Top global weather story of 2009: drought in the Horn of Africa

I'm in Atlanta at the 90th Annual Meeting of the American Meteorological Society, and the picture I'm getting from the presentations here is that the most significant weather event of 2009 was the failure of the summer rains in the Horn of Africa. Rainfall over most of the Horn of Africa between February and September 2009 was 2 - 12 inches (50 - 300 mm) below average, leading to a continuation of the region's deadly 6-year drought. This drought has very likely contributed significantly to the ongoing civil wars and high levels of violence in some of the affected countries, as the affected population competes for scarce resources. The Horn of Africa has two rainy seasons, a main rainy season in April/May, and then the "short rains" of October/November. The failure of the 2009 main rainy season was the worst such failure of the past six years. The "short rains" of the secondary October/November were mostly near average over the region, fortunately, but millions of people in Kenya, Ethiopia, Somalia, Uganda and Tanzania face hunger and poverty due to withered crops, dead livestock, and dried up ponds and streams, according to the aid group Oxfam. Cattle prices have tumbled from $200 to $4 in some areas as families try to sell dying animals to buy food. Over 1.5 million animals have died in Kenya, Tanzania and Uganda, with an estimated net worth to the region of nearly $360 million, Oxfam said. Cattle represent the only wealth for many nomadic families, and the death of these animals can begin a spiral into poverty and dependency that can trap a family for generations. The those areas where the "short rains" failed--like large parts of the Turkana region of northern Kenya, which received just 12mm of rain October through December--almost one person in three is malnourished. This region of Kenya now has the opposite problem to contend with--severe flooding. Massive downpours, probably linked to El Niño conditions, hit the region December 27 - January 5, resulting in heavy flooding that killed at least 34 people and left 10,000 people homeless. The flooding was worsened by the preceding drought, which killed much of the vegetation that ordinarily would have stabilized the soil and absorbed rainwater before it could run off and create destructive floods. Thousands of cattle were killed and large areas of crops were ruined by the flooding.

The current endemic lawlessness in countries such as Somalia and Yemen are very likely due, in large part, to the extreme drought conditions that have gripped the Horn of Africa over the past six years. Thus the continuation of this drought in 2009 likely contributed to hundreds or thousands of deaths. According to the Associated Press, in addition to the war in Somalia, which has killed at least 300,000 people since 1991 and left 1/2 of the nation's 7.2 million people in need of external aid, rebel groups are battling the central government in Ethiopia, which has restricted access to aid agencies. In northern Kenya and parts of Uganda, heavily armed ethnic militias conduct cattle raids and fight over precious grazing ground and water.


Figure 1. Hydrological drought conditions over the Horn of Africa for a 1-year period (left) and 3-year period (right) as computed using the Standardized Precipitation Index (SPI). Exceptional drought on a 1-year and 3-year time scale was affecting approximately 20 million people in the Horn of Africa, according to the Global Drought Monitor.


Figure 2. Rainfall over most of the Horn of Africa between February and September 2009 was 2 - 12 inches (50 - 300 mm) below average, leading to a continuation of the deadly 6-year drought in the region. Image credit: NOAA Climate Prediction Center.

Droughts and civil war in Africa
African countries are highly dependent on rain-fed agriculture for both employment and economic production, with agriculture accounting for more than 50% of gross domestic product and up to 90% of employment across much of the continent (World Development Indicators 2009, World Bank). One third of the population of Africa lives in drought-prone areas (World Water Forum, 2000), and about 25% of the population of Africa currently experiences high water stress. Since increased drought in Africa leads to increased competition for life-giving water, and it is logical to assume that reduced rainfall will result in increases in civil war. Several scientific studies have shown this to be true. For example, Raleigh and Urdal (2007) found that "decreasing levels of freshwater are associated with higher risks on conflict". They found this relationship was compounded by higher population densities and therefore more competition for resources. Applying a similar approach, Levy et al. (2005) found that when rainfall was significantly below normal, the likelihood of conflict outbreak was higher the subsequent year. Hendrix and Glaser (2007) also found that water availability increased the chances of conflict, but that large year-to-year changes in rainfall were more important in triggering war. For example, a dry year immediately following a wet year was more likely to cause conflict than two dry years in a row, since societies have trouble adjusting to large changes in water availability.

However, we should not just be looking at precipitation, but temperature as well, since higher temperatures also contribute to drought. Higher temperatures increase crop evapotranspiration and accelerate crop development. The combined effect of these two mechanisms is predicted to reduce the yield of African staple crops by 10% - 30% per °C of warming (Lobell et al., 2008). A 2009 study by Burke et al. titled, "Warming increases the risk of civil war in Africa", found a correlation between rising temperatures and civil war in Africa. The researchers found that a 1°C warming--the amount of warming that is expected for Africa by 2030 under some of the typical IPCC climate change scenarios--has historically caused a remarkable 49% relative increase in the incidence of civil war. The authors concluded "this historical response to temperature suggests a roughly 54% increase in armed conflict incidence by 2030, or an additional 393,000 battle deaths if future wars are as deadly as recent wars". While a 1°C warming of temperature will have little impact to societies in many parts of the world, this research suggests that Africa will be very sensitive to global warming. More than two-thirds of the countries in sub-Saharan Africa have experienced civil conflict since 1960, resulting in millions of deaths and monumental human suffering. A 3°C warming by 2100 could kill an additional million people in Africa, if the conclusions of this research are correct. It's easy to think of climate change as a long way off, the researchers said in a press release, but their study shows how sensitive many human systems are to small increases in temperature, and how fast the negative impacts of climate change could be felt. "Our findings provide strong impetus to ramp up investments in African adaptation to climate change, for instance by developing crop varieties less sensitive to extreme heat and promoting insurance plans to help protect farmers from adverse effects of the hotter climate," said lead author Marshall Burke of Stanford's Program on Food Security and the Environment. One promising research development is the recent isolation of a "thermometer gene" that helps plants sense temperature. The discovery could lead to the development of food plants able to flower in much higher temperatures.


Figure 3. The forecast change in precipitation for the period 2090 - 2100, as predicted by 21 climate models used to formulate the 2007 IPCC report on climate change. The "A1B Scenario" results here are for a moderate-case warming, with a best estimate temperature rise of 2.8°C with a likely range of 1.7 - 4.4°C (5.0°F with a likely range of 3.1 - 7.9°F). Blue areas show where more than 90% of the 21 models agree that precipitation increases are likely, while orange areas show where more than 90% of the 21 models agree that precipitation decreases are likely. Image credit: Intergovernmental Panel on Climate Change (IPCC) 2007 Report.

The future of drought in Africa
Global warming theory predicts that although global precipitation should increase in a warmer climate, droughts will also increase in intensity, areal coverage, and frequency (Dai et al., 2004). This occurs because when the normal variability of weather patterns brings a period of dry weather to a region, the increased temperatures due to global warming will intensify drought conditions by causing more evaporation and drying up of vegetation. However, the models used in the 2007 IPCC report on climate change mostly predict an increase in rainfall over the Horn of Africa and the Sahel region of Africa (the southern boundary of the Sahara Desert) by the end of this century (Figure 3). The increased precipitation may act to limit the length and areal extent of droughts in these regions in coming decades. The droughts that do occur may increase in intensity, though, since temperature are predicted to increase by several degrees Centigrade. Could increased rainfall lead to a re-greening of the Sahara towards the lush conditions that existed 12,000 years ago? It is possible, argues Stefan Kropelin of the Institute of Prehistoric Archaeology at the University of Cologne in Germany. Satellite imagery has shown a greening of some southern portions of the Sahara (the Sahel) in recent years, he points out. However, some climate models show lower precipitation in coming decades for the Sahel and Horn of Africa, leading architect Magnus Lasson to propose building a 6,000 km long wall across the Sahara Desert to stop the spread of the desert. The wall would effectively be made by "freezing" the shifting sand dunes, turning them into sandstone using a bacterium called Bacillus pasteurii commonly found in wetlands. The microorganism chemically produces calcite--a kind of natural cement.

What the future ultimately holds for African climate is highly uncertain at this point. While the models used to formulate the 2007 IPCC report do a reasonable job simulating the the current climate over most of the world, they do a poor job of simulating Africa's current climate. The models put too much precipitation in southern Africa, and displace the band of heavy thunderstorms called the Intertropical Convergence Zone (ITCZ) too far south. The 2007 IPCC report concludes, "the absence of realistic variability in the Sahel in most 20th-century simulations casts some doubt on the reliability of models". In other words, since these models do a poor job simulating the current climate of the Sahel region of Africa, we shouldn't trust their predictions for the future climate.

References
Burke, M.B., Miguel, E., Satyanath, S., Dykema, J.A., and D. B. Lobell, "Warming increases the risk of civil war in Africa", PNAS 2009 106: 20670-20674.

Dai A., K.E. Trenberth, and T. Qian, 2004: A global data set of Palmer Drought Severity Index for 1870-2002: Relationship with soil moisture and effects of surface warming", J. Hydrometeorol., 5, 11171130.

Hendrix, C.S., and S.M. Glaser (2007), "Trends and triggers: Climate, climate change and civil conflict in sub-Saharan Africa". Political Geography 26:695-715.

Levy, M. A., Thorkelson, C., Vörösmarty, C., Douglas, E., and M. Humphreys (2005), "Freshwater availability anomalies and outbreak of internal war: results from a global spatial time series analysis". Paper presented at the International Workshop on Climate Change and Human Security, Oslo, Norway, June 21-23.

Lobell, D.B. et al. (2008), "Prioritizing climate change adaptation needs for food security in 2030", Science 319:607-610.

Raleigh and Urdal, 2007, "Climate change, environmental degradation and armed conflict", Political Geography 26 (6) (2007), pp. 674-694.

Sheffield, J., K. M. Andreadis, E. F. Wood, and D. P. Lettenmaier, 2009, "Global and continental drought in the second half of the 20th century: severity-area-duration analysis and temporal variability of large-scale events", J. Climate 22, pp 1962-1981.

Portlight successfully gets much-needed water filtration systems and medical supplies into Haiti
Portlight.org, the disaster-relief charity that has sprung up from the hard work and dedication of many members of the wunderground.com community, has successfully shipped medical equipment and a water filtration unit capable of supplying the needs of 3,500 people per day to the Dominican Republic. The supplies were loaded on trucks and driven into Haiti, and have reached the earthquake zone. These supplies are targeted to go to those with disabilities, or to those who are living in areas forgotten by the main aid efforts. Portlight is working through the local Catholic Church in Haiti, which is probably best positioned to deliver private aid donations to those in need. Paul Timmons, leader of the Portlight relief efforts, wrote this yesterday:

Thanks to Wunderground blogger Dak Simonton (Dakster) we were made aware of Richard Lamarque, a Haitian expatriate and 15 year veteran of the Miami Police Department who was planning to go back to Haiti this week to look for family members and to help with recovery efforts. Our on scene coordinator, Richard Lamarque, will be leaving for Haiti in a few days. He is from there, is well connected there, and has a skill set and life experiences which will be invaluable to our work there.

He will be traveling by ship. We have committed to purchasing for him a small truck to take with him. The truck will be loaded with supplies. Upon arrival, the benefits of having a vehicle on site are self evident. The truck will cost roughly $3,000 - $5,000. We have already earmarked $2000.00 for this.

We want this to be a uniquely Weather Underground community initiative. We will place WU signage on the truck...and we will be able to post photos of it at work in Haiti.

The Weather Underground community has been the genesis of our efforts. And the WU truck will be a long term, tangible symbol of the generosity of the WU community.

The next $3000 we receive will be earmarked for the WU truck. Please post this announcement to blogs...and forward it to all your WU friends.

So, please visit the Portlight.org blog to learn more and to donate. Floodman's blog has the latest info on Portlight's plan for Haitian relief. The Reeve Foundation, founded by Christopher and Dana Reeve has awarded Portlight Strategies a $10,000 Quality of of Life grant to assist in the relief efforts in Haiti. This is very big and will allow Portlight to pursue more aggressive relief efforts over the course of the next few weeks.

For those of you more interested in helping out with the long-term rebuilding of Haiti's shattered infrastructure from the quake, I recommend a contribution to Lambi Fund of Haiti, a charity that is very active in promoting reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level in Haiti. I've developed a great respect for the work they do in the country in the five years I've been a supporter.

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My next post will be Thursday.

Jeff Masters