Elodie Blanc

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 worlds 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.

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.

The impact of climate change on cropland productivity: evidence from satellite based products at the river basin scale in Africa

We investigate the effect of climate change on crop productivity in Africa using satellite derived data on land use and net primary productivity (NPP) at a small river basin scale, distinguishing between the impact of local and upper-catchment weather. Regression results show that both of these are determining factors of local cropland productivity. These estimates are then combined with climate change predictions obtained from two general circulation models (GCMs) under two greenhouse gas emissions (GHG) assumptions to evaluate the impact of climate change by 2100. For some scenarios significant decreases are predicted over the northern and southern parts of Africa.

The Use of Panel Models in Assessments of Climate Impacts on Agriculture

Assessments of climate change impacts on agriculture are increasingly relying on panel models to examine the relationship between agricultural outcomes and weather fluctuations. This article reviews the strengths and weaknesses of such models. We argue that panel models are ideal for assessing climate impacts on agriculture because they use group fixed effects to absorb all time-invariant variation and thus rely on weather deviations from the mean that are random and exogenous. Using this random and exogenous source of variation is crucial to identifying a causal relationship between agricultural outcomes and weather. In addition, the large number of observations offered by a panel data set allows the identification of a nonlinear response function, which is an important step in modeling the effects of climate change, as the response can be highly nonlinear. Despite these strengths of panel models, they may still suffer from omitted variable biases of time-varying variables, such as pollution shocks, which are correlated with the weather shocks. Moreover, because group fixed effects absorb a lot of the signal in the weather variables, the signal:noise ratio might decrease. Thus researchers should be careful when constructing the weather variables in order to avoid having noise in the data that causes downward biases in the coefficients.

Is Current Irrigation Sustainable in the United States? An Integrated Assessment of Climate Change Impact on Water Resources and Irrigated Crop Yields

Key Points Climate and socioeconomic changes will increase water shortages and strongly reduce irrigated crop yields in specific regions or crops GHG mitigation has the potential to alleviate the effect of water stress on irrigated crop yields

Assessing the Impact of Typhoons on Rice Production in the Philippines

This study quantifies the impact of typhoons on rice production in the Philippines. To this end, satellite-derived reflectance data are used to detect the location of rice fields at 500-m resolution. Utilizing typhoon-track data within a wind field model and satellite-derived precipitation measures, fragility curves are then employed to proxy the damage of storms on rice production within each rice field. The results from a panel spatial regression model show that typhoons substantially reduced local provincial production in the quarter of the strike, having caused losses of up to 12.5 million tons since 2001. Using extreme value theory to predict future losses, the results suggest that a typhoon like the recent Haiyan, which is estimated to have caused losses of around 260 000 tons, has a return period of 13 years. This methodology can provide a relatively timely tool for rice damage assessments after tropical cyclones in the region.

The Impact of the EU Emissions Trading System on Air Passenger Arrivals in the Caribbean

We estimate the impact of additional costs imposed on airlines by the European Union (EU) Emissions Trading System (ETS) on tourist arrivals in 26 Caribbean states. At an EU emission allowance price of €10, we find that the policy will, on average, increase return airfares from Europe to the Caribbean by

DETERMINANTS OF CROP YIELD AND PROFIT OF FAMILY FARMS: EVIDENCE FROM THE SENEGAL RIVER VALLEY

17 for indirect flights and

Water availability and crop growth at the crop plot level in South Africa modelled from satellite imagery

21 for direct flights. These price changes reduce region-wide arrivals to the Caribbean from the EU by between 1.4% and 2%, and decrease total arrivals (from all regions) by less than 0.4%. The decrease in total arrivals is the largest for Martinique (1.7%), and relatively large decreases are also predicted for Antigua and Barbuda, Bonaire, Barbados, Curacao, and Suriname. We conclude that the EU ETS will have a moderate impact on visitor arrivals relative to the United Kingdom’s Air Passenger Duty (APD) and the European financial crisis.

Climate Change and Food Situation

This paper investigates the determinants of the performance of family farms in Senegal using both production and profit functions. The econometric analysis is based on agricultural inputs and outputs information from a survey of 504 agricultural households, member of a farmer organization in the Saint Louis region in 2009. Our main results indicate that the size of the cultivated plots has a negative effect on crop yields, representing diseconomies of scale. This finding suggests potential for improvements in farm management and organization. We also find that the development of commercialization sectors and loans could boost agricultural inputs. In terms of profitability, our results show that yields and prices play significant and important roles for all crops. An increase in the bargaining power of farmers would be required to increase unit prices and consequently their profits.