Environmental Biology Unit 6 Review: Causes and Consequences

What's Climate Change?

• Climate change refers to long-term shifts in global or regional climate patterns
• Includes changes in temperature, precipitation, and wind patterns that occur over several decades or longer
• Can have both natural and anthropogenic (human-induced) causes
• Currently, the term often refers to the rapid changes observed in Earth's climate since the early 20th century
• Primarily attributed to increasing levels of atmospheric greenhouse gases produced by human activities such as burning fossil fuels (coal, oil, and natural gas)
• Has led to rising global temperatures, known as global warming, as well as changes in weather patterns
• Impacts are visible in the form of melting glaciers, rising sea levels, more intense heat waves, and shifts in plant and animal ranges

The Science Behind It

• Earth's climate is regulated by the balance between incoming solar radiation and outgoing infrared radiation
• Greenhouse gases (GHGs) in the atmosphere, such as carbon dioxide (CO2), methane (CH4), and water vapor, absorb and re-emit infrared radiation
  • This process traps heat in the lower atmosphere, causing the greenhouse effect
• Increased concentrations of GHGs due to human activities enhance the greenhouse effect, leading to global warming
• Climate models, based on physical principles and mathematical equations, simulate the interactions of the atmosphere, oceans, land surface, and ice
  • These models are used to project future climate changes under different scenarios of GHG emissions
• Paleoclimatology, the study of past climates, provides evidence of how Earth's climate has changed over time
  • Proxy data, such as tree rings, ice cores, and sediment layers, are used to reconstruct past climate conditions
• Scientific consensus, based on multiple lines of evidence, indicates that human activities are the primary driver of current climate change

Natural vs Human-Caused Factors

• Natural factors that influence Earth's climate include variations in solar output, volcanic eruptions, and changes in Earth's orbit and axis tilt (Milankovitch cycles)
  • These factors operate on timescales ranging from decades to millions of years
• Solar variability, such as the 11-year sunspot cycle, can cause small fluctuations in Earth's energy balance
  • However, the observed warming since the mid-20th century cannot be explained by changes in solar activity alone
• Volcanic eruptions can have a cooling effect on global temperatures by releasing sulfate aerosols into the stratosphere, which reflect incoming solar radiation
  • The cooling effect is typically short-lived (a few years) and is not responsible for long-term climate change
• Human activities, particularly the burning of fossil fuels and land-use changes (deforestation), have significantly increased atmospheric GHG concentrations since the Industrial Revolution
• The rate and magnitude of the current warming are unprecedented in the last 2,000 years and cannot be explained by natural factors alone
• Human influence on the climate system is clear, as stated in the Intergovernmental Panel on Climate Change (IPCC) reports

Greenhouse Gases and Their Sources

• The primary GHGs contributing to climate change are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O)
• CO2 is the most significant anthropogenic GHG, with atmospheric concentrations increasing from pre-industrial levels of ~280 ppm to over 410 ppm today
  • Main sources include burning fossil fuels, deforestation, and cement production
• CH4 is a more potent GHG than CO2 but has a shorter atmospheric lifetime (~12 years)
  • Sources include agriculture (livestock and rice cultivation), landfills, and fossil fuel production (natural gas and petroleum)
• N2O is a long-lived GHG produced by agricultural practices (fertilizer use), industrial processes, and fossil fuel combustion
• Water vapor is the most abundant GHG, but its atmospheric concentration is not directly affected by human activities
  • However, as air temperatures rise due to other GHGs, more water vapor can be held in the atmosphere, amplifying the greenhouse effect
• Other GHGs include ozone (O3), chlorofluorocarbons (CFCs), and hydrochlorofluorocarbons (HCFCs)
  • These gases have been regulated by the Montreal Protocol due to their role in depleting the ozone layer

Global Temperature Trends

• Global average surface temperatures have increased by approximately 1.1°C (2°F) since the pre-industrial era (1850-1900)
• The warmest years on record have all occurred since 2000, with 2016 and 2020 being the warmest years
• The rate of warming has accelerated in recent decades, with the last three decades being successively warmer than any preceding decade since 1850
• Warming is not uniform across the globe, with land areas warming faster than the oceans and high latitudes (Arctic) warming faster than the tropics
• The observed warming is consistent with the expected response to increasing GHG concentrations in the atmosphere
• Climate models project that global average temperatures will continue to rise throughout the 21st century, with the magnitude of warming depending on future GHG emissions scenarios
  • The Paris Agreement aims to limit global warming to well below 2°C, preferably to 1.5°C, compared to pre-industrial levels

Environmental Impacts

• Rising global temperatures lead to the melting of glaciers and ice sheets, causing sea level rise
  • Threatens low-lying coastal areas and small island nations with increased flooding and erosion
• Warming oceans expand in volume (thermal expansion), further contributing to sea level rise
• Changes in precipitation patterns, with some regions experiencing more frequent and intense droughts, while others face increased flooding
• Shifts in the geographic ranges and timing of seasonal activities (phenology) of plant and animal species
  • Some species may adapt, while others face increased risk of extinction
• Ocean acidification occurs as the oceans absorb excess atmospheric CO2, reducing the pH of seawater
  • Negatively impacts marine organisms with calcium carbonate shells or skeletons (corals, mollusks)
• Increased frequency and intensity of extreme weather events, such as heat waves, hurricanes, and wildfires
• Thawing of permafrost in Arctic regions releases stored carbon and methane, further amplifying warming (positive feedback loop)
• Disruptions to ecosystems and biodiversity, with the potential for cascading effects on food webs and ecosystem services

Societal and Economic Effects

• Climate change impacts human health through increased heat stress, air pollution, and the spread of vector-borne diseases (malaria, dengue fever)
• Food security is threatened by changes in crop yields, shifts in agricultural zones, and increased frequency of droughts and floods
• Water scarcity and reduced water quality in some regions due to changes in precipitation patterns and melting glaciers
• Damage to infrastructure (roads, bridges, coastal properties) from sea level rise, flooding, and extreme weather events
• Displacement of populations due to sea level rise, drought, or other climate-related factors, leading to climate refugees
• Economic losses from reduced agricultural productivity, damage to infrastructure, and increased healthcare costs
• Unequal distribution of impacts, with developing countries and marginalized communities often being the most vulnerable and least able to adapt
• Potential for increased social and political instability as resources become scarce and populations are displaced

Mitigation and Adaptation Strategies

• Mitigation strategies aim to reduce GHG emissions and limit the magnitude of future climate change
  • Transitioning to renewable energy sources (solar, wind, hydro) and phasing out fossil fuels
  • Improving energy efficiency in buildings, transportation, and industry
  • Implementing carbon pricing mechanisms (carbon taxes, cap-and-trade systems) to incentivize emissions reductions
  • Promoting sustainable land management practices (reforestation, reducing deforestation, soil carbon sequestration)
• Adaptation strategies help communities and ecosystems cope with the impacts of climate change that are already occurring or are unavoidable
  • Developing early warning systems and emergency response plans for extreme weather events
  • Investing in resilient infrastructure (flood defenses, drought-resistant crops, water storage systems)
  • Promoting sustainable water management and efficient irrigation practices
  • Protecting and restoring natural ecosystems that provide critical services (coastal wetlands, mangroves)
• Climate change education and public awareness campaigns to encourage individual and collective action
• International cooperation and agreements, such as the Paris Agreement, to coordinate global efforts in addressing climate change