• Outline the causes of global warming – including the role of greenhouse gases (carbon dioxide and methane, CH4) in the greenhouse effect.

• Describe the effects of global warming (rising temperature, changing rainfall patterns and seasonal cycles) on plants and animals (distribution of species, development and life cycles).

• Explain the effect of increasing temperature on the rate of enzyme activity in plants, animals and micro-organisms.

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What is global warming?

The term “global warming” is often used in connection with climate change, but what does it mean?

Global warming refers to the increase in the Earth’s temperature due to the greenhouse effect, which can cause changes in climate.

However, the term “global warming” is now being used to refer to the warming predicted to occur as a result of increased emissions of greenhouse gases and other human activities. This enhanced greenhouse effect may lead to significant climate change.

Remember, global warming and climate change are not the same thing and should not be used interchangeably.

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The greenhouse effect

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Three types of data recovered from the Vostok ice cores over 400 000 years of Earth history.

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Greenhouse gas levels in the Holocene (from 10 000 years ago).

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Changing levels of atmospheric CO2.

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What is climate change?

What could be causing this, and should we be concerned?

Scientists have predicted that the climate could increase by up to 6°C in the next 150 years.

Climate change is a natural phenomenon and normally takes place over several centuries.

The term ‘climate change’ is being used now to refer to the current climate. This is because recent scientific records show that the global climate seems to be warming up more rapidly than usual.

The average global temperature has increased by 0.6°C in 140 years.

The ten hottest years for the last 100 years have occurred since 1990.

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Impacts of climate change

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Evidence for global warming

• Polar ice melt

• Glacier retreats

• Rising sea levels

• Changing weather and ocean current patterns

• Coral bleaching

• Other bioindicators

Changes in the distribution of organisms

Autumn crocus, an historic record of changing distribution.

Recognising correlations and causal relationships

• The distributions of parasites causing diseases may also be affected by climate change.

• For example, the dangerous human disease of malaria is currently described as ‘marching north’ as the mosquito begins to re-colonise areas of Europe and the USA.

• Typical of most reptiles, the alligator deposits its eggs in warm conditions (such as piles of rotting vegetation), rather than incubating them in nests, as birds do.

• In the alligator, relatively low temperatures give females; higher temperatures give males.

• Lizards show this same pattern, turtles the reverse pattern. And the temperature at which a shift in sex ratio occurs varies with species, too.

• Photosynthesis is a biochemical process involving a series of interconnected reactions. All these reactions contribute to the overall rate of the process.