Crop water stress under climate change uncertainty : global policy and regional risk

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 113-121).Fourty percent of all crops grown in the world today are grown using irrigation, and shifting precipitation patterns due to climate change are viewed as a major threat to food security. This thesis examines, in the framework of the MIT Integrated Global System Model, the potential impacts of climate change on crop water stress and the risk implications for policy makers due to underlying uncertainty in climate models. This thesis presents the Community Land Model - Agriculture module (CLM-AG) that models crop growth and water stress. It is a global generic crop model built in the framework of the Community Land Model and was evaluated for maize, cotton and spring wheat. A full climate model, the IGSM-CAM, was first used to force CLM-AG and show the regional disparity of the response to climate change. Some areas like the Midwest or Equatorial Africa benefit from the higher precipitations associated to climate change while others like Europe or Southern Africa see the irrigation need for crops increase. The effect of a mitigation policy appeared contrasted, as water-stress for some areas (including Europe and Africa) is increased if greenhouse gases emissions are limited while for other areas (Central Asia, United States) it is reduced. A second analysis was carried in Central Zambia using uncertainty ensembles. The ensembles demonstrate the notable extent of the uncertainty stemming from different climate sensitivities and different regional patterns in climate models. Crops are impacted differently but a consistent result is that climate mitigation policies reduce uncertainty in crop water stress, making it easier to plan for any anticipated future climate change.by Arthur Gueneau.S.M.in Technology and Polic

CLM-AG: An Agriculture Module for the Community Land Model version 3.5

It is estimated that 40% of all crops grown in the world today are grown using irrigation. As a consequence, shifting precipitation patterns due to climate change are viewed as a major threat to food security. This report presents the Community Land Model-Agriculture module (CLM-AG), which models crop growth and water stress. The CLM-AG model is a global generic crop model built in the framework of the Community Land Model version 3.5. This report describes the structure and main routines of the model. Two different evaluations of the model are then considered. First, at a global level, CLM-AG is run under a historic climatology and compared to the Global Agro-Ecological Zones, an existing model of irrigation need. Second, the irrigation need computed for the United States is compared to survey data from the United States Department of Agriculture. For both evaluations, CLM-AG results are comparable to either the model results or the surveyed data.Development of the IGSM applied in this research was supported by the U.S. Department of Energy, Office of Science (DE-FG02-94ER61937); the U.S. Environmental Protection Agency, EPRI, and other U.S. government agencies and a consortium of 40 industrial and foundation sponsors. For a complete list see http://globalchange.mit.edu/sponsors/current.htm

The Future of Global Water Stress: An Integrated Assessment

We assess the ability of global water systems, resolved at 282 large river basins or Assessment Sub Regions (ASRs), to the meet water requirements over the coming decades under integrated projections of socioeconomic growth and climate change. We employ a Water Resource System (WRS) component embedded within the MIT Integrated Global System Model (IGSM) framework in a suite of simulations that consider a range of climate policies and regional hydroclimatic changes through the middle of this century. We find that for many developing nations water-demand increases due to population growth and economic activity have a much stronger effect on water stress than climate change. By 2050, economic growth and population change alone can lead to an additional 1.8 billion people living in regions with at least moderate water stress. Of this additional 1.8 billion people, 80% are found in developing countries. Uncertain regional climate change can play a secondary role to either exacerbate or dampen the increase in water stress due to socioeconomic growth. The strongest climate impacts on relative changes in water stress are seen over many areas in Africa, but strong impacts also occur over Europe, Southeast Asia and North America. The combined effects of socioeconomic growth and uncertain climate change lead to a 1.0 to 1.3 billion increase of the world's 2050 projected population living in regions with overly exploited water conditions— where total potential water requirements will consistently exceed surface-water supply. Under the context of the WRS model framework, this would imply that adaptive measures would be taken to meet these surface-water shortfalls and would include: water-use efficiency, reduced and/or redirected consumption, recurrent periods of water emergencies or curtailments, groundwater depletion, additional inter-basin transfers, and overdraw from flow intended to maintain environmental requirements.We assess the ability of global water systems, resolved at 282 large river basins or Assessment Sub Regions (ASRs), to the meet water requirements over the coming decades under integrated projections of socioeconomic growth and climate change. We employ a Water Resource System (WRS) component embedded within the MIT Integrated Global System Model (IGSM) framework in a suite of simulations that consider a range of climate policies and regional hydroclimatic changes through the middle of this century. We find that for many developing nations water-demand increases due to population growth and economic activity have a much stronger effect on water stress than climate change. By 2050, economic growth and population change alone can lead to an additional 1.8 billion people living in regions with at least moderate water stress. Of this additional 1.8 billion people, 80% are found in developing countries. Uncertain regional climate change can play a secondary role to either exacerbate or dampen the increase in water stress due to socioeconomic growth. The strongest climate impacts on relative changes in water stress are seen over many areas in Africa, but strong impacts also occur over Europe, Southeast Asia and North America. The combined effects of socioeconomic growth and uncertain climate change lead to a 1.0 to 1.3 billion increase of the world's 2050 projected population living in regions with overly exploited water conditions— where total potential water requirements will consistently exceed surface-water supply. Under the context of the WRS model framework, this would imply that adaptive measures would be taken to meet these surface-water shortfalls and would include: water-use efficiency, reduced and/or redirected consumption, recurrent periods of water emergencies or curtailments, groundwater depletion, additional inter-basin transfers, and overdraw from flow intended to maintain environmental requirements

A CGE-W study

Non-PRIFPRI5EPT

Modeling U.S. Water Resources under Climate Change

Water is at the center of a complex and dynamic system involving climatic, biological, hydrological, physical, and human interactions. We demonstrate a new modeling system that integrates climatic and hydrological determinants of water supply with economic and biological drivers of sectoral and regional water requirement while taking into account constraints of engineered water storage and transport systems. This modeling system is an extension of the Massachusetts Institute of Technology (MIT) Integrated Global System Model framework and is unique in its consistent treatment of factors affecting water resources and water requirements. Irrigation demand, for example, is driven by the same climatic conditions that drive evapotranspiration in natural systems and runoff, and future scenarios of water demand for power plant cooling are consistent with energy scenarios driving climate change. To illustrate the modeling system we select “wet” and “dry” patterns of precipitation for the United States from general circulation models used in the Climate Model Intercomparison Project (CMIP3). Results suggest that population and economic growth alone would increase water stress in the United States through mid‐century. Climate change generally increases water stress with the largest increases in the Southwest. By identifying areas of potential stress in the absence of specific adaptation responses, the modeling system can help direct attention to water planning that might then limit use or add storage in potentially stressed regions, while illustrating how avoiding climate change through mitigation could change likely outcomes.ISSN:2328-427

U.S. Water Resource System under Climate Change

The MIT Integrated Global System Model framework, extended to include a Water Resource System component, is used for an integrated assessment of the effects of alternative climate policy scenarios on U.S. water systems. Climate patterns that are relatively wet and dry over the US are explored. Climate results are downscaled to yield estimates of surface runoff for 99 river basins in the continental U.S., which are combined with estimated groundwater supplies. An 11- region economic model sets conditions driving water requirements estimates for five sectors, with detailed sub-models employed for analysis of irrigation and thermoelectric power generation. The water system of interconnected basins is operated to minimize water stress. Results suggest that, with or without climate change, U.S. average annual water stress is expected to increase over the period 2041 to 2050, primarily because of an increase in water requirements. The largest water stresses are projected in the Southwest. Policy to lower atmospheric greenhouse gas concentrations has a beneficial effect, reducing water stress intensity and variability in the concerned basins