CLIMATE CHANGE : Detailed Notes & Exam Questions | Grade 12 Geography Unit 2

Hello dear student! Welcome to Unit 2. In this unit, we will study one of the most important issues facing our world today — Climate Change. You have probably heard about it on the news, but do you really understand what it means, what causes it, and how it affects Ethiopia and the world? By the end of this lesson, you will be able to answer all these questions confidently. Let us begin step by step!

2.1 Basic Concepts of Climate Change

Before we talk about climate change, we need to understand some basic concepts clearly. Many students confuse weather and climate. Can you tell the difference? Let us find out!

Weather vs. Climate

Weather refers to the short-term conditions of the atmosphere at a specific place and time. It includes temperature, rainfall, wind, humidity, and atmospheric pressure measured over a short period — such as a day, a week, or even a month. For example, saying “Today is rainy and 22°C in Addis Ababa” is describing weather.

Climate refers to the long-term average of weather conditions over a long period — usually 30 years or more. For example, saying “Addis Ababa has a mild climate with an average annual rainfall of about 1,200 mm” is describing climate.

What Is Climate Change?

Climate change refers to significant and lasting changes in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It includes changes in average weather conditions, as well as changes in the frequency and intensity of extreme weather events.

In modern usage, “climate change” usually refers specifically to the changes observed since the mid-20th century and the changes expected in the future, which are largely attributed to human activities — particularly the burning of fossil fuels.

Global Warming vs. Climate Change

Are these two terms the same? Not exactly!

Global warming refers specifically to the increase in the Earth’s average surface temperature. It is just one aspect of climate change.

Climate change is a broader term that includes global warming AND all the other changes that result from it — such as changes in rainfall patterns, rising sea levels, more frequent extreme weather events, shifts in ecosystems, and more.

The Greenhouse Effect

Now, here is a very important concept. Have you ever been inside a greenhouse used for growing plants? It gets warm inside even when it is cold outside, right? Something similar happens to our Earth!

The greenhouse effect is a natural process where certain gases in the Earth’s atmosphere trap heat energy from the Sun, keeping the Earth warm enough to support life. Without the natural greenhouse effect, the Earth’s average temperature would be about $-18°C$ instead of the current average of about $+15°C$.

Here is how it works, step by step:

1. Solar radiation (shortwave) passes through the atmosphere and reaches the Earth’s surface.
2. The Earth’s surface absorbs this energy and warms up.
3. The warmed Earth then radiates heat back as infrared radiation (longwave).
4. Greenhouse gases in the atmosphere absorb some of this infrared radiation and re-radiate it in all directions, including back toward the Earth’s surface.
5. This trapped heat keeps the atmosphere warm — like a blanket around the Earth.

Greenhouse Gases (GHGs)

The main greenhouse gases in the atmosphere are:

Think about this: Water vapor is actually the most abundant greenhouse gas, but human activities do not directly control its amount. The gases that humans are increasing significantly are carbon dioxide, methane, and nitrous oxide.

Practice Questions — Basic Concepts

Q1. Differentiate between weather and climate. Give one example of each from your local area.

Q2. Why is the greenhouse effect considered both a natural and a human-caused process?

Q3. List the four main anthropogenic (human-caused) greenhouse gases and state the largest contributor.

2.2 Trends in Global Climate Change

Now that we understand what climate change is, let us look at the actual evidence. Is the Earth really getting warmer? What do the numbers tell us?

Rising Global Temperatures

Yes, the Earth is definitely getting warmer. Scientific records show that the Earth’s average surface temperature has increased by about $1.1°C$ since the pre-industrial era (1850–1900). Most of this warming has occurred in the past 40 years, and the past 10 years have been the warmest on record.

This may sound like a small number, but remember — this is the AVERAGE over the entire planet. Some regions are warming much faster. And even a $1.1°C$ increase in global average temperature represents an enormous amount of additional heat energy trapped in the Earth’s system.

Rising Atmospheric CO₂ Concentration

Before the Industrial Revolution, the concentration of $\text{CO}_2$ in the atmosphere was about 280 parts per million (ppm). By 2023, it had risen to over 420 ppm — an increase of about 50%!

Other Observed Trends

• Rising sea levels: Global sea level has risen by about 20 cm since 1900, and the rate is accelerating.
• Shrinking ice: Arctic sea ice is declining rapidly. Glaciers and ice sheets in Greenland and Antarctica are losing mass.
• Changing rainfall patterns: Some areas are getting wetter, others drier. Extreme rainfall events are becoming more frequent.
• More extreme weather: Heatwaves, droughts, floods, and tropical storms are increasing in frequency and intensity.
• Ocean acidification: The oceans absorb about 25% of human-emitted $\text{CO}_2$, making the water more acidic and threatening marine life.

Practice Questions — Trends

Q4. Calculate the percentage increase in atmospheric $\text{CO}_2$ concentration from pre-industrial levels (280 ppm) to the current level of approximately 420 ppm.

Q5. List five observable trends that provide evidence of global climate change.

2.3 Natural and Human Induced Climate Change

Not all climate change is caused by humans. The Earth’s climate has changed naturally throughout its history. But what is different now? Let us understand both types of causes.

Natural Causes of Climate Change

The Earth’s climate has changed many times in the past due to natural factors:

1. Volcanic Eruptions: Large volcanic eruptions release huge amounts of ash and sulfur dioxide ($\text{SO}_2$) into the atmosphere. These particles form an aerosol layer that reflects sunlight back into space, causing a temporary cooling effect. For example, the 1991 eruption of Mount Pinatubo caused global temperatures to drop by about $0.5°C$ for about two years.

2. Solar Variability: The amount of energy the Sun emits changes over time in cycles (approximately 11-year sunspot cycles). When the Sun is more active, slightly more energy reaches Earth, causing some warming. However, solar changes alone cannot explain the rapid warming observed since the mid-20th century.

3. Orbital Changes (Milankovitch Cycles): The Earth’s orbit around the Sun changes over tens of thousands of years in three ways: changes in eccentricity (shape of orbit), obliquity (tilt of Earth’s axis), and precession (wobble of the axis). These cycles are responsible for the coming and going of ice ages over geological time scales.

4. Natural Greenhouse Gas Variations: $\text{CO}_2$ levels have naturally varied between about 180 ppm (during ice ages) and 280 ppm (during warm periods) over the past 800,000 years. These changes were driven by natural processes, but they happened very slowly over thousands of years — NOT rapidly like today.

Human-Induced (Anthropogenic) Causes of Climate Change

The rapid climate change we are experiencing today is primarily driven by human activities. Let us study each cause carefully:

1. Burning of Fossil Fuels: This is the NUMBER ONE cause. When we burn coal, oil, and natural gas for energy (electricity, transport, industry), we release enormous amounts of $\text{CO}_2$ into the atmosphere. This has been the dominant source of the increased $\text{CO}_2$ since the Industrial Revolution.

2. Deforestation: Trees absorb $\text{CO}_2$ from the atmosphere through photosynthesis. When forests are cut down (for agriculture, logging, or urban expansion), this natural “carbon sink” is removed. Additionally, when trees are burned or decompose, the stored carbon is released back into the atmosphere.

3. Agriculture and Livestock: Rice paddies, cattle farming, and manure management produce significant amounts of methane ($\text{CH}_4$). Cows and sheep produce methane during digestion. The use of nitrogen-based fertilizers releases nitrous oxide ($\text{N}_2\text{O}$).

4. Industrial Processes: Manufacturing cement, chemicals, and metals releases $\text{CO}_2$ and other greenhouse gases. Industrial processes also produce CFCs and other synthetic greenhouse gases.

5. Urbanization: Cities produce the “urban heat island effect” — concrete and asphalt absorb heat, buildings block wind, and human activities (vehicles, air conditioning) generate additional heat. While this is more of a local effect, it contributes to the overall warming trend.

6. Waste Disposal: Landfills produce methane as organic waste decomposes without oxygen (anaerobic decomposition).

Practice Questions — Causes

Q6. Explain how burning fossil fuels contributes to the enhanced greenhouse effect.

Q7. Why do volcanic eruptions typically cause short-term COOLING rather than warming?

Q8. “Deforestation is a double problem for climate change.” Explain this statement.

2.4 Consequences of Climate Change

Climate change affects almost every aspect of our lives and the natural environment. Let us look at the major consequences one by one. As you read, think about which of these consequences are most relevant to Ethiopia.

1. Rising Temperatures and Heatwaves

As global temperatures rise, heatwaves become more frequent, more intense, and last longer. This can cause heat-related illnesses and deaths, reduce agricultural productivity, increase water demand, and strain energy supplies (more air conditioning needed).

2. Changing Rainfall Patterns

Climate change alters the water cycle, leading to changes in when, where, and how much rain falls. Some regions experience more intense rainfall and flooding, while others experience prolonged droughts. For Ethiopia, this is particularly concerning because agriculture is heavily dependent on rainfall.

3. Rising Sea Levels

Sea levels rise due to two main factors:

• Thermal expansion: As ocean water warms, it expands (takes up more volume).
• Melting ice: Melting glaciers and ice sheets (especially Greenland and Antarctica) add more water to the oceans.

Rising sea levels threaten coastal communities, infrastructure, and ecosystems through flooding, erosion, and saltwater intrusion into freshwater supplies.

4. Melting Ice and Glaciers

Arctic sea ice, mountain glaciers, and the ice sheets of Greenland and Antarctica are all melting at accelerating rates. This not only contributes to sea level rise but also disrupts ecosystems and the livelihoods of people who depend on glacial meltwater for freshwater.

5. More Extreme Weather Events

Climate change increases the frequency and intensity of extreme weather events including:

• Tropical cyclones and hurricanes (warmer oceans provide more energy)
• Heavy rainfall and flooding (warmer air holds more moisture)
• Droughts (changing rainfall patterns and increased evaporation)
• Wildfires (hotter, drier conditions)

6. Impact on Agriculture and Food Security

Climate change threatens food security by:

• Reducing crop yields due to heat stress and water scarcity
• Shifting growing seasons and suitable areas for different crops
• Increasing pest and disease outbreaks
• Reducing livestock productivity due to heat stress

For Ethiopia, where over 80% of the population depends on rain-fed agriculture, this is a critical concern.

7. Impact on Water Resources

Changes in rainfall patterns, accelerated glacier melt, and increased evaporation affect freshwater availability. Many regions, including parts of Ethiopia, may face increased water scarcity.

8. Impact on Human Health

• Heat-related illnesses and deaths
• Spread of vector-borne diseases (malaria, dengue) to new areas as temperatures warm
• Respiratory problems from increased air pollution and wildfires
• Malnutrition from reduced food production
• Mental health impacts from displacement and disaster trauma

9. Impact on Biodiversity and Ecosystems

Many species cannot adapt quickly enough to changing conditions. Climate change causes habitat loss, shifts in species distribution, altered migration patterns, and increased extinction risk. Coral reefs are particularly vulnerable — warming oceans cause coral bleaching and death.

10. Socioeconomic Consequences

• Climate refugees and migration (people displaced by sea level rise, drought, or extreme events)
• Economic losses from damage to infrastructure and reduced agricultural output
• Increased poverty and inequality (poor communities are most vulnerable)
• Potential for conflicts over diminishing resources (water, arable land)

Practice Questions — Consequences

Q9. Explain the two main reasons why sea levels are rising due to climate change.

Q10. Why is Ethiopia particularly vulnerable to the impacts of climate change? Give three reasons.

Q11. How does climate change affect the spread of diseases like malaria? Explain the mechanism.

2.5 Adaptation and Mitigation Strategies to Climate Change

Now that we understand the problem, what can we do about it? There are two main approaches: adaptation and mitigation. Do you know the difference? Let us learn!

Adaptation

Adaptation means adjusting to the actual or expected effects of climate change. It is about learning to LIVE with the changes that are already happening or that we cannot avoid. Adaptation reduces vulnerability and builds resilience.

Examples of adaptation strategies:

• Agricultural adaptation: Planting drought-resistant crop varieties, changing planting dates, practicing crop diversification, using irrigation systems instead of relying only on rain
• Water management: Building water harvesting structures (ponds, dams), improving water use efficiency, rainwater harvesting
• Infrastructure: Building flood defenses, strengthening buildings against extreme weather, elevating roads in flood-prone areas
• Health systems: Strengthening disease surveillance, establishing early warning systems for heatwaves and disease outbreaks
• Ecosystem-based adaptation: Restoring mangroves to protect coastlines, reforestation to prevent soil erosion and regulate water flow
• Community-level adaptation: Diversifying livelihoods, community-based disaster risk reduction, traditional knowledge practices

Mitigation

Mitigation means reducing the emission of greenhouse gases or increasing carbon sinks to reduce the magnitude of climate change. It is about addressing the ROOT CAUSE — stopping the problem from getting worse.

Examples of mitigation strategies:

• Energy: Shifting from fossil fuels to renewable energy sources (solar, wind, hydro, geothermal), improving energy efficiency
• Transportation: Promoting public transport, electric vehicles, cycling, and walking instead of private car use
• Forestry: Reducing deforestation, afforestation (planting new forests), reforestation (replanting degraded forests)
• Agriculture: Improved livestock management to reduce methane emissions, better fertilizer management to reduce $\text{N}_2\text{O}$, practices that increase soil carbon storage
• Industry: Using cleaner production technologies, carbon capture and storage (CCS)
• Waste management: Capturing methane from landfills, recycling, composting organic waste

Practice Questions — Adaptation and Mitigation

Q12. Differentiate between climate change adaptation and mitigation. Give one example of each that is relevant to Ethiopia.

Q13. Explain why afforestation is considered both an adaptation and a mitigation strategy.

2.6 International Conventions and Agreements on Climate

Climate change is a global problem that no single country can solve alone. That is why countries around the world have come together to create international agreements. Let us learn about the most important ones!

1. The United Nations Framework Convention on Climate Change (UNFCCC)

Established in 1992 at the Earth Summit in Rio de Janeiro, Brazil. It is the foundational international treaty on climate change. Key features:

• Recognized that climate change is a serious global problem
• Established the principle of “common but differentiated responsibilities” — all countries have a shared responsibility, but developed countries (which historically emitted the most GHGs) should take the lead
• Set the ultimate objective of stabilizing greenhouse gas concentrations at a level that would prevent dangerous human interference with the climate system
• Has been ratified by virtually every country in the world (nearly 200 parties)

2. The Kyoto Protocol (1997)

Adopted in 1997 in Kyoto, Japan. It was the first legally binding international agreement to reduce greenhouse gas emissions. Key features:

• Set specific emission reduction targets for developed (Annex I) countries only
• Developing countries (including Ethiopia) were NOT required to reduce emissions
• Compliance mechanisms were established
• The first commitment period was 2008–2012
• The United States never ratified it, and Canada withdrew
• Had limited effectiveness due to these issues

3. The Paris Agreement (2015)

Adopted in 2015 at the COP21 conference in Paris, France. This is currently the most important global climate agreement. Key features:

• Universal participation: Unlike Kyoto, ALL countries (developed AND developing) make commitments to reduce emissions
• Temperature targets: The central aim is to keep global temperature rise this century well below $2°C$ above pre-industrial levels, and to pursue efforts to limit it to $1.5°C$
• Nationally Determined Contributions (NDCs): Each country sets its own climate action plan (NDC) specifying how it will reduce emissions and adapt to climate change
• 5-year cycle: Countries update and strengthen their NDCs every 5 years
• Climate finance: Developed countries committed to providing $100 billion per year to help developing countries with mitigation and adaptation
• Entered into force in 2016 — remarkably fast for an international treaty

Practice Questions — International Agreements

Q14. What is the principle of “common but differentiated responsibilities” and why is it important in international climate agreements?

Q15. Compare the Kyoto Protocol and the Paris Agreement in terms of country participation and approach to emission reductions.

2.7 Pillars of Climate Resilient Green Economy (CRGE) of Ethiopia

Now let us look at what Ethiopia is specifically doing about climate change. This is very important for your exam because questions about Ethiopia’s climate policy come up frequently!

Ethiopia launched its Climate Resilient Green Economy (CRGE) strategy in 2011. The CRGE has two main goals:

1. Mitigation: Achieve middle-income status through green growth (reducing GHG emissions while growing the economy)
2. Adaptation: Build resilience to the impacts of climate change

The CRGE strategy is built on four pillars:

Pillar 1: Improving Crop and Livestock Production Practices

This focuses on agricultural adaptation and mitigation:

• Promoting drought-resistant and high-yielding crop varieties
• Improving soil fertility and water management
• Reducing emissions from livestock (better feed, manure management)
• Expanding small-scale irrigation
• Shifting from traditional to modern agricultural practices

Pillar 2: Protecting and Restoring Forests

This focuses on the forestry sector as a carbon sink:

• Reducing deforestation (the main source of Ethiopia’s $\text{CO}_2$ emissions)
• Reforestation and afforestation programs
• Sustainable forest management
• The Green Legacy Initiative (planting billions of seedlings) is a recent example

Pillar 3: Scaling Up Renewable Energy

This focuses on clean energy development:

• Expanding hydropower (e.g., Grand Ethiopian Renaissance Dam — GERD)
• Developing geothermal energy (especially in the Rift Valley)
• Promoting solar and wind energy
• Improving energy efficiency
• Expanding electricity access to rural areas

Pillar 4: Using Energy-Efficient Technologies in Transport, Industry, and Buildings

This focuses on reducing energy demand and emissions from non-agricultural sectors:

• Promoting fuel-efficient vehicles and public transport
• Using energy-efficient industrial processes
• Building energy-efficient homes and buildings
• Reducing reliance on biomass (wood, charcoal) for cooking and heating
• Promoting clean cooking technologies (e.g., biogas, electric stoves)

Practice Questions — CRGE

Q16. State the four pillars of Ethiopia’s Climate Resilient Green Economy (CRGE) strategy and give one specific action under each pillar.

Q17. Why is Ethiopia’s CRGE strategy described as treating climate change as an “opportunity” rather than just a “problem”?

Unit Summary Review

Q18. Briefly describe the complete chain from human activities to climate change consequences, using the following terms: fossil fuels, greenhouse effect, $\text{CO}_2$, global warming, climate change, consequences.