Impacts of climate change

Environmental Management (0680) · Cambridge IGCSE · 4 min read · Updated: 7 Sept 2026

Welcome to the Impacts of Climate Change!

In our previous studies, we looked at how human activities increase the amount of greenhouse gases like carbon dioxide (\(CO_2\)), methane (\(CH_4\)), and water vapour (\(H_2O\)) in the atmosphere. This causes the enhanced greenhouse effect, leading to global warming.

But what does a warmer planet actually mean for us and the environment? In this chapter, we explore the "ripple effect" of global warming. Don't worry if it seems like a lot of information—we will break it down into what happens to our oceans, our weather, and our lives.

1. Impacts on the Oceans

The Earth’s oceans are massive, and they absorb a huge amount of the extra heat and \(CO_2\) we produce. This leads to three major problems:

A. Ocean Warming

Just as the air gets warmer, so does the water. Even a small rise in temperature can disrupt marine life. For example, many fish species can only survive in specific temperature ranges; if the water gets too hot, they must move to colder areas or they may die.

B. Ocean Acidification

This is a "hidden" impact. When there is too much \(CO_2\) in the atmosphere, a lot of it dissolves into the ocean. When \(CO_2\) mixes with seawater, it makes the water more acidic.
Analogy: Imagine if the water you lived in slowly started turning into weak vinegar. It would make it very hard for creatures like corals and shellfish to build their hard shells and skeletons.

C. Sea-level Rise

Sea levels are rising for two main reasons:
1. Melting Ice: Glaciers and ice sheets on land melt, and the water flows into the sea.
2. Thermal Expansion: This is a scientific rule—when liquids get warmer, they expand (take up more space). Because the ocean is warming, the water itself is physically expanding!

Quick Review: The oceans are becoming warmer, more acidic, and higher in volume. This threatens coastal cities and marine ecosystems.

2. Impacts on Biodiversity and Food Chains

Biodiversity refers to the variety of living things on Earth. Climate change puts this variety at risk.

Changing Habitats

As temperatures rise, habitats change. For example, some plants may grow earlier in the year, or some areas may become too dry for trees to survive. If a plant species dies out or moves, the animals that eat it have no food. This causes a break in the food chain.

Extinction Risks

Animals that cannot adapt quickly enough or move to new areas face the risk of extinction. This is especially true for species living in sensitive areas like the Arctic or coral reefs.

Key Takeaway: When one part of an ecosystem changes due to climate, it creates a "domino effect" that can collapse entire food webs.

3. Impacts on Humans and Weather

Climate change isn't just about polar bears; it affects our food, our safety, and where we live.

Extreme Weather

Global warming adds more energy to the atmosphere. This leads to extreme weather events becoming more frequent and intense, such as:
- More powerful tropical cyclones (hurricanes/typhoons).
- Longer and more severe droughts.
- Heavier rainfall leading to flooding.

Food Shortages

Agriculture depends on steady weather. Climate change makes farming difficult because:
- Droughts dry up the water needed for crops.
- Floods wash away fertile soil and destroy harvests.
- Heatwaves can kill livestock (farm animals) and reduce crop yields (the amount of food grown).

Forced Migration

When people can no longer grow food, or when their homes are destroyed by rising sea levels and floods, they are forced to move. This is called forced migration. These people are often called "climate refugees" because they are moving to survive environmental changes.

Common Mistake to Avoid:

Students often confuse "weather" and "climate." Remember: Weather is what happens today (it's raining). Climate is the pattern over many years (this region is usually dry). Climate change is a shift in those long-term patterns.

Summary Checkbox

Before you move on to the next chapter on managing these issues, make sure you can identify these key impacts:

Ocean Warming: Rising water temperatures.
Ocean Acidification: Seawater becoming more acidic due to absorbed \(CO_2\).
Sea-level Rise: Caused by melting land ice and thermal expansion.
Biodiversity Loss: Species dying out or food chains breaking.
Extreme Weather: More intense storms, floods, and droughts.
Food Shortages: Lower crop yields and loss of livestock.
Forced Migration: People moving because their land is no longer habitable.

Note: To learn how we can reduce our carbon footprint or adapt to these changes, please see the chapter "Managing and adapting to climate change."

Quick check

Can you answer these now?

Open each question to check the key ideas from this chapter.

What is the enhanced greenhouse effect and its primary result?

The enhanced greenhouse effect is caused by human activities increasing greenhouse gases like \(CO_2\) and \(CH_4\), leading to global warming.

How does ocean warming impact marine life?

Warming oceans disrupt marine life by forcing fish species to migrate to colder waters or face death if they cannot survive the higher temperatures.

What causes ocean acidification and what is its effect on marine organisms?

Ocean acidification is caused by the ocean absorbing excess atmospheric \(CO_2\), which makes it difficult for corals and shellfish to build shells and skeletons.

What are the two main reasons for sea-level rise?

The two main causes are the melting of land-based ice (glaciers and ice sheets) and the thermal expansion of seawater as it warms.

How does climate change cause a break in the food chain?

Climate change alters habitats and plant growth cycles; if a plant species dies out or shifts its timing, the animals dependent on it lose their food source.

Which environments are at the highest risk for species extinction due to climate change?

Species in sensitive or specialized areas like the Arctic and coral reefs are at the highest risk because they cannot easily adapt or move.

What types of extreme weather are linked to global warming?

Global warming leads to more frequent and intense tropical cyclones, more severe droughts, and heavier rainfall resulting in flooding.

How does climate change cause food shortages?

Food shortages occur because droughts dry up water for crops, floods destroy fertile soil, and heatwaves kill livestock and reduce crop yields.

What is forced migration in the context of climate change?

Forced migration occurs when people, often called 'climate refugees,' must move because rising sea levels or extreme weather make their homes uninhabitable.

What is the difference between weather and climate?

Weather refers to short-term daily conditions, while climate is the long-term pattern of weather in a region over many years.

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