Unit 9: Global Change

Overview of Global Change in AP Environmental Science

Definition of Global Change: Refers to large-scale shifts in Earth’s climate and atmosphere occurring over decades to centuries, affecting ecosystems, resources, and human societies internationally.
Main Topics:
- Climate change (caused by increasing greenhouse gas concentrations)
- Stratospheric ozone depletion (caused by specific chemicals that destroy ozone)
Common Misconception: Climate change and ozone depletion are not the same; they are connected only through atmospheric chemistry and human impacts, differing in causes, mechanisms, consequences, and solutions.

Earth’s Energy Budget

Energy Balance Concept: Earth must balance the energy received from the Sun with the energy returned to space. - Incoming Energy: Primarily shortwave solar radiation (visible and ultraviolet radiation). - Reflection of Incoming Energy: Reflects back to space by clouds, aerosols, ice, and light-colored surfaces. - Absorption: Remaining energy is absorbed by Earth’s surface and atmosphere, warming the planet. - Outgoing Energy: Warm Earth emits energy as longwave (infrared) radiation back into space.
Energy Balance Mechanics: If absorbed energy increases or outgoing energy decreases, the planet warms until a new balance is achieved.
Albedo & its Role:
  - Definition of Albedo: Fraction of incoming solar radiation that is reflected.
  - Reflection Equation:
     $\text{Reflected solar energy} = \text{albedo} \times \text{incoming solar energy}$
  - Higher Albedo: Ice, snow, and some clouds lead to increased reflection and cooling.
  - Lower Albedo: Oceans, forests, and asphalt lead to increased absorption and warming.

The Greenhouse Effect

Definition: A natural process that warms Earth's lower atmosphere and surface; not inherently negative, as it is crucial for habitability.   - Mechanism:
    1. Sunlight reaches Earth; surface absorbs some energy and warms.
    2. Warm surface emits infrared radiation upward.     3. Greenhouse gases absorb some outgoing infrared radiation and re-emit it in all directions, including back to the surface, enhancing temperatures compared to a planet without these gases.

Greenhouse Gases (GHGs)

Key Greenhouse Gases and Their Sources:
- Carbon Dioxide (CO2): Emitted from fossil fuel combustion, deforestation, and cement production; natural sources include respiration and volcanic activity. - Methane (CH4): Emitted from livestock digestion, rice cultivation, landfills, fossil fuel extraction, and wastewater management. - Nitrous Oxide (N2O): Emitted from agricultural soils (especially with nitrogen fertilizers), manure management, and certain industrial processes. - Water Vapor (H2O): Most abundant GHG, considered a feedback rather than the initial driver. - Fluorinated Gases: Includes hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6); tied to industrial processes and consumer products.
Clarifications:
  - Oxygen (O2) and nitrogen (N2) are not significant GHGs as they do not effectively absorb infrared radiation.
  - Water vapor amplifies warming initiated by long-lived gases like CO2 since warm air holds more moisture.
  - Black carbon (soot), not a gas but a particle/aerosol, contributes to warming by absorbing sunlight and darkening ice surfaces, thus reducing albedo.

Positive Feedback Loops

Definition: Occur when an initial change triggers effects that amplify (positive feedback) or reduce (negative feedback) the original change.
Key Positive Feedbacks:
  - Ice-Albedo Feedback:
    - Warming melts ice/snow, lowering albedo.
    - Darker surfaces absorb more solar energy, causing further warming and melting.
  - Water Vapor Feedback:
    - Warming increases evaporation, raising atmospheric water vapor, thus strengthening the greenhouse effect.
  - Arctic Methane Feedback:
    - Thawing permafrost releases methane, a potent GHG, thus enhancing warming.

Greenhouse Gas Sources by Sector

Common Human Activity Sectors:
  - Energy Supply: Major source from burning coal, natural gas, and oil.
  - Transportation: Fossil fuels burned for travel (road, rail, air, marine).
  - Industry: On-site fossil fuel burning and cement manufacturing.   - Commercial and Residential Buildings: On-site energy generation and burning fuels.   - Land Use and Forestry: Deforestation and land clearing affecting carbon sinks.
  - Agriculture: Particularly from soil management and livestock.
  - Waste and Wastewater: Methane emissions from landfills and wastewater treatment.

Climate Change Impacts Beyond Polar Regions

Example of Arctic Sea Ice Decline Effects:
- Reduced ice extent leads to dark ocean surfaces with lower albedo, increasing absorption of solar energy. - Warmer oceans delay refreezing and further reduce future ice extent, explaining polar amplification (regions warming faster than the global average). - Large-scale weather systems and ocean-atmosphere circulation transport energy to the poles, reinforcing this rapid warming.

Exam Focus on Climate Change Science

Typical Questions:
  - Describe greenhouse gas warming using the energy budget.
  - Predict temperature changes due to albedo variations.
  - Identify greenhouse gases and their anthropogenic sources.
  - Distinguish gases from non-gas warmers such as black carbon.
Common Mistakes:
- Misrepresenting greenhouse effect mechanisms (blocking sunlight instead of trapping outgoing infrared).
- Confusing ozone depletion with climate change. - Mischaracterizing water vapor as the main long-term driver of climate change instead of a feedback.

Evidence for Climate Change and Primary Drivers

Climate vs. Weather:
- Weather refers to short-term atmospheric conditions; climate is the long-term average over decades.
- Short-term cold spells do not contradict climate warming; change detected through sustained trends and extremes.
Multiple Lines of Evidence for Climate Change:
  - Instrumental temperature records.
  - Ocean heat content reveals stored excess heat.   - Glacier and ice sheet mass balances.
  - Sea level rise instances.   - Phenology and species range shifts.
  - Paleoclimate proxies (ice cores, tree rings, sediment cores).
Role of Oceans:
- Oceans store more CO2 than the atmosphere, affecting climate dynamics and acidification.
Significance of CO2:
- Major human-generated emissions source linked to fossil fuel use, persistent in atmosphere allowing accumulation.
- Deforestation reduces carbon storage, releasing more CO2 than absorption.

Anthropogenic Drivers of Climate Change

Major Human Contributors:
1. Fossil fuel combustion (electricity, transportation, industry). 2. Deforestation and land-use changes. 3. Agriculture (methane and nitrous oxide emissions). 4. Industrial processes emitting various gases. 5. Waste management issues leading to methane emissions.

Natural Drivers of Climate Change

Natural Factors:
  - Solar variability (small temperature influence).
  - Volcanic eruptions (produce temporary cooling).
  - Milankovitch cycles (long-term earth orbital changes).
  - Tectonic processes altering landscape and long-term carbon cycling.
Recent Warming Context:
- Current rapid warming cannot solely be explained by these natural drivers.

Correlation vs. Causation

Analytical Expectations:
- Graphical data pairing CO2 concentration with global temperature supports the link hypothesis, but a stronger conclusion involves correlational evidence with established mechanisms and additional data.
Oceans and Temperature Variability:
- Despite fluctuations, persistent greenhouse gas increases create an ongoing energy imbalance, leading to continuous ocean warming as a climate metric.

Exam Focus on Climate Change Evidence

Typical Questions:
  - Interpret graphs on temperature or CO2 trends.
  - Distinguish anthropogenic from natural drivers.
  - Explain CO2 role in deforestation in the carbon cycle context.
  - Compare solar-cycle effects to modern warming.
Common Mistakes:
  - Using one cold event to dismiss warming trends.
  - Suggesting volcanoes as primary recent warming causes.
  - Failing to link correlation to relevant mechanisms.

Impacts of Climate Change on Earth Systems

Inequity in Climate Change Effects

Varying Impacts: Climate change effects are not uniform due to geography, socioeconomic conditions, and resource availability.
Environmental Justice Issues: Under-resourced communities face greater threats with less capacity to adapt.

Physical Impacts

Weather Extremes:
  - Increased heat waves.
  - Shifted precipitation patterns resulting in floods or droughts.
  - Increased storm intensity attributable to rising ocean temperatures.

Ocean and Heat Circulation Effects

Heat Distribution: Ocean currents transport heat, impacting climate globally.
Sea Level Rise Mechanisms:
1. Thermal expansion of warming water.
2. Melting land ice contributes to sea levels.
Coastal Threats: Physical changes threaten ecosystems and societies, with estimates suggesting substantial population relocations due to flooding and erosion.

Cryosphere Impacts

Glacier Retreat:
- Retreat affects water availability and is widespread globally.
- Antarctica holds significant ice mass; substantial loss can lead to extreme sea-level rises (up to 60 m).

Oceanic Changes

Ocean Warming and Acidification:
- Temperature alterations disrupt currents and habitats.
- Acidification reduces pH due to CO2 absorption, affecting marine life.

Ecosystem and Biodiversity Impacts

Species Responses:
- Organisms shift geographical ranges and change life-event timing. - Species unable to adapt face extinction risks.
Interactions with Other Stressors: Climate change compounds pre-existing threats like habitat fragmentation and pollution.

Agricultural and Human Health Implications

Food Security: Climate change alters crop yields through various stressors such as pests and extreme weather.
Public Health Impact: Increased vector-borne diseases, heat-related illnesses, and waterborne diseases rise in warmer climates.
Infrastructure Vulnerability: Coastal areas face risks from storm surges and flooding due to sea level changes.

Historical Context of Sea Level Change

Longitudinal Changes: Over the last 18,000 years, sea levels have risen approximately 120 m. In the modern era, the rise is noted at around 3 mm per year, chiefly from thermal expansion and land ice melt.

Adaptation to Climate Change

Definition and Strategies

Adaptation Definition: Adjustments made to human systems to minimize climate change impacts; does not replace mitigation, which reduces emissions.
Adaptation Strategy Types:
- Infrastructure Adaptations: Elevation of buildings, improved drainage, seawalls, levees. - Nature-based Solutions: Restoration of wetlands/mangroves, urban tree canopy increases. - Agricultural Adjustments: Adoption of drought-tolerant crops, enhanced irrigation methods. - Public Health Preparedness: Implementation of heat warning systems and disaster preparedness frameworks.

Managed Retreat and Resilience

Managed Retreat: A strategy for moving developments out of high-risk zones may be necessary despite challenges.
Equity in Climate Resilience: Strong resilience effects depend on community infrastructure, social networks, and governance frameworks.

Exam Focus on Adaptation

Typical Questions:
  - Develop an adaptation plan for specific climate impacts.
  - Analyze engineered vs. nature-based adaptation strategies and discuss trade-offs.
  - Identify barriers to adaptation correlating with equity issues.
Common Mistakes:
- Proposing solutions without explaining how they reduce risks.

Mitigation of Climate Change

Goals and Strategies

Mitigation Objective: Limit future climate change magnitude through emission reductions and increased carbon sequestration.
Major Mitigation Approaches:
1. Decarbonizing Electricity: Shift to renewable energy sources, nuclear power, and improved efficiency metrics. 2. Electrifying End Uses: Transitioning heating and vehicles to electricity can curtail emissions. 3. Transportation Emissions Reduction: Enhance public transportation, efficiency, and alternative fuels. 4. Methane and Nitrous Oxide Reduction: Efficient agricultural practices can promptly counteract potent warming gases. 5. Protect and Expand Carbon Sinks: Forest management and soil health initiatives enhance storage.

Policy Tools for Emission Reduction

Carbon Taxes: Fees proportional to carbon content making high-carbon options more costly.
Cap-and-Trade: Sets emissions limits and allows trading among entities.
Regulations and Standards: Mandated emissions controls for various sectors.

International Climate Agreements

Key Agreements:
- Kyoto Protocol: Aimed at reducing greenhouse gas emissions through legally binding targets.
- Paris Agreement: Targets mitigation plans, striving to maintain temperature rises below 2°C above pre-industrial levels.

Exam Focus on Mitigation

Typical Questions:
- Propose mitigation strategies for certain sectors; explain their rationale.
- Compare carbon tax to cap-and-trade mechanisms.
Common Mistakes:
- Confusing recycling with broader mitigation strategies.

Stratospheric Ozone and Ozone Depletion

Ozone Characteristics

Ozone Role Variation: Beneficial in the stratosphere, harmful as a pollutant in the troposphere.
Ozone Layer Location: Approximately 15-40 km above the surface, absorbing harmful UV-B radiation.

Ozone Dynamics and Human Impact

Natural Creation and Breakdown: UV breaks O2 into atomic oxygen, forming ozone; destruction mechanisms exist.
Ozone Depletion Mechanisms: Human activities introducing CFCs and halogens leading to catalyzed ozone destruction.
Antarctic Ozone Hole: Severe depletion linked to polar stratospheric clouds and the polar vortex.

Impacts and Responses to Ozone Depletion

UV-B Exposure Impacts

Human Health: Adverse outcomes include increased skin cancer rates, cataracts, and immune suppression.
Ecosystem Effects: Phytoplankton reduction with cascading aquatic ecosystem impacts; reduced agricultural yields.
Materials Damage: Increased UV can degrade materials leading to reduced product lifetimes.

Solutions and Policies

Montreal Protocol: Successful treaty phasing out CFC production, highlighting policy's role in addressing environmental problems.
Further Strategies: Legal frameworks and consumer engagement to reduce ozone-depleting chemicals.

Exam Focus on Ozone Issues

Typical Questions:
- Analyze impacts of UV-B exposure on human and ecosystem health. - Identify and describe the Montreal Protocol’s role in ozone recovery.

Biodiversity, Endangered Species, and Invasive Species

Biodiversity Connection to Climate Change

Impact Mechanisms: Habitat shifts, altered life-cycle timing, and extreme event stress lead to biodiversity losses.

Species Vulnerability and Invasive Dynamics

Vulnerabilities of Plants vs. Animals: Plants face unique challenges due to slow dispersal and inability to migrate.
Invasive Species: Non-native species can disrupt ecosystems, economies, and human health (e.g., Dutch elm disease, zebra mussels).
Endangered Species: Species at high extinction risk due to various factors, necessitating protection efforts.

Strategies for Biodiversity Maintenance

Conservation Techniques: Establish sanctuaries, breeding programs, habitat management, enforce protective laws, and reduce invasive species.

Exam Focus on Biodiversity

d- Typical Questions:
- Distinguish between adaptation and acclimatization; apply in scenarios. - Explain habitat fragmentation's impact on migration and biodiversity.

Integrative Approaches in Global Change

Systems Thinking in Global Change

Interconnectedness: Global change is best understood through systems thinking; emissions impact atmospheric conditions influencing ecosystems and human systems.

Causal and Responding Structures

Clear Causal Chains for Exams: - Identify key causes and connect them to effects and responses (e.g., GHG emissions leading to climate impacts and subsequent responses).

Evaluating Solutions and Trade-offs

Evaluation Aspects: When assessing solutions, consider their effectiveness, feasibility, costs, and social equity implications.

Exam Focus

Comparative Questions:
- Propose, evaluate solutions for climate and ozone issues, considering trade-offs and specifying mechanisms.