Tuesday, December 22, 2015

El Nino summary

It's been an interesting journey writing this blog so this is just a quick summary of my thoughts on El Niño Southern Oscillation and its importance for water and development in Africa.

Firstly, El Niño Southern Oscillation is a fascinating natural phenomenon, and I've learned so much about how it works and where it impacts in the world. Particularly since El Niño Southern Oscillation occurs in the Pacific Ocean and Africa has no direct connection, it's been interesting for me to learn how something in one part of the world can come to affect regions halfway across the world.

Secondly, recognition of the importance of El Niño Southern Oscillation has been obviously growing; from being closely reported in the news, to even making an appearance on the Ellen Degeneres TV show! I think this is good news for research and for people seeking to understand how climate changes might affect them. The impacts of El Niño and La Niña years can also be used to further understanding of how long-term changes to climate might impact different areas. For example, Epstein (2000) explains how the meteorological changes that occur under El Niño years can simulate changes under warming temperatures and help in assessing the likely impacts. His particular study focuses on health, and how waterborne disease outbreaks are associated with the extreme weather of El Niño that could soon be commonplace due to increasing global temperatures.

Thirdly, with predictions that there will be an increased frequency of El Niño events due to climate change, it is important that research into the potential impacts is further developed. More countries may be affected by future El Niño events, so it is beneficial for all to study the results of historic El Niño events (such as the one just passed/that we're in the middle of this winter) and improve projections of impacts for future El Niño events.

Finally, understanding how El Niño Southern Oscillation events can affect communities is a part of mitigating for future climate changes. As Nick describes in his blog post, building resilience to changing climate is important, particularly for smallholder farmers. Understanding the likely conditions El Niño or La Niña could create is part of this. Therefore, initiatives such as the Gro Futures El Niño Monitoring in Tanzania, are important for mitigation and adaptation to climate change. This initiative looks to measure how heavy rains associated with the El Niño Southern Oscillation replenish groundwater resources in Tanzanian wellfields. As stated, this will bring better understanding to sustainable management of the wellfield, as well as inform "strategies for amplifying replenishment". Studies like these are vital to continuing to measure and understand El Niño effects, particularly as they can be linked to high variability that is unsustainable and unpredictable.

El Niño Southern Oscillation events still remain rather mysterious and hard to predict; each El Niño or La Niña year results in different consequences and patterns and the spatial distribution of effects can be difficult to predict. I hope with further studies we will begin to understand this fascinating phenomenon in more depth, and be better equipped to react and plan for its potentially deadly effects.

Friday, December 11, 2015

El Niño effects on water access

Welcome back to El Niño 101! Today I want to share some thoughts I have about how ENSO can affect the ability of populations to access water. Just as a quick recap, access to safe water is defined by the United Nations as "the proportion of population with access to an adequate amount of safe drinking water located within a convenient distance from the user's dwelling". The World Health Organisation defines an "adequate amount" as 20-40 litres per person per day, and the quality of the water obviously plays a major role in being considered "safe".

Therefore, I think the biggest challenges that ENSO can create for access to water are affecting water quality and the damages to the socio-economic structure of a population. This area may be less researched than the scientific side of ENSO and the direct output of El Niño/La Niña years (particularly rainfall), but it highly important for development and water management.

Last month, Unicef released a statement to emphasise the impact the El Niño winter and potential La Niña year could have on vulnerable communities. They summarised the threat to Africa as follows: "An estimated 11 million children are at risk from hunger, disease and lack of water in eastern and southern Africa as a result of a strengthening El Niño". Hunger, disease and adequate water for living are all linked back to having good access to safe water supplies. Firstly, as the previous blog post mentions, the variability of rainfall under ENSO conditions can cause problems for water availability for both domestic and agricultural use. If we are to expect more and more El Niño years, southern Africa must be prepared for droughts or else suffer a major shortage of water.


Secondly, waterborne diseases can be massively exacerbated by rainfall variability and contamination. The IPCC acknowledges that the frequency and duration of cholera outbreaks
are associated with heavy rainfall in, "with a possible association with the El Niño-Southern Oscillation", in western African and southern African countries. Cann et al. (2013) also studied weather events and waterborne diseases and suggest that "extreme water-related weather events" (such as El Niño) lead to the highest numbers of cases of waterborne illness. ENSO-related outbreaks of cholera were also highly linked to extreme water temperature change due to Vibrio cholerae having an increased growth rate at increased temperatures. In general, they summarised that extreme water-related events (one-off or recurring) represent a risk to public health. Further studies of specific countries and diseases, such as de Magny et al. (2012), Mendelsohn and Dawson (2008), Mabaso et al. (2006) and Kilian et al. (1999), all agree that increased rainfall due to ENSO seemed to result in higher incidence of waterborne diseases like cholera and malaria in Africa. This also seems to ring true in other parts of the world affected by ENSO, such as India and Sri Lanka. However, Patz et al. (2000) astutely reminds us all that ENSO is not responsible for all epidemics, such as the Ethiopian epidemics in 1953 and 1958, neither of which were El Niño years. In fact, Patz and Lindsay (1999) argue that in some cases, heavy rainfall could even wash larvae from breeding sites, thus reducing the incidence of malaria. Regardless of the patterns of disease, it is obvious that when water sources are contaminated (such as with cholera), or when incidence of other diseases are high, it is difficult for that population to have adequate access to safe water for use.

Thirdly, ENSO can also indirectly affect access to water through socio-economic and health issues. For example, severe droughts from ENSO conditions can lead to increased malnutrition and a threat to food security, which results in difficulty accessing safe water (as one can see, this is a vicious loop as little access to safe water can lead to problems that result in a decreased ability to ensure a safe water supply for oneself). Food security is a particularly important aspect that can be adversely affected by ENSO through highly variable rainfall for agricultural production. If water availability for agriculture is reduced, domestic consumption may be sacrificed in order to meet food demands, thus reducing access to safe water. Cane et al. (1994) used sea surface temperature to forecast maize yield in Zimbabwe and found that there was a strong correlation between the El Niño Index and maize yields, so much so that it correlated stronger than the El Niño Index and rainfall did. They found that more than 60% of the variance in maize yield in Zimbabwe was accounted for by sea surface temperatures in the eastern equatorial Pacific Ocean - where El Niño conditions are created.

Other socio-economic impacts of ENSO, other than health and food, include the economy, education and infrastructure. Cashin et al. (2015) conducted a study of the macroeconomics of El Niño, observing that South Africa (among many other countries such as Chile, Indonesia and Australia) see a "short-lived fall in economic activity" as a response to a typical El Niño event. This is mainly due to the increased in temperature and persistent dry conditions of El Niño, which impact agricultural production (which makes up 10% of South Africa's GDP). In addition, after particularly strong El Niño (and to some extent, La Niña) events, there may be other costs, such as the estimated $1.8 billion in damages of infrastructure and property in Kenya following the 1997-1997 El Niño flooding. And it isn't just flooding or droughts that cost money; ENSO can influence storms across Africa that can also contribute to costs. Donnelly and Woodruff (2007) show that while a strong El Niño year can hinder hurricane development through increased vertical wind shear, a strong La Niña year could increase North Atlantic hurricane activity. Damages to the economy can result in reduced access to water, particularly in the users are reliant on paying for water through vendors or kiosks. Infrastructure damage not only hinders access to water through costs but through the potential to damage water supply systems, roads to access water supply/health treatments, and other vital components of having an adequate supply of safe water to live. ENSO can also affect education through damage to infrastructure, limiting the ability of people to access areas, or in the worst cases, transforming school facilities into emergency shelters due to extreme events like floods. Education is not only vital for development, but it can contribute to improving access to water through NGOs like Water Aid, whose educational element is an important part of improving access to safe water in a sustainable manner.

Finally, the threats of ENSO conditions can leave many families crippled through deaths that could be related to floods, mudslides, famine, storms, or through separation due to a need to seek work elsewhere. Unicef emphasises that this could leave children vulnerable, as well as putting pressure on them to source water. Fewer members in a family evidently reduces access to water and further exacerbate all the problems already mentioned.

It can be very disconcerting to think about how ENSO events can impact the real ability of populations to access safe water and lead their everyday lives. Weather and climate are perhaps the most important aspect of water resources and it is therefore incredibly useful to have good prediction and forecasting systems in place to understand the potential impacts of ENSO on different regions around the world. I've really enjoyed learning about this and I think it's a positive sign that El Niño is becoming a more discussed topic in news and mainstream media and not just in the scientific and academic community. Hopefully our understanding of ENSO (not just El Niño but also La Niña!) continues to improve so we can better plan and mitigate for future ENSO events.

Thursday, December 3, 2015

El Niño effects on water availability

So now I hope we all have a better understanding of how El Niño Southern Oscillation can affect weather globally, and the two extremes that are El Niño and La Niña. To tie this in with the theme of water and development in Africa, the next two blogs will be exploring some ways ENSO can affect water resources in Africa.

Water resources can be impacted by ENSO through many different factors (see the table below for a quick summary). There are aspects (conditions) that ENSO affects like sea temperature, droughts, rainfall variability and storms. These natural changes (ENSO is a natural phenomenon after all, but arguably likely to be intensified due to climate change) can exacerbate man-made aspects of water resources such as flooding in poorly drained cities, contamination of water sources (due to flooding or drought) and more. This blog post will focus on water availability, or how ENSO can affect natural variability in water (such as rainfall), and the next blog post will focus on water access, or how ENSO can affect the ability of people to access water resources for use (such as contamination).

Condition:
Effect:
  • warmer sea temperatures
  • plankton and fish kills in coastal waters
  • lower sea levels
  • exposure of underwater, fragile coral reefs
  • higher sea levels
  • salt water intrusion into water supplies
  • coastal erosion and damage to shoreline and
    property
  • flooding/increased rainfall
  • contamination of drinking water systems
  • flooding of wastewater systems
  • contamination of recreational sites and estuaries
  • waterborne illness
  • droughts
  • crop failure
  • increase in disease due to lack of water for
    sanitation and hygiene
  • blowing dust
  • pollution of viable water sources
  • decrease in near-shore coastal water quality
  • warmer, wetter, more humid weather
  • boom in mosquito population and subsequent
    increase in malaria and dengue fever
  • boom in termite population resulting in damage
    to buildings and homes























  • In Africa, east and southeast Africa are the main areas affected by ENSO. During an El Niño winter, southeast Africa tends to be drier and warmer, and east Africa tends to be wetter. During a La Niña winter, the opposite occurs, with southeast Africa wetter than normal and east Africa drier than normal. These generic changes are by no means easily predicted and vary hugely within El Niño and La Niña years (and one must also remember that El Niño and La Niña years are not easily predicted either, nor does a La Niña year necessarily follow an El Niño year or vice versa). But this general pattern that occurs with ENSO dictates changes in weather that affect water resources.

    For Africa, the biggest effects I would say ENSO has on water availability are affecting rainfall and influencing droughts. However, as I mentioned, this is highly variable even within El Niño years. For example, the 1997-1998 El Niño that is argued to be the last "truly massive" El Niño we've seen globally, had less of a disastrous effect on southern Africa than expected. The 1997-1998 El Niño may have cost an estimated $35 billion in destruction and 23,000 deaths around the world, but areas like southern Africa were surprised when the predicted catastrophic drought failed to materialise and seasonal rainfall was largely near or even above average. This is argued to have been because of a warm sea surface temperature anomaly in the South Atlantic that created upper easterly winds to counteract the ENSO-induced upper westerly winds over the Atlantic, and shielded southeastern Africa from ENSO (Jury, 1998).

    In general though, ENSO tends to lead to a decrease in rainfall in southeastern Africa and drought periods. Rouault and Richard (2003) used the Standardised Precipitation Index to quantify intensity and spatial extension of droughts that have occurred in the 93 rainfall "districts" of the South Africa Weather Service. They found that there have been 10 dry years with an average of 44 dry districts since 1962, seven of which were El Niño years (1966, 1970, 1973, 1979, 1983, 1987, 1992 and 1995). This evidently shows that El Niño can play a major role in whether or not there are droughts in southeastern Africa. Available water resources during droughts are diminished as the water table drops, and effective management is crucial. In southeastern Africa, droughts can put pressure on important water sources like rivers, aquifers, dams and boreholes. This region of Africa is also historically dependent on rainfall for agriculture, and more intense and more frequent drought periods have large impacts on agriculture.


    Cartoon depicting the unpredictability of El Niño

    On the other end of the spectrum, ENSO can also bring bouts of increased rainfall and flooding to Africa. In the news recently, the 2015 El Niño has brought "the worst drought in 30 years" to Ethiopia, at the same time as flooding and landslides to its neighbour Somalia. This variability within the area of eastern Africa shows how harsh and uneven ENSO can be. Eastern Africa in particular is vulnerable to huge variability of rainfall during El Niño years, with coastal countries like Somalia and Kenya facing increased rainfall and areas more inland like Ethiopia and South Sudan facing drought. Have a look at this great snapshot of predicted El Niño impacts on eastern Africa.

    Therefore, water availability can be increased during El Niño (and decreased during La Niña) in eastern Africa due to rainfall. This can be highly variable though as more rain does not always mean more water resources that are available for use. For example, flash floods and corresponding mudslides can occur in eastern Africa during the rainy season created by El Niño, thus damaging crops and livestock. Eltahir (1996) studied the natural variability of the flow of the Nile River and suggests that 25% of natural variability is associated with ENSO. This was due to a positive correlation of sea level pressure anomalies in the Ethiopian Plateau (the source of the Nile) and at Darwin, Australia (where surface pressure can be an indicator of the onset of ENSO). A positive anomaly in annual sea level pressure over the Ethiopian Plateau is associated with decreased rainfall and hence a negative anomaly of the annual flow of the Blue Nile. Since the Blue Nile originates in Ethiopia (and contributes most of the inter-annual variability of the Nile), the negative relationship between ENSO and the flood of the Nile can have a strong forcing on water availability in Ethiopia.

    This look into southern Africa and eastern Africa and how they respond to ENSO events gives an indication to how something as simple as changing rainfall patterns due to ENSO can have a major effect on water availability. In the future, I think it's vital that countries have plans for potential El Niño and La Niña years. Governments, farmers, development agencies and other interested parties desperately need to have prediction systems, mitigation strategies and continuing research to understand ENSO and to ensure water availability for all. The scary thing is that El Niño and La Niña events are occurring more frequently, so much so that even if one extreme follows the other (such as increased rainfall following drought due to La Niña following El Niño), they cannot compensate for each other. Jennifer Olson sums it up: "Those kinds of shocks to the system, whether it's drought or flooding, are usually just enough that people can’t recover anymore.”