Global Warming - PSM University Exam Notes

1. Definition

2. The Greenhouse Effect (Mechanism)

1. The Sun emits solar radiation (short-wave) that passes through the atmosphere and is absorbed by the Earth's surface.
2. The Earth re-emits this energy as infrared (long-wave) radiation back toward space.
3. Greenhouse gases in the atmosphere absorb this infrared radiation and re-emit it in all directions, trapping heat - like a blanket around the Earth.
4. This raises the Earth's surface temperature above what it would otherwise be.

Park's PSM: "Atmospheric trapping of thermal radiation from the Earth's surface is known as the greenhouse effect."

3. Greenhouse Gases (GHGs) - Sources and Sinks

• CO₂ concentration has been rising sharply since the Industrial Revolution.
• Methane concentrations have more than doubled from the 19th century to 2023 (Harrison's 22e).
• CO₂ and CH₄ are the two most important anthropogenic GHGs.

4. Evidence and Scale of Warming

• The average surface temperature of Earth has increased by 1.09°C from 1850-1900 to 2010-2019 (IPCC Sixth Assessment Report).
• The current rate of warming is unprecedented in the last 50 million years (Harrison's).
• The 5°C of warming at the end of the last ice age (~12,000 years ago) took ~5000 years; a similar increment may happen within 150 years if GHG emissions are not reduced.
• Park's predicts an increase of ~3°C in average global surface temperature by 2030 and a sea level rise of 0.1-0.3 m by 2050.

5. Consequences / Effects of Global Warming

A. Physical / Environmental Effects

B. Health Effects (PSM High-Yield)

• Global warming increases frequency and severity of heat waves.
• Leads to: heat exhaustion, heat stroke, dehydration, excess cardiovascular and respiratory deaths.
• Vulnerable groups: elderly, outdoor workers, urban populations.

• Warmer temperatures expand the geographic range of disease vectors.
• Malaria: range expanding to higher altitudes and latitudes.
• Dengue fever: Aedes aegypti distribution expanding globally; epidemic potential increasing.
• Lyme disease: Tick vector (Ixodes scapularis) range expanding northward into Canada; annual peak cases arriving ~6 weeks earlier than 25 years prior.
• Babesiosis, West Nile virus, Chikungunya: all expanding geographically.

• Increased heavy rainfall events contaminate water supplies.
• 51% of waterborne disease outbreaks in the USA were preceded by precipitation above the 90th percentile.
• Pathogens most commonly involved: Vibrio and Leptospira species.
• Combined sewer overflows increase with heavy rains, causing release of untreated sewage.

• Higher temperatures increase ground-level ozone (smog) formation.
• Wildfire smoke increases particulate matter (PM2.5) exposure.
• Worsens asthma, COPD, allergies.
• Longer pollen seasons due to warmer weather worsen allergic respiratory disease.

• Reduced agricultural output due to drought, heat stress, and altered rainfall.
• Flooding destroys crops.
• Changes in fisheries affect nutrition.

• Displacement from floods, loss of livelihoods, and trauma from extreme weather events cause anxiety, depression, and PTSD.
• "Eco-anxiety" - chronic fear about environmental destruction.

• Low-income countries, indigenous communities, children, elderly, pregnant women, and people with chronic diseases bear the greatest burden.

6. The "Heat Island" Effect

• Concrete and asphalt absorbing and retaining heat.
• Reduced vegetation and evaporative cooling.
• Waste heat from vehicles, industry, air conditioning.

7. Impact on Ecosystems (Park's PSM)

• Changes in jet streams, ocean currents, and prevailing winds alter rainfall distribution.
• Affects local, regional, and global ecosystems.
• Change in insect vector distribution (disease implication).
• Temperature rise overwhelms many species' capacity to adapt.
• Catastrophe theory - small additional changes in existing trends could have massive, disproportionate consequences.

8. Control and Prevention of Global Warming

Primary Prevention (Mitigation)

1. Reduce fossil fuel combustion - shift to renewable energy (solar, wind, hydro, nuclear).
2. Reduce deforestation - protect forests; afforestation and reforestation programs.
3. Energy efficiency - fuel-efficient vehicles, green buildings, efficient appliances.
4. Reduce methane emissions - improve landfill management, reduce livestock methane.
5. Replace HFCs - phase out ozone-depleting/GHG-producing refrigerants (Montreal Protocol + Kigali Amendment).
6. International agreements: Kyoto Protocol, Paris Agreement (limiting warming to 1.5°C above pre-industrial levels).

Secondary Prevention (Adaptation)

1. Early warning systems for extreme heat events.
2. Vector control programs as disease ranges expand.
3. Improved water treatment infrastructure.
4. Urban heat island mitigation - green spaces, cool roofs, urban trees.
5. Crop variety adaptation - heat-tolerant and drought-resistant crops.
6. Flood preparedness and coastal defense infrastructure.

9. Key International Agreements (for MCQs)

10. Quick-Recall Facts (MCQ Targets)

• Most important GHG by overall warming effect: CO₂
• Most abundant GHG: Water vapour
• Most potent per molecule (common GHGs): Methane > CO₂
• Temperature increase since pre-industrial: ~1.09°C (to 2019)
• Park's predicted temperature rise by 2030: ~3°C
• Park's predicted sea level rise by 2050: 0.1-0.3 metres
• Vector-borne disease most commonly reported in North America: Lyme disease (~60,000 cases/year)
• 51% of waterborne outbreaks preceded by: precipitation above 90th percentile
• Main pathogen after heavy precipitation: Vibrio and Leptospira

11. Sample Long-Answer Framework (University Exam)