Climate Change

What Climate Change covers

Climate Change is examined in Component 03, Geographical debates. It covers how past climates are reconstructed from natural archives; icehouse and greenhouse Earth, from Cenozoic cooling to the Holocene; the natural drivers of climate, from continental drift and volcanic activity to Milankovitch cycles and solar output; the natural greenhouse effect; and the evidence of warming in the atmosphere and oceans, retreating ice, shrinking snow cover and rising sea level. It also covers why emissions have risen and how their balance has shifted from advanced to emerging countries; the enhanced greenhouse effect; the global warming debate and the parts governments, international organisations and the media play in it; climate models, feedback and future scenarios; impacts and vulnerability; mitigation through energy efficiency, low-carbon energy, carbon capture, forestry and geoengineering; adaptation in homes, cities and economies; contrasting responses in the Netherlands and Bangladesh; and the IPCC and international agreements.

The 22 subtopics

Each one has its own page.

• Reconstructing past climates from natural archivesRecall questions on climate proxies, oxygen isotopes and foraminifera in marine sediments, varves and pollen in lake sediments, the temperature and trapped air records of ice cores and their 800,000-year reach, volcanic dating horizons, tree rings and their limits, fossil beetles and corals, and why several proxies are combined.Open →
• Icehouse and greenhouse Earth, from Cenozoic cooling to the HoloceneRecall questions on greenhouse and icehouse Earth, cooling over the last 100 million years and its causes, silicate weathering, the glaciation of Antarctica and ocean gateways, the Quaternary glacial cycles and their changing rhythm, the Last Glacial Maximum and its ice sheets, the Holocene, the Medieval Warm Period and the Little Ice Age.Open →
• Continental drift and volcanic activity as drivers of climateRecall questions on how drifting continents, polar landmasses, mountain building and Pangaea change climate, how stratospheric aerosols from eruptions such as Mount Pinatubo and Tambora cool the planet, volcanic warming over long timescales, large igneous provinces, ocean gateways and the Isthmus of Panama, and the timescales of each driver.Open →
• Milankovitch cycles and changes in solar outputRecall questions on eccentricity, obliquity and precession and their periods, summer insolation at 65° N and ice sheet growth, why orbital cycles need feedbacks, the sunspot cycle and solar irradiance, the Maunder Minimum, the faint young Sun paradox, and why solar output cannot explain recent warming.Open →
• The natural greenhouse effect and the atmosphere's greenhouse gasesRecall questions on how the natural greenhouse effect works and the warming it provides, why nitrogen and oxygen are not greenhouse gases, water vapour as a feedback, carbon dioxide, methane and nitrous oxide, pre-industrial and glacial CO₂ levels, residence time, and why the greenhouse effect does not trap heat indefinitely.Open →
• Warming of the surface, atmosphere and oceans since the late 19th centuryRecall questions on the scale and uneven pattern of warming since the 19th century, the instrumental record, faster warming on land, Arctic amplification, night-time temperatures and stratospheric cooling, ocean heat content and profiling floats, rising water vapour, evidence beyond thermometers, and why the urban heat island cannot explain the trend.Open →
• Retreating ice, shrinking snow cover and rising sea levelRecall questions on retreating valley glaciers and mass balance, the effect of glacier loss on mountain water supply, ice loss from Greenland and Antarctica and how satellites measure it, sea level rise since 1900 and its acceleration, thermal expansion and meltwater, sea ice decline and albedo, falling snow cover, and thawing permafrost.Open →
• Why greenhouse gas emissions have risen since the pre-industrial eraRecall questions on fossil fuel combustion as the main CO₂ source, today's concentration and the Mauna Loa record, population growth and affluence, deforestation, agricultural methane and nitrous oxide from fertiliser, cement making, the rise in methane, halocarbons, electricity demand, and the acceleration after 1950.Open →
• The changing global balance of emissions, from an AC to an EDCRecall questions on ACs and EDCs, the historic dominance of Europe and North America, China as the largest annual emitter, annual, cumulative and per-person emissions, consumption-based accounting, the halving of United Kingdom emissions and its net zero law, the rise of China's emissions and its pledges, and arguments for unequal responsibility.Open →
• The enhanced greenhouse effect and the global energy balanceRecall questions on the enhanced greenhouse effect, radiative forcing since 1750 and the share from CO₂, climate sensitivity, incoming and reflected solar radiation, Earth's energy imbalance, aerosols masking warming and the effect of cleaning the air, land use change and albedo, black carbon, and the urban heat island.Open →
• The evolution of the global warming debateRecall questions on Tyndall, Arrhenius and Keeling, the 1970s expectation of cooling, the 1988 Senate testimony, the shift from whether warming is happening to what to do, the hockey stick graph, the 2009 stolen emails, scientific consensus, uncertainty as an argument for delay, economic interests, extreme weather, and the debate over solutions.Open →
• Governments, international organisations and the media in the climate debateRecall questions on the United Nations and Conferences of the Parties, the European Union and its Green Deal, why governments find action hard, the free-rider problem and electoral cycles, false balance and framing in the media, fossil fuel interests, pressure groups, greenwashing, social media, scientific academies, and political polarisation.Open →
• Climate models, the carbon cycle and feedbackRecall questions on general circulation models and how they are tested, ensembles, clouds and ice sheets as uncertainties, downscaling, the carbon cycle in models, the main carbon stores and sinks, ocean acidification, positive feedbacks such as ice-albedo and permafrost thaw, negative feedbacks including CO₂ fertilisation, and tipping points.Open →
• Future emission scenarios and projected temperature and sea level riseRecall questions on emission scenarios and why they give projections, low and high emission pathways and warming by 2100, similar warming to 2040, committed warming, projected sea level rise and why it continues for centuries, carbon budgets, negative emissions, and the uncertainty of regional and sea level projections.Open →
• Impacts on ecosystems, health and extreme weatherRecall questions on shifting species ranges, mountain and polar species, phenology and mismatch, coral bleaching on the Great Barrier Reef, ocean acidification, vector-borne disease, heatwave health risks and vulnerable groups, food supply, heavier rainfall, stronger tropical cyclones, wildfire risk, attribution science, and compounding future impacts.Open →
• The vulnerability of people and environments to climate changeRecall questions on vulnerability, exposure and adaptive capacity, the number of highly vulnerable people, river deltas and Bangladesh, small island developing states, how poverty and gender raise vulnerability, Arctic indigenous communities, the most vulnerable ecosystems, habitat fragmentation, and why vulnerability is more than exposure.Open →
• Mitigation through energy efficiency, fuel shifts and low-carbon energyRecall questions on mitigation, energy efficiency and conservation, home insulation and LEDs, combined heat and power, the rebound effect, coal-to-gas switching and its limits, wind, solar and nuclear power, falling solar costs, intermittency and grid solutions, objections to nuclear, and the difficulty of decarbonising heat and heavy industry.Open →
• Carbon capture and storage, forestry strategies and geoengineeringRecall questions on carbon capture and storage, its geological settings, Sleipner and the energy penalty, objections to it, bioenergy with carbon capture, afforestation and reforestation, schemes paying countries to keep forests, the limits of forestry and high-latitude planting, and geoengineering, stratospheric aerosol injection and termination shock.Open →
• Retreat, accommodation and protection as adaptationRecall questions on adaptation and how it differs from mitigation, the retreat, accommodate and protect options, managed realignment at Medmerry, raised houses and early warning systems, the Thames Barrier, how advanced and lower-income countries adapt differently, maladaptation, and mangrove restoration.Open →
• Adapted homes, cities, transport and economiesRecall questions on homes designed for a warmer climate, passive design and heat pumps, green roofs, sustainable drainage and street trees, the 15-minute city, net zero transport and electric cars, the circular economy, green hydrogen, a just transition, and Copenhagen's pursuit of carbon neutrality.Open →
• Contrasting countries: impacts, opportunities and the challenges of respondingRecall questions on contrasting responses to climate change in the Netherlands and Bangladesh: the Delta Works and Room for the River, Dutch impacts and water expertise, Bangladesh's low emissions and high exposure, cyclone shelters and floating gardens, the technological, socio-economic and political challenges of mitigation, and climate finance.Open →
• The IPCC, international agreements and policy from global to localRecall questions on the IPCC, its Summary for Policymakers and confidence language, the 1992 Earth Summit, the Kyoto Protocol and its limits, the Clean Development Mechanism, the Paris Agreement and its temperature goal, cap and trade and the EU Emissions Trading System, carbon credits and offsetting, the UK Climate Change Act, and sub-national action.Open →

What you need to know

Answer each one before you reveal it.

Take Climate Change further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Natural greenhouse effect vs Enhanced greenhouse effect

  Natural greenhouse effect: the warming produced when water vapour, carbon dioxide and methane absorb outgoing longwave radiation, worth roughly 33 °C and essential to life on Earth. Enhanced greenhouse effect: The extra warming that occurs when human emissions push concentrations of heat-trapping gases above their pre-industrial levels.

• Mitigation vs Adaptation

  Mitigation: tackling the cause of warming, by cutting emissions of heat-trapping gases or removing carbon from the atmosphere. Adaptation: Managing the consequences of warming by adjusting to changes that happen anyway, through sea walls, warning systems or drought-tolerant crops.

• Sea ice vs Ice sheet

  Sea ice: frozen salt water floating on the ocean, which already displaces its own weight and so adds no volume when it melts. Ice sheet: A vast mass of frozen fresh water resting on land, as on Greenland and Antarctica, whose meltwater does raise ocean levels.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is a climate proxy?

   Model answer

   A climate proxy is a natural record, such as a tree ring or a layer of ice, that preserves a measurable signal of climate conditions from before instrumental measurements began.

2. 2

   Why must climate before about 1850 be studied indirectly?

   Model answer

   Reliable instrumental measurements of temperature only became widespread from the mid-19th century, so earlier conditions have to be inferred from natural archives.

3. 3

   How do oxygen isotope ratios in marine sediments record past climate?

   Model answer

   The shells of foraminifera lock in the ocean ratio of ¹⁸O to ¹⁶O, and because the lighter ¹⁶O is preferentially evaporated and stored in ice sheets during glacials, shells formed then are enriched in ¹⁸O.

4. 4

   Name the microscopic marine organisms whose shells in ocean-floor sediment are used to reconstruct past ocean conditions.

   Model answer

   They are foraminifera, single-celled organisms whose calcite shells record the isotopic composition of the seawater they grew in.

5. 5

   Give one advantage of marine sediment cores over ice cores as a climate archive.

   Model answer

   Marine sediments accumulate on almost every ocean floor and extend back tens of millions of years, far beyond the roughly 800,000 years covered by the longest ice cores.

6. 6

   What is a varve, and why is it useful to a climate scientist?

   Model answer

   A varve is the pair of sediment layers laid down in a lake in a single year, coarse and pale in summer and fine and dark in winter, so counting varves dates a lake sequence year by year.

What is inside Levo

Six ways to work the same material.

Climate Change revision questions

What does Climate Change cover in OCR A-Level Geography?

22 subtopics: reconstructing past climates from natural archives, icehouse and greenhouse earth, from cenozoic cooling to the holocene, continental drift and volcanic activity as drivers of climate, milankovitch cycles and changes in solar output, the natural greenhouse effect and the atmosphere's greenhouse gases, warming of the surface, atmosphere and oceans since the late 19th century, retreating ice, shrinking snow cover and rising sea level, why greenhouse gas emissions have risen since the pre-industrial era, the changing global balance of emissions, from an ac to an edc, the enhanced greenhouse effect and the global energy balance, the evolution of the global warming debate, governments, international organisations and the media in the climate debate, climate models, the carbon cycle and feedback, future emission scenarios and projected temperature and sea level rise, impacts on ecosystems, health and extreme weather, the vulnerability of people and environments to climate change, mitigation through energy efficiency, fuel shifts and low-carbon energy, carbon capture and storage, forestry strategies and geoengineering, retreat, accommodation and protection as adaptation, adapted homes, cities, transport and economies, contrasting countries: impacts, opportunities and the challenges of responding and the ipcc, international agreements and policy from global to local. Each one has its own page with questions and model answers.

How is Climate Change organised?

By the OCR H481 specification, subtopic by subtopic, so it matches the order you are taught it in.