[CAIRO] Scientists in Saudi Arabia say that by the end of 2050 parts of the country will be hotter and have reduced precipitation, which could affect agricultural productivity.
The work was published in February's issue of the Arabian Journal for Science and Engineering.  It predicts that average temperatures in Saudi Arabia could increase by as much as four degrees Celsius, increasing agricultural water demands by up to 15 per cent to maintain current productivity levels.
Researchers investigated the effects of climate change on water resources in Saudi Arabia by analysing data on precipitation, relative humidity, soil moisture, temperature and wind speed from 1978 to 2003.
- A study warns that climate changes threatens Saudi agricultural production and drinking water supplies
- While some parts of the country will face drought, other parts will see increases in surface run-off
- Scientists urge for more climate-proof infrastructure, better drainage systems, and water harvesting
Lead researcher Shakhawat Chowdhury, of the King Fahd University of Petroleum and Minerals, and his colleague Muhammad Al-Zahrani, based at the same university, found that higher temperatures could increase the levels of dissolved organic matter — such as ammonia, nitrogen and phosphorus — in surface water, especially after long periods of drought.
They say reductions in deep aquifer recharge, as a result of lower rates of rain as well as a rise in temperature, and surface run-off may dry out some of the country's valley basins, further reducing agricultural productivity.
Similar predictions have been made in previous reports, such as the 2012 World Bank report on climate change adaptation in the Middle East and North Africa region. 
Co-author for the World Bank report and climate change adaptation expert at the African Development Bank, Balgis Osman-Elasha, emphasises that it is a regional effect, with southern Saudi Arabia and East Africa, including the headwaters of the Nile, expected to see up to 50 per cent more run-off by 2050. The Saudi Desert could receive more rain in late summer.
The regional differences reflect the limited amount of regional and global climate models, making both conventional weather forecasting and climate modeling difficult.
Elasha says extreme rainfall events will increase in intensity and frequency, such as the 2010 flooding in Jeddah, Saudi Arabia, which killed over 150 people. Jeddah's flooding was initiated by an intense rainfall that dumped 90 millimeters of rain in four hours over an area that normally receives 45 millimeters per year.
To prepare for these she recommends "more climate-proof infrastructure, better drainage systems and networks, and water harvesting mechanisms".
Chowdhury urges for better management of water resources, such as maximising the use of treated wastewater, and shifting the crop growing periods.
David Downie, director of the Environmental Studies programme at US-based Fairfield University, says the report — and others like it — show that the negative impacts of climate change will affect all countries.
He adds that without serious attempts to limit greenhouse gas emissions, the long-term negative economic and societal impacts of climate change will exceed the cost of limiting emissions.
Link to abstract in Arabian Journal for Science and Engineering