Welcome to Your Study Notes on Climate Change!
Hey everyone! Get ready to dive into one of the most important topics in Geography today: Climate Change. You hear about it on the news, on social media, and maybe even at home. But what does it all mean? Why is it such a big deal? Don't worry, we're going to break it all down together.
In these notes, we'll explore what climate change is, what's causing it, how it's affecting our world (and Hong Kong!), and what we can do about it. It might seem like a huge topic, but we'll take it one step at a time. Let's get started!
1. The Basics: Weather vs. Climate
First things first, let's clear up a common mix-up. Weather and climate are related, but they're not the same thing!
Think of it like this:
Weather is like your mood on a particular day – it can be sunny, grumpy (rainy), or angry (a thunderstorm!). It's what's happening outside right now or over a short period.
Climate is like your overall personality – the average of all your moods over many years. It's the long-term pattern of weather in a particular area.
So, what's the official definition?
- Weather: The day-to-day condition of the atmosphere at a particular place and time. (e.g., "It's hot and humid in Hong Kong today.")
- Climate: The average weather conditions of a place over a long period, usually at least 30 years. (e.g., "Hong Kong has a subtropical climate.")
Evidence That Our Climate is Changing
So how do we know the Earth's "personality" is changing? Scientists have collected a lot of proof. It's like looking at a person's diary over many years and noticing their moods are getting more extreme.
Here's the key evidence:
- Rising Global Temperatures: The average temperature of the Earth has been rising sharply, especially in the last few decades. It's like the Earth has a fever!
- More Extreme Weather: We're seeing more frequent and intense heat waves, droughts, heavy rainfall, and powerful typhoons.
- Melting Glaciers and Ice Sheets: Huge bodies of ice in places like Greenland and the poles are melting at an alarming rate.
- Sea-Level Rise: As ice melts, the water flows into the ocean. Also, as water warms, it expands. Both these things cause the sea level to rise, leading to more coastal flooding.
Key Takeaway for Section 1
Weather is short-term, climate is long-term. We know the climate is changing because of clear evidence like rising temperatures, melting ice, rising sea levels, and more extreme weather events.
2. Global Warming: The Earth's Fever Explained
The main driver of climate change is global warming. To understand this, we need to look at something called the Greenhouse Effect.
The Greenhouse Effect: Earth's Natural Blanket
The Greenhouse Effect is a natural and essential process. Without it, the Earth would be too cold for life to exist!
Imagine the Earth wearing a perfect, invisible blanket. Here's how it works:
- The sun sends energy (short-wave radiation) to Earth.
- The Earth's surface absorbs this energy and warms up.
- The warm Earth then sends heat (long-wave radiation) back out towards space.
- Some gases in our atmosphere, called greenhouse gases (GHGs) like Carbon Dioxide (CO₂), trap some of this outgoing heat, keeping our planet warm. This is the natural "blanket".
The Enhanced Greenhouse Effect: The Blanket Gets Too Thick!
The problem starts when we add extra greenhouse gases to the atmosphere. This is the enhanced greenhouse effect.
Human activities are pumping more GHGs into the air. This makes the Earth's "blanket" thicker, trapping more heat and causing the planet's temperature to rise. This is the main cause of global warming.
Causes of Global Warming: Natural vs. Human-induced
The climate has always changed naturally, but the recent rapid warming is mostly due to human activities.
Natural Causes (a small part of the current story)
- Volcanic Eruptions: Can release gases and ash that temporarily cool or warm the planet.
- Variations in Solar Activity: The sun's energy output changes slightly over time.
Human-induced (Anthropogenic) Causes (the main problem!)
These are the activities that are making the greenhouse gas blanket thicker. Here's a simple way to remember the main ones with the mnemonic F.A.D.E.S.:
- F - Fossil Fuel Burning: Burning coal, oil, and natural gas for electricity, transport, and industry releases huge amounts of CO₂, the main greenhouse gas.
- A - Agriculture: Livestock (like cows) release methane, another powerful GHG. Also, the use of certain fertilisers releases nitrous oxide.
- D - Deforestation: Trees absorb CO₂. When we cut down forests, we lose this natural "carbon sink". Burning forests also releases all the stored CO₂ back into the atmosphere.
- E - Emission of CFCs: Chlorofluorocarbons (CFCs), used in old refrigerators and aerosol cans, are very powerful greenhouse gases.
- S - Solid Waste (Garbage Burning): When we burn our rubbish in incinerators or landfills decompose, they release CO₂ and methane.
The Great Debate: Fluctuation or Irreversible Trend?
Is this warming just a natural up-and-down cycle, or have we changed our planet for good? This is a key debate.
Arguments that global warming is a long-term fluctuation (a natural cycle):
- The Earth's climate has always changed throughout history, with ice ages and warm periods.
- Natural factors like solar activity could be playing a bigger role than we think.
Arguments that global warming is an irreversible trend (caused by humans):
- The current rate of warming is happening much faster than any known natural cycle.
- The sharp increase in CO₂ in the atmosphere directly matches the increase in human industrial activity.
- The vast majority of climate scientists agree that human activities are the main cause.
Key Takeaway for Section 2
The enhanced greenhouse effect, caused by human activities like burning fossil fuels and deforestation, is trapping too much heat and causing global warming. While there's a debate, most evidence points to this being a human-caused, irreversible trend.
3. Local Climate Change: The Urban Heat Island Effect
Climate change isn't just a global issue; we can see its effects right here in our cities. Have you ever noticed that it feels much hotter in busy areas like Mong Kok or Central compared to the countryside in Sai Kung?
This is called the Urban Heat Island (UHI) Effect, where urban areas are significantly warmer than their surrounding rural areas, especially at night.
What Causes Urban Heat Islands?
- Dark Surfaces: Concrete buildings and dark asphalt roads absorb and store more of the sun's heat compared to grass and trees.
- Less Vegetation: Fewer trees and parks mean less cooling from shade and a process called evapotranspiration (where plants release water vapour, cooling the air).
- Urban Geometry: Tall buildings create "urban canyons" that trap heat and block cooling winds.
- Waste Heat: Think of all the heat released from cars, buses, air conditioners, and factories. It all adds up!
Did you know? The Hong Kong Observatory has recorded that the temperature in urban Tsim Sha Tsui is often several degrees warmer than in the rural New Territories. This is a perfect local example of the UHI effect!
How UHI Affects a City's Microclimate
The UHI doesn't just raise temperatures. It changes the local weather (the microclimate) in several ways:
- Atmospheric Composition: More air pollution and dust particles.
- Temperature: Higher average temperatures.
- Wind: Lower wind speeds due to buildings acting as barriers.
- Humidity: Generally lower relative humidity because there's less water and vegetation.
- Precipitation: Sometimes more rainfall over the city, as the warm, rising air can trigger cloud formation.
Key Takeaway for Section 3
Cities are hotter than the countryside due to the Urban Heat Island effect. This is caused by heat-absorbing materials, less vegetation, and waste heat from human activities, creating a unique city microclimate.
4. Impacts, Actions, and Agreements
So, our planet is getting warmer and our cities are getting hotter. What does this mean for us, and what can we do?
Consequences of Climate Change: Winners and Losers
Climate change affects different parts of the world in different ways. There are no real "winners" in the long run, but some short-term effects can be positive for a few, while being disastrous for many others.
- Impact on Sea Level & Flooding: Low-lying coastal areas and island nations face a huge risk of flooding and even disappearing. (Big Losers)
- Farming Opportunities: Some very cold regions, like parts of Siberia or Canada, might be able to grow crops for the first time as temperatures rise. (Potential Winners) However, many traditional farming areas will suffer from droughts and crop failure. (Big Losers)
- Health Risks: Increased heat waves can cause heatstroke, and warmer conditions can help diseases like dengue fever spread more easily.
- Extreme Weather Events: More frequent and stronger typhoons, hurricanes, droughts, and floods will affect millions of people worldwide.
- Unpredictable Climate: It's becoming harder for scientists to predict weather patterns, which is a problem for everyone, from farmers to city planners.
Fighting Back: Mitigation and Adaptation
There are two main ways we can respond to climate change. It's crucial to know the difference!
- Mitigation: This means tackling the causes of climate change to reduce its severity.
Analogy: If your bathtub is overflowing, mitigation is turning off the tap!
Examples: Switching to renewable energy (solar, wind), planting trees, improving energy efficiency, using public transport. - Adaptation: This means adjusting to the effects of climate change that are already happening or are unavoidable.
Analogy: If the water is already on the floor, adaptation is using a mop and putting towels down.
Examples: Building sea walls to protect against sea-level rise, developing drought-resistant crops, creating early warning systems for heat waves and storms.
Why Is It So Hard to Reach a Global Agreement?
If everyone knows this is a problem, why can't the world just agree on a solution? It's complicated.
- Conflicting Views: Developed countries (who have historically polluted the most) and developing countries (who need to grow their economies, often using cheaper fossil fuels) disagree on who should take the most action and who should pay for it.
- Economic Concerns: Shifting away from fossil fuels can be expensive in the short term, and some countries worry it will harm their economy and lead to job losses.
- Political Differences: National interests often come before global cooperation. It's hard to get nearly 200 countries to agree on strict, binding rules.
Final Key Takeaway
The impacts of climate change are widespread and unequal. We can respond with mitigation (tackling the cause) and adaptation (dealing with the effects). Reaching a global solution is difficult due to complex economic and political disagreements between nations. Your generation's awareness and action will be key to facing this challenge!