Unit 2: Global climate

Atmosphere

• Input: Solar heat, evaporation (water), CO₂, O₂

• Output: Weather, precipitation, oxygen distribution, ozone protection

• Key gases: 78% N₂, 21% O₂, 1% CO₂/Ar/trace

Biosphere

• Input: CO₂ (for plants), O₂ (for organisms), water

• Output: O₂ + H₂O (photosynthesis), CO₂ + H₂O (respiration)

Hydrosphere

• Input: Precipitation from atmosphere

• Output: Evaporation & sublimation → water vapour to atmosphere

• 97% ocean water, 2/3 of freshwater stored in ice

Lithosphere

• Input: Water from hydrosphere into rocks (groundwater)

• Little direct impact from climate change (compared to others)

Cryosphere

• Input/Overlap: Frozen water + frozen ground (hydrosphere + lithosphere)

• Output: Releases water if melting

Atmosphere ⇄ Hydrosphere

• Water enters atmosphere by:

  • Evaporation (liquid → gas)

  • Sublimation (solid → gas)

• Controlled by temperature → warmer air holds more water vapour

• Output back to Earth: Precipitation (rain/snow/hail)

• Human impacts: reservoirs, irrigation, draining wetlands

Atmosphere ⇄ Biosphere

• Photosynthesis

  • Input: CO₂ (air), H₂O (soil)

  • Output: O₂ + water vapour (transpiration)

• Respiration

  • Input: O₂

  • Output: CO₂ + water vapour

• Normally a balanced cycle, but humans disrupt via deforestation & pollution

Bangladesh case study

• The majority of the country is less than 12 m above sea level. (prone to flooding)

• rising sea levels (1 m) could reduce land area by 10%

• Prone to cyclones and flooding caused by the summer monsoons.

• Over 60% of the population is engaged in farming and lives in rural areas

• Literacy rate: 61.5%.

Mitigation strategies:

• Reduce energy use (transport,vehicles)

• Replace fossil fuels (solar power, Wind power, hydropower, geothermal energy)

• Reduce emissions from agriculture (less fertilisers, Cultivating rice varieties that can be grown in drier conditions)

carbon dioxide removal techniques:

• land use management

• absorption by oceans

• carbon capture storage

Carbon credit:

a tradable permit (or certificate) that allows a country/industry/organisation to produce 1 metric tonne of carbon dioxide.

Cap and Trade

an economic system used to control carbon emissions. An upper limit or cap sets the maximum emission allowed. It also allows for extra capacity to be traded between organisations.

Carbon offset

when operators sponsor activities or projects in other countries that will reduce the amount of carbon dioxide in the atmosphere. The aim being to compensate for their own emissions.

government led adaptations:

• Coastal systems and low-lying areas

• Water resources

• Health