Introduction to Climate Change

Introduction to Climate Change – Study Notes

1. What Is Climate Change?

• Definition – Long‑term alteration of temperature, precipitation, wind patterns, and other aspects of the Earth’s climate system.
• Distinction from Weather – Weather = short‑term atmospheric conditions (hours‑days). Climate = average of weather over decades‑centuries.
• Key Components
  • Atmospheric composition (greenhouse gases, aerosols)
  • Energy balance (incoming solar radiation vs. outgoing infrared radiation)
  • Feedback mechanisms (water‑vapor, ice‑albedo, carbon cycle)

2. Drivers of Climate Change

Current scientific consensus: > 99 % of the observed warming since the mid‑20th century is attributable to human activities.

3. The Greenhouse Effect

1. Solar radiation reaches Earth as short‑wave (visible) energy.
2. Surface absorbs energy and re‑emits it as long‑wave (infrared) radiation.
3. Greenhouse gases (GHGs) absorb and re‑emit part of this infrared radiation, trapping heat in the lower atmosphere.
4. Result: Global average surface temperature rises.

Major GHGs (by radiative forcing, 2020):

• CO₂ (≈ 1.68 W m⁻²) – fossil fuels, cement, land‑use change
• CH₄ (≈ 0.48 W m⁻²) – livestock, rice paddies, fossil‑fuel extraction
• N₂O (≈ 0.17 W m⁻²) – agriculture, industrial processes
• Fluorinated gases (≈ 0.20 W m⁻²) – refrigerants, electronics

4. Evidence of Climate Change

5. Impacts of Climate Change

1. Physical Environment
   • Melting ice sheets → sea‑level rise, coastal flooding
   • Ocean acidification (↑ CO₂) → coral bleaching, shell‑forming organism stress
   • Shifts in ecosystems and species ranges