Bishop Hill Drought in the Horn of Africa
Jul 21, 2012 Climate: WG2 During our joint appearance on the Jeremy Vine show, George Monbiot said something that intrigued me, namely that there had been a decades long trend towards drought in the Horn of Africa.
This was interesting to me, as I'd heard this suggested before and had actually spent a short time trying to verify the claim about six months ago. However, I had been distracted by other things and had never bottomed it out.
After hearing George make the claim again, I decided it was worth digging a bit further and this post is the result. Although I can't say I have checked every available source, my researches have turned up very little to support the idea.
An IPCC report on the Regional Impacts of Climate Change produced this map of precipitation trends. It's rather old - dating from 1997 - but does seem to suggest a trend towards increasing rainfall in the area:
;)
There have been two droughts in the area in recent years - 2006 and 2011 - but the map above does seem to preclude a "decades-long" trend towards drought.
I wonder what George's source is?
Bishop Hill
From the African Journal of Agricultural Research:
Different researches had been conducted to assess the spatial and temporal patterns of rainfall in different parts of the country. Wing et al. (2008) in studied the trends and spatial distribution of annual and seasonal rainfall in different parts of Ethiopia using data from 134 stations in 13 watersheds between 1960 and 2002, and showed no significant changes in annual watershed rainfall for any of the watersheds examined, rather a significant decline in June to September rainfall (that is, Kiremt) were recorded in watersheds located in the southwestern and central parts of Ethiopia. Similarly, Osman and Sauerborn (2002) noted that summer rainfall in the central highlands of Ethiopia declined in the second half of the 20th century. On the other hand Seleshi and Zanke (2004) failed to find such a trend over central, northern, and northwestern Ethiopia. Instead, similar to Verdin et al. (2005) they found a decline of annual and Kiremt rainfall in eastern, southern, and southwestern Ethiopia. Woldeamlak and Conway (2007) argued declining of annual rainfall in the northwestern part rather there were no clear trend of annual rainfall during their observation time. Generally, Wing et al. (2008) in many parts of Ethiopia, Woldeamlak and Conway (2007) in drought prone areas of Amhara region (Northwestern Ethiopia), Seleshi and Zanke (2004) in central, northern, and north-western Ethiopia and Conway et al. (2004) in the central Ethiopian highlands and Conway (2000) in northeastern Ethiopian highlands agreed that there is no significant and clear trend in the annual rainfall pattern.
Reader Comments (53)
Richard
I think it's fair to say then that Monbiot's remarks were not supported by the scientific evidence then.
Jul 26, 2012 at 7:36 AM | Bishop Hill
They are supported by the AR4 PDSI figure which may very well be where George got it from. I think it is quite usual - and understandable - for writers to rely on the most recent IPCC report for their info. He may not be aware of the uncertainties in this - to be fair to George, this is not at all clear in AR4.
I think it is a case of the science having moved on, and not having been presented with appropriate caveats in AR4 (in this particular case).
This is why we need an update in the form of AR5....! :-)
Re: Jul 26, 2012 at 12:30 AM | Richard Betts
"The IPCC SREX report was slightly less confident than AR4 on whether widespread increases in drought are being seen worldwide. This is going to be an extremely interesting aspect of AR5."
Certainly is, Richard, it seems that the Lead Authors have been busy amending the drafts to support the CAGW meme already, as Steve McIntyre reports -
"Tailoring of AR5?
The AR5 Zero Order Draft on paleoclimate stated, in language reminiscent of Soon and Baliunas, “multiple studies suggest that current drought and flood regimes are not unusual within the context of last 1000 years”.
However, the First Order Draft was substantially changed to language apparently tailored to avoid a direct contradiction of alarmist narrative...
Note carefully that the First Order Draft suppressed any explicit mention of historical megadroughts exceeding those in the modern instrumental record (attested in the Zero Draft by a substantial literature. In my opinion, the language in the Zero Order Draft was a better assessment of paleoclimate information.
What was the justification for IPCC authors removing this important information from paleoclimate? It appears to me that the information was deleted because it was inconsistent with alarmist narrative on droughts and not for a valid reason.
To borrow a phrase from Phil Jones, one might say that the evasive language of the First Order Draft was a trick to hide the megadroughts."
So it seems that the Lead Authors are building up to a megadrought extravaganza - good thing that Steve McIntyre is keeping a close eye on things!
http://climateaudit.org/2012/08/01/hide-the-megadroughts/