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Effects of Climate Change

Pupils' Information Sheet

Introduction

In lessons one and two, the greenhouse effect and the role of greenhouse gases were explained. The greenhouse effect was found to occur because of certain absorbing gases in the Earth's atmosphere known as the greenhouse gases, the most important of which are water vapour and carbon dioxide.

The enhanced greenhouse effect will change climates around the world, but so far the effects of these changes have not been described. Perhaps in the UK we will have longer, hotter summers, but is this such a good thing? What other effects will there be, and how will this affect us and people living around the world?

To answer these questions, some areas where climate change is likely to have an effect will be explored in more detail. You should remember that nobody can accurately predict how climates are going to change, or how dramatic the effects of these changes might be.

How will temperatures change around the world?

The average temperature of the Earth is about 15C. Over the past 100 years this has increased by about 0.6C (Figure 1), and may continue to rise for a long time to come (Figure 2). It has been predicted that average temperatures will carry on rising by about 0.3C per decade, but some areas will warm up much faster than others, whilst some may even cool down. Scientists also fear that natural disasters like floods will be more extreme, and occur more frequently.

Figure 1: Global Warming in the last 150 years

This is why we should be worried about climate change: while some countries might not notice any change, others will be very badly affected. The UK will probably warm up at about the global average rate.

What will happen to the oceans?

As the atmosphere warms up, so will the oceans. Water which is heated expands slightly (in the same way as mercury expands in a thermometer), hence if we increase the temperature of seawater the sea level will rise.

The melting of ice in a warmer climate is another reason why sea levels might rise. Whether this happens depends on where the ice originates from. If ice comes from the land (as glaciers or ice-sheets in Antarctica) then it will help increase sea level, but if ice-masses floating in the Arctic Sea melt, sea level will not rise. This is illustrated by the experiment included in this lesson.

Most scientists expect the sea to rise by 90cm by 2100. Some land might flood to become shallow sea or marsh, floods may occur more often, towns might need to build walls to stop the sea reaching sea-fronted buildings. Ecosystems on the coast such as sand dunes or mudflats might be changed or destroyed, harming wildlife.

There are currents in the ocean which might change if the water warms up. This is important because some of these currents can affect climate. In the winter, an ocean current called the Gulf Stream helps to keep the British weather relatively warm compared to the same latitude on the east coast of America.

Some species of fish, such as cod or salmon, migrate from one part of the ocean to another. If the ocean currents change the life cycle of these species could be disrupted, and important industries like fishing would be affected.

Will there be more or less freshwater?

If temperatures increase across the world, water would evaporate more quickly from lakes and rivers, and from the soil. Plants would lose more water to the atmosphere by transpiration. This may result in less freshwater left for use by humans and animals. On the other hand, more water in the atmosphere from evaporation might mean that there was more rainfall, but nobody is sure. Most scientists think that there would be less water available, especially where it is already quite dry.

People can't drink seawater because of the salt it contains. If the sea rises, the salt might infiltrate our freshwater supplies. This would be a problem because much of the water we drink in Britain (especially in the southeast of England) is taken from under the ground. In this country we use a lot of water, and we could manage by using much less. In some other countries, people hardly have any water to drink, or wash in, or to water their crops.

Will we be able to grow enough food?

Lesson two looked at carbon dioxide, and explained that its concentration in the atmosphere will continue to increase through the next century unless we do something to stop the upward trend.

Through a process called photosynthesis, plants use carbon dioxide, light, and water to grow. If there is more carbon dioxide in the air, plants might be able to grow more quickly (provided they have enough water and light). This is true for some plants such as wheat and rice, but others like maize and sugarcane will not grow any faster.

There is a possibility that, if carbon dioxide concentrations increase, farmers will start growing the faster-growing crops. In practice however, warmer weather could mean that crop growth might be limited by more pests, insufficient water in the soil, or more evaporation from irrigation channels.

One important question is whether climate change will mean there is more or less food grown in the world. A lot of the world's food is grown in a fairly small area and predicting climate for these areas is very difficult. Hence nobody is sure if the amount of food in the world will change or not.

In rich countries, like the UK, we have enough money to spend on things like irrigation and drainage to make sure that our food supplies don't dwindle. A lot of countries will suffer food shortages if there are more droughts.

At the moment, some countries are too cold to grow certain crops, and so an increase in temperature may allow a more varied range of foodstuffs to be grown. For example, a crop such as maize cannot be grown in the UK at the present time, but if average temperatures increase by just 0.5C, it could be cultivated across much of southern England. Russia is another place that might be able to grow more crops if its climate was warmer.

Are any species at risk from global warming?

If the world warmed up then some species would find themselves in climates which were too warm or too dry for their particular habitat. A species would have to either adapt to the changes, or move to cooler areas further away from the equator, or higher above sea level. If it did not, or were physically unable to move the distances required, the species might disappear from that region, or even become extinct. For example, pandas only live in the wild in a very small area of China. If the climate changed, and the bamboo plant (the panda's main source of food) was unable to grow in that particular region any more, the pandas would lose their most important dietary source and would either have to move to a new area where bamboo could grow or become extinct.

Whether or not this happened would depend on how fast the climate changed, and how quickly the species population moved or adapted to its new surroundings.

How will some people be affected?

Just as plants and animals may have to move because of climate change, so might humans. People living in hot, dry countries would be forced into moving if there was even less water for them to use; people living on low-lying flood plains near the sea might have their homes and fields flooded too often to stay in that area. This would be most likely to happen in countries too large or poor to protect themselves against climate change. Wherever these people would move to they would need food, water and eventually land to farm and build on. This might be difficult, especially if there were already many people populating the area.

Questions/further work

1. Can you think of any parts of the UK that could be affected by sea-level rise?

2. How do you think people in very dry areas could manage with even less water?

3. Can you think of any species that might be affected by global warming?

4. What might life be like in the UK if the climate was much hotter?

5. Assume the average July temperature in the UK is 15C. Given the estimated rate of increase in temperature, what will the July temperatures be in a) 2010, b) 2050, c) 2100?


EXPERIMENT

Introduction

The world's ice can be divided into two types: sea-ice and land-ice. Both are at risk of melting by global warming and climate change. This experiment looks at the relative importance of land-ice and sea-ice when assessing the effects of climate change.

Aim

To find out if the melting of land and/or sea-ice will contribute to sea-level rise.

Equipment

  • 2 watertight boxes of maximum dimensions 20cm x 10cm x 10cm deep
  • 2 small pieces of stone or dense wood, covering about half the surface area of the boxes.
  • 2 rulers (6 inches)
  • ice cubes
  • water
  • blu-tac

Method: Comparison of Land and Sea Ice

Place the pieces of wood inside the boxes.

Fix a 6" ruler vertically on the inside of each box with the blu-tac.

Place half the ice in the bottom of one box (the sea-ice box), and the other half on the piece of wood in the other box (the land-ice box).

Pour water into each box until the level is just below the top of the wood.

Record the water level in each box using the ruler.

Leave the boxes until the ice in both has completely melted.

Record the water level in each box again.

Results

For the sea-ice box:original water leve =   cm

final water level =   cm

change in level =   cm

For the land-ice box:original water level =   cm

final water level =   cm

change in level =   cm

Compare the first and second measurements for each box. Subtract the first from the second to find out how much the water level has risen.

You will find that the water level in the sea-ice box has not changed, whereas the level in the land-ice box has risen.

Conclusion

The melting of land-ice contributes to sea level rise, but sea-ice does not.

Further Work

Can you find out where some of the largest masses of land and sea-ice are?

Can you suggest reasons why the melting of sea-ice doesn't increase sea levels?