both climate change impacts and climate change mitigation are projected to have the strongest effect on land use sectors in the same regions ‐ the low‐ and middle‐income countries ‐ it is useful to examine the two sides of this coin in a single coherent framework.

A large body of literature has investigated the social impacts from climate change, and an extensive overview is provided through the synthesis work of the Intergovernmental Panel on Climate Change (IPCC), in particular Working Group II (IPCC, 2014a). Understanding the extent and location of these impacts is a complicated task, in particular for the agricultural sector, due to the complexity of the chain of effects and their uncertainties. Increases in GHG atmospheric concentrations and additional anthropogenic perturbations of the climate system affect the spatial and temporal distribution of weather regimes which contribute to shaping the diversity of agricultural activities throughout the world. But beyond the shared diagnostic of a future increase in the mean surface temperature, the different general circulation models (GCMs) do not agree on the magnitude, location and direction of change for variables that are crucial to agricultural activities, such as precipitation.

Crop yield and harvest quality as well as operational aspects of agricultural production are directly affected by changing patterns of precipitation, temperature, wind, air moisture and incoming shortwave solar energy, but also indirectly through water availability for irrigation. Livestock is also affected through pasture yield and quality, heat stress and water availability (Thornton _et al._ , 2009). Other forms of stress, particularly dependent on climate (pests, disease, sea level rise) can also affect agricultural activities. Crop and vegetation models permit estimation of the impacts of such drivers on crop and pasture yields. In conjunction with scenarios which account for various climate projection uncertainties, these models translate climatic impact into a biophysical impact. In addition to climate projection related uncertainties, crop models face their own intrinsic sources of uncertainties (e.g., the response of crop growth to elevated atmospheric CO2 concentration remains a large source of divergence in model results). Assumptions on the nitrogen stress is also raised as a critical parameter underpinning model result discrepancies (Rosenzweig _et al._ , 2014).

4