Geography (9230) | Climate change

🌍 Comprehensive Study Notes: Climate Change (Geography 9230)

Welcome, Future Geographers!

Hi there! This chapter might seem big, but don't worry—we'll break it down into simple, easy-to-understand parts. Climate change is one of the most important topics in modern geography, and understanding it is key to dealing with future natural hazards.

We will explore what climate change is, why it happens, and how we are trying to manage this massive challenge. Ready? Let’s dive in!

1. Understanding Climate Change

What is the Difference Between Weather and Climate?

This is the first concept you must nail down. It’s simple, but often confused!

• Weather: What is happening outside right now, or over a short period (e.g., cloudy today, raining tomorrow). Think of it as your mood.
• Climate: The average weather conditions measured over a very long period, usually 30 years. Think of it as your personality—long-term and stable.

Key Terms to Define

1. Climate Change: A significant, long-term shift in the average weather patterns and temperatures globally or regionally. This is natural, but humans are now speeding it up dramatically.

2. Global Warming: Specifically refers to the recent, ongoing rise in Earth’s average temperature, mainly caused by human activity. It is the most significant observable aspect of climate change.

2. The Earth’s Energy Blanket: The Greenhouse Effect

To understand why the planet is getting warmer, we need to understand how the atmosphere traps heat. This process is called the Greenhouse Effect.

a) The Natural Greenhouse Effect (The Good One!)

The Earth has a natural layer of gases (like carbon dioxide) that act like a blanket.

Step-by-Step Process:

1. The Sun sends shortwave radiation (light and heat) to Earth.
2. The Earth absorbs this energy and warms up.
3. The Earth then sends longwave radiation (heat) back into space.
4. Greenhouse Gases (GHGs) in the atmosphere trap some of this longwave radiation, keeping the planet warm enough for life (+15°C).

Analogy: The natural GHE is like the blanket you need to stay warm on a cool night. It keeps us alive!

b) The Enhanced Greenhouse Effect (The Problem!)

The "enhanced" effect means humans are adding too many Greenhouse Gases to the atmosphere.

When we add extra gases, the blanket gets thicker. It traps too much heat, leading to Global Warming.

Did you know? The two most important human-caused Greenhouse Gases are:

• Carbon Dioxide (CO₂): Primarily from burning fossil fuels (coal, oil, gas).
• Methane (CH₄): From livestock farming (cows!) and decomposing waste in landfill sites.

3. Why is the Climate Changing?

Changes in climate have two main origins: natural factors and human factors.

a) Natural Causes (Minor in recent warming)

Over millions of years, natural changes have caused ice ages and warmer periods.

1. Variations in Solar Activity:

The Sun's output of energy is not perfectly steady. Periods of increased solar flares (sunspots) can mean slightly more heat reaches Earth. However, scientists agree this has had a very small impact on the recent warming trend.

2. Volcanic Eruptions:

Large, explosive eruptions (like Mount Pinatubo in 1991) throw huge amounts of ash and dust into the atmosphere. This dust acts like a sunshield, reflecting sunlight back into space, usually causing a temporary cooling effect for a few years.

b) Human (Anthropogenic) Causes (Major Cause Since 1750)

Human activity has drastically increased the concentration of Greenhouse Gases.

Key Human Activities Causing GHGs:

1. Burning of Fossil Fuels:

• When we burn coal, oil, and natural gas to power factories, cars, and homes, we release vast amounts of CO₂.

2. Deforestation:

• Trees absorb CO₂ during photosynthesis. When forests are cut down (often by burning them) for farming or logging, two bad things happen: 1) the stored CO₂ is released, and 2) there are fewer trees left to absorb CO₂ from the atmosphere.

3. Agriculture:

• Methane is released from the digestive systems of farm animals (cattle, sheep) and from rice paddy fields.
• The use of chemical fertilisers releases Nitrous Oxide (N₂O).

4. How Do We Know Climate Change is Happening?

Scientists have lots of different pieces of evidence that point to a rapidly warming world.

a) Direct Measurements

These are measurements taken over the last century:

• Rising Global Temperatures: Records show the 10 warmest years on record have all occurred since 2010.
• Rising Sea Levels: Global sea levels have risen due to two factors: the melting of land ice (glaciers) and thermal expansion (water expands as it gets warmer).
• Shrinking Ice and Glaciers: Satellite images show massive reduction in Arctic sea ice and the disappearance of mountain glaciers (e.g., in the Alps and Himalayas).

b) Proxy Data (Looking into the Past)

For data before thermometers existed, scientists use "proxy data" (substitute information).

• Ice Cores: Scientists drill deep into ice sheets (like in Antarctica). The ice contains tiny air bubbles from centuries ago. By studying the gas trapped in these bubbles, we can measure past CO₂ levels and temperatures. They act like time capsules!
• Pollen Analysis: Different plants grow in different climates. By identifying ancient pollen found in preserved lake sediments, scientists can determine what the local climate used to be like.

5. The Consequences: Impacts of Climate Change

Climate change is a natural hazard because it increases the frequency and intensity of extreme weather events, affecting every aspect of life.

a) Environmental Impacts

• Increased Extreme Weather: More intense tropical storms (cyclones/hurricanes), longer periods of drought, and more severe flooding events.
• Ecosystem Changes: Rising sea temperatures cause coral bleaching (destroying reef ecosystems). Animals are forced to migrate or face extinction.
• Coastal Flooding: Low-lying areas (like Bangladesh or island nations like the Maldives) face permanent inundation as sea levels rise.
• Melting Permafrost: Permanently frozen ground (permafrost) is melting, releasing vast amounts of trapped Methane (a strong GHG), which makes warming worse.

b) Social and Economic Impacts

• Water Scarcity: Changing rainfall patterns lead to less reliable water supplies, especially in arid regions. This hurts farming and access to drinking water.
• Food Security Issues: Droughts and floods reduce crop yields, leading to starvation and rising food prices globally.
• Increased Health Risks: Warmer weather can increase the spread of diseases carried by insects, such as malaria and dengue fever.
• Migration and Displacement: People who lose their homes and farms due to coastal flooding or severe droughts become climate refugees, putting pressure on surrounding areas.
• Damage Costs: The economic cost of repairing infrastructure and providing insurance coverage for floods and storms increases sharply.

6. Managing the Challenge: Responses to Climate Change

We manage climate change using two main strategies: Mitigation and Adaptation. Don't confuse these—they target different things!

a) Mitigation (Tackling the Cause)

Mitigation means reducing the output of Greenhouse Gases to slow down global warming.

• Developing Renewable Energy: Switching from fossil fuels to clean energy sources like solar, wind, and hydro power.
• Carbon Capture and Storage (CCS): Technology that captures CO₂ emissions from power stations before they enter the atmosphere and stores them deep underground.
• International Agreements: Countries signing treaties (like the Paris Agreement) to commit to reducing their national CO₂ emissions.
• Afforestation/Reforestation: Planting more trees to absorb CO₂ from the air.

b) Adaptation (Coping with the Effects)

Adaptation means adjusting our lives and infrastructure to cope with the climate changes that are already happening or are inevitable.

• Managing Water Supply: Building large reservoirs or using desalination plants (turning seawater into fresh water) to combat drought.
• Coping with Rising Sea Levels: Building sea walls, constructing artificial offshore barriers, and raising the height of existing defenses (e.g., in the Netherlands).
• Changing Agricultural Practices: Planting different crops that are more drought-resistant and developing irrigation techniques that use less water.

You’ve covered all the core concepts of climate change! Keep reviewing these key terms and you will be well prepared for your exam. Good luck!