Droughts, or rather ‘air subsidence, hence low precipitation and high evaporation’ belong to the subtropics – therefore much of North Africa and the Middle East is covered by (semi) desert. What is a concern though, is possible further drying due to climate change in agriculturally productive areas, such as Egypt’s Nile Delta, the western Sahel and especially the so-called ‘Fertile Crescent‘, encompassing much of Israel, Lebanon, Syria and Iraq.
There has of course always been agriculture in Egypt’s Nile Delta, where annual river floods compensating for a lack of rain. There were however considerably fewer people, and droughts, crop failure and famine did occur throughout Mediterranean history. The tree ring record the new study is based on can only look back to the Middle Ages. Image, the grave chamber of Menna, ancient Egypt, 1422-1411 BC. Credit: Wikimedia Commons.
A new metastudy that was published this month in the Journal of Geophysical Research illustrates just how complicated the story really is. The recent drought in Syria that we wrote about before (lasting from from 2007-2011 – the onset of the Arab Spring) is part of larger, longer-lasting drought in the Eastern Mediterranean, also referred to as Levant, that the authors say started around the year 1998.
Comparing this recent dry period to the historical ‘drought atlas’ of the region (Old World Drought Atlas, OWDA), a paleoclimatic record based on tree-ring measurements, finds the recent drought was probably the strongest since the start of that record, around the year 1100 – at a calculated likelihood of 89 percent over the last 900 years, and a likelihood of 98 percent for the last 500 years.
The researchers also conclude that droughts of ‘similar magnitude’ have occurred throughout the record – as the graph below illustrates:
Palmer Drought Severity Index (scPDSI) – a measure for dryness based on temperature and precipitation (‘sc’ means it is the ‘self calibrating’ version, including soil characteristics and comparable for different global regions), graphed for the entire period between the year 1100 and 2012, indicating a recent record-drought in the eastern Mediterranean (Levant). Also in other regions of the Mediterranean, like Greece and western Turkey – and the western Mediterranean (Spain and northern Morocco) this was a relatively dry period in the climatological record.
The researchers have looked for connecting climate patterns. They state that Mediterranean droughts show a connection with for instance NAO (North Atlantic Oscillation) in winter. A positive NAO index, which leads to Atlantic depressions following a northerly course over Europe, bringing mild and rainy winters – is accompanied with higher air pressure over southern Europe – and clearly below average precipitation in Spain. However the Levant might be too far to the southeast to be part of this direct connection and actually experience decreased drought condition under positive NAO. Hence other possible teleconnecting factors are investigated, including the ‘Scandinavian Pattern’ (SCA) and the Eastern Atlantic Pattern (EA):
The authors of the study are Benjamin Cook, a climatologist at NASA’s Goddard Institute for Space Studies, Kevin Anchukaitis, Ramzi Touchan, David Meko and Edward Cook, specialists in dendrochronological climate reconstructions (tree ring research) of the University of Arizona and the Lamont-Doherty Earth Observatory in New York.
You have to take your hats off to such scientists, who go to such lengths, trying to really understand what’s going on – with our climate.
Let’s be extremely unscientific and try to draw our own simpler conclusions
For a climate science communicator life is much easier than for these established paleoclimatologists. We don’t actually have to gather data ourselves, nor do we have to use those statistical testing methods that our lazier brains can’t properly concentrate on. There’s no such thing as proper peer review within the ‘science communicating community’ [hello colleagues!] and all we do – let’s be honest – in terms of evidence, is linking to other stuff that we ourselves wrote before, using the same sloppy methods. We work just like the internet. Quick and dirty.
Having said all that, we think our somewhat dumber methods, can just very occasionally be helpful too. Without properly understanding all these complicated teleconnecting factors that the researchers investigated to understand the record Levant droughts we are well equipped to suggest the unsuggestable: Let’s ignore teleconnections altogether. Because if you find a connection between the North Atlantic Oscillation and eastern Mediterranean precipitation, you might then find the North Atlantic Oscillation itself might not be subject to a long-term climate change trend – or worse, find that it in turn depends on yet other poorly understood teleconnections, like the irregular ENSO cycle – the slightly better predictable AMOC cycle – or changes in the solar cycle.
If you just trust in what you do know you can get to a simpler holistic story: That our atmosphere contains ever more greenhouse gases and therefore absorbs more energy, therefore both temperature and net evaporation go up and the general circulation intensifies, with a declining Polar Cell and an expanding and poleward migrating Hadley Cell. You come very close to developing a ‘scientific gut feeling’ of expected climate trends for the Mediterranean: Of course it’s getting drier – on average – and subsequent dry periods could well be worse than the one between 1980 and 2012.
In other words: If it’s dry now – it will probably be worse in the future, as global climatic warming continues. And yes, that is very bad news – because of another trend.
Why this study zooms in on this region – while damaging climatic changes occur across the entire globe…
Now of course the eastern Mediterranean receives special attention following the Arab Spring and subsequent conflicts and migrations – that some attribute (partly) to climate change. To us the above study suggests that connection might only be partly true. Although Syria experienced an extreme drought in the 4 years prior to the conflict, other countries in the wider region, Tunisia, Libya, Yemen, Eritrea, had different climatic conditions before unrest started [although of course global markets also play a role, and there too climate connections exist, like increased food prices following the Russian drought of 2010].
We think another easily-overlooked factor – one that is almost too simple for science – plays a far larger role in the Arab Spring and the current migration crisis: Demography. The various Arab Spring countries have shown a tripling and sometimes quadrupling of local populations in the decades before unrest started – a population rise that UN models forecast will continue throughout the region. It is this rapid local population growth that is truly unsustainable – and what makes these new droughts hurt so much.
Yes. You heard it from us. The folks that say ‘Climate-caused Holocene Mass Extinction‘ 60 times each morning – the folks that religiously believe flying is the most stupid thing a man can do and that personally even attribute developing a grey beard to climate change: Sometimes other (in)sustainability issues worry us more. Captured in this one graph.
© Rolf Schuttenhelm | www.bitsofscience.org