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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.techfore.2006.05.027 Byline: Francesco N. Tubiello (a)(b), Gunther Fischer (a) Keywords: Agriculture; Climate impacts; Mitigation; World food supply Abstract: What are the implications for agriculture of mitigating greenhouse gas emissions? By when and by how much are impacts reduced? Where does it matter most? We investigated these questions within the new A2 emission scenario, recently developed at the International Institute of Applied Systems Analysis with revised population and gross domestic product projections. Coupling an agro-ecological model to a global food trade model, two distinct sets of climate simulations were analyzed: 1) A non-mitigated scenario, with atmospheric CO.sub.2 concentrations over 800 ppm by 2100; and 2) A mitigation scenario, with CO.sub.2 concentrations stabilized at 550 ppm by 2100. Impacts of climate change on crop yield were evaluated for the period 1990-2080, then used as input for economic analyses. Key trends were computed over the 21st century for food demand, production and trade, focusing on potential monetary (aggregate value added) and human (risk of hunger) impacts. The results from this study suggested that mitigation could positively impact agriculture. With mitigation, global costs of climate change, though relatively small in absolute amounts, were reduced by 75-100%; and the number of additional people at risk of malnutrition was reduced by 80-95%. Significant geographic and temporal differences were found. Regional effects often diverged from global net results, with some regions worse off under mitigation compared to the unmitigated case. Author Affiliation: (a) Land-Use Change and Agriculture Program at the International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria (b) Goddard Institute for Space Studies, Columbia University, New York, NY, USA Article History: Received 7 February 2006; Revised 12 April 2006; Accepted 24 May 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.techfore.2006.05.021 Byline: Gunther Fischer (a), Francesco N. Tubiello (a)(b), Harrij van Velthuizen (a), David A. Wiberg (a) Keywords: Water; Agriculture; Irrigation; Climate change; Mitigation Abstract: Potential changes in global and regional agricultural water demand for irrigation were investigated within a new socio-economic scenario, A2r, developed at the International Institute for Applied Systems Analysis (IIASA) with and without climate change, with and without mitigation of greenhouse gas emissions. Water deficits of crops were developed with the Food and Agriculture Organization (FAO)-IIASA Agro-ecological Zone model, based on daily water balances at 0.5[degrees] latitudex0.5[degrees] longitude and then aggregated to regions and the globe. Future regional and global irrigation water requirements were computed as a function of both projected irrigated land and climate change and simulations were performed from 1990 to 2080. Future trends for extents of irrigated land, irrigation water use, and withdrawals were computed, with specific attention given to the implications of climate change mitigation. Renewable water-resource availability was estimated under current and future climate conditions. Results suggest that mitigation of climate change may have significant positive effects compared with unmitigated climate change. Specifically, mitigation reduced the impacts of climate change on agricultural water requirements by about 40%, or 125-160billionm.sup.3 (Gm.sup.3) compared with unmitigated climate. Simple estimates of future changes in irrigation efficiency and water costs suggest that by 2080 mitigation may translate into annual cost reductions of about 10billion US$. Author Affiliation: (a) Land-Use Change and Agriculture Program at the International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria (b) Goddard Institute for Space Studies, Columbia University, New York, NY, USA Article History: Received 7 February 2006; Revised 10 May 2006; Accepted 24 May 2006

Using newly available data from the 2015 Forest Resources Assessment (FRA), we refined the information, currently available through the IPCC AR5 and FAOSTAT, on recent trends in global and regional net CO 2 emissions and removals from forest land, including from net forest conversion (used as a proxy for deforestation) and forest remaining forest. The new analysis is based on the simplified forest carbon stock method of the FAOSTAT Emissions database, equivalent to a Tier 1, Approach 1 IPCC methodology, limited to biomass carbon stocks. Our results indicated that CO 2 emissions from net forest conversion decreased significantly, from an average of 4.0 Gt CO 2 yr −1 during 2001–2010 to 2.9 Gt CO 2 yr −1 during 2011–2015. More than half of the estimated reductions over the last five years, some 0.6 Gt CO 2 yr −1 , took place in Brazil. Detailed analyses further indicated that remaining forests continued to function as a net carbon sink globally, with an average net removal of −2.2 Gt CO 2 yr −1 during 2001–2010, and −2.1 Gt CO 2 yr −1 during 2011–2015. Annex I Parties represented the bulk of this sink, contributing 60% of the total in 2011–2015, down from 65% in 2001–2010. Compared to previous FAOSTAT assessments for the period 2001–2010, based on the 2010 FRA and published in the IPCC AR5, the use of FRA 2015 data led to estimates of net forest conversion that were consistent with previous ones (4.0 vs. 3.8 Gt CO 2 yr −1 ), while the estimated forest sinks were 22% larger (−2.2 vs. −1.8 Gt CO 2 yr −1 ). The net contribution of forests to anthropogenic forcing based on FRA2015 data was thus smaller than previously estimated by the IPCC AR5. Finally, we separated for the first time net emissions and removals from forest land into a sink component and a degradation component. Results indicated that, contrary to CO 2 emissions from deforestation, CO 2 emissions from forest degradation increased significantly, from 0.4 Gt CO 2 yr −1 in the 1990s, to 1.1 Gt CO 2 yr −1 in 2001–2010 and 1.0 Gt CO 2 yr −1 in 2011–2015. Emissions from forest degradation were thus one-fourth of those from deforestation in 2001–2010, increasing to one-third in 2011–2015. [ABSTRACT FROM AUTHOR]

Abstract: Recent conclusions that new free-air carbon dioxide enrichment (FACE) data show a much lower crop yield response to elevated CO2 than thought previously – casting serious doubts on estimates of world food supply in the 21st century – are found to be incorrect, being based in part on technical inconsistencies and lacking statistical significance. First, we show that the magnitude of crop response to elevated CO2 is rather similar across FACE and non-FACE data-sets, as already indicated by several previous comprehensive experimental and modeling analyses, with some differences related to which “ambient” CO2 concentration is used for comparisons. Second, we find that results from most crop model simulations are consistent with the values from FACE experiments. Third, we argue that lower crop responses to elevated CO2 of the magnitudes in question would not significantly alter projections of world food supply. We conclude by highlighting the importance of a better understanding of crop response to elevated CO2 under a variety of experimental and modeling settings, and suggest steps necessary to avoid confusion in future meta-analyses and comparisons of experimental and model data. [Copyright &y& Elsevier]

Several crop models may be used to simulate the effects of elevated CO2 on crop productivity. Yet no summary exists in the literature attempting to describe differences among models and how simulations might differ under climate change conditions. We provide an introductory review focusing on simulating the impacts of elevated CO2 on crops. We describe and discuss modeling approaches, component modules, applications to climate change and model validation and inter-comparison studies. By searching the recent peer-reviewed literature from 1995 to present, we found that about 20% of published crop modeling studies have focused on climate change impacts. About half of these studies explicitly analyzed the effects of elevated CO2 on crop growth and yield. Our analysis further suggested that the crop models that have been used the most in climate change assessments are also those that have been evaluated the least using available data from elevated CO2 experiments. Based on our review, we identify a set of recommendations aimed at improving our confidence in predictions of crop production under elevated CO2 and climate change conditions. These include continued model evaluation with existing field experiment data; increased focus on limiting factors such as pest, weeds, and disease; and attention to temporal and spatial scaling issues. [Copyright &y& Elsevier]

Recent flooding and heavy precipitation events in the US and worldwide have caused great damage to crop production. If the frequency of these weather extremes were to increase in the near future, as recent trends for the US indicate and as projected by global climate models (e.g., US National Assessment, Overview Report, 2001, The Potential Consequences of Climate Variability and Change, National Assesment Synthesis Team, US Global Change Research Program, Washington, DC; Houghton et al., 2001, IPCC Climate Change 2001: The Scientific Basis, Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, 335pp.), the cost of crop losses in the coming decades could rise dramatically. Yet current assessments of the impacts of climate change on agriculture have not quantified the negative effects on crop production from increased heavy precipitation and flooding (Impacts of climate change and variability on agriculture, in: US National Assessment Foundation Document, 2001. National Assessment Synthesis Team, US Global Change Research Program, Washington DC.). In this work, we modify a dynamic crop model in order to simulate one important effect of heavy precipitation on crop growth, plant damage from excess soil moisture. We compute that US corn production losses due to this factor, already significant under current climate, may double during the next thirty years, causing additional damages totaling an estimated $3 billion per year. These costs may either be borne directly by those impacted or transferred to private or governmental insurance and disaster relief programs. [Copyright &y& Elsevier]