Climate Change Concepts - GEOG 203

Climate Change Overview

(How) Has Climate Been Changing?

  • Historical Context

    • Ice cores from Antarctica reveal patterns of temperature changes over thousands of years.

    • Notable climate periods include:

    • Bölling-Alleröd: Warmer period during the last glacial.

    • Holocene Maximum: Maximum temperatures recorded.

    • Younger Dryas: A cooler period marked by significant temperature drops.

Current Climate Trends

  • Temperature Anomaly (°C)

    • Recent data shows a significant increase in global temperatures:

    • Average increase of approximately 1.3^ ext{°C} (or 2.3^ ext{°F}) since 1880.

    • Top 24 warmest years recorded since 2001, with 2024 projected as the warmest.

  • Diurnal Temperature Range

    • Nighttime temperatures (Tmin) are increasing faster than daytime temperatures (Tmax).

  • Precipitation Trends

    • Increase of 5-10 rac{%}{30-85^ ext{°N}} since 1900.

  • Sea Level Rise

    • Average rise of +18.5 ext{ cm} (or +7 ext{ in}) since 1900.

  • Snow Cover and Glacial Retreat

    • Decreased snow extent and earlier spring melt, extending the growing season.

Examples of Ice and Glacier Changes

  • Arctic Sea Ice: Significant reduction in September extent (2001 vs 2012 data).

  • Muir Glacier: Receded over 7 miles and thinned by over 2600 ext{ ft} from 1941 to 2004.

Future Climate Change Predictions

  • Projected Outcomes

    • Global temperature increase projected to range from 1.4 - 4.4^ ext{°C} by 2100.

    • Precipitation changes expected, with some regions increasing or decreasing by up to 30 rac{%}{}.

    • Increase in extreme weather events, including more intense heat waves and tropical cyclones.

Why is Climate Changing?

  • Natural Mechanisms

    • Solar output: Variation in the energy output from the sun.

    • Earth-sun relationships: Changes in orbit characteristics: eccentricity, axial parallelism, and fixed tilt cycle.

    • Movement of continents: Historical land shifts affect climate patterns.

    • Atmospheric variability: Natural changes in atmospheric conditions.

    • Volcanic activity: Eruptions can temporarily cool climate due to ash and gases.

  • Human Mechanisms:

    • Land use changes: Urbanization and deforestation impacting natural landscapes.

    • Greenhouse gases: Mainly CO₂, increased by human activities since 1959 from 315.98 ext{ ppm} to 424.61 ext{ ppm} in 2024.

Critical Points About Greenhouse Gases

  • Greenhouse gas warming is primarily caused by CO₂ (approx. 64 rac{%}{} of the warming).

  • The current rate of increase in CO₂ is unprecedented in the last 10,000 years, which poses a serious risk to climate stability.

Future Climate Models

  • General Circulation Models (GCMs) simulate Earth's climate system, providing predictions based on historical and current data.

  • Important for understanding potential climate change scenarios and planning mitigation efforts.

Implications of Potential Climate Change

  • Severe flooding in coastal areas from projected sea level rises:

    • Loss from melting of permafrost, sea ice, and ice sheets could significantly raise sea levels:

    • All permafrost thaws: 3-10 ext{ cm}

    • All Greenland ice sheet melts: 6.5 ext{ m} (or 21 ext{ ft})

    • All Antarctic ice melts: 60 ext{ m} (or 197 ext{ ft})

  • Understanding these impacts is crucial for global sustainability and policy-making.