Agriculture depends on a favourable climate, hence is among the sectors of the global economy where most concern currently lies in the context of climate change in order to maintain global food security, and avoid large-scale human suffering in developing countries where significant portions of gross domestic product (GDP) are dedicated to agricultural production and where rural populations are most vulnerable (Mertz et al., 2009). The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (FAR) (IPCC, 2007) stated that there is now little doubt that human-induced climate change is a reality, and identified agriculture as a critical sector. Unfortunately, in the Third Assessment Report (TAR) (IPCC, 2001) there was considerable uncertainty as to the likely impacts of climate change on agriculture. Considerably more literature contributed to providing greater certainty in predictions of climate change impacts in agriculture for the FAR, yet the certainty levels were still only classified at the 'moderate' level in IPCC speak. Since the FAR in 2007, the volume of literature on the likely impacts of climate change has increased considerably, hence this chapter summarizes IPCC findings and provides an update on the state of knowledge of expected changes in climate and the resultant impacts on agriculture.

This chapter is divided into two main sections: scenarios of climate change; and the expected impacts on agricultural production. We start by providing a brief explanation of the available methods for developing climate change scenarios, summarizing the current state of play and likely future developments. The chapter then provides a summary of what the models say about the future climate. Both global and regional perspectives are taken, with summary tables describing the likely

© CAB International 2010. Climate Change and Crop Production (ed. M.P. Reynolds)

impacts in the two windows of study. We make special effort to interpret the latest results from both global climate models (GCMs) and regional climate models (RCMs), taking an agricultural perspective. We do this by looking at variables relevant to agricultural production potential, agronomic management and pest/disease presence and prevalence, and we also look at some specific extreme events for which agriculture is especially exposed. The second section of the chapter examines the impacts that the expected changes in climate will have on crop production, addressing three specific issues. First, a summary of the state of knowledge on the direct impacts on crop yields, taking advantage of recent studies which have broadened our knowledge base on the subject. We then look at the impacts on agricultural pests and diseases, and finish by examining the likely positive impacts of CO2 fertilization on productivity. The chapter concludes with a synthesis of findings, and identifies some key areas for future research to fill the knowledge gaps that still exist.

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