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El Nino looms


Latest forecasts from the South African Weather Service (SAWS) indicate that over the next few months, sea surface temperatures over the equatorial Pacific Ocean will become warmer than normal. This means the area is going into an El Nino phase which will peak toward the end of this year. Forecasts indicate a 70% probability of El Nino occurrence from mid-Spring into summer.

Typically we can expect warmer temperatures and less rainfall in our normal summer rainfall areas. The South African Weather Service predicts that El Nino is “Highly likely” to hit South Africa towards the end of 2018.

The weather is expected to follow normal winter patterns in the Lowveld, with some rainfall a possibility, during late spring and late winter, although recently, reliable scientific evidence suggests that an El Nino phenomenon is looming for Southern Africa towards the end of 2018.

For 2 months in a row now the National Oceanic and Atmospheric Administration (NOAA) has issued an El Niño watch meaning all eyes are open and forecasts thus far are looking favourable for an El Niño to develop again later this year. So with three El Nino Watches having been issued in June, July and August 2018 all eyes are open and awaiting the next month of ENSO updates from NOAA and the IRI.

South Africa is no stranger to El Niño, having been through numerous droughts in the past as a result. There has still not been nearly enough rainfall for the areas water sources to recover from one of the worst droughts in decades. The South African Weather Services recorded the 2015/16 hydrological year as the driest on record, with several weather stations recording new record-high temperatures in the Lowveld.

Intense drought has expanded and strengthened since the earliest stages of 2015/16, driven by possibly one of the strongest El Niño events of the past 50 years. It now looks like a second El Niño in four years could exacerbate the problem.

Climate acts with geology as a critical determinant of the ecological potential of a landscape. The climate of the Lowveld follows a trend from wetter and cooler weather in the south and west to drier and hotter in the areas of the north and east. These trends cut across the diverse geological belts to provide a wide variety of habitats, accounting for the great variety in the vegetation and wildlife of the region.

The consequence of rainfall being confined to only six months of the year is that the re-charging of water sources, including the water-table is confined to these crucial six months. When seasonal rainfall is seriously below average or normal, ground and dam levels fall dangerously low. Should these conditions occur in swift succession as we experienced recently in 2016/17, there may be insufficient time for natural resources to recover from each rainfall-deficit period. The effect of abnormally high temperatures is an increase in evapo-transpiration as well as stress on plant-life, whilst further depleting surface-water reserves through evaporation.

So is the climate changing?

Firstly, we need to untangle the difference between weather and climate change. In a nutshell, the difference is time. Weather is the conditions in the atmosphere over a short period of time. Climate change is how the atmosphere behaves over a longer period of time.

When we talk about climate change, that generally means changes in long-term averages of daily levels of temperature and rainfall. So we may see a change in average or typical weather over a number of years, but we can still experience extremes in any one year. According to the Intergovernmental Panel on Climate Change IPCC, an international body set up to assess the science of climate change, we can continue to expect an increase in the average global temperature. That means we will be experiencing warmer years in the future. But at the same time, we may see changes to the extremes, which could become more frequent in the case of high temperature or heavy rainfall, or less frequent in the case of extreme cold. This means that the distribution, occurrence and expected averages of our weather (for example, temperature and rain) throughout the year may change, resulting in warmer years on average with more extreme hot days, and fewer extreme cold days in the future as we are currently experiencing in the Lowveld.