Lesson Notes By Weeks and Term v4 - SHS 1
CLIMATE VARIABILITY
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CLIMATE VARIABILITY
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Subject: Agricultural Science
Class: SHS 1
Term: 1st Term
Week: 20
Grade code: 1.3.2.LI.2
Strand code: 4
Sub-strand code: 1
Content standard code: 1.3.2.CS.2
Indicator code: 1.3.2.LI.2
Theme: AGRICULTURE AND CLIMATE
Subtheme: CLIMATE VARIABILITY
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This lesson introduces the concept of climate variability and distinguishes it from the broader term, climate change. We will explore the natural and human factors that cause our climate to fluctuate from year to year. Most importantly, we will examine how these unpredictable changes—such as late rains, severe harmattans, or unexpected droughts—directly affect farming, fishing, and livestock rearing in Ghana. Understanding climate variability is crucial for developing smarter, more resilient agricultural practices that can ensure our food security now and in the future.
A. Weather, Climate, Climate Variability, and Climate Change
To understand climate variability, we must first be clear about some basic terms. Weather: This is the condition of the atmosphere at a specific place and time. It is short-term. *Example:* "Today in Kumasi, it is cloudy and humid with a high chance of rain this afternoon." Climate: This is the average weather pattern of a place over a long period, usually 30 years or more. *Example:* "The climate of Northern Ghana is characterized by a single rainy season (May-October) and a long, dry harmattan season." Climate Variability: This refers to the short-term fluctuations or "ups and downs" of the climate around its long-term average. It is the year-to-year variation in climate. *Example:* The harmattan in 2021 was mild, but in 2022 it was very severe, with dense dust for many weeks. The long-term average climate hasn't changed, but those two years were very different. This is variability. Climate Change: This is a long-term, continuous shift in the average weather patterns of a region or the entire planet. The long-term average itself is changing. *Example:* Scientists have observed that over the last 50 years, the average annual temperature in Ghana has been steadily increasing.
Simple Analogy: Imagine your grades in Agricultural Science. Weather: Your score on today's quiz (e.g., 8/10). Climate: Your average grade over the entire school year (e.g., you are a B-average student). Climate Variability: One term you get a C, and the next term you get an A. Your performance varies, but your overall average for the year is still a B. Climate Change: Over three years of SHS, your average grade slowly and consistently drops from a B to a C. The long-term average has shifted. B. Causes of Climate Variability
Climate variability is caused by a combination of natural and human factors. Natural Causes: El Niño-Southern Oscillation (ENSO): This is one of the most significant natural causes. It is a cycle of warming (El Niño) and cooling (La Niña) of the surface waters of the eastern Pacific Ocean. How it affects Ghana: During an El Niño year, West Africa, including Ghana, often experiences warmer and drier conditions. This can lead to reduced rainfall and potential drought, especially in the north. A La Niña event can sometimes bring heavier-than-normal rainfall. Volcanic Eruptions: Large volcanic eruptions (like those in the Philippines or Indonesia) can spew huge amounts of ash and sulphur dioxide into the atmosphere. This cloud can block sunlight, leading to a temporary cooling of the Earth's surface for one or two years. Changes in Ocean Currents: The oceans store and transport vast amounts of heat. Slow, natural changes in major ocean currents can alter regional weather patterns for several years at a time. Human-induced (Anthropogenic) Causes: While these are the main drivers of long-term climate change, they also increase the intensity and frequency of short-term extreme events (variability). Deforestation and Land Use Change: Cutting down forests, especially for farming, charcoal burning, or illegal mining ('galamsey'), has serious effects. Trees release moisture into the air (transpiration), which contributes to local rainfall. Removing them can make an area drier and hotter. Bare land increases runoff, making floods more severe when rain does fall. Greenhouse Gas Emissions: Burning fossil fuels (in cars, 'trotros', factories) and other activities release gases like carbon dioxide. These gases trap heat in the atmosphere, leading to warmer temperatures and more energy in the climate system. This extra energy can fuel more extreme weather events, like more intense rainstorms or longer heatwaves. C. Effects of Climate Variability on Agriculture in Ghana