Hotter, drier, dustier
By Dr. Mansour Almazroui
 
 
SOME 100 km northeast of Jeddah, the remains of date palms can be seen: broken, bent, felled down or left without leaves. For more than 80 years the once-tall palms had colored the Gudaid valley in Kholais with their lush greenery, drawing people to harvest the dates in the summer and enjoy a dip in the region’s naturally replenishing springs.
However, all that has changed for some years now.
Due to the lack of rainfall since the early 1980s, the springs have gradually dried and the trees have wilted, unable to survive the abnormally prolonged drought.
Other areas like Madina, Yanbu and Bisha, have also been similarly hit by a significantly increasing warming trend in the Saudi Arabian region, which could change the weather pattern systems, reduce our water resources, affect our surrounding environment, and significantly constrain our future lifestyle.
As a result of global warming, the Arabian Peninsula is now facing one of the most severe and prolonged droughts in recent history.
Water supplies in major reservoirs and many groundwater basins are already well below average. Plus, the frequency of sandstorms has significantly increased.
A classic example of the impact of drought from what is mainly attributed to climate change in the region is the complete disappearance of Lake Layla in Alflaj, south of Riyadh, by the end of 2000. It used to be the largest natural lake in the Arabian Peninsula.
Drought – not necessarily an absolute absence of rainfall but rather an extremely high reduction in rainfall amounts – is a slow process and its impact increases when it occurs persistently for a long period.
The ongoing drought, coupled with the effect of high temperatures, is expected to increase desertification. Consequently, with loss of vegetation cover, the frequency of sandstorms in Saudi Arabia might also intensify.
Our local climate is not isolated from the perturbations of the global atmospheric circulation patterns. Recent studies have established that dry weather circulation patterns associated with drought have increased in recent decades in the Arabian Peninsula while wet weather circulation patterns favorable to the occurrence of rainfall have decreased. These wet types are linked to the eastern Mediterranean cyclonic activity, migrating from west to east.
Analysis of atmospheric circulation over the Mediterranean region indicates a northward and northeastward shift of some of the Mediterranean storm track that is supposed to reach our region.
Weather systems over the Arabian Peninsula are partly affected by variations in air circulation patterns in the Northern Hemisphere. From the projections of various Global Climate Models, many places in the Middle East region are going to face drought episodes mainly due to an unfavorable alteration in the behavior of the circulation patterns.
This could explain the prolonged drought in the northern parts of the Arabian Peninsula – Jordan, Syria, Iraq, Turkey, and some parts of northern Saudi Arabia.
This alteration in the behavior of the circulation patterns could also explain the increase in severe rainstorms in the southern parts of the Peninsula, affecting mainly Oman (e.g. Cyclone Guno in June 2007), the UAE, Yemen and southern Saudi Arabia.
The North Atlantic Oscillation (NAO) index, which measures the surface pressure difference between the Subtropical high (Azores) and the Sub-polar low, is one of the most important indicators of the weather patterns over the Mediterranean region.
If the difference is negative in winter, southern Europe and the Mediterranean region will be affected by more wet and warm conditions, and this would result in an increased number of storms bringing much-needed rains.
On the other hand, if the difference is positive, it means that southern Europe and the Mediterranean region will be affected by dry and cold conditions in winter.
A significant correlation is found between the negative phase of the NAO and temperature and rainfall in Saudi Arabia.
In the negative phase, we would expect wet weather conditions, particularly over the northern parts of the Arabian Peninsula.
The main concern here is that the NAO has witnessed an unprecedented upward – or positive – increase in the last 30 years of records. This trend would lead to dominance of dry weather over the region, which could explain the recent prolonged droughts.
There is still a debate among climate scientists on whether this alarming trend is due to man-induced factors or is it simply natural variations. Also, will more negative NAO values recur?
Regardless of which side is winning the debate, it is very likely that the current trend will persist for years to come. Which means the worst-case weather scenarios over the Arabian Peninsula may be expected.

Annual mean global air surface
temperature anomaly from 1850 to 2008

Global warming which started in the beginning of the early 20th century has become more pronounced in recent decades. The nature of the warming trend can be clearly seen in this figure showing the annual mean of global surface temperatures from 1850 to 2008, which is constructed from global observational land weather stations and marine observations from ships. The rise is 0.6°C over the past century. The rate of warming in the last 50 years has doubled from what was observed over the last 100 years. More interestingly, global temperatures are predicted to continuously rise further through the present century. According to the Intergovernmental Panel on Climate Change (IPCC), this warming is unequivocal and most probably (more than 90% certainty) related to human modification of the composition of the atmosphere. – Dr. Mansour Almazroui
– Dr. Mansour Almazroui is Head of the Department of Meteorology, King Abdulaziz University, Jeddah, Saudi Arabia, and Associate Fellow in Climatic Research Unit, University of East Anglia, Norwich, UK. Feedback: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
 

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