Agriculture and climate change in global scenarios: why don't the models agree

Abstract

Agriculture is unique among economic sectors in the nature of impacts from climate change. The production activity that transforms inputs into agricultural outputs involves direct use of weather inputs (temperature, solar radiation available to the plant, and precipitation). Previous studies of the impacts of climate change on agriculture have reported substantial differences in outcomes such as prices, production, and trade arising from differences in model inputs and model specification. This article presents climate change results and underlying determinants from a model comparison exercise with 10 of the leading global economic models that include significant representation of agriculture. By harmonizing key drivers that include climate change effects, differences in model outcomes were reduced. The particular choice of climate change drivers for this comparison activity results in large and negative productivity effects. All models respond with higher prices. Producer behavior differs by model with some emphasizing area response and others yield response. Demand response is least important. The differences reflect both differences in model specification and perspectives on the future. The results from this study highlight the need to more fully compare the deep model parameters, to generate a call for a combination of econometric and validation studies to narrow the degree of uncertainty and variability in these parameters and to move to Monte Carlo type simulations to better map the contours of economic uncertainty. JEL classifications: Q10, Q11, Q16, Q21, Q54, Q55

Modelling the Economic Impacts of Climate Change on Global and European Agriculture. Review of Economic Structural Approaches

“…On the other hand, when focusing on the magnitude of results, the price effects of climate change are much smaller (or less pessimistic) in general equilibrium simulations than in partial equilibrium simulations. This finding is consistent with other studies, which have been explained by the use of more flexible economic functional forms by CGE models (Ciscar et al, 2009;Nelson et al, 2014;von Lampe et al, 2014).…”

“…At a global level, Nelson et al (2014Nelson et al ( , 2013, presented results from a global economic model inter-comparison exercise with harmonised data for future yield changes. The main aim of these exercises was to provide uncertainty estimates for the economic phase of the impact assessment process.…”

“…Using a similar approach, Nelson et al (2014) supplied yield projections from two global crop growth models for two implementations of the RCP8.5 emission scenario in two GCMs, all under the SSP2. These scenarios were designed to assess the upper end of climate change impacts (omitting CO 2 fertilisation and adaptation mechanisms).…”

Climate Change, Agriculture and Migration: A Survey

“…Crop models, also called biophysical models, are based on a set of parameters related to a particular crop capable of simulating its growth process, under different assumptions concerning both environmental realizations (e.g., temperature, precipitation, solar radiation, nutrients) and management practices (e.g., planting dates, fertilization levels). The outputs of several agronomic models, virtually one for each relevant crop or agricultural activity, are then integrated into a partial or general equilibrium model with a view to simulating the agricultural system [18,19]. The resulting Integrated Assessment Model (IAM) can be used to replicate farm economic behavior with the aim of estimating the changes in consumption, production, trade, and welfare, given some projection of future climate changes.…”

An integrated decision-support process for adaptation planning: climate change as impetus for scenario planning in an agricultural region of Canada

“…Presently, scenarios used in agricultural contexts have largely been developed by agricultural experts to consider impacts of climate change on crop production and yield under different climate and management scenarios (IFRI 2010;Ö born et al 2011;Nelson et al 2014) or by economists to evaluate the impacts of climate change and global trade on commodity prices, food prices, and global markets (Willenbockel 2011;von Lampe et al 2014). So far, scenario approaches have not been used to a large extent to generate dialogue regarding the future of regional agriculture or to explore linkages between adaptation actions and policy development.…”