2.4

• How does the Earth receive energy?

  As incoming solar radiation; dark surfaces absorb it and radiate it back as heat.
• What do greenhouse gases (GHGs) do?

  They absorb and reflect some radiated heat back to Earth, warming the surface.
• By how much does the natural greenhouse effect warm Earth’s surface?

  By about 16°C—making it habitable.
• what is CO2?

  CO2: 89% of GHGs, main sources are Fossil fuel burning and deforestation, 30% increase since 1850
• what is methane?

  methane: 7% of GHGs, main sources Gas leaks and cattle farming, 21x more warming power than CO2, 250% increase since 1850
• what is nitrous oxide?

  nitrous oxide: 3% of GHGs, main sources Jet engines, vehicles and sewage, 250x more warming power than CO2, 16% increase since 1850
• what are halocarbons?

  halocarbons: 1% of GHGs, main sources Industry cooling equipment, 3000x more warming power than CO2
• How much have GHG concentrations increased since 1750?

  By 25%.
• What caused 75% of CO₂ emissions since the 1980s?

  Burning of fossil fuels.
• How do human activities contribute to GHG levels?

  They release natural carbon and nitrogen stores, which combine with oxygen to form GHGs.
• How does warming increase water vapor in the atmosphere?

  Higher temperatures cause more evaporation and condensation, increasing cloud cover and heat retention.
• How do oceans contribute to carbon sequestration?

  Phytoplankton absorb CO₂ and pump it into ocean stores through photosynthesis.
• How do terrestrial plants regulate CO₂ levels?

  They absorb CO₂ through photosynthesis and release it via respiration and decomposition.
• What factors impact carbon sequestration?

  Changes in phytoplankton populations or forest areas.
• What role does organic matter play in the soil carbon system?

  It passes carbon through the system and supports microorganisms for decomposition.
• How is soil carbon store calculated?

  Inputs (plant litter/animal waste) – outputs (decomposition, erosion, plant uptake).
• What is primary productivity?

  The rate at which plants produce biomass.
• How much solar energy is captured by photosynthesis?

  Only about 1% of solar insolation.
• When is the carbon cycle in equilibrium?

  When carbon sources and sinks are balanced.
• What stabilizes global temperatures?

  A steady concentration of atmospheric CO₂.
• How does fossil fuel combustion affect carbon pathways?

  It accelerates carbon release and increases flows.
• How does climate change affect Europe’s water sources?

  Summer meltwater from Alpine glaciers is critical, but glaciers could disappear by 2100
• What happens as glaciers retreat?

  Water discharge and sediment yield fall, affecting water quality.
• Where are the largest temperature increases expected?

  East and North Europe in winter; Southern Europe in summer.
• What’s the trend in precipitation across Europe?

  It will increase in the north, decrease in the south.
• What is Arctic amplification?

  The Arctic is warming twice as fast as the global average.
• What’s an example of species migration due to warming?

  The red fox is moving north, competing with the Arctic fox in Alaska.