UNIT 6:CLIMATE IN RWANDA
Key Unit competence: The student-teacher should be able to analyze the climate of Rwanda and its impact on human activities.
Introductory Activity
Carefully study the photographs below and answer the questions that follow:
1. Explain what the above photographs represent.
2. Give the difference between weather and climate.
3. Identify the main effects of climate change.
4. Describe the main seasons of Rwanda.
6.1. Climatic zones and factors influencing climate in Rwanda.
Learning activity 6.1
1. What is the key factor in distinction of climatic zones in Rwanda?
2. Explain why Rwanda experience tropical and temperate climate and not equatorial despite its proximity to the equator.
3. Describe how altitude greatly influences the climate of Rwanda.
6.1.1. Climatic zones of Rwanda
Climate refers to the average weather condition of a place, measured and recorded over a very long period of time usually 30-45years while weather is the state of the atmosphere of a specific area for a short period of time.
Although located near to the equator, Rwanda does not experience a hot equatorial climate. It usually has a tropical climate, tempered by altitude. It is a tropical climate with a hot dry season.
The variation of temperature and rainfall in various regions of the country is governed by differences in altitude.
Climatic zones of Rwanda
Source : Oxford (2010), 3600 Atlas for primary, East Africa, Nairobi, Kenya.
According to the landforms and the distribution of rainfall, Rwanda is divided into the following climatic regions:
1. The Eastern plains (1000-1500 m) This region is very hot and fairly dry. It presents the average annual temperature ranging from 20o Cto 22o C with an annual rainfall between 700 mm and 1100 mm.
2. The central plateau region (1500 - 2000 m) This zone is moderately humid and fairly temperate, characterized by an average temperature between 19o C and 20o C. The central plateau has moderate rain. Rainfall is between 1000 and 1200 mm.
3. The Western and Northern highland region (the Congo-Nile peak and Birunga region) between 1800 m and 4507 m Rainfall is abundant and always above 1200 mm.
4. The Lake Kivu side region (1500-2000 m) This region is warm and moderately dry but temperatures are moderate on the lakeside. Rainfall significantly decreases with altitude. Briefly, as the altitude increases, temperature decreases and rainfall increases.
6.1.2. Factors that influence the climate of Rwanda
The principal factors that control the climate of Rwanda are explained below: Altitude: The distribution of temperature and rainfall in Rwanda is influenced by the altitude. It provokes the orographic or relief rainfall. As the altitude of Rwanda increases from east to west, the amount of rainfall also increases from east to west. It stops increasing at the Congo-Nile crest where it begins to decrease as the air descends to the sides towards Lake Kivu.
Latitudinal position: The latitude of Rwanda (1⁰ 04’-2⁰51’ South Latitude) allows the vertical position of sun’s rays to strike directly to the ground and heat it. The intense heat on the ground causes the humid warm and unstable air mass to rise, cool and condense into clouds that later give convectional rainfall.
Vegetation: The presence of vegetation has had a great impact on the climate of Rwanda. It has contributed a lot to the climatic variations presently witnessed. In areas where there are dense forests such as Nyungwe, Gishwati and mukura, more rainfall is experienced than in the savannah grassland areas of the Eastern plateau.
Presence of water bodies: The absence of large water bodies in Rwanda has contributed a lot to the occurrence of the type of climate experienced in the country.
Water bodies play a great role in the modification of climate where convectional rainfall is created through the hydrological cycle.
Influence of winds: Local winds that blow in Rwanda are Breezes. There are land and lake breezes, mountain or hill and valley breezes. They modify temperature and increase rainfall in Rwanda.
Human activities: Human activities like mining, urbanization, rural settlement, industries, transport, agriculture, etc. have great impact on the climate of Rwanda because they lead to deforestation, pollution, draining of wetland, degradation of the soil, etc.
Application activity 6.1
1. Explain how landlockedness of Rwanda affects its climate.
2. Explain how Lake Kivu side region influence the climate of the surrounding areas.
3. With reference to the human activities, explain how they influence the climate positively in Rwanda.
6.2. Climate change and global warming
Learning activity 6.2
1. Distinguish between climate and climate change.
2. Explain the term global warming.
3. Describe any three effects of global warming.
6.2.1. Climate change
i) Definition of climate change
Climate change: It is a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.
ii) Causes of climate change
Human activities have been mostly responsible for atmospheric alterations.
Human activities contribute highly in atmospheric pollution leading to the change in the state of the atmosphere.
The atmosphere is polluted by human activities in the following ways:
• Increased emission of greenhouse gases (CO2 , CH4 , N2 O, HFCs). Greenhouse gases include carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs). Greenhouse gas concentrations have increased in the atmosphere and human activities are the primary cause.. Other sources of emissions of greenhouses gases are industries, energy, waste, agriculture activities and volcanic eruptions.
Forest and grassland fire: it increases the concentration of carbon dioxide in atmosphere resulting from the burning of trees and grassland which are cut and put under fire for different purposes.
• Deforestation and land use changes: When people clear large areas of forests and grasslands for cooking or construction, they reduce the main sink of carbon dioxide from atmosphere by photosynthesis. Deforestation leads to the increase of carbon dioxide, and eventually to the increase of temperature on the earth surface.
• Industrial developments: Industries which are involved in cement production, fertilizers, coal mining activities, oil extraction produce harmful greenhouse gases. The CO2 emissions are generated by mineral industries, metal industries, and non-energy products from fuels and solvent use.
• Waste and landfills: Landfills filled with garbage produce carbon dioxide and methane gas contributing significantly to greenhouse effect. GHG emissions from waste are the emission from solid waste disposal site; biological treatment of solid waste and waste incineration.
• Urbanization: The urban activities contribute in increasing the concentrations of greenhouse gases in atmosphere leading to the rise in temperature.
• Energy: the energy in buildings encompasses the energy consumption for cooking, heating (room heating, water heating), cooling (air-conditioning), lighting and operating electrical appliances. CO2 emissions were mainly generated from combustion activities of liquid fuels in transportation and electricity generation, while emissions of CH4 and N2 O were mainly generated from combustion activities of biomass in households and institutions/commercial activities.
• Increase in Population: It is obvious that this last two decades the people have been huge increase in the population. Now, this has resulted in increased demand for food, cloth and shelter.
• New manufacturing hubs have come up with cities and towns that release some harmful gases into the atmosphere which increases the greenhouse effect. Population growth is also one of the drivers of the growth in greenhouse gases that contribute to climate change.
• Agriculture activities: the main gases emitted by agricultural activities are: Carbon dioxide (CO2 ) which is released by burning agricultural wastes; Methane (CH4 ) which is associated with cattle and livestock manure and Nitrous oxide (N2 O) which comes from using fertilizer and manure.
iii) Effects of climate change
Rwanda experiences some rainfall events that cause unexpected flooding and catastrophic events such as landslides etc. These extreme events are attributed to climate change. The figure below represents some effects of extreme rainfall events of climate change in Rwanda.
The following are effects of climate change in Rwanda:
• Significant increase in precipitation in highland.
• Presence of strong wind which cause the displacement of people and the destruction of crops and other infrastructures including houses, classrooms.
• The landslides and floods caused by heavy rainfall.
• The significant increase in mean annual temperatures.
• Prolonged droughts episodes have been registered in Rwanda notably in eastern and south-eastern regions.
• More occurrences of lightning combined with the thunderstorms causing loss of lives.
• Extensive damage to water supply and sanitation infrastructure, including pipelines and pumping stations.
• Roads and houses damaged from flooding. • Losses of crops and stock from heavy rains and floods.
• Food shortages from crop losses affected children’s health.
• Increased incidence of water-borne diseases following flooding.
• Schooling of children disrupted by destroyed roads, as well as demands for children to trek for clean water.
• Reduced hydropower production from low water levels.
• Increased time spent searching for water in rural areas.
6.2.2. Global warming
Global warming is a phenomenon of climate change characterized by a general increase in average temperatures of the Earth, which modifies the weather balances and ecosystems for a long time. It is directly linked to the increase of greenhouse gases in our atmosphere, worsening the greenhouse effect.
In short, Global warming refers only to the Earth’s rising surface temperature, while climate change includes warming and the “side effects” of warming like melting glaciers, heavier rainstorms, or more frequent drought.
i) Causes of global warming
• Global warming occurs when greenhouse gases together with other air pollutants are increased in the atmosphere and keep or absorb sunlight and solar radiation that have reflected from the earth’s surface.
• The massive use of fossil fuels is obviously the first source of global warming, as burning coal, oil and gas produces carbon dioxide the most important greenhouse gas in the atmosphere as well as nitrous oxide
• Deforestation has a major role in climate change. Trees help to reduce the concentration of CO2 from the atmosphere.
• Another cause of global warming is intensive farming, including the use of fertilizers and livestock. For example Cattle and sheep produce large amount of methane when digesting their food, while fertilizers produce nitrous oxide emissions.
• Waste management methods like landfills and incineration emit greenhouse and toxic gases including methane that are released into the atmosphere.
• Mining and industry activities: contribute to the increase of greenhouse gas emissions in atmosphere.
ii) Greenhouse gases effects
• The sunlight reaches the Earth coming from the Sun. About half of the light reaching Earth’s atmosphere passes through the air and clouds.
• Some energy is absorbed and then reflected back in the atmosphere in form of infrared heat.
• Most of the heat is absorbed by the greenhouse gases and reflected in all direction for warming the earth.
iii) Effects of global warming
Below are some consequences of Global Warming:
1. On biodiversity
The increase of temperatures and the climate is one of the major changes responsible to disturb the ecosystems, modify the conditions and cycles of plant reproduction and lead to the loss of some species.
The scarcity of resources and climate change contribute to habitats destruction and influence migration of animals.
2. On oceans
Because of global warming, ice are melting massively at the poles and increasing the sea level.
3. On the weather
Until now, meteorologists and climatologists around the world have been observing the effects of global warming on the weather phenomena. The effects are huge like more droughts and heat waves, more precipitations, more natural disasters like floods, hurricanes, storms and wildfires.
4. On humans
Global warming leads to climate change which has impacts on human health and activities. The scarcities of natural resources give rise to new conflicts. Rising of sea levels, floods and increased temperature cause population migration.
6.2.3. Adaptation and mitigation measures for climate change
Mitigation measures:
Mitigation is an action to reduce the sources or to increase the sinks of greenhouse gases such as:
• Use of improved cooking stoves
• Use of energy saving material in household (Lamps, Warming water with solar heaters);
• Verification of control technique automobile;
• Public transport;
• Afforestation, reforestation and agroforestry;
• Reduce uncontrolled forest and grassland burning.
Adaptation measures: refer to measures to reduce potential harm, or vulnerability, resulting from actual and expected changes in climate and extreme weather events. The following are the adaptation measures:
• Planting drought-resistant crops to better in drier climate;
• Use of organic manure;
• Radical terraces and Anti-erosive measures;
• Irrigation;
• Use of weather and seasonal forecasting, meteorological advisories and guidance;
• Rainwater harvesting (Installation of water tanks);
• Housing (imidugudu etc.) planning with consideration of Climate Change impacts (floods, landslides, strong winds, lightening etc.);
• Roads protection;
• Information systems to support early warning systems and proactive planning;
• Buy crop insurance.
Mitigation is attempting to slow the degree of warming and adaptation is reducing vulnerability to hazards.
Application activity 6.2
1. Describe the effects of climate change in Eastern and Western provinces of Rwanda.
2. Describe how the following activities have an impact on weather and climate:
a) Urbanisation
b) Deforestation
3. Suggest measures that should be taken to minimize the effects of global warming.
Skills lab
After completing this unit about climate, climate change and global warming, give advice to the people who mostly depend on weather patterns.
End unit assessment
1. Explain how climate is different from climate change.
2. With examples, explain the importance of weather forecasting
3. Explain the impact of relief on the climate of Rwanda.
4. Describe factors that cause the typical weather we experience in each season.
5. Discuss the source of greenhouse gases and how can we reduce the increase of them in the atmosphere.