This topic will provide an overview of the basic concepts of climate change, including the greenhouse effect, causes of climate change, and the role of human activities in exacerbating global warming.
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 Greenhouse Effect – The Core Mechanism
| Component |
Role in the Atmosphere |
| Solar Radiation |
Short‑wave energy from the Sun reaches Earth’s surface. |
| Surface Absorption & Re‑emission |
Land & oceans absorb energy, then radiate it as long‑wave (infrared) radiation. |
| Greenhouse Gases (GHGs) |
CO₂, CH₄, N₂O, water vapor, and others trap a portion of the outgoing infrared radiation, warming the lower atmosphere. |
| Feedbacks |
Processes that amplify (positive) or dampen (negative) the initial warming (e.g., ice‑albedo feedback, water‑vapor feedback). |
3. Major Greenhouse Gases & Sources
| Gas |
Atmospheric Lifetime |
Main Sources |
| Carbon Dioxide (CO₂) |
100‑300 years |
Fossil‑fuel combustion, cement production, deforestation, land‑use change |
| Methane (CH₄) |
~12 years |
Agriculture (ruminants, rice paddies), landfills, natural gas production, wetlands |
| Nitrous Oxide (N₂O) |
~114 years |
Synthetic fertilizers, industrial processes, manure management |
| Fluorinated Gases (HFCs, PFCs, SF₆) |
1‑10,000 years |
Refrigeration, electronics manufacturing, aluminum production |
4. Evidence of Climate Change
- Temperature Records
- Global mean surface temperature ↑ ~1.2 °C since pre‑industrial (1850‑1900) baseline.
- Most of the warming occurred since the 1970s.
- Cryosphere Changes
- Arctic sea‑ice extent ↓ ~40 % since 1979.
- Glacial retreat worldwide; Greenland ice sheet mass loss ≈ 3.8 mm sea‑level equivalent per year (2003‑2022).
- Sea‑Level Rise
- Global mean sea level ↑ ~210 mm since 1900; rate accelerating to ~3.4 mm yr⁻¹ (1993‑2022).
- Ocean Changes
- Surface warming ~0.13 °C per decade.
- Ocean acidification: pH down ~0.1 units (≈ 30 % increase in acidity) since the industrial era.
- Extreme Weather Trends
- Increased frequency/intensity of heatwaves, heavy precipitation events, and tropical cyclones.
5. Climate System Feedbacks
| Feedback Type |
Example |
Effect on Warming |
| Positive |
Ice‑albedo feedback: melting ice reduces surface reflectivity, absorbing more solar energy. |
Amplifies warming |
| Negative |
Planck feedback: as Earth warms, it radiates more infrared energy to space, providing a stabilizing effect. |
Dampens warming |
| Carbon Cycle Feedback |
Permaf |
|