Environmental Science and Climate Change

Grade 12 · Science · Study Guide

Explore the mechanisms of climate change, greenhouse gas dynamics, and the ecological consequences of a warming planet.

Climate change refers to long-term shifts in global temperatures and weather patterns. While natural factors like volcanic eruptions and solar variation have always driven climate fluctuations, since the Industrial Revolution (mid-1800s), human activities — primarily burning fossil fuels — have become the dominant driver.

The greenhouse effect is Earth's natural thermostat. Solar radiation penetrates the atmosphere and warms the surface. That heat radiates outward as infrared radiation, which is absorbed and re-emitted by greenhouse gases (CO₂, CH₄, N₂O, water vapor). This keeps Earth ~33°C warmer than it would otherwise be. The problem: since 1750, atmospheric CO₂ has risen from ~280 ppm to over 420 ppm, intensifying this effect and trapping excess heat.

Consequences cascade through interconnected systems. Ocean warming causes thermal expansion, contributing to sea level rise. Melting ice sheets and glaciers add additional water. Warming disrupts precipitation patterns, intensifies extreme weather events, causes coral bleaching, and shifts species ranges poleward. Ocean acidification — from dissolved CO₂ forming carbonic acid — threatens marine ecosystems.

Mitigation strategies include transitioning to renewable energy, carbon capture, reforestation, and international agreements like the Paris Accord targeting net-zero emissions by 2050.

Key terms

Greenhouse Effect: The natural process by which atmospheric gases trap heat from the sun, warming Earth's surface.
Anthropogenic: Caused or influenced by human activity, especially regarding environmental changes.
Carbon Cycle: The biogeochemical cycle by which carbon is exchanged between the atmosphere, oceans, soil, and living organisms.
Albedo: The reflectivity of a surface; ice and snow have high albedo, absorbing less solar energy.
Positive Feedback Loop: A process where an initial change amplifies itself — e.g., ice melts, less heat is reflected, more warming occurs, more ice melts.

Flashcards

Greenhouse Gases: Atmospheric gases (CO₂, CH₄, N₂O, H₂O, ozone) that absorb and re-emit infrared radiation, trapping heat.
Carbon Dioxide (CO₂): Primary anthropogenic greenhouse gas; released by burning fossil fuels, deforestation, and cement production.
Global Warming Potential (GWP): Measure of how much heat a greenhouse gas traps relative to CO₂ over a given time period.
Ocean Acidification: Decrease in ocean pH caused by absorption of atmospheric CO₂, which forms carbonic acid.
Albedo Effect: High-albedo surfaces (ice, snow) reflect more solar energy; melting ice reduces albedo, accelerating warming.
Carbon Sink: A natural reservoir (ocean, forest, soil) that absorbs and stores more carbon than it releases.
Mitigation: Actions to reduce or prevent greenhouse gas emissions, such as renewable energy or reforestation.
Paris Agreement: 2015 international treaty aiming to limit global warming to 1.5-2°C above pre-industrial levels.

Questions

Which gas is the most abundant long-lived greenhouse gas produced by human activities?
1. Methane (CH₄)
2. Nitrous oxide (N₂O)
3. Carbon dioxide (CO₂)
4. Water vapor (H₂O)
Show answer
Answer: Carbon dioxide (CO₂)
CO₂ is the most significant long-lived anthropogenic greenhouse gas by volume and cumulative impact, responsible for about 66% of the enhanced greenhouse effect.
Ocean acidification is caused by the ocean absorbing excess CO₂ from the atmosphere.
Show answer
Answer: True
When oceans absorb CO₂, it reacts with water to form carbonic acid (H₂CO₃), which dissociates and lowers ocean pH — a process called ocean acidification.
The term 'albedo' refers to:
1. The amount of CO₂ absorbed by oceans
2. The reflectivity of a surface
3. The rate of glacier melt
4. The pH of ocean water
Show answer
Answer: The reflectivity of a surface
Albedo is the fraction of solar radiation reflected by a surface. Snow and ice have high albedo (~0.8-0.9); forests and oceans have low albedo (~0.1-0.2).
A situation where warming causes ice melt, which reduces reflectivity and causes further warming, is an example of a ___ feedback loop.
Show answer
Answer: positive
A positive feedback loop amplifies the original change. Warming → ice melts → less reflectivity → more warming → more melting. This accelerates climate change.
What is the primary mechanism driving sea level rise?
1. Increased precipitation only
2. Thermal expansion of seawater and melting land ice
3. Reduced evaporation rates
4. Deeper ocean trenches from tectonic activity
Show answer
Answer: Thermal expansion of seawater and melting land ice
Sea level rises from two main causes: thermal expansion of warming seawater (water expands when heated) and meltwater added from glaciers and ice sheets.

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