Given the size of the oil and gas industries therein, it comes as little surprise to learn that the Middle East churns out a shedload of greenhouse gases.
In a surprise discovery, however, researchers led by Efstratios Bourtsoukidis from Germany’s Max Planck Institute for Chemistry have identified a second, natural source in the region – so large that it easily matches the anthropogenic output of the United Arab Emirates, Kuwait or Oman.
In a paper published in the journal Nature Communications, Bourtsoukidis and colleagues reveal significant differences between standard model predictions for emissions of non-methane hydrocarbons (NMHCs) such as ethane and propane across the Middle East and the actual results.
The discrepancy was important not only because of its size – the researchers describe it as “a strong underprediction” – but because NMHCs are significant pollutants.
Oxidation of propane and ethane in the atmosphere produces tropospheric ozone and a class of chemicals known as peroxyacetyl nitrates, which are components of photochemical smog and known to be harmful to plants and humans.
NMHCs are produced by human and natural sources. Human production is tightly linked to fossil fuel production and use – and has shown an overall drop since late last century as many countries increased their use of renewable energy. (The US is a notable exception.)
Natural sources include volcanoes and deep-sea geothermal vents. They were, obviously, the only sources of ethane and propane generation in pre-industrial times. They are included in global modelling for NMHC production, forming the baseline level against which anthropogenic activity is measured.
Thanks to Bourtsoukidis and colleagues, that baseline has now been significantly raised. In checking out the discrepancy between predicted NMHC presence over the Middle East and actual readings, the researchers realised they were dealing with a large out-gassing from an undiscovered source.
Further investigation revealed that the geographic location of the emissions was the deep water zone of the Red Sea, which lies between the Arabian and African continental plates. Tectonic activity in the sea has resulted in some unique features – notably, at depths between 300 and 2000 metres, the saltiest and warmest sea water in the world.
The chemical mix thus engendered, added to abundant oil and gas deposits in the underlying rocks, and a degree of volcanic activity, may well explain the hefty emissions. However, the researchers suggest that seepage from poorly maintained deep sea fossil fuel wells might also be a contributing factor.
Bourtsoukidis and colleagues note that the findings will likely have significant impact on environmental management strategies for the region. The Red Sea NMHCs will inflate a total emissions load that is already set to rise in the coming decades as shipping increases in the area.
The resulting phytochemical pollution, they warn, will affect air quality in the area, “for example in Neom city, a cross-border megaproject in the Tabuk Province of north-western Saudi Arabia”.
Barry Keily is a science journalist based in Victoria, Australia.
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