For centuries Peruvian
fishermen have watched with alarm as fish stocks suddenly shrunk
every 3 to 7 years. They called this phenomenon El Niño (the
Christ Child) as it always seemed to occur just after Christmas.
El Niño is
an abnormal warming of the sea and is part of a wider phenomenon
ENSO (El Niño/Southern Oscillation). In addition to a warm
phase, El Niño itself, that typically lasts from 8 to 10
months, ENSO often also includes a cold phase, La Niña. The
whole ENSO phenomenon normally lasts from 3 to 7 years.
Over recent decades
the regular ENSO pattern has changed. Although it is not yet known
exactly what causes ENSO, it is suspected that the departure from
the regular pattern is partly linked to the greenhouse effect.
What is known with
certainty is that the phenomenon does not only influence sea temperature
off the Peruvian coast, but has an impact much further afield. It
seems that even East Africa is affected by the ENSO phenomenon.
After every El Niño drought is experienced - after a time
lag - in the Kivu region, with a subsequent reduction in plant growth.
Satellite images are
ideally suited to monitoring change processes. In this case they
are used to identify changes in sea surface temperature and abnormal
fluctuations in vegetation cover.
By revealing links between ENSO, climate and fluctuations in plant
growth in East Africa, it will not only be easier to predict when
the next El Niño will come, but also what areas will be affected
and in what way.