1.4 Introduction to climate change and global warming

Climate change is reshaping our world. Long-term shifts in temperature, precipitation, and other climate variables are driven by greenhouse gases from human activities. These changes are causing rising sea levels, extreme weather, and threats to ecosystems and human societies.

Understanding climate science is crucial for addressing this global challenge. It helps us identify drivers and consequences of climate change, develop models for future projections, and inform strategies for mitigation and adaptation. This knowledge is key to international cooperation and public action.

Understanding Climate Change and Global Warming

Definition of climate change

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• Long-term shifts in global or regional climate patterns occur over decades to millennia
• Caused by natural factors (volcanic eruptions, solar variability) or human activities (greenhouse gas emissions, land-use changes)
• Encompasses changes in temperature, precipitation, wind patterns, and other climate variables

Causes of contemporary climate change

• Greenhouse gases (GHGs) absorb and emit infrared radiation, trapping heat in the atmosphere
  • Main anthropogenic GHGs: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O)
  • CO2 concentrations have increased from pre-industrial levels of ~280 ppm to over 410 ppm today
• Anthropogenic activities release GHGs into the atmosphere
  • Burning fossil fuels (coal, oil, natural gas) for energy production and transportation
  • Deforestation and land-use changes reduce carbon sinks and release stored carbon
  • Agricultural practices like livestock farming (methane emissions) and rice cultivation (methane and nitrous oxide emissions)
  • Industrial processes such as cement production and chemical manufacturing release GHGs
• Positive feedback loops amplify the effects of climate change
  • Ice-albedo feedback: melting ice and snow reduce Earth's reflectivity, leading to more heat absorption
  • Permafrost thawing releases stored methane and CO2, further warming the atmosphere
  • Water vapor feedback: warmer air holds more moisture, a potent GHG, leading to additional warming

Impacts and Importance of Studying Climate Change

Impacts on nature and society

• Natural systems experience significant changes
  • Rising sea levels due to thermal expansion of oceans and melting of glaciers and ice sheets (Greenland, Antarctica)
  • Changes in precipitation patterns lead to more frequent and severe droughts and floods
  • Shifts in species distribution and ecosystem composition as organisms adapt to changing conditions
  • Ocean acidification occurs as oceans absorb more atmospheric CO2, impacting marine life (coral reefs)
• Human societies face numerous challenges
  • Food security threatened by changes in agricultural productivity (crop yields, growing seasons)
  • Increased frequency and intensity of extreme weather events cause damage to infrastructure and loss of life (heatwaves, hurricanes, wildfires)
  • Spread of vector-borne diseases (malaria, dengue fever) as changing climate conditions expand the range of disease-carrying organisms
  • Displacement of populations due to sea-level rise, coastal erosion, and other climate-related hazards (climate refugees)

Importance of climate science

• Understanding the mechanisms and impacts of climate change is crucial
  1. Identify the main drivers (GHG emissions, land-use changes) and consequences (temperature rise, sea-level rise) of climate change
  2. Develop and refine climate models to project future changes under different emission scenarios (RCPs)
  3. Attribute observed changes to human activities or natural variability using detection and attribution studies
• Climate science informs mitigation and adaptation strategies
  • Provides scientific evidence to support the development of policies aimed at reducing GHG emissions (carbon pricing, renewable energy incentives)
  • Guides the implementation of adaptation measures to minimize risks posed by climate change (coastal protection, water resource management)
• Facilitates international cooperation and decision-making
  • Contributes to global assessments, such as the Intergovernmental Panel on Climate Change (IPCC) reports, which synthesize the latest scientific findings
  • Supports the negotiation and implementation of international agreements to address climate change (Paris Agreement, Kyoto Protocol)
• Raises public awareness and promotes climate action
  • Communicates the findings of climate science to the general public and stakeholders through accessible channels (media, educational programs)
  • Encourages individual and collective actions to reduce carbon footprints and build resilience to climate impacts (energy efficiency, sustainable transportation)