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G. A. Manful and Y. Opoku-Ankomah
is essential to farmers so that they can prepare the land and sow in order to use the
early rains for crop development, especially in an environment where rainfall is not
very reliable and can fail. While onset is variable, studies show that the end of the
rainy season remains fixed, resulting in a shortening of rainy seasons. Furthermore,
the average annual rainfall amount has not changed as the rainy season duration has
decreased, meaning that there is an increase in the frequency of extreme rainfall
events. Studies carried out by Sylla et al. (2016) show that extreme precipitation
intensity will tend to increase across the basin in the near future (2036–65) to the late
twenty-first century when greater GHG forcing will produce greater precipitation
intensity. The southern part of the basin is estimated to experience an increase of
more than 30%, and the northern part an increase of 10% to 20% compared to the
reference period 1976–2005.
Dry spell duration during the rainy season or lack of continuity of the rainy season
can disrupt rain-fed agriculture. Dry spell length is defined as the maximum number
of consecutive dry days that rainfall is less than 1 mm/day. Projection of dry spell
length is very small, from −5 to 5%, for mid-level GHG forcing in the near future.
In contrast, dry spell length for high-level GHG forcing for the same period is about
10%, and by the late 21st century, projections for high-level GHG forcing could be
up to 30% in the south and middle part of the basin. Under these conditions, farmers
in the basin will have to adapt to shortened and intensified rainy seasons coupled
with dry spells, through the use of crops and cultivars that are more suitable for
such conditions. Climate change will also require the use of reservoirs to capture,
store and use the surface runoff for irrigating crops, as well as the conjunctive use of
surface water with groundwater.
5 Agriculture, Water Resources and Climate Change
5.1 Climate Change Impacts on Crop Production
and Adaptation Strategies
The latest Special Report of the Intergovernmental Panel on Climate Change indicates
global warming of 1.5 °C above pre-industrial levels. Related assessment of global
greenhouse gas emission pathways indicates that the earth is already experiencing
the adverse impacts of 1 °C of global warming through more extreme weather, among
other changes, and that warming of 1.5 °C is not ‘safe’ for most nations, communities,
ecosystems, and sectors, posing significant risks to natural and human systems due
to the likelihood of increased frequency of extreme weather events coupled with
land-use change resulting in increased frequency of flood events (IPCC 2018).
Using a statistical metric of multidimensional climate change to quantify the emergence of global climate change hotspots in the CMIP5 (Fifth phase of the Coupled
Model Intercomparison Project climate model ensemble), Diffenbaugh and Giorgi
(2012) observed that the Sahel and tropical West Africa are among the persistent
G. A. Manful and Y. Opoku-Ankomah
is essential to farmers so that they can prepare the land and sow in order to use the
early rains for crop development, especially in an environment where rainfall is not
very reliable and can fail. While onset is variable, studies show that the end of the
rainy season remains fixed, resulting in a shortening of rainy seasons. Furthermore,
the average annual rainfall amount has not changed as the rainy season duration has
decreased, meaning that there is an increase in the frequency of extreme rainfall
events. Studies carried out by Sylla et al. (2016) show that extreme precipitation
intensity will tend to increase across the basin in the near future (2036–65) to the late
twenty-first century when greater GHG forcing will produce greater precipitation
intensity. The southern part of the basin is estimated to experience an increase of
more than 30%, and the northern part an increase of 10% to 20% compared to the
reference period 1976–2005.
Dry spell duration during the rainy season or lack of continuity of the rainy season
can disrupt rain-fed agriculture. Dry spell length is defined as the maximum number
of consecutive dry days that rainfall is less than 1 mm/day. Projection of dry spell
length is very small, from −5 to 5%, for mid-level GHG forcing in the near future.
In contrast, dry spell length for high-level GHG forcing for the same period is about
10%, and by the late 21st century, projections for high-level GHG forcing could be
up to 30% in the south and middle part of the basin. Under these conditions, farmers
in the basin will have to adapt to shortened and intensified rainy seasons coupled
with dry spells, through the use of crops and cultivars that are more suitable for
such conditions. Climate change will also require the use of reservoirs to capture,
store and use the surface runoff for irrigating crops, as well as the conjunctive use of
surface water with groundwater.
5 Agriculture, Water Resources and Climate Change
5.1 Climate Change Impacts on Crop Production
and Adaptation Strategies
The latest Special Report of the Intergovernmental Panel on Climate Change indicates
global warming of 1.5 °C above pre-industrial levels. Related assessment of global
greenhouse gas emission pathways indicates that the earth is already experiencing
the adverse impacts of 1 °C of global warming through more extreme weather, among
other changes, and that warming of 1.5 °C is not ‘safe’ for most nations, communities,
ecosystems, and sectors, posing significant risks to natural and human systems due
to the likelihood of increased frequency of extreme weather events coupled with
land-use change resulting in increased frequency of flood events (IPCC 2018).
Using a statistical metric of multidimensional climate change to quantify the emergence of global climate change hotspots in the CMIP5 (Fifth phase of the Coupled
Model Intercomparison Project climate model ensemble), Diffenbaugh and Giorgi
(2012) observed that the Sahel and tropical West Africa are among the persistent