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.