15.2 Climate Change and Atmospheric Science

Climate change is reshaping our world. Greenhouse gases trap heat in Earth's atmosphere, causing global warming. This topic explores the science behind climate change, its impacts, and strategies to address it.

From rising sea levels to extreme weather, climate change affects us all. We'll examine key greenhouse gases, their sources, and how they contribute to global warming. We'll also look at ways to mitigate and adapt to these changes.

Greenhouse Gases and Global Warming

The Greenhouse Effect and Global Warming

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• Greenhouse effect traps heat in Earth's atmosphere by absorbing and re-emitting infrared radiation
• Greenhouse gases (CO2, methane, water vapor) allow sunlight to pass through but absorb heat radiating from Earth's surface
• Global warming refers to the long-term increase in Earth's average temperature due to enhanced greenhouse effect
• Atmospheric composition changes contribute to global warming
  • Pre-industrial CO2 levels: ~280 ppm
  • Current CO2 levels: >410 ppm
• Natural greenhouse effect maintains Earth's habitable temperature (~15°C average)
• Enhanced greenhouse effect from human activities leads to additional warming

Key Greenhouse Gases and Their Sources

• Carbon dioxide (CO2) primary contributor to global warming
  • Sources include fossil fuel combustion, deforestation, and cement production
  • Atmospheric lifetime: 300-1000 years
• Methane (CH4) more potent greenhouse gas than CO2
  • Sources include livestock, rice paddies, landfills, and natural gas leaks
  • Atmospheric lifetime: ~12 years
  • Global warming potential 28-36 times that of CO2 over 100 years
• Water vapor acts as a feedback mechanism
  • Warmer atmosphere holds more water vapor, amplifying warming effect
• Other greenhouse gases include nitrous oxide and fluorinated gases (CFCs, HFCs)

Impacts of Climate Change

Sea Level Rise and Ocean Acidification

• Sea level rise caused by thermal expansion of oceans and melting of land-based ice
  • Current rate: ~3.3 mm/year
  • Projected rise by 2100: 0.3-2.5 meters depending on emissions scenarios
• Low-lying coastal areas and small island nations at risk of inundation
• Ocean acidification results from increased CO2 absorption by seawater
  • pH of surface ocean waters decreased by 0.1 units since pre-industrial times
  • Threatens marine ecosystems, particularly coral reefs and shellfish
• Impacts on marine food webs and fisheries

Extreme Weather Events and Atmospheric Changes

• Increased frequency and intensity of extreme weather events
  • Heat waves (2003 European heat wave)
  • Droughts (California drought 2011-2017)
  • Hurricanes (Hurricane Harvey 2017)
  • Floods (Thailand floods 2011)
• Changes in precipitation patterns affect water availability and agriculture
• Ozone layer depletion in stratosphere
  • Caused by chlorofluorocarbons (CFCs) and other ozone-depleting substances
  • Montreal Protocol successfully phased out CFCs
  • Ozone hole over Antarctica showing signs of recovery
• Tropospheric ozone increase
  • Forms from reactions between pollutants and sunlight
  • Contributes to urban smog and respiratory problems

Addressing Climate Change

Climate Models and Projections

• Climate models simulate Earth's climate system using mathematical equations
• General Circulation Models (GCMs) incorporate atmosphere, oceans, land surface, and ice
• Ensemble modeling uses multiple models to improve accuracy and assess uncertainty
• Intergovernmental Panel on Climate Change (IPCC) scenarios
  • Representative Concentration Pathways (RCPs) project future greenhouse gas concentrations
  • Shared Socioeconomic Pathways (SSPs) consider different socioeconomic development trajectories
• Model projections inform policy decisions and adaptation planning

Mitigation and Adaptation Strategies

• Mitigation strategies aim to reduce greenhouse gas emissions
  • Renewable energy adoption (solar, wind, hydroelectric)
  • Energy efficiency improvements in buildings and transportation
  • Carbon pricing mechanisms (carbon tax, cap-and-trade systems)
  • Reforestation and afforestation to increase carbon sinks
• Adaptation strategies help communities cope with climate change impacts
  • Coastal protection measures (sea walls, mangrove restoration)
  • Drought-resistant crop varieties and improved irrigation techniques
  • Urban heat island mitigation (green roofs, reflective surfaces)
  • Early warning systems for extreme weather events
• International cooperation and agreements
  • Paris Agreement aims to limit global temperature increase to well below 2°C above pre-industrial levels
  • Nationally Determined Contributions (NDCs) outline country-specific climate action plans