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Climate Change Lecture Notes

Climate vs. Weather

  • Weather: The condition of the atmosphere in a specific area at a given time.
  • Climate: The long-term average of weather conditions in an area.
  • Major elements of both include:
    • Temperature
    • Air pressure
    • Wind
    • Solar energy
    • Humidity
    • Precipitation
    • Topography

Key Terminology

  • Greenhouse Effect: A natural process where certain gases in the atmosphere trap heat, keeping the Earth warm.
  • Global Warming: Refers specifically to the increase in Earth's average surface temperature due to rising levels of greenhouse gases.
  • Climate Change: A broader term that includes any change in climate over time, whether due to natural variability or human activity.

The Greenhouse Effect

  • Process:
    • Solar radiation passes through the atmosphere.
    • Some is reflected back to space, while some is absorbed and re-emitted by greenhouse gases.
    • This process warms the Earth's surface and the lower atmosphere.
  • Key Gases: Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs).
  • Importance: This process is essential for life on Earth, but human activities have enhanced it, causing global warming.

Measuring Global Average Temperature

  • Scientists gather temperature measurements from various locations around the globe.
  • They convert these to temperature anomalies: the difference from long-term averages.
  • Multiple independent analyses show a consistent upward trend in global temperatures.

Understanding Temperature Anomalies

  • Positive Anomalies: Above average temperatures.
  • Negative Anomalies: Below average temperatures.

Natural vs. Anthropogenic Factors

  • The Earth has undergone natural warming periods, but current changes are largely attributed to human activities, mainly fossil fuel combustion and deforestation.
  • Astronomical factors can also affect climate cycles (e.g., Earth's orbital variations).

Composition of Earth's Atmosphere

  • Mostly nitrogen and oxygen.
  • Permanent Gases: Constant concentrations.
  • Variable Gases: Fluctuate due to natural processes and human activities.

Global Warming Potential (GWP)

  • A measure comparing how much heat a greenhouse gas traps in the atmosphere relative to CO2, which has a GWP of 1.
  • Examples of GWP:
    • Methane: 28–36 times greater than CO2.
    • Nitrous Oxide: 265–298 times greater than CO2.

Sources of Carbon Dioxide

  • Human activities contribute 87% of CO2 emissions, primarily from burning fossil fuels. Deforestation and agriculture also play significant roles.

Impact of Emissions and Climate Change

  • Rising global temperature: Averaged about 1.53°F (0.85°C) increase from 1880 to 2012.
  • Extreme Weather: Increasing frequency and intensity of hurricanes, floods, and droughts.
  • Melting Ice: Decreased sea ice and rising sea levels, significantly impacting biodiversity and human settlements.

Paleoclimate Evidence

  • Ice Cores: Provide historical climate data through trapped gases and isotopes.
  • Tree Rings: Rings reveal climatic conditions over time.
  • Ocean Sediment: Accumulation of marine organisms reflects past temperatures and ice cover.

The Keeling Curve

  • Represents the increase of atmospheric CO2 levels since measurements began in 1957 at Mauna Loa Observatory.

Indicators of Climate Change

  • Humidity, global temperatures, sea-level rise, ocean heat content, glacial retreat, and snow cover are major indicators of climate warming.

Impacts of Climate Change

  • Global temperature rise, ice melting, sea-level rise, altered precipitation patterns, and extreme weather events all signal significant changes in our climate.

Conclusion

  • Climate change poses threats on multiple fronts, affecting natural ecosystems and human societies.
  • Responses must include both mitigation and adaptation strategies to navigate these challenges effectively.