Climate Change Over Saudi Arabia

Model Validation
Climate of Saudi Arabia
Future Climate Change Over Saudi Arabia




The climate change over Saudi Arabia at the end of the 21st century is investigated using PRECIS software, a regional climate model system that can be run on a personal computer, developed by the Hadley Center at the UK Met Office to produce high resolution climate scenarios. The Intergovernmental Panel on Climate Change produced reports on potential emission scenarios, from which two scenarios (A2 and B2) were adopted for this study.

The study area is divided into six regions and thirty-seven selected locations over Saudi Arabia. Temperature, precipitation, evaporation, wind speed, soil moisture and runoff were investigated. Results indicated that the years 2071 – 2100 under A2 scenario will generally experience warmer temperature, more precipitation, less evaporation, and more runoff than under the B2 scenario compared to the present. A significant result was the increase of mean daily temperature by 3.0 oC to 4.2 oC, and the increase of precipitation by 23% to 41%.



Many scientists believe that global warming and its consequences are highly influenced by human activities and not by natural fluctuations (Hardy, 2003). The reasoning of this belief has to do with the time scale. The recent recognized warming of the Earth is considered abrupt compared to the time scale accompanied with natural climate change episodes. Earth’s natural climate changes gradually over long periods of time (tens of thousands to millions of years), but we have been witnessing an abrupt change over the past 200 years. The industrial revolution depended on fossil fuels as its main source of energy, which caused a steady emission of carbon dioxide and other greenhouse gases. Those anthropogenic gases trapped heat, causing an increase of temperature in the lower atmosphere. Several studies show the sensitivity of water resources to climate change (Rajab and Prudhomme, 2002). The variation in precipitation, temperature, evaporation, the recharge to aquifers, and the general hydrologic cycle are all interactive.

Climate change is recognized as a serious challenge to human survival, and international communities, through the United Nations, created a special group to focus on climate change. In 1988 the Intergovernmental Panel on Climate Change (IPCC) was created by the World Meteorological Organization (WMO) and the United Nations Environmental Program (UNEP) to help decision-makers and the public to understand the issues of climate change. In 1992, an Earth Summit was conducted where representatives of 172 governments were present at Rio de Janeiro, Brazil, to discuss the threat of global warming. In December 2003, the United Nations General Assembly officially declared the years 2005 to 2015 to be the international decade for action with “Water for Life” as the UN theme to raise worldwide awareness (Gleick, 2006). The IPCC published several reports regarding human-induced emissions of greenhouse gases and various aspects of climate change. Subsequently, the IPCC’s four assessment reports on climate change became a standard reference for scientists, students, and the general public. Global warming has been detected since the mid 1970s. Mean Earth temperature has been increasing by 0.15 oC per decade (Brohan et al., 2006). The warmest year in fact was 1998 with 0.546 oC above the norm calculated for the years 1961-1990, which was 14 oC. The year 2007 was 0.40 oC above the normal global mean temperature, which is the eighth warmest on record, preceded by 1998, 2005, 2003, 2002, 2004, and 2001 (Figure 1.1).

The IPCC made a strong statement in its fourth assessment report that includes the warming of the oceans as well as the mean global air temperature (Treut et al., 2007): “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, wide-spread melting of snow and ice, and rising global average sea level.” The IPCC predicts that the global mean surface temperature will increase by the end of the 21st century by 3.4 oC (2.0 oC to 5.4 oC) for the A2 scenario, which describes an intensification of the hydrologic cycle and a general global increase of the mean precipitation, water vapor, and evaporation. The IPCC indicated a future increase in surface temperature by 2.4 oC (1.4 oC to 3.8 oC) for the B2 scenario, which describes a world with a population increasing at a slower rate than the A2 scenario. Under the B2 scenario, the sea level is expected to rise by 0.20 to 0.43 meters and under the A2 scenario by 0.23 to 0.51 meters.
Climate Research Unit, UEA, United Kingdom
Figure 1.1: Global mean anomaly (difference from the mean) since 1840. (From Climate Research Unit, UEA, United Kingdom)

Recently, unusually strong tropical storms, heavy precipitation causing devastating floods, more frequent heat-waves, frequent droughts, and other events, brought greater attention to the inevitable climate change. The government of Saudi Arabia has recognized that change by signing the Kyoto Protocol and participating on various world summits to help protect the Earth. The Kyoto Protocol calls for implementation of a commitment to stabilize greenhouse emissions and furnish a national report describing the current status of climate change to be reviewed by the United Nations Framework Convention on Climate Change (UNFCCC).

Model Validation

For validation of PRECIS for the same domain covering the area of Saudi Arabia, a period of 30 years, 1961 to 1990, was downscaled by PRECIS in two separate experiments. Date was obtained from the Hadley Center global atmospheric model (HadAM3p) for the 1st experiment, and for the second experiment the reanalysis observation data (ERA-40) was obtained from the European Center for Medium Range Weather Forecast. Also, weighted domain values were compared for means and standard deviation and visual differences.
A comparison between PRECIS (simulated) and the observed mean and standard deviation values of average daily temperature, precipitation, evaporation, wind speeds, and runoff are presented in table 2.4 and shown graphically (Figures 2.8 – 2.12). PRECIS has a cold bias of approximately 2 oC, but visual comparison (Figure 2.8) indicates a wide deviation north and outside the concerned area.  The fact that the model tended to worsen near the edges of the domain was expected and taken care of when the experiment was designed by choosing margins wide enough to get much better values for the region of interest (Saudi Arabia).

Similarly, comparisons of simulated and observed average daily precipitation, evaporation, wind speeds, and surface runoff showed more agreement over Saudi Arabia than at the far ends of the domain. The model has a negative bias (approx. 23%) on the mean daily precipitation, a negative bias (approx. 2%) on the mean daily evaporation, a positive bias (approx 3%) on the mean wind speeds, and a positive bias (approx. 4%) on the mean daily surface runoff. Overall, the model is expected to serve well in simulating the future for Saudi Arabia, taking into account the biases of the model and knowing that no model is capable of producing a perfect validation against observation.

There are several major uncertainties when dealing with climate projections, but GCMs provide the best tool to deal with various aspects of future climates (Houghton, 2004). The future emission scenarios, the carbon and hydrological cycles, the natural variation of the climate system, and the used downscaling techniques, are important sources of uncertainty (Jones et al., 2004).


Figure 2.6: PRECIS interface window



Table 2.4: PRECIS simulation weighted area mean and standard deviation








Temperature  oC





Precipitation mm/day





Evaporation mm/day





Wind Speed














Figure 2.8: Simulated (a) and observed (b) average daily temperature for years 1961-1990



Figure 2.9: Simulated (a) and observed (b) average daily precipitation for years 1961-1990



Figure 2.10: Simulated (a) and observed (b) average daily evaporation for years 1961- 1990



Figure 2.11: Simulated (a) and observed (b) average daily wind speeds for years 1961-1990



Figure 2.12 Simulated (a) and observed (b) average daily surface runoff in mm / day for years 1961-1990


Climate of Saudi Arabia

Future Climate Change Over Saudi Arabia


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1.                  United Kingdom Meteorological Office:

2.                  PRECIS website:

3.                  The United Nations Framework Convection on Climate Change (UNFCCC):

4.                  United Nations Division for Sustainable Development:

5.                  Climate Research Unit at University of East Anglia, UK:

6.                  The SRES web site:


Faisal Makki Al Zawad
P. O. Box 18037, Qatif 31911, Saudi Arabia,