In-Depth Notes on Climate Change and the Atmosphere

Learning Outcomes

  • Differences between the troposphere and stratosphere.
  • Factors influencing natural climate variability.
  • Explanation of the greenhouse effect and its impact on climate change.
  • Understanding the evidence of recent climate changes and their causes.
  • Effects of climate change on various systems.
  • Strategies to minimize global climate change.

The Atmosphere

  • Earth's atmosphere comprises predominantly nitrogen and oxygen with trace gases, extending up to about 500 kilometers.
  • It contains four main zones:
    • Troposphere: Closest to earth, where we experience weather.
    • Stratosphere: Contains high concentrations of ozone with very little water vapor.
    • Higher zones include the mesosphere and thermosphere.
Function of the Atmosphere
  • The atmosphere captures solar energy:
    • ¼ reflected by clouds and gases.
    • ¼ absorbed by greenhouse gases.
    • ½ reaches Earth's surface.
  • Albedo values (reflectivity):
    • Fresh snow: 80-85%
    • Water: 50-80%
    • Dark soil: 3%

The Greenhouse Effect

  • Essential to life on Earth; without it, average temperatures would be dramatically lower.
  • Greenhouse gases trap reemitted energy, maintaining a temperature conducive to liquid water.
  • Notable greenhouse gases include CO2, CH4, and N2O, with CO2 being the most significant due to its volume and longevity in the atmosphere.

Climate Change Evidence

  • Recent increases in CO2 levels highly correlated with rising global temperatures, highlighted by Mauna Loa observatory data.
  • Keeling Curve shows a rise from 315 ppm in 1958 to 393 ppm by 2012.
  • Climate models predict that if trends continue, CO2 could approach 500 ppm by the end of the century.
Consequences of Climate Change
  • Modern temperatures are unprecedented in over 2000 years.
  • Global sea levels have risen approximately 20 cm (8 inches) this century.
  • Evidence includes melting permafrost, retreating glaciers, and shifts in growing seasons.

Factors Behind Climate Change

  • Natural causes include:
    • Orbital eccentricity: Variation in Earth's orbit over 100,000 years.
    • Axial tilt and precession: Affecting climate patterns over different time scales.
  • Anthropogenic (human-caused) changes are the primary drivers of current climate trends.
Scientific Consensus
  • The IPCC confirmed significant human contribution to climate change, concluding with 99% certainty from recent assessments.
  • Observational data points to accelerating greenhouse gas emissions and rising temperatures.

Solutions for Climate Change

  • Policy approaches include:
    • Transitioning from coal to cleaner energy sources like solar and wind.
    • Emission trading schemes to cap total greenhouse emissions.
    • Supporting research and technology for renewable energy.
International Initiatives
  • Efforts made through the UN Earth Summit and the Kyoto Protocol to stabilize emissions, though challenges remain with participating countries.

Wedge Analysis

  • Proposed by Pacala and Socolow to break down climate change mitigation into manageable pieces (wedges), each representing 1 Gigatonne of carbon emissions reduced by 2058.
  • Accomplishing multiple wedges collectively could significantly curb emissions and mitigate climate impact without massive lifestyle changes.

Local Initiatives

  • Countries like Britain and Germany are leading by example through energy efficiency measures and transitioning away from coal.
  • Potential large-scale investments in carbon capture and storage technology for managing CO2 emissions.