This chapter is concerned with the development and application of a modelling framework to investigate the sensitivity of the flows in the upper River Jordan to changes in daily and seasonal rainfall patterns, and the likely changes in the daily runoff in response to anthropogenic climate change. To this end, idealised climate scenarios as well as projections of future near-surface air temperature and precipitation from the HadRM3 climate model are used with a modelling framework incorporating the Pitman and INCA rainfall-runoff models to determine flow sensitivity to rainfall and the flow response to a scenario of projected climate change. The Pitman model was used to estimate the hydrologically effective rainfall (HER); the INCA model was used for simplified flood-routing. The INCA model was calibrated for the period 1989 to 1993, commensurate with the observed daily mean flows, and the goodness of fit coefficient R2 was 0.7, indicating a good fit to the observed dynamics, although the simulated flows were an overestimate of those observed owing to unquantifiable river abstractions. On a seasonal timescale, comparison between sensitivity scenarios with long and short rainy seasons showed that rainfall in the winter months had the greatest impact on flow. In response to projected changes in the climate for 2071–2100, the modelled flood flows in the scenario period were reduced by approximately 31% for the largest simulated flood and 25% for the 10th percentile flow in comparison to those in the control period from 1961 to 1990. […]

Wadi Faynan, southern Jordan, provides an archaeological record of human settlement from the Lower Palaeolithic to the Islamic period, and indeed into the present day. As for any long-term record of settlement, an understanding of the changes in economy and society requires knowledge about the impacts of climate and environment change on human communities, especially when dealing with settlement in arid landscapes. This chapter attempts to place the 10,000 years of Holocene settlement in Wadi Faynan between c. 12,000 and 2,000 years ago into its hydrological context. A rainfall-runoff model is used to examine the potential impacts of both Holocene climatic change and human behaviour on the hydrological behaviour of the wadi and then on human settlement. Wade et al. (this volume, Chapter 12) have shown that rainfall-runoff models can successfully simulate the behaviour of the present-day wadi system, demonstrating how such behaviour is sensitive to variability in rainfall and infiltration rates. Here we use the results of regional climate modelling to determine statistical properties of palaeo-rainfall for the Wadi Faynan and then use a stochastic weather generator (this volume, Chapter 5) to create a rainfall series which is used to drive the hydrological model. Results are used to explore the potential impacts of climatic variability on human communities from 12,000 to 2,000 years ago, demonstrating that palaeohydrology may provide a bridge between regional-scale climate data and local-scale cultural developments.

A survey of publicly available data from the Intergovernmental Panel on Climate Change (IPCC) suggests that the Middle East will become significantly drier as greenhouse gas levels rise – with potentially devastating consequences. Simulating the climate of the eastern Mediterranean and the Middle East is, however, a tough challenge for climate models and those results should be interpreted with caution. The cyclones which migrate from west to east across the Mediterranean in winter and early spring, and which deliver much of the annual precipitation to the Middle East, are not well resolved by global climate models of the type included in the IPCC archive. Furthermore, the local climate is modified by coastlines and mountains throughout the region. For these reasons we provide a supplement to the IPCC results with simulations from a regional climate model. As in the global models, the regional model projects that, under an A2 (business-as-usual) scenario, precipitation will decrease significantly in the Middle East. Further investigation of the daily statistics of the weather, along with tracking of weather systems in the present day and future climate scenarios, suggest that the dominant mechanism for these changes is a reduction in the strength of the Mediterranean storm track. The Mediterranean storm track is fairly well simulated by the regional climate model, increasing confidence in this projection. […]

The arid climate of the Middle East means that variations in rainfall on all timescales from days to years have an enormous impact on the people who live in the region. Understanding this variability is crucial if we are to interpret model simulations of the region's climate and make meaningful predictions of how the climate may change in the future and how it has changed in the past (Chapters 3 and 4). This study uses rain gauge measurements in conjunction with other meteorological data to address the following questions. How does rainfall vary from day to day and from year to year? How does rainfall vary spatially within Jordan and Israel? How does the atmospheric circulation over the Mediterranean region affect the daily probability of rain? What effect do large-scale modes of variability such as the North Atlantic Oscillation have on rainfall variability in the region?

When used in conjunction, climate models and palaeoenvironmental data can lead to a more complete understanding of past climate than is possible using either method in isolation. Moreover, the veracity of climate models can be evaluated, which then lends credence to their use for predicting future climate change. In this study we investigate the transition to aridity in the eastern Mediterranean that occurred in the Holocene, a transition with marked consequences for settlement of the Middle East. We show that the general pattern of a transition during the Holocene to a wetter northern Europe and a drier Middle East is seen in both the palaeoenvironmental record and climate model simulations. The pattern of precipitation changes projected by the climate model for the past is similar to those projected for the end of the twenty-first century under GHG-driven climate change. The climate model's ability to represent the past – as tested against palaeoenvironmental observations – thus lends credence to the future projections.

This chapter is concerned with a model-based assessment of the effects of projected climate change on water security in the rural west of Jordan. The study area is the Wadi Hasa, a large (2,520 km2) catchment which drains from the Jordanian plateau to the Dead Sea at Ghor Safi. The Wadi Hasa is regionally important in terms of both water resources and archaeology. A substantial database was collated to describe the hydrological functioning of the catchment and a new monthly time-step hydrological model, HYSIMM, was developed and applied within a modelling framework, which also includes the HadRM3 regional climate model and a weather generator, to provide future projections of mean monthly flows. Under the A2 storyline, the climate in the region of Wadi Hasa in 2071–2100 was projected to become drier, with a mean annual precipitation 25% less than the present day, and warmer; winter and summer temperatures were projected to increase by approximately 4 and 6 degrees centigrade, respectively. Spatial differences in the projected precipitation depths and temperatures are apparent across the region. The modelled outcomes suggest that the mean monthly flows will decrease in winter because of the reduced precipitation, and the modelled flows were more sensitive to changes in precipitation than potential evapotranspiration. Overall, the monthly flood flows are predicted to decrease by 22% and the base flow by 7% by the end of the century under the A2 storyline. […]