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examBoard: Cambridge
examType: IGCSE
lessonTitle: Enhanced Greenhouse Effect
The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. However, human activities have enhanced this effect, leading to global climate change.
Key Definitions:
The natural greenhouse effect makes Earth habitable. Without it, our planet would be about 33°C colder! Greenhouse gases like water vapour and carbon dioxide trap heat in the atmosphere, maintaining an average global temperature of about 15°C.
Human activities have increased the concentration of greenhouse gases in the atmosphere, trapping more heat and raising global temperatures. This is causing climate patterns to change, sea levels to rise and more extreme weather events.
Several gases contribute to the greenhouse effect. Human activities have increased the concentration of these gases significantly since the Industrial Revolution.
Sources: Burning fossil fuels, deforestation, cement production
Lifespan in atmosphere: 300-1000 years
Responsible for about 76% of human-caused greenhouse gas emissions
Sources: Livestock, rice paddies, landfills, natural gas
Lifespan in atmosphere: About 12 years
25 times more potent than CO₂ at trapping heat over 100 years
Sources: Fertilisers, industrial processes, vehicle emissions
Lifespan in atmosphere: About 114 years
298 times more potent than CO₂ at trapping heat over 100 years
Since the Industrial Revolution, human activities have significantly increased the concentration of greenhouse gases in the atmosphere.
Coal, oil and natural gas are burned for electricity, heat and transportation. This releases CO₂ that had been stored underground for millions of years. Energy production accounts for about 73% of global greenhouse gas emissions.
Trees absorb CO₂ during photosynthesis. When forests are cleared for agriculture, development, or timber, this carbon sink is lost and stored carbon is released back into the atmosphere. About 11% of global emissions come from forestry and land use changes.
Livestock produce methane during digestion. Rice paddies also release methane. Fertilisers release nitrous oxide. Agriculture accounts for about 12% of global emissions.
Manufacturing processes, especially cement production, release CO₂. Some industrial processes also release other potent greenhouse gases like hydrofluorocarbons (HFCs).
Climate change is affecting every region on Earth, with impacts becoming increasingly severe as temperatures rise.
Caused by melting ice sheets and thermal expansion of seawater. Threatens coastal communities and low-lying islands. Global sea levels rose about 20cm in the 20th century.
More frequent and intense heatwaves, droughts, floods and storms. Weather patterns become less predictable, affecting agriculture and water supplies.
Changing habitats and temperatures threaten species. Coral reefs are particularly vulnerable to ocean warming and acidification.
The Arctic is warming at twice the rate of the global average. Arctic sea ice has declined by about 13% per decade since 1979. This creates a feedback loop: as white ice (which reflects sunlight) is replaced by dark ocean water (which absorbs heat), warming accelerates further. The melting ice threatens Arctic wildlife like polar bears and affects global weather patterns. Indigenous communities in the region are experiencing disruption to traditional ways of life as hunting grounds disappear and permafrost thaws.
Climate change affects different regions in various ways, with some areas experiencing more severe impacts than others.
Areas like Bangladesh, the Netherlands and small island nations face threats from rising sea levels. The Maldives, with an average height of just 1.5 metres above sea level, could become largely uninhabitable by 2100 if current trends continue.
Many African countries are experiencing more severe droughts and unpredictable rainfall. This threatens food security in a region where many people depend on rain-fed agriculture for their livelihoods.
Australia's Great Barrier Reef, the world's largest coral reef system, has experienced multiple mass bleaching events since 1998 due to rising ocean temperatures. In 2016 and 2017, back-to-back bleaching events affected two-thirds of the reef. Coral bleaching occurs when corals expel the algae living in their tissues due to stress from high temperatures, turning the corals white and often leading to their death. The reef supports thousands of marine species and contributes about £4 billion annually to Australia's economy through tourism and fishing.
Addressing climate change requires both mitigation (reducing emissions) and adaptation (adjusting to changes already happening).
The UK has set a legally binding target to reach net-zero greenhouse gas emissions by 2050. Key policies include phasing out coal power (coal generated 40% of UK electricity in 2012 but less than 2% in 2020), supporting renewable energy (which provided over 40% of electricity in 2020) and planning to ban the sale of new petrol and diesel cars by 2030. The UK has reduced its emissions by about 44% since 1990 while growing its economy by 78%, showing that economic growth can be decoupled from carbon emissions.
Climate change is a global problem requiring international cooperation. Several agreements have been made to address it.
The enhanced greenhouse effect is a human-caused intensification of a natural process. By burning fossil fuels, cutting down forests and engaging in other activities that release greenhouse gases, we're trapping more heat in Earth's atmosphere. This is causing global temperatures to rise, leading to a range of impacts from rising sea levels to more extreme weather events.
Addressing climate change requires both reducing our greenhouse gas emissions (mitigation) and preparing for the changes that are already happening (adaptation). While the challenge is significant, there are many solutions available, from renewable energy to sustainable agriculture. International cooperation, technological innovation and individual actions all have important roles to play in tackling this global challenge.
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