The latest attack on the IPCC's credibility, following a widely publicized error about the rate of Himalayan glacier melt in its 2007 report, zeroes in on African agriculture and the report's conclusion that climate change could reduce rain-fed North African production by up to 50 percent.
Britain's Sunday Times trumpeted: "Africagate: top British scientist says UN panel is losing credibility," and cited professor Chris Fields, an IPCC author, as saying "that he could find nothing in the report to support the claim." Hundreds of news outlets pounced on the story. The Telegraph said the "report is disintegrating under closer examination."
However, the evidence did in fact support that claim about rain-fed African agriculture, a group of climate scientists writes at RealClimate. The wording of the IPCC report is: "By 2020, in some countries, yields from rain-fed agriculture could be reduced by up to 50%," while the more detailed argument, paraphrased in the Synthesis Report, is that "In other countries, additional risks that could be exacerbated by climate change include greater erosion, deficiencies in yields from rain-fed agriculture of up to 50% during the 2000-2020 period, and reductions in crop growth period."
The problem, according to the IPCC's detractors? The evidence was buttressed by so-called "gray literature," which is not put through traditional peer-review processes.
But is this actually a problem? The scientists go on to write:
"It is indispensable to use gray sources, since many valuable data are published in them: reports by government statistics offices, the International Energy Agency, World Bank, UNEP and so on. This is particularly true when it comes to regional impacts in the least developed countries, where knowledgeable local experts exist who have little chance, or impetus, to publish in international science journals."
The question, then, should be one of accuracy and the severity of the threat to African agriculture.
As Stanford scientist David Lobell told IRIN news agency,
"Part of the problem was that the scientific literature on some of these issues was quite lacking at the time [when the report was being compiled — the report takes three years to write]. One risk now is that people could interpret the IPCC statement as being wrong, saying that Africa doesn't really face a threat, or that other IPCC statements are also in doubt. In fact, we think Africa faces some of the toughest impacts on agriculture in the world, just not as extreme as the IPCC statement suggested."
Consider some more recent economic analysis on the effects of climate change on African agriculture.
Wolfram Schlenker, a professor at Columbia, and Lobell, in a study published in Environmental Research Letters, provide some numbers for sub-Saharan Africa. They find that with increased drought conditions and other expected effects of climate change that, in their mid-range estimates, there will be median production drops of 22 percent for maize (corn), 17 percent for sorghum, 17 percent for millet, 18 percent for groundnuts, and 8 percent for cassava, with a 95 percent chance of yields decreasing at least 5 percent (with the exception of cassava) and a 5 percent chance of yields decreasing by over 27 percent, in some cases, over 40 percent.
Considered without context, it's clear that these dangers are potentially devastating. But agriculture is especially important for the mostly rural economies of Africa. As Berkeley economist Alain de Janvry comments,
"Agriculture has multiple functions for the development of these countries in helping to trigger growth at early stages, reduce poverty [and] increase food security."
Other analysts agree, as do Lobell and Schlenker, writing,
"There is arguably little scope for substantial poverty reductions in SSA [sub-Saharan Africa] without large improvements in agricultural productivity. ... The results presented here suggest that this challenge will get even more difficult in a warming climate."
Moreover, as they emphasize, agriculture contributes an average of 17 percent of GDP in those countries. In some of them, that number exceeds 40 percent. (Other sources find a much higher average contribution of agriculture to GDP).
Damage to agriculture in Africa, marvelous techno-fixes placed to the side, means that those countries won't develop. Additionally, most of the rural people in sub-Saharan Africa are poor, and lesser crop yields will have grievous effects on their livelihoods. The vast majority of sub-Saharan Africa's farms are small and have small capital reserves, meaning they can easily be harmed by yield reductions.
And yield reductions are coming. Economist William Cline of the Center for Global Development has predicted drops of between 17 and 28 percent for African agricultural production by 2080. For Morocco and Zimbabwe, his figures are in the region of 29 to 39 percent. And populations are obviously expected to grow throughout this time-span, as well.
In another research paper, Lobell found declining average yields across much of Africa by 2030.
So, what's to be taken from this barrage of models, based on prognostications about the effects of carbon-fertilization — plants respond well, historically, to increases in atmospheric CO2 levels — guesses about whether irrigated vs. non-irrigated farmland will increase and at what rate, and the rest?
Climate science analyzing future agricultural yields is necessarily speculative. It could not be anything else. If there's something modelers agree upon, however, it's that global warming will harm African agriculture. If there's something development economists generally agree upon, it's that Africa can't develop without agricultural growth.