Geo chapter 2 - depth study 1

Global Climate Change

climate change def

A long-term shift in weather conditions (temperature, rainfall, winds), climate change may be due to natural causes or human causes

Describe the spatial distribution of global temperature patterns.

• Hottest near the Equator (low latitudes) – direct sunlight year-round.

• Temperature decreases toward the poles (high latitudes).

• Influenced by altitude (mountains = colder), ocean currents, distance from sea.

• Example: Equatorial Africa avg >27°C, Antarctica avg <–20°C.

Describe the spatial distribution of global rainfall patterns.

• High rainfall near Equator (Intertropical Convergence Zone – convectional rain).

• Low rainfall at ~30° N & S (subtropical high-pressure zones → deserts).

• High rainfall in coastal/mountain regions (orographic rain).

• Example: Amazon Basin >2,000mm/year vs Sahara <250mm/year.

Define the heat budget.

The balance between incoming solar radiation (insolation) and outgoing terrestrial radiation that determines Earths temperature.

Define the greenhouse effect.

The natural process where greenhouse gases absorb and re-radiate heat, keeping Earth ~33 degrees warmer than without it.

Key stats in the global heat budget diagram

• Incoming solar radiation: 100%

• Reflected to space by: (clouds 20%, atmosphere 6%, surface 4%)

Absorbed by:

- Atmosphere: 16%

-land and oceans: 51%

-air: 3%

• radiated to space from:

-clouds and atmosphere: 64%

-earth: 6%

Define the hydrological cycle.

The continuous movement of water between the atmosphere, land and oceans through processes such as evaporation, condensation, precipitation and runoff.

What is the hydrological (water) cycle?

• Continuous movement of water between atmosphere, land, and oceans.

• Processes: evaporation, transpiration, condensation, precipitation, infiltration, runoff.

• Stats: ~500,000 km³/yr evaporated → 78% falls back on oceans, 22% on land; ~40,000 km³/yr runs off land to oceans.

What is the carbon cycle?

The continuous movement of carbon between the atmosphere, biosphere, lithosphere, and hydrosphere through processes such as photosynthesis, respiration, decomposition, combustion, and exchange with oceans.

Key stats in the carbon cycle.

• Atmosphere: ~750 Gt carbon.

• Vegetation/soil/biota: ~2,000 Gt.

• Oceans: ~38,000 Gt (largest active store).

• Fossil fuels: ~5,000 Gt (lithosphere).

• Human activity adds ~10 Gt CO₂/year from burning fossil fuels + land clearing.

Explain the carbon cycle diagram.

• Inputs: CO₂ enters plants via photosynthesis → stored in biomass.

• Transfers: Carbon moves through food chains → animals → soils (decomposition).

• Outputs: Returned to atmosphere by respiration, combustion, decay.

• Oceans: Absorb CO₂ (dissolution) and release it back (outgassing).

• Lithosphere: Long-term storage in rocks & fossil fuels; volcanic eruptions return carbon.

What is atmospheric circulation?

The large-scale movement of air that redistributes heat and moisture across the Earth, driven by unequal heating of the atmosphere by the Sun.

Key stats in atmospheric circulation.

• Earth receives most heat at Equator → warm air rises.

• Circulation forms 3 cells per hemisphere:

  • Hadley cell (0–30°) – rising at Equator, descending at 30°.

  • Ferrel cell (30–60°) – mid-latitudes.

  • Polar cell (60–90°) – rising at 60°, sinking at poles.

• Creates global wind belts: Trade winds, Westerlies, Polar easterlies.

Explain the atmospheric circulation diagram.

• At Equator: warm air rises (low pressure) → heavy rainfall (tropics).

• At 30° N/S: cool air sinks (high pressure) → arid zones/deserts.

• At 60° N/S: warm air rises again → temperate rainfall zones.

• At Poles: cold air sinks → polar deserts.

• Coriolis effect deflects winds → curved wind patterns.

What are Milankovitch cycles (changes in Earth’s orbit)?

Long-term variations in Earths orbit around the Sun (eccentricity, tilt, precession) that change the amount and distribution of solar radiation, influencing glacial and interglacial periods.

Explain a diagram of the Milankovitch cycles.

• Eccentricity: Shape of orbit changes every ~100,000 yrs (circular ↔ elliptical) → alters distance from Sun.

• Axial tilt (obliquity): Tilt varies 22.1°–24.5° every ~41,000 yrs → affects seasonal contrasts.

• Precession: Earth’s axis wobbles every ~26,000 yrs → shifts timing of seasons.

• Together these cycles change Earth’s insolation → trigger ice ages & warm periods.

How does agriculture cause climate change?

• Livestock (esp. cattle) release methane (CH₄) through digestion.

• Rice paddies emit methane from anaerobic decay.

• Fertilisers release nitrous oxide (N₂O).

• Agriculture contributes ~18% of global GHG emissions (FAO).

How does deforestation cause climate change?

• Trees remove CO₂ via photosynthesis → clearing reduces carbon sink.

• Burning/decay of trees releases stored CO₂.

• Accounts for ~10% of global CO₂ emissions.

• Example: Amazon lost 54m ha (2001–2020); major source of emissions.

What are ice cores and how are they used?

• Cylinders of ice drilled from ice sheets (e.g. Antarctica, Greenland).

• Contain air bubbles with past atmosphere.

• Measure gases (CO₂, CH₄) + oxygen isotopes (O¹⁸/O¹⁶) → past temp & climate.

What evidence do ice cores give for climate change?

• Provide records for ~800,000 years (Vostok, Dome C).

• CO₂ cycles: 180 ppm (ice ages) ↔ 280–300 ppm (warm interglacials).

• Show clear link: higher GHG = warmer temps.

How is the atmosphere used as evidence for climate change?

• Instrumental records (thermometers, satellites, weather stations) track temp & GHGs.

• Direct CO₂ measurements at Mauna Loa, Hawaii (since 1958).

• Shows short-term, precise trends in recent human history.

What evidence does the atmosphere give for climate change?

• Global avg temp ↑ ~1.1°C since 1880 (NASA).

• CO₂ rose from ~280 ppm (1750) → 420+ ppm today.

• Warmest years on record = last decade.

• Clear link between industrialisation & rising temps.

How does surface reflectivity (albedo) link LCC and climate?

• Albedo = proportion of solar radiation reflected by a surface.

• Forests/vegetation: low albedo (~0.1–0.2) → absorb heat.

• Ice/snow: high albedo (~0.8–0.9) → reflect heat.

• LCC impact: Deforestation increases reflectivity short term, but reduces evapotranspiration → warmer climate overall.

• Example: Arctic melting ↓ albedo → more absorption → positive feedback.

What is natural carbon sequestration and how does it link LCC and climate?

• Carbon sequestration = natural storage of carbon in plants, soils, and oceans.

• Forests + soils absorb ~2.6 Gt CO₂/year (IPCC).

• LCC impact: Deforestation reduces sequestration → more CO₂ in atmosphere → enhanced greenhouse effect.

• Example: Amazon rainforest = world’s largest terrestrial carbon sink (~100 Gt stored). Clearing releases CO₂ + weakens sink.

Present impacts of climate change on ice sheets & glaciers

• Rapid retreat & thinning.

• Greenland losing ~270 billion tonnes of ice/yr (2002–2019).

• Himalayan glaciers shrinking → threatens rivers (Ganges, Mekong).

• Sea level rise already ~20 cm since 1900.

Projected impacts of climate change on ice sheets & glaciers

• Continued melting → major sea level rise.

• Greenland + Antarctica could add up to 1m by 2100 (IPCC, high-emissions scenario).

• Loss of glacial water sources → 1.9b people face reduced freshwater supply.

• Positive feedback: less ice → ↓ albedo → more warming.

Present impacts of climate change on urban settlements

• ↑ frequency of heatwaves & flooding.

• 2023: Europe heatwave hit 45°C, record hospitalisations.

• Coastal cities (e.g. Miami, Jakarta) already face nuisance flooding during high tides.

• Economic costs: damages in 2022 = US$275b globally (Swiss Re).

Projected impacts of climate change on urban settlements

• By 2050, 570+ coastal cities threatened by sea level rise.

• Extreme heat: many cities may face >50 days/yr above 35°C.

• Climate migrants: up to 200m displaced by 2050 (World Bank).

• Infrastructure damage: trillions in adaptation/repair costs.