AQA GCSE Geography Notes: Climate Change Evidence, Causes, Mitigation, and Adaptation

Evidence for Climate Change

• Shrinking Glaciers and Melting Ice: Ice sheets and glaciers worldwide are losing ice mass and retreating at accelerated rates.
• Rising Sea Levels: Global sea levels are increasing due to the thermal expansion of warming ocean water and the influx of meltwater from land-based ice.
• Seasonal Changes: Biological and atmospheric timing shifts are occurring across species, such as birds migrating earlier in the year.
• Antarctic Ice Cores: Deep ice core samples extracted from Antarctica are analyzed to reconstruct historical atmospheric compositions and global temperature data from the past.

Physical Causes of Climate Change

• Earth's Orbit (Milankovitch Cycles):
  • Orbital Shape (Eccentricity): Earth's orbit shifts between a circular shape and an elliptical shape over a cycle lasting $100,000\,\text{years}$. This change alters Earth's distance from the Sun at different times, causing significant global temperature variations.
  • Axial Wobble (Precession): The Earth wobbles on its rotational axis, causing specific geographic regions to experience periods of warmer or colder conditions.
  • Axial Tilt (Obliquity): The angle of Earth's axial tilt shifts back and forth over a cycle of $41,000\,\text{years}$, resulting in long-term cyclical periods of climate warming and cooling.
• Solar Activity and Sunspots:
  • Sunspots: Sunspots are darker, cooler patches on the surface of the Sun caused by magnetic activity.
  • Heat Output Fluctuations: When sunspot activity reaches its highest levels, the Sun emits increased amounts of heat radiation towards Earth. Conversely, when sunspot activity is low, solar energy output is reduced, leading to lower global temperatures.
  • The Little Ice Age: Very few sunspots were observed between $1645$ and $1715$, a period that directly coincided with significantly reduced global temperatures known as The Little Ice Age.
• Volcanic Activity:
  • Volcanic Ash: Eruptions release vast quantities of volcanic ash into the upper atmosphere, blocking incoming solar radiation and reducing temperatures. This represents a short-term cooling effect.
  • Sulphuric Acid Aerosols: Ejected sulphur dioxide ($SO_2$) converts into sulphuric acid droplets in the atmosphere. These act as tiny mirrors that reflect solar heat back into space, producing a longer-lasting cooling effect.
  • Volcanic Winter: The atmospheric blocking and reflection of solar radiation following major volcanic events can lead to a overall drop in global temperatures termed a volcanic winter.

Human Causes of Climate Change

• The Greenhouse Effect:
  • Mechanism: The Earth's atmosphere naturally acts like a greenhouse. Certain gases permit solar radiation to pass through to the surface while trapping the reflected heat, keeping Earth warmer than it would normally be.
  • Essential for Life: This natural insulation process is essential for maintaining global temperatures capable of supporting life.
• The Enhanced Greenhouse Effect:
  • Human Impact: Human activities add excessive amounts of greenhouse gases to the atmosphere, creating an intensified and more powerful greenhouse effect.
  • Nitrous Oxides ($N_2O$): Generated through the widespread use of agricultural fertilisers, vehicle car exhausts, and thermal power stations.
  • Carbon Dioxide ($CO_2$): Emitted through mass deforestation, the burning of wood, and the combustion of fossil fuels such as coal, oil, and natural gas.
  • Methane ($CH_4$): Emitted through agricultural activities including flooded rice farming, digestive emissions from livestock, and the burning of biomass.

Effects of Climate Change

• Displacement of People: Forced migration and human population displacement resulting from rising sea levels, severe weather, and habitat loss.
• Loss of Employment and Farmland: Degradation, desertification, and inundation of agricultural land cause widespread unemployment in rural and farming sectors.
• Resource Insecurity: Shifts in precipitation patterns disrupt ecosystems and result in a severe lack of reliable water and food supplies.
• Species Endangerment: Rapidly altering weather and climate patterns outpace species' capacity to adapt, causing habitat loss and endangerment.
• Rising Sea Levels: Coastal flooding, land erosion, and loss of low-lying island habitats driven by thermal expansion of oceans and melting land ice.

Mitigation of Climate Change

• Definition of Mitigation: Management strategies aimed at stopping, preventing, or reducing the underlying causes of climate change.
• Alternative Energy Production: Transitioning energy generation away from fossil fuels to clean, low-carbon alternatives such as solar power, wind power, wave energy, hydroelectric power (HEP), and nuclear power.
• Carbon Capture and Storage: Utilizing technological systems to capture carbon dioxide ($CO_2$) emitted from industrial sources and store it safely underground in liquid form.
• Afforestation and Tree Planting:
  • Carbon Sinks: Trees function as natural carbon sinks, removing atmospheric carbon dioxide ($CO_2$) through photosynthesis.
  • Evapotranspirative Cooling: Trees release moisture into the atmosphere, which generates a localized cooling effect.
• International Agreements:
  • $2005$ Kyoto Protocol: The first international treaty to become law, where $170$ countries agreed to legally binding targets to reduce carbon emissions.
  • $2015$ Paris Agreement: The first legally binding global deal on climate change, which established that:
  • Global greenhouse gas emissions must peak as soon as possible.
  • The global average temperature increase must be kept well below $2^\circ\text{C}$ above pre-industrial levels.
  • A fund of $\$100\text{bn}$ per year is provided to support climate change mitigation and adaptation efforts in developing countries.

Adaptation to Climate Change

• Definition of Adaptation: Changing human behaviors, infrastructure, and agricultural systems to cope with the existing and expected effects of climate change.
• Agricultural Adaptation:
  • Constructing new and efficient irrigation systems.
  • Developing and planting drought-resistant crop varieties.
  • Planting trees across agricultural land to provide shade for crops and livestock.
  • Altering traditional cropping patterns, such as shifting sowing and harvesting dates to match altered climate cycles.
• Water Supply Adaptation:
  • Glacial Dependence in Asia: Millions of people across Asia depend on major rivers fed by melting glaciers and snowpacks, most of which are shrinking.
  • Artificial Glaciers in Ladakh, India: In Ladakh, India, winter runoff water is directed through artificial channels into catchment areas where it freezes. This artificial glacier stores solid ice through the winter and melts during springtime to supply vital agricultural and drinking water.
• Sea Level Rise Adaptation:
  • Maldives Vulnerability: The low-lying island nation of the Maldives faces extreme existential risks from rising sea levels.
  • Implemented Measures:
  • Restoration of coastal mangrove ecosystems to absorb wave energy and slow erosion.
  • Engineering and building artificial higher elevated islands for habitation.
  • Constructing elevated residential homes built on stilts.
  • Building hard engineering sea walls along vulnerable coastlines.
  • Planning evacuation and relocation frameworks to move citizens safely to neighboring countries such as India and Sri Lanka.