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.