Asian irrigation, African rain: Remote impacts of irrigation

Vrese, Philipp de; Hagemann, Stefan; Claußen, Martin

doi:10.1002/2016gl068146

Cited by 113 publications

(100 citation statements)

References 56 publications

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“…The differences between the simulations are briefly summarized in Table 1. To determine whether differences between individual simulations are robust we determined their statistical significance using a two sample, two sided Student's t-test (p < 0.05) and additionally compared them to the MPI-ESM's internal variability (de Vrese et al 2016a).…”

Section: Resultsmentioning

confidence: 99%

“…For the study, the MPI-ESM's land surface model JSBACH was equipped with an irrigation scheme very similar to the one used in a previous study with the MPI-ESM (Tuinenburg et al 2014;de Vrese et al 2016a). For the irrigation scheme, dedicated tiles, i.e.…”

Section: Irrigation Schemementioning

confidence: 99%

“…In turn Δ V4 exhibits larger relative irrigation amounts and consequently larger impacts during autumn and winter. As the winds transporting water vapour vary on a seasonal scale (de Vrese et al 2016a), these differences affect the remote impacts of irrigation. However, a detailed seasonal comparison would go beyond the scope of this work.…”

Section: Influence Of Irrigation Characteristicsmentioning

confidence: 99%

“…Studies using a variety of models have investigated how this redistribution affects the availability of freshwater (Döll and Siebert 2002;Tiwari et al 2009;Liu and Yang 2010;Wada et al 2012Wada et al , 2013Yoshikawa et al 2013) and climate. The majority of the studies that investigate irrigation's climate impact is focused on regional climate (Douglas et al 2006;Kueppers et al 2007;Douglas et al 2009;Lobell et al 2009;Saeed et al 2009;Lawston et al 2015), but also larger scales have been addressed in recent studies (Boucher et al 2004;Sacks et al 2009;Wei et al 2013;de Vrese et al 2016a;Krakauer et al 2016;Thiery et al 2017). The impact of irrigation has been compared to that of other anthropogenic influences such as deforestation (Gordon et al 2005;Lobell et al 2006b), and it has been investigated under changing climate conditions (Lobell et al 2006a;Puma and Cook 2010;Cook et al 2011Cook et al , 2014.…”

Section: Introductionmentioning

confidence: 99%

“…Sacks et al (2009) concluded that indirect effects such as a change in cloud cover have an impact at least comparable in magnitude to the evaporative cooling of the surface. Moreover, there are some important regional processes such as the South and East Asian monsoon which can directly be affected by irrigation (Douglas et al 2009; Lee et al 2009;Niyogi et al 2010;Saeed 2011;Saeed et al 2013;Tuinenburg et al 2014;de Vrese et al 2016a). Finally, the advection of water vapor can alter precipitation, cloud cover and surface temperature even in remote regions (Wei et al 2013;de Vrese et al 2016a).…”

Section: Introductionmentioning

confidence: 99%

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Uncertainties in modelling the climate impact of irrigation

Vrese

Hagemann

2017

Clim Dyn

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Irrigation-based agriculture constitutes an essential factor for food security as well as fresh water resources and has a distinct impact on regional and global climate. Many issues related to irrigation's climate impact are addressed in studies that apply a wide range of models. These involve substantial uncertainties related to differences in the model's structure and its parametrizations on the one hand and the need for simplifying assumptions for the representation of irrigation on the other hand. To address these uncertainties, we used the Max Planck Institute for Meteorology's Earth System model into which a simple irrigation scheme was implemented. In order to estimate possible uncertainties with regard to the model's more general structure, we compared the climate impact of irrigation between three simulations that use different schemes for the land-surface-atmosphere coupling. Here, it can be shown that the choice of coupling scheme does not only affect the magnitude of possible impacts but even their direction. For example, when using a scheme that does not explicitly resolve spatial subgrid scale heterogeneity at the surface, irrigation reduces the atmospheric water content, even in heavily irrigated regions. Contrarily, in simulations that use a coupling scheme that resolves heterogeneity at the surface or even within the lowest layers of the atmosphere, irrigation increases the average atmospheric specific humidity. A second experiment targeted possible uncertainties related to the representation of irrigation characteristics. Here, in four simulations the irrigation effectiveness (controlled by the target soil moisture and the non-vegetated fraction of the grid box that receives irrigation) and the timing of delivery were varied. The second experiment shows that uncertainties related to the modelled irrigation characteristics, especially the irrigation effectiveness, are also substantial. In general the impact of irrigation on the state of the land surface is more than three times larger when assuming a low irrigation effectiveness than when a high effectiveness is assumed. For certain variables, such as the vertically integrated water vapour, the impact is almost an order of magnitude larger. The timing of irrigation also has non-negligible effects on the simulated climate impacts and it can strongly alter their seasonality.

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Section: Resultsmentioning

confidence: 99%

Section: Irrigation Schemementioning

confidence: 99%

Section: Influence Of Irrigation Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Uncertainties in modelling the climate impact of irrigation

Vrese

Hagemann

2017

Clim Dyn

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Present‐day irrigation mitigates heat extremes

et al. 2017

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Irrigation is an essential practice for sustaining global food production and many regional economies. Emerging scientific evidence indicates that irrigation substantially affects mean climate conditions in different regions of the world. Yet how this practice influences climate extremes is currently unknown. Here we use ensemble simulations with the Community Earth System Model to assess the impacts of irrigation on climate extremes. An evaluation of the model performance reveals that irrigation has a small yet overall beneficial effect on the representation of present‐day near‐surface climate. While the influence of irrigation on annual mean temperatures is limited, we find a large impact on temperature extremes, with a particularly strong cooling during the hottest day of the year (−0.78 K averaged over irrigated land). The strong influence on extremes stems from the timing of irrigation and its influence on land‐atmosphere coupling strength. Together these effects result in asymmetric temperature responses, with a more pronounced cooling during hot and/or dry periods. The influence of irrigation is even more pronounced when considering subgrid‐scale model output, suggesting that local effects of land management are far more important than previously thought. Our results underline that irrigation has substantially reduced our exposure to hot temperature extremes in the past and highlight the need to account for irrigation in future climate projections.

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Can climate‐effective land management reduce regional warming?

et al. 2017

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Limiting global warming to well below 2°C is an imminent challenge for humanity. However, even if this global target can be met, some regions are still likely to experience substantial warming relative to others. Using idealized global climate simulations, we examine the potential of land management options in affecting regional climate, with a focus on crop albedo enhancement and irrigation (climate‐effective land management). The implementation is performed over all crop regions globally to provide an upper bound. We find that the implementation of both crop albedo enhancement and irrigation can reduce hot temperature extremes by more than 2°C in North America, Eurasia, and India over the 21st century relative to a scenario without management application. The efficacy of crop albedo enhancement scales with the magnitude, where a cooling response exceeding 0.5°C for hot temperature extremes was achieved with a large (i.e., ≥0.08) change in crop albedo. Regional differences were attributed to the surface energy balance response with temperature changes mostly explained by latent heat flux changes for irrigation and net shortwave radiation changes for crop albedo enhancement. However, limitations do exist, where we identify warming over the winter months when climate‐effective land management is temporarily suspended. This was associated with persistent cloud cover that enhances longwave warming. It cannot be confirmed if the magnitude of this feedback is reproducible in other climate models. Our results overall demonstrate that regional warming of hot extremes in our climate model can be partially mitigated when using an idealized treatment of climate‐effective land management.

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Asian irrigation, African rain: Remote impacts of irrigation

Cited by 113 publications

References 56 publications

Uncertainties in modelling the climate impact of irrigation

Uncertainties in modelling the climate impact of irrigation

Present‐day irrigation mitigates heat extremes

Can climate‐effective land management reduce regional warming?

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