CSIR climate modellers believe that 2015 is on its way to be the warmest year ever recorded. This is partially due to climate-change, and partially due to a massive El Nino event currently developing in the Pacific Ocean. Temperatures over subtropical southern Africa have risen at more than twice the global rate over the last five decades.

Moreover, further warming of between 4 - 6 ºC over the subtropics and 3 - 5 ºC over the tropics are projected by the end of the century under low mitigation, relative to the present-day climate. This was revealed in a CSIR study using a regional climate model integrated on a powerful computer-cluster at its Centre for High Performance Computing (CHPC), to obtain detailed projections of future climate change over Africa.

This study comes ahead of the United Nations Framework Convention on Climate Change (UNFCCC)'s 21st Conference of the Parties (CoP 21), due to take place in Paris, France in November 2015. This meeting aims to achieve a legally binding and universal agreement on climate, with the aim of keeping global warming below 2 ºC.

"If the negotiations fail to ensure a high-mitigation future, we are likely to see rapidly rising surface temperature across the continent," says Dr Francois Engelbrecht, CSIR Principal Researcher and leader of the study entitled, Projections of rapidly rising surface temperatures over Africa under low mitigation.

Africa is particularly vulnerable to excessive temperature increases due to the continent's dependence on subsistence farming and rain-fed agriculture. "For many regions, the impact of temperature increases on the agricultural and biodiversity sectors may be significant, stemming from temperature-related extreme events such as heat-waves, wild fires and agricultural drought," explains Dr Engelbrecht.

Heatwaves are rare events over Africa under present day conditions. The highest number of heat wave days occurs over the Limpopo river basin region in southern Africa, the eastern interior and east coast regions of South Africa and the Mediterranean coast of North Africa. Drastic increased occurrences of heat wave days may be expected across the continent under climate change, contributing to decreased maize crop yield through the exceedance of critical temperature thresholds increases in livestock mortality and adverse impacts on human health. If a heat wave occurs during a drought, which dries out vegetation, it can contribute to bushfires and wildfires. Wildfires cause large financial losses to agriculture, livestock production and forestry in Africa on an annual basis.

"Globally, Africa is the single largest source of biomass burning emissions," says Engelbrecht. "It is very important to understand the impacts of increasing occurrences of fires on the African savannas, as well as potential feedbacks to the regional and global climate system". Moreover, Engelbrecht and his co-authors point out in the paper that general reductions in soil-moisture are plausible to occur across the continent, as a result of enhanced evaporation that occurs in response to increasing surface temperatures. "In the subtropics, this effectively implies a longer burning season and a shorter growing season", says Engelbrecht.

Considering the fact that African temperatures in the subtropics are projected to rise at 1.5 times the global rate of temperature increase (an estimate that may be conservative) and the aim of the upcoming UNFCCC negations seeking to keep global warming below 2 ºC compared to pre-industrial temperatures - the Long Term Global Goal (LTGG), Engelbrecht is of the opinion that the trends and projections of rapidly rising African temperatures should be a key consideration at the UNFCCC negotiations. "The relatively high rate of temperature increases over Africa should be considered when deciding on the suitability of the LTGG of the UNFCCC in terms of climate-change impacts in Africa" Under low mitigation, the world is likely to experience an increase in global average surface temperature of 3 ºC or more, and the relatively strong temperature signal over Africa is of particular concern within this context."

The full paper, which has been published in Environmental Research Letters, is available here: http://iopscience.iop.org/article/10.1088/1748-9326/10/8/085004/meta

About the CSIR

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