Geo 3/24

GEOG 110 Lecture 11: Climate Change and Future Warming

Announcements

  • No Homework during Break

  • Exam Grades to be posted when available, likely during or just after break

Unit 1: The Natural Climate System

  • Topics Covered:
      - Radiative forcing and greenhouse gases (GHGs)
      - Atmospheric circulation
      - Ocean circulation
      - Short and long-term carbon cycling
      - Natural climate variability

Recommended Courses (By Interest)

  • If interested in atmospheric circulation:
      - GEOG 354: Climate Dynamics (Offered Every Spring)

  • If interested in ocean circulation:
      - GEOL 103: Intro to Oceanography (Offered Every Semester, includes Honors option)

  • If interested in carbon cycling:
      - GEOL 319/ENVIRSCI 319: Environmental Geochemistry (Offered every Fall)
      - GEOL 415: Global Chemical and Environmental Cycles (Offered every Spring)

  • If interested in plate tectonics/volcanoes:
      - GEOL 101: The Earth (Offered Every Semester)
      - GEOL 105: Dynamic Earth (covering earthquakes, tsunamis, volcanoes, landslides) (Every Spring)

  • If interested in climate proxies:
      - GEOSCI 590S: Environmental Stable Isotopes (Offered Every other Spring)
      - GEOSCI 558: Paleoclimatology (Offered Every Spring)

  • If interested in Earth climate evolution:
      - GEOL 394LI: Earth History and Its Life (Offered Every Spring)

  • If interested in glacial-interglacial changes:
      - GEOSCI 563: Glacial Geology (Offered Every Fall)

Unit 2: Modern Climate Change

  • Key Topics:
      - CO2 emissions
      - Temperature and precipitation changes
      - Ice sheets and sea level rise
      - Ocean acidification
      - Extreme weather events
      - The role of the human sphere in climate change

Outline of Lecture

  1. CO2 Levels and Predicting Climate Change

  2. How the Climate System Will Respond

CO2 Levels

  • February 2025 measured pCO2: 427 ppm

  • Ice-core data used for historical data before 1958; Mauna Loa data used post-1958.
      - Historical CO2 Levels: 190 ppm (past), 280 ppm (pre-industrial)

CO2 Emissions vs Atmospheric CO2 Levels Graph

  • Carbon Dioxide Levels (Gigatonnes)
      - Emissions show a significant increase since 2000.

CO2 Concentrations

  • 405 ppm concentration correlates to approximately 3000 gigatonnes (Gt) of CO2 (where 1 Gt = 10^9 tons = 10^15 grams).

Climate Change Prediction Models

  • Climate models include:
      - Horizontal Grid (Latitude-Longitude)
      - Vertical Grid (Height or Pressure)

  • Models consider:
      - Solar terrestrial radiation
      - General circulation models

Simplest Climate Model

  • Flux In = Flux Out
      - Allows calculation of Earth's temperature at approximately 253 K (-20°C).

  • Absorbed Solar Energy:
      - Earth: 238 W/m²
      - Mars: 125 W/m²
      - Venus: 132 W/m²

  • Calculated Temperatures:
      - Earth: 254 K (-18.5°C)
      - Mars: 216 K (-57°C)
      - Venus: 730 K (457°C)

  • Actual Temperatures:
      - Earth: 289 K (16°C)
      - Mars: 220 K (-53°C)
      - Venus: 730 K (457°C)

Major Equations in Climate Modeling

  • Water Vapor Evaporation Equation

  • Precipitation Equation

  • Salt Equation

  • Ice Equation

  • Thermodynamic Equation

  • Radiation Equation of Motion

  • Sensible Heat Equation

  • Radiative Transfer Equation

  • Surface Stress Equation of Motion

Coupled Ocean-Atmosphere Models

  • First models developed in 1980s included interactions between ocean and atmosphere.

GFDL HiFLOR Prototype Seasonal Prediction Model

  • Example data on storm wind speeds.

Shared Socioeconomic Pathways (SSP)

  • SSP replaces RCP (Representative Concentration Pathways).

  • Various scenarios such as SSP5-8.5, SSP3-7.0, etc., used for predicting future climate conditions.

Geographical Expression of Global Warming

  • Various effects of warming, geographically expressed across different climate system components.

Quick Adjustments in the Atmosphere

  • The atmosphere adjusts rapidly:
      - Impacts temperature, humidity, precipitation, circulation patterns.

Ocean Temperature Adjustments

  • Oceans have a much higher heat capacity than land and air.

  • Surface temperature adjusts over years to decades, while deep ocean adjustments take centuries to millennia.

Ocean Stabilization

  • Oceans play a stabilizing role in Earth's temperature, slowing down warming.

Cryosphere Dynamics

  • Includes Greenland and Antarctica ice data:
      - Extent of Arctic sea ice down to approximately 4 million square kilometers.
      - Sea ice responds quickly to climatic changes.

Albedo Effect

  • Albedo is the fraction of light reflected by Earth.
      - Earth's albedo is approximately 0.3.
      - Specifically noting its significance with sea ice as a fast positive feedback mechanism.

Impacts of Temperature Increase on Climate Systems

  • Warming increases air's capability to hold water vapor, leading to significant changes in weather patterns.

Historical Context of Climate Change

  • Changes projected at various global warming thresholds:
      - Changes at 1°C, 1.5°C, 2°C, and 4°C projected impacts.