Explain why it is wrong to say that the greenhouse effect is causing global warming.

Because the greenhouse effect is a permanent and beneficial feature of the planet, not a problem, and it was operating for billions of years before humans existed. Blaming it for warming implies that the goal should be to remove it, which would leave the Earth at about minus 18 degrees Celsius. The correct statement is that human emissions have enhanced the greenhouse effect by raising the concentration of greenhouse gases, and that it is this enhancement, the extra absorption of outgoing longwave radiation, which is causing the observed warming. Examiners treat the distinction as a test of whether a candidate understands the mechanism, and confusing the two is the single commonest error in this topic.

Why is it wrong to confuse the enhanced greenhouse effect with the hole in the ozone layer?

Because they are separate problems with different gases, different mechanisms and different effects. Ozone depletion is the destruction of stratospheric ozone, mainly by chlorine released from chlorofluorocarbons, which allows more harmful ultraviolet radiation to reach the surface, increasing skin cancer and damaging ecosystems; it is worst over Antarctica in spring. The enhanced greenhouse effect is the trapping of more outgoing longwave radiation by higher concentrations of greenhouse gases, which raises surface temperature. A thinner ozone layer does not cause global warming, and it in fact cools the stratosphere. The two are connected only in that chlorofluorocarbons happen to be both ozone-depleting and extremely powerful greenhouse gases, so controlling them under the Montreal Protocol helped with both.

Demonstrate knowledge and understanding of the greenhouse gases that matter, and of the human sources of each.

Carbon dioxide is much the most important overall, released by burning coal, oil and gas, by cement manufacture and by deforestation and land-use change. Methane comes from ruminant livestock, flooded rice paddies, landfill sites, and leakage from coal mines and from oil and gas production. Nitrous oxide comes chiefly from nitrogen fertilisers and manure on farmland, and from some industrial processes and vehicles. Halocarbons, including chlorofluorocarbons and their replacements, come from refrigeration, air conditioning, foam blowing and aerosols. Tropospheric ozone forms from vehicle and industrial pollution. Water vapour is the most abundant greenhouse gas but its concentration is set by temperature rather than directly by emissions.

CCEA A-Level Geography 3910

Processes That Shape Fluvial Environments

Topic overview The drainage basin as an open system Storm hydrographs Factors influencing storm hydrographs Annual hydrographs and river regimes River erosion and transportation Deposition and the Hjulstrom curve Erosional and mixed river landforms Depositional river landforms

Human Interaction in Fluvial Environments

Topic overview Why rivers are channelised, and the methods used Environmentally sensitive and sustainable river management The causes of river flooding The effects of flooding on people, property and land

Global Biomes

Topic overview The global distribution of biomes The tundra biome: climate and soils The temperate grassland biome: climate and soils Climate change and tundra ecosystems

Small-Scale Ecosystems

Topic overview Biotic and abiotic components Ecosystems as open systems Trophic structure and ecological pyramids Nutrient cycling and the nutrient cycling model Plant succession and seral stages Climatic climax and plagioclimax vegetation

The Processes That Shape Our Weather and Climate

Topic overview The global energy balance Vertical and horizontal heat transfer in the atmosphere Ocean currents and the transfer of heat Pressure belts, the Coriolis effect and the pressure gradient The tri-cellular model, the global winds, and where it breaks down Jet streams and the upper westerly winds Global patterns of temperature, pressure, wind and precipitation Factors influencing air temperature

Weather in the British Isles

Topic overview How precipitation forms Air masses affecting the British Isles The polar front and the birth of a depression The life cycle of a depression, and its fronts The sequence of weather as a depression passes Anticyclones in summer and winter Isobars, wind, and the front symbols on a synoptic chart Station circles, recognising systems, and satellite images

Global Weather Issues

Topic overview The Pacific in a normal year: the Walker circulation El Niño events and their global consequences La Niña events and their global consequences How tropical cyclones form The structure of a tropical cyclone The impacts of a tropical cyclone on people and property Managing tropical cyclones: prediction, preparation and response

Population Data

Topic overview Census taking, vital registration, and how the data is collected The reliability of the data, and the use made of it

Population Change

Topic overview Fertility and mortality measures, and why crude rates are crude The demographic transition model The epidemiological transition

Population and Resources

Topic overview Overpopulation, underpopulation and optimum population Malthus and Boserup, and how they hold up Fertility policies, and evaluating one

Settlement Change and the Rural-Urban Fringe

Topic overview Defining rural and urban settlement The rural-urban continuum Issues affecting the rural-urban fringe Greenfield and brownfield development Suburbanisation Counterurbanisation

Planning in Rural Environments

Topic overview Why the countryside needs planning protection ASSIs and SSSIs Areas of Outstanding Natural Beauty National parks A national park for Northern Ireland: the case for, the case against, and the verdict

Urban Challenges in MEDC and LEDC Cities

Topic overview Economic and social deprivation in the MEDC inner city Re-urbanisation in the MEDC city Gentrification and its consequences Urban growth and informal settlements in the LEDC city Service provision in the LEDC city Economic activity and the informal economy in the LEDC city

Measuring Development

Topic overview Why 'development' resists definition Two economic measures: GDP and GNI per capita Two social measures: infant mortality and adult literacy Two composite measures: the HDI and the Gender Inequality Index Using the measures together to describe global contrasts

Reducing the Development Gap

Topic overview The Millennium Development Goals: aims and framework Evaluating two Millennium Development Goals The 2030 Agenda and the Global Goals How the Global Goals build on the Millennium Development Goals Globalisation as a route to development in LEDCs Aid and development in LEDCs, and judging development in one

Emerging Markets

Topic overview What an emerging market is BRICS and MINT: what the labels group, and why they are contested Why emerging markets have grown, and one economy studied

Data Collection

Topic overview Collecting primary data in the field Sampling methods: random, systematic, stratified and pragmatic Point, line and quadrat sampling Ordnance Survey maps and map reading Photographs and satellite images as evidence Synoptic charts and remotely sensed data

Data Processing

Topic overview Geographical information systems, and mapping techniques Annotated sketch maps, and the graph types Triangular graphs Mean, median, mode and range Spearman's rank correlation Nearest neighbour analysis Chi-squared (A2 only)Location quotient (A2 only)Developing investigative skills, and the conventions of mapping and graphical work

Fieldwork Skills and Techniques

Topic overview Framing a geographical question and designing the enquiry Fieldwork safety, hazards and contingency planning Choosing and justifying sampling techniques for an investigation Collecting quantitative and qualitative evidence Describing and evaluating data collection methods Presenting evidence in cartographic, diagrammatic and graphical form Choosing and applying statistical techniques Analysing evidence and drawing conclusions Evaluating methods, evidence and the limitations of conclusions

Planning and Recording an Investigation

Topic overview Choosing an issue, hypothesis or question Identifying appropriate sources and methods Describing the study area, stating aims, and recording data

Plate Tectonics: Theory, Margins and LandformsTectonics

Topic overview The structure of the Earth and the driving mechanism The evidence for continental drift and plate tectonics Constructive margins: processes, ocean ridges and rift valleys Conservative margins: processes and why they build nothing Destructive margins: subduction, trenches and island arcs Collision margins and fold mountains Matching landform to margin: the classic confusions

Volcanic Activity and Its ManagementTectonics

Topic overview Magma composition, viscosity and eruption style Volcanic activity at constructive margins Volcanic activity at destructive margins Hot spots and intraplate volcanic activity Hazards of volcanic activity Benefits of volcanic activity Preparing for volcanic activity: monitoring, planning and protection Responding to volcanic activity and evaluating the response

Seismic Activity and Its ManagementTectonics

Topic overview The nature of a seismic event Seismic waves: P, S and L waves Seismic shaking and its impacts Liquefaction Tsunamis Attempts to predict seismic events Preparing for seismic activity Responding to seismic activity and evaluating the response

Locations and Climates of the Major Tropical BiomesTropical

Topic overview The Hadley cell and the ITCZ Tropical forest: distribution, climate and biomass Tropical grassland: distribution, climate and biomass Hot desert, and the tropical biomes compared

Management and Sustainability in Arid and Semi-Arid Tropical EcosystemsTropical

Topic overview Why irrigation is needed, and the methods used The benefits of irrigation and its environmental problems The socio-economic problems of irrigation, and the solutions

Management and Sustainability in the Tropical Forest EnvironmentTropical

Topic overview Trophic structure, the nutrient cycle, and why clearance is so damaging The zonal soil of the tropical forest Large-scale development and its threats to the forest ecosystem Attempts to achieve sustainable development in the tropical forest

Coastal Processes and FeaturesCoastal

Topic overview Waves and wave energy Wave refraction and coastal alignment Marine erosion, transport, longshore drift and deposition Landforms of high-energy coasts Landforms of low-energy coasts

Regional Coastlines: Submergence, Emergence and Rising Sea LevelCoastal

Topic overview Eustatic and isostatic change Coastlines of submergence Coastlines of emergence Rising sea level and the threat of climate change

Coastal Management and SustainabilityCoastal

Topic overview Environmental Impact Assessment and Cost-Benefit Analysis Sediment cells and Shoreline Management Plans Hard engineering strategies Soft engineering strategies Choosing and evaluating a management strategy

Natural Climate Change: Evidence, Causes and the Arrival of the HoloceneClimate

Topic overview Evidence for past climate change: ice cores, pollen and ocean-floor deposits Causes of long- and medium-term climate change The end of the last glaciation and the arrival of the Holocene

Lowland Glacial LandscapesClimate

Topic overview Ice sheet formation and glacial and fluvioglacial processes Landforms of glacial deposition: till, drumlins, moraines and erratics Landforms of fluvioglacial deposition: eskers and outwash plains Socio-economic development in lowland post-glacial environments

Current Global Climate Change: Human Causes and ImpactsClimate

Topic overview The greenhouse effect and the enhanced greenhouse effect Evidence for recent climate change and its links to human activity Present and potential impacts of climate change

Managing Global Climate ChangeClimate

Topic overview Mitigation: reducing greenhouse gas emissions and capturing carbon Adaptation: reducing vulnerability to climate change International action: the Kyoto Protocol, the IPCC and progress so far

Cultural Groups, Social Inequality and LandscapeCultural

Topic overview Why cultural groups exist Differences between cultural groups Cultural nationalism and its expression Social inequality: exclusion and discrimination as distinct mechanisms Inequality by ethnicity, race, religion, gender, sexuality and class Social constructions of nature and landscape

MigrationCultural

Topic overview Push and pull factors: economic, social, political, cultural and environmental Barriers to migration, and its implications for services, the economy and stability Voluntary and forced migration, and immigration as a political issue

The Geographies of CyberspaceCultural

Topic overview Cyberspace, economic change and cultural globalisation Minority cultures, virtual communities and the digital divide

Sustainable Development in SettlementsPlanning

Topic overview Sustainability, and the urban ecological footprint Carbon footprints and waste management Energy consumption and water supply

Urban Design, Planning and Management for SustainabilityPlanning

Topic overview Eco-towns, eco-cities, residential space and defensible space How greenfield and brownfield development relate to sustainability Retail parks, leisure facilities and open space

Traffic and TransportPlanning

Topic overview The sustainability of transport by sea, air and land Public transport, integrated networks, and restrictions on car use Pedestrian and cycling policies, and judging a traffic management strategy

Defining EthnicityEthnic

Topic overview Race, nationality, language and religion as defining factors Ethnicity as socially constructed and self-ascribed Role, residential concentration, age and gender in perceived identity

Processes That Create and Maintain Ethnic DiversityEthnic

Topic overview Colonisation, annexation and international migration Segregation as a process maintaining diversity Multiculturalism as a process maintaining diversity Economic, social and spatial outcomes of ethnic diversity

Ethnic ConflictEthnic

Topic overview The causes of ethnic conflict The nature of ethnic conflict Social, economic and territorial outcomes of ethnic conflict Ethnic cleansing, international intervention and peace processes

The Changing Nature of TourismTourism

Topic overview The growth of mass tourism as a global industry Positive social and economic impacts of tourism The pleasure periphery and the Butler model of resort development

Challenges and Management of Mass TourismTourism

Topic overview The challenges arising from mass tourism Strategies to reduce the negative impacts of mass tourism

Ecotourism: Opportunities, Challenges and RegulationTourism

Topic overview Defining ecotourism The benefits of ecotourism The negative impacts of ecotourism Regulating ecotourism internationally

Decision Making in Geography

Topic overview What a decision-making exercise asks of you Adopting and maintaining a role Reading maps as evidence Reading photographs as evidence Reading statistics and data as evidence Reading reports and written sources as evidence Reading infographics and diagrams as evidence Processing and presenting supplied quantitative data Interpreting and evaluating the information provided Examining conflicting values Considering alternative choices Making and justifying a recommendation on greater overall benefits Structuring and supporting the decision

Current Global Climate Change: Human Causes and Impacts

3 subtopics
9 things to know
Unit A2 1
A2 1 option D, Climate Change: Past and Present

What Current Global Climate Change: Human Causes and Impacts covers

Current global climate change: human causes and impacts is examined in Unit A2 1, Physical Processes, Landforms and Management. It covers the greenhouse effect and the enhanced greenhouse effect, evidence for recent climate change and its links to human activity and present and potential impacts of climate change.

Where it is assessed

Unit A2 1

Physical Processes, Landforms and Management, one option of four, 24% of A level.

Check the CCEA specification ↗

The 3 subtopics

Each one has its own page.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain the natural greenhouse effect step by step.

Key term

What difference does the natural greenhouse effect make to the Earth's temperature?

Key term

What is the enhanced greenhouse effect, and how does it differ from the greenhouse effect?

Numbers

What does the instrumental temperature record show?

Key term

What biological and seasonal evidence is there for recent climate change?

Key term

What has happened to weather extremes?

Key term

What impacts are already being felt in high latitudes, and who is affected?

Key term

What is happening to mountain glaciers, and why does it matter for people downstream?

Key term

What is a glacial lake outburst flood?

Take Current Global Climate Change: Human Causes and Impacts further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

Enhanced greenhouse effect vs Natural greenhouse effect
Enhanced greenhouse effect: the extra warming caused by human emissions. Natural greenhouse effect: the warming that would occur without any of them.
Greenhouse effect vs Enhanced greenhouse effect
Greenhouse effect: the natural warming produced by gases that trap outgoing radiation. Enhanced greenhouse effect: the additional warming produced by human emissions of those gases.

Questions from this topic

Each one with the model answer underneath.

1
Explain the natural greenhouse effect step by step.
Model answer
Incoming solar radiation is mostly shortwave, and the atmosphere is largely transparent to it, so about half of it passes through and is absorbed at the Earth's surface, warming the ground and the sea. The warmed surface then re-radiates that energy upwards, but because the surface is far cooler than the Sun it radiates at much longer wavelengths, in the infrared. Certain trace gases in the atmosphere - water vapour, carbon dioxide, methane, nitrous oxide and ozone - are transparent to shortwave radiation but absorb longwave radiation strongly. They absorb the outgoing infrared and re-emit it in all directions, including back down to the surface. The surface therefore receives energy from the atmosphere as well as from the Sun, and settles at a higher temperature than it otherwise would.
2
What difference does the natural greenhouse effect make to the Earth's temperature?
Model answer
Without any greenhouse gases the Earth's mean surface temperature, given the solar radiation it receives and the fraction it reflects, would be about minus 18 degrees Celsius. The observed mean is about 15 degrees Celsius. The natural greenhouse effect is therefore worth roughly 33 degrees of warming, and without it the planet would be frozen and effectively uninhabitable, with liquid water rare at the surface. It is entirely natural, it has operated throughout Earth history, and it is the reason life as we know it is possible. Venus and Mars illustrate the two extremes, one with a runaway greenhouse and one with almost none.
3
What is the enhanced greenhouse effect, and how does it differ from the greenhouse effect?
Model answer
The greenhouse effect is the natural process described above, which keeps the planet about 33 degrees warmer than it would otherwise be and makes it habitable. The enhanced greenhouse effect is the additional warming caused by human activity increasing the concentration of those same greenhouse gases, and adding some entirely new ones. A higher concentration absorbs a greater proportion of the outgoing longwave radiation, so less energy escapes to space and the surface must warm until the balance between incoming and outgoing energy is restored. It is an intensification of a natural process, not a new or separate one, and the human contribution is the enhancement, not the effect itself. Saying the greenhouse effect causes global warming is therefore wrong; the enhanced greenhouse effect does.
4
Explain why it is wrong to say that the greenhouse effect is causing global warming.
Model answer
Because the greenhouse effect is a permanent and beneficial feature of the planet, not a problem, and it was operating for billions of years before humans existed. Blaming it for warming implies that the goal should be to remove it, which would leave the Earth at about minus 18 degrees Celsius. The correct statement is that human emissions have enhanced the greenhouse effect by raising the concentration of greenhouse gases, and that it is this enhancement, the extra absorption of outgoing longwave radiation, which is causing the observed warming. Examiners treat the distinction as a test of whether a candidate understands the mechanism, and confusing the two is the single commonest error in this topic.
5
Why is it wrong to confuse the enhanced greenhouse effect with the hole in the ozone layer?
Model answer
Because they are separate problems with different gases, different mechanisms and different effects. Ozone depletion is the destruction of stratospheric ozone, mainly by chlorine released from chlorofluorocarbons, which allows more harmful ultraviolet radiation to reach the surface, increasing skin cancer and damaging ecosystems; it is worst over Antarctica in spring. The enhanced greenhouse effect is the trapping of more outgoing longwave radiation by higher concentrations of greenhouse gases, which raises surface temperature. A thinner ozone layer does not cause global warming, and it in fact cools the stratosphere. The two are connected only in that chlorofluorocarbons happen to be both ozone-depleting and extremely powerful greenhouse gases, so controlling them under the Montreal Protocol helped with both.
6
Demonstrate knowledge and understanding of the greenhouse gases that matter, and of the human sources of each.
Model answer
Carbon dioxide is much the most important overall, released by burning coal, oil and gas, by cement manufacture and by deforestation and land-use change. Methane comes from ruminant livestock, flooded rice paddies, landfill sites, and leakage from coal mines and from oil and gas production. Nitrous oxide comes chiefly from nitrogen fertilisers and manure on farmland, and from some industrial processes and vehicles. Halocarbons, including chlorofluorocarbons and their replacements, come from refrigeration, air conditioning, foam blowing and aerosols. Tropospheric ozone forms from vehicle and industrial pollution. Water vapour is the most abundant greenhouse gas but its concentration is set by temperature rather than directly by emissions.

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Processes That Shape Fluvial Environments

Human Interaction in Fluvial Environments

Global Biomes

Small-Scale Ecosystems

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Current Global Climate Change: Human Causes and Impacts revision questions

What does Current Global Climate Change: Human Causes and Impacts cover in CCEA A-Level Geography?: 3 subtopics: the greenhouse effect and the enhanced greenhouse effect, evidence for recent climate change and its links to human activity and present and potential impacts of climate change. Each one has its own page with questions and model answers.
How is Current Global Climate Change: Human Causes and Impacts organised?: By the CCEA 3910 specification, subtopic by subtopic, so it matches the order you are taught it in.

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