Summary
Climate change is evidenced by global temperature data, ice cores, and historical records, showing a significant warming trend. Natural causes include Milankovitch cycles, sunspot activity, and volcanic eruptions, while human activities like burning fossil fuels and deforestation have accelerated climate change.
- Global Temperature Records — systematic measurements showing a warming trend since the late 1800s.
Example: Global average temperature has risen approximately 1.1°C since pre-industrial times. - Ice Core Evidence — ice cores contain trapped air bubbles that reveal past CO₂ levels and temperatures.
Example: Recent CO₂ levels (415+ ppm) are unprecedented in the last 800,000 years. - Milankovitch Cycles — long-term variations in Earth's orbit affecting solar radiation.
Example: Eccentricity, axial tilt, and precession cycles linked to ice ages. - Sunspot Activity — solar cycles influencing Earth's climate over short periods.
Example: The Maunder Minimum coincided with the coldest part of the Little Ice Age. - Volcanic Activity — eruptions that inject particles into the atmosphere, causing temporary cooling.
Example: Mount Pinatubo's 1991 eruption cooled global temperatures by ~0.5°C for two years. - Enhanced Greenhouse Effect — human activities increasing greenhouse gas concentrations.
Example: CO₂ levels have risen from 280 ppm to over 415 ppm since the Industrial Revolution.
Exam Tips
Key Definitions to Remember
- Global Temperature Records
- Ice Core Evidence
- Milankovitch Cycles
- Enhanced Greenhouse Effect
Common Confusions
- Confusing natural and human causes of climate change
- Misunderstanding the timescales of natural climate variations
Typical Exam Questions
- Describe the trend shown in global temperature data since 1880? Global temperatures have risen approximately 1.1°C, with the warmest years on record since 2015.
- Explain how ice cores provide evidence of climate change? Ice cores contain air bubbles that reveal past CO₂ levels and temperatures, showing natural fluctuations and recent unprecedented levels.
- Explain how deforestation contributes to climate change? Deforestation reduces CO₂ absorption and releases stored carbon, increasing atmospheric CO₂ levels.
What Examiners Usually Test
- Ability to describe evidence of climate change
- Understanding of natural vs. human causes
- Explanation of how human activities enhance the greenhouse effect