♻️AP Environmental Science Unit 9 – Global Change

Key Concepts and Definitions

• Global change encompasses large-scale, long-term alterations in Earth's systems (atmosphere, biosphere, hydrosphere, and geosphere)
• Climate change refers to shifts in global or regional climate patterns attributed to increased atmospheric greenhouse gas concentrations
  • Greenhouse gases (carbon dioxide, methane, water vapor) trap heat in the atmosphere leading to rising global temperatures
• Anthropogenic activities are human-induced actions that contribute to environmental change (fossil fuel combustion, deforestation, agriculture)
• Radiative forcing quantifies the difference between solar energy absorbed by Earth and energy radiated back to space
• Feedback loops amplify or diminish the effects of climate change (melting Arctic ice reduces albedo, leading to more absorption of solar radiation)
• Tipping points are thresholds beyond which abrupt or irreversible changes occur in Earth's systems (collapse of the West Antarctic Ice Sheet)
• Resilience describes the capacity of a system to absorb disturbances and maintain its basic structure and function

Historical Context and Trends

• Earth's climate has naturally fluctuated over geological timescales due to variations in solar output, volcanic eruptions, and orbital cycles
• Since the Industrial Revolution, human activities have become the primary driver of global climate change
  • Burning fossil fuels releases carbon dioxide, a potent greenhouse gas, into the atmosphere
  • Deforestation reduces carbon sequestration and alters land surface properties
• Global average surface temperature has increased by approximately 1.0°C since pre-industrial times
• Sea level has risen by about 20 cm over the past century due to thermal expansion of oceans and melting of land-based ice
• Extreme weather events (heatwaves, droughts, floods) have become more frequent and intense in many regions
• Arctic sea ice extent has declined by roughly 40% since satellite records began in 1979
• Observed changes in precipitation patterns include more frequent heavy rainfall events and prolonged droughts in some areas

Major Drivers of Global Change

• Greenhouse gas emissions from human activities are the primary cause of current climate change
  • Carbon dioxide concentrations have increased from ~280 ppm in pre-industrial times to over 410 ppm today
  • Methane emissions from agriculture, landfills, and fossil fuel extraction contribute to warming
• Land-use changes, such as deforestation and urbanization, alter Earth's surface properties and carbon cycle
• Population growth and economic development increase energy demand and resource consumption
• Globalization facilitates the spread of invasive species and diseases, disrupting ecosystems
• Technological advancements can either mitigate or exacerbate environmental impacts (renewable energy vs. plastic production)
• Societal values and behaviors influence consumption patterns and environmental stewardship

Environmental Impacts

• Rising temperatures lead to more frequent and intense heatwaves, affecting human health and ecosystems
• Changes in precipitation patterns can cause droughts, floods, and altered water availability
  • Droughts reduce agricultural productivity and strain water resources
  • Heavy rainfall events increase soil erosion and nutrient runoff into waterways
• Sea level rise threatens coastal communities and ecosystems through flooding and saltwater intrusion
• Ocean acidification, caused by absorption of atmospheric CO2, impairs marine organisms' ability to build shells and skeletons
• Melting glaciers and polar ice sheets contribute to sea level rise and alter freshwater availability
• Shifts in species' ranges and phenology disrupt ecological interactions and ecosystem functioning
• Increased frequency and intensity of wildfires, driven by hotter and drier conditions, impact air quality and biodiversity

Social and Economic Consequences

• Climate change disproportionately affects vulnerable populations, exacerbating existing inequalities
  • Low-income communities have fewer resources to adapt to changing conditions
  • Indigenous peoples' traditional livelihoods and cultural practices are disrupted
• Extreme weather events damage infrastructure (roads, bridges, power grids) and disrupt economic activities
• Reduced agricultural yields and fisheries productivity threaten food security and livelihoods
• Water scarcity strains resources and can lead to conflicts over access and management
• Climate-related migration and displacement create social and political challenges
• Adaptation and mitigation efforts require significant financial investments, potentially diverting resources from other priorities
• Impacts on tourism and recreation industries affect local economies dependent on natural assets

Mitigation Strategies

• Reducing greenhouse gas emissions is crucial for limiting future climate change
  • Transitioning to renewable energy sources (solar, wind, hydro) reduces reliance on fossil fuels
  • Improving energy efficiency in buildings, transportation, and industry minimizes energy demand
• Implementing carbon pricing mechanisms (carbon taxes, cap-and-trade systems) incentivizes emissions reductions
• Protecting and restoring natural carbon sinks (forests, wetlands, soils) enhances carbon sequestration
• Sustainable land management practices (reduced tillage, cover cropping) improve soil health and carbon storage
• Promoting sustainable transportation (public transit, electric vehicles, cycling) reduces emissions from the transportation sector
• Encouraging behavioral changes (reduced meat consumption, energy conservation) can have significant cumulative impacts
• Investing in research and development of low-carbon technologies accelerates the transition to a clean energy future

Adaptation Measures

• Adapting to the impacts of climate change is necessary to reduce vulnerability and build resilience
  • Developing early warning systems for extreme weather events saves lives and minimizes damage
  • Implementing flood protection measures (sea walls, natural buffers) protects coastal communities
• Improving water management (efficient irrigation, rainwater harvesting) helps communities cope with changing water availability
• Diversifying crops and adopting drought-resistant varieties enhances agricultural resilience
• Protecting and restoring ecosystems (coral reefs, mangroves) provides natural defenses against climate impacts
• Upgrading infrastructure (roads, bridges, power grids) to withstand extreme weather events
• Promoting sustainable urban planning (green spaces, permeable surfaces) reduces urban heat island effects and improves stormwater management
• Fostering community-based adaptation initiatives empowers local communities to develop context-specific solutions

Future Projections and Challenges

• Climate models project continued warming, with the magnitude dependent on future greenhouse gas emissions
  • Under a high-emissions scenario, global average surface temperature could increase by 2.6-4.8°C by 2100
  • Even with ambitious mitigation efforts, some degree of warming is locked in due to past emissions
• Sea level rise is expected to accelerate, with projections ranging from 0.3-1.1 m by 2100
• Extreme weather events are likely to become more frequent and intense, with regional variations
• Biodiversity loss and ecosystem degradation will continue without effective conservation and restoration efforts
• Adapting to climate change will become increasingly challenging and costly as impacts intensify
• Addressing climate change requires global cooperation and ambitious action across all sectors of society
• Balancing mitigation, adaptation, and sustainable development goals presents complex trade-offs and challenges
• Uncertainty in climate projections and the potential for irreversible tipping points underscore the urgency of action