Global Climate Change

Layers of the Atmosphere

  • SUN

  • UV Radiation

  • Mesosphere

  • Stratosphere
      - Ozone Layer

  • Troposphere

  • EARTH
      - Height of Atmosphere:
        - Troposphere: 11 km
        - Stratosphere: 50 km
        - Mesosphere: 80 km

The Greenhouse Effect

  • Describes the warming of the Earth's surface due to several factors:
      - Some solar radiation is reflected by the Earth and the atmosphere.
      - Majority of radiation is absorbed by the Earth's surface, causing warming.
      - Some infrared radiation passes through the atmosphere.
      - A fraction of this infrared is absorbed and then re-emitted by greenhouse gas molecules in all directions, which contributes to warming both Earth's surface and lower atmosphere.
      - The cycle involves:
        - Atmosphere
        - Earth's Surface
        - Infrared Radiation emitted by Earth's surface.

Topic 9.5 - Global Climate Change

Enduring Understanding

  • STB-4: Local and regional human activities can have impacts on a global scale.

Learning Objective

  • STB-4.F: Explain the impact of climate change over both short-term and long-term on ecosystems.

Essential Knowledge

  • STB-4.F.1:
      - Climate change has occurred throughout Earth's geologic history, with significant temperature shifts leading to periods of warming and cooling, inferred through:
        - CO₂ data, ice core analysis.

  • STB-4.F.2: Effects of climate change include:
      - Rise in global temperatures.
      - Melting of permafrost and sea ice.
      - Elevated sea levels.
      - Displacement of coastal populations.

  • STB-4.F.3: Marine ecosystems are affected by climate change, with contrasting impacts:
      - Positively: New habitats emerging from flooded continental shelves.
      - Negatively: Some deeper marine communities no longer remain within the photic zone, negatively affecting photosynthetic life.

  • STB-4.F.4: Atmospheric circulation influences heat transport globally.
      - Changes in climate can alter patterns of circulation, impacting Hadley cells and the jet stream.

  • STB-4.F.5: Oceanic currents, also known as the ocean conveyor belt, distribute heat globally.
      - Any alteration in these currents significantly impacts global climate, particularly in coastal areas.

  • STB-4.F.6: Climate change affects soil through variations in temperature and precipitation, impacting soil viability and instigating possible erosion.

  • STB-4.F.7: Polar regions respond to climate change more swiftly, primarily due to their ice and snow reflecting most solar energy back into space, creating positive feedback loops.

  • STB-4.F.8: Melting ice in polar regions reduces the reflection of solar energy, leading to greater absorption by Earth's surface and further warming.

  • STB-4.F.9: The Arctic's rapid response to climate change is due to feedback loops involving melting sea ice, thawing tundra, and the release of greenhouse gases like methane.

  • STB-4.F.10: Loss of ice habitat affects species reliant on ice for survival and sustenance.

Historical Climate Change

  • Throughout history, Earth’s climate has fluctuated significantly.

  • Over the past 650,000 years, there have been seven cycles of glacial advance and retreat.

  • The recent end of the last ice age around 11,700 years ago ushered in modern climatic conditions and the era of human civilization.

  • Climate changes are often attributed to slight variations in Earth’s orbital configurations, affecting solar energy reception.

Recent CO₂ Concentrations

  • Findings reveal that for over 400,000 years, CO₂ levels remained below 300 ppm until the increase to approximately 419 ppm by March 2022.

Global Temperature Changes

  • Since around 1880, direct temperature measurements have allowed NASA to graph temperature fluctuations over time.

  • While annual temperature differences exist, a gradual increase has been noted from 1880 to present.
      - Global temperature has increased by 1.1°C (2.0°F) from 1880 to 2017.
      - 17 out of the 18 warmest years recorded since 1880 occurred between 2000 and 2017.

Temperature Discrepancies

  • An average temperature increase of 1.1°C (2.0°F) is not uniform worldwide:
      - Some areas like parts of Antarctica experienced cooler conditions.
      - Certain ocean regions showed no temperature change.
      - Northern latitudes have recorded increases of 1.0°C to 4.0°C (1.8°F to 7.2°F).
      - Substantial northern temperature increases have led to significant ice cap melting (approximately 45%).

Permafrost Analysis

  • Permafrost is defined as soil that remains frozen (32°F or colder) for at least two consecutive years.
      - It primarily occurs in high-latitude areas and high mountains.
      - Permafrost covers about 25% of the land in the Northern Hemisphere.

  • As global warming progresses, permafrost that has remained frozen for millennia is thawing.
      - Thawing releases stored carbon as CO₂ and methane, which exacerbates warming, creating a feedback loop.
      - Thawing permafrost impacts infrastructure, causing damage to buildings and roads that were once stable.

Impact of Thawing Permafrost

  • Thawing results in the decomposition of plant materials (organic carbon) trapped in the frozen soil, releasing greenhouse gases.
      - Notably, ancient bacteria and viruses, some over 400,000 years old, can also thaw and pose health risks.

Polar Region Insights

  • The Arctic has been warming three times faster than the global average.
      - The albedo effect plays a role, as melting snow and ice reduce reflectivity, leading to further warming.
      - Feedback loops are notable, as less ice leads to more absorption of solar energy, driving additional warming.

Rising Sea Levels

  • Sea level rise has dramatically changed over the past 18,000 years, notably:
      - Risen 400 feet (120 m) since the last ice age's peak.
      - Pre-Industrial rate: approximately 0.1 to 0.2 mm/year; current rate: ~3 mm/year (tenfold increase).

  • By 2100, the IPCC predicts a global rise of 20-40 inches (500-1000 mm), greatly impacting coastal cities and island nations.

Consequences of Rising Sea Levels

  • Impacts include increased property damage from storm surges, altering ecosystems through salinity changes, and loss of fishery yields.
      - Flooding can lead to increased insurance costs and property devaluation, while saltwater intrusion negatively impacts agriculture and aquaculture.
      - The United Nations estimates 150 million people may need relocation by 2050 due to coastal threats and disruptions, like flooding and erosion.

Ecosystem Changes Due to Sea Level Rise

  • Shift of ecosystems inland may occur, with potential enhancement of marine habitats.
      - Coral reefs may be adversely affected if submerged deeper, losing sunlight and becoming smothered by sediment.

Atmospheric Circulation Patterns

  • Hadley Cells: Large-scale wind currents affecting weather patterns in subtropical regions.
      - Recent studies show these cells are expanding toward the poles due to climate change, altering the distribution of rainfall and exacerbating desertification.

Jet Stream Effects

  • Global warming alters the jet stream dynamics, impacting weather patterns globally.
      - The reduced temperature contrast in polar regions leads to weaker jet streams, which can stall weather patterns, intensifying weather anomalies.

Oceanic Circulation and Climate Change

  • The ocean conveyor belt (thermohaline circulation) is influenced by climatic factors affecting saltwater-freshwater balance, shifting heat across the planet.
      - Changes in the Gulf Stream can lead to colder climates in Europe, whilst increased heat in the Atlantic may fuel more coastal storms and raise sea levels.

Climate Change Effects on Soils and Agriculture

  • Climate change alters soil functions, crop production, leading to increased soil erosion and changes in nutrient cycles due to higher temperatures.
      - Water scarcity could challenge agricultural sustainability, leading to further land degradation in the future.