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Rainfall Trends And Variability
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Rainfall characteristics in Nigeria have been examined for dominant
trend notably by Olaniran (1990, 1992) and by Olaniran and summer (1989,
1990). They showed that there has been a progressive early retreat of
rainfall over the whole country, and consistent with this pattern, they
reported a significant decline of rainfall frequency in September and
October which, respectively coincide with the end of the rainy season in
the northern and central parts of the country. The pattern of rainfall
in northern Nigeria is highly variable in spatial and temporal
dimensions with inter-annual variability of between 15 and 20% (Oladipo,
1993). As a result of the large inter-annual variability of rainfall,
it often results in climate hazards, especially floods and severe and
droughts with their devastating effects on food production and
associated calamities and sufferings (Oladipo, 1993; Okorie, 2003;
Adejuwon, 2004). Rainfall is one of the key climatic resources of
Nigeria. Crops and animals derived their water resources largely from
rainfall. It is considered as the main determinant of the types of crops
that can be grown in the area and also the period of cultivation of
such crops and the farming systems that can be practiced.
1.2 THE STATEMENT PROBLEM
Variations in rainfall trends are still burning issues in the research
frontiers. Global warming and climate change have been identified as the
major factors influencing rainfall trend and variability. Climate
change in particular constitute a major menace to rainfall patterns
which will directly or indirectly affects the ecosystems. According to
the Department of Ecology 2015, state of Washington, climate change
leads to rising levels of carbon dioxide and other heat-trapping gases
in the atmosphere have warmed the Earth and are causing wide-ranging
impacts, including rising sea levels; melting snow and ice; more extreme
heat events, fires and drought; and more extreme storms, rainfall and
floods.
Furthermore, scientists project that variation in rainfall
trends will continue to accelerate, posing significant risks to human
health, our forests, agriculture, freshwater supplies, coastlines, and
other natural resources that are vital to a country’s economy,
environment, and quality of life. This is because so many system are
tied to climate, a change in climate can affect many related aspects of
where and how people, plants and animals live, such as food production,
availability and use of water, and health risks. In addition, a change
in the usual timing of rains or temperatures can affect when plants
bloom and set fruit, when insects hatch or when streams are their
fullest. This can affect historically synchronized pollination of crops,
food for migrating birds, spawning of fish, water supplies for drinking
and irrigation, forest health, and more (Todd et al 2001; Dominic et al
2004; Adams & Faure 1997).
1.3 SIGNIFICANCE OF STUDY
Climate change and global warming has increased at an alarming rate as a
result of anthropogenic factors such as urbanization. Therefore study
is relevant because it will assist researchers to understand the future
consequences of rainfall variation due to climate change. This is
because climate change has been linked to the climate, which in turn
would affect where and how people make a living, how the flora and fauna
species would thrive, how food would be produced which would be
influenced by availability of water. Studies has shown that both plant
and animal require a specific amount of water for their existence,
excess or inadequate supply of water could lead to their demise. Carbon
dioxide is emitted into the atmosphere at an accelerated rate and also
the depletion of the ozone layer which has caused the earth’s surface to
be heated up.
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