Planethopia

Ever since the Intergovernmental Panel on Climate Change’s (or one word IPCC) 2007 report on the impacts of  climate change was discovered to contain a major  error­ that the Himalayan glaciers will be largely gone by 2035.  But  it misses the point to focus on individual errors sprinkled through the report.

The IPCC presented  the second section of  its 2007 report in April  that year and its message was clear: climate change is happening now, and  its impacts will be increasingly felt as more and more carbon dioxide is pumped into the atmosphere.

This article focuses on three key topics:

• impact of  climate change on water supplies
• impact on food
• impact on biodiversity

One of the most dramatic forecasts of the report was that 20 – 30 % of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5°C – 2.5°C above current levels.

The key source is a Nature paper by 19 authors headed by Chris Thomas published in 2004. The pioneering study modelled changes to the “climate envelope” in which species  live. It
found  that such warming would leave 15%  – 37% of species “committed to extinction”, doomed as their habitats dissappeared.

Problematically, Thomas’s study was the only one to claim global coverage while others were focused on specific regions and taxa.

One of the IPCC’s lead authors, Guy Midgley says they wanted a major statement on biodiversity threats but knew the Thomas paper alone was not sufficient evidence so Midgley and his colleagues reanalyzed the other regional and taxa predictions. This was complex, but  the results broadly matched  those of the Thomas paper. So the IPCC authors presented the “20% – 30%”extinction in the papers.

IPCC’s statement on the impacts of drought in Africa was another headline statement at the report’s presentation. It said that by the 2020s, “between 75 and 250 million people in Africa are projected to be exposed to an increase in water stress due to climate change”.

The report attributes the source of  this conclusion to a 2004 paper by Nigel Arnell’s study on the Walker Institute for Climate System Research at the University of Reading.

The study  found that an additional 74 to 239 million Africans would suffer from increased “water stress”, depending on the different climate and population scenarios, with an average of about 152 million. The IPCC rounded this range to 75 to 250 million.

But its interpretation of Arnell’s paper is questionable. The IPCC report ignores another table showing the number of people in different regions who will have access to more water under climate change. The total across African  regions ranges between 11 and 175 million, with  an  average of 111 million. In Arnell’s paper, the two tables were given equal prominence.

Water shortages matter most in poor countries because of their influence on food production. The IPCC’s chapter on food concludes that while crop yields in higher latitudes will probably increase under modest warming, “at  lower latitudes, crop productivity is projected to decrease for even small local temperature increases (1°C to 2°C)”. It says rice yields will be unchanged, but wheat and maize will decline.

This global assessment is thorough but again, the section of the report that discusses crop forecasts for Africa is problematic. Its summary highlights the finding that “projected reductions
in yield in some countries could be as much as 50% by 2020″.

Many commissioned reports have sound findings and this one was written by a known expert,
Moroccan Ali Agoumi. IPCC authors insist that citing it was legitimate. It covers only three countries: Morocco, Tunisia and Algeria. It simply asserts, without identifying specific evidence or a peer­ reviewed source, that “studies on the future of vital agriculture in the region” have identified a number of risks which are linked to climate change, including “deficient yields from rain-based agriculture of up to 50% during the 20 years period”.

Crucially, the IPCC ignored that Agoumi’s prediction applies only to rain­-fed agriculture. In arid North Africa much farming is irrigated rather than rain-fed. So the IPCCe’s prediction that some African nations could lose half of their crops is in fact based on a fraction of agriculture in three North African nations. The fact is we still know far too little about how African food production will be affected by climate change.

What is going to happen, years will show if our future is bright or not.

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