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.
• Key Distinction:
  • Weather = short‑term atmospheric conditions.
  • Climate = average weather over decades to millennia.
• Primary Driver (Current Era): Human activities that increase concentrations of greenhouse gases (GHGs) in the atmosphere.

2. The Science Behind It

2.1 Greenhouse Gases (GHGs)

3. Evidence of Climate Change

1. Temperature Records

   • Global surface temperature has risen ~1.1 °C above pre‑industrial levels (1850–1900 baseline).
   • Last decade = warmest on record.

2. Melting Cryosphere

   • Arctic sea‑ice extent ↓ ~13 % per decade.
   • Greenland and Antarctic ice sheets losing mass → sea‑level rise.

3. Sea‑Level Rise

   • Global average sea level ↑ ~20 cm since 1900; rate accelerating to ~3.4 mm yr⁻¹ (1993‑2023).

4. Ocean Changes

   • Surface ocean warming → heat content ↑ 93 % of excess energy.
   • Ocean acidification: pH down ~0.1 (≈30 % increase in acidity) since 1850.

5. Extreme Weather

   • Increased frequency/intensity of heatwaves, heavy precipitation events, and droughts.
   • Attribution studies link many of these trends to anthropogenic warming.

4. Impacts