Ch8 Global Climates

Chapter 8: Global Climates and Climate Change

Understanding Climate

  • Climate Definition: Refers to the average weather over a 30-year period.

  • Climatology: The study of climate and its variations.

  • Climatic Regions: Areas characterized by similar weather statistics.

  • Reminder: Distinction between climate and weather.

Classifying Climates

  • Climographs: Tools that display average monthly temperature (curve) and rainfall (bars).

  • Indicators: Temperature and precipitation serve as key indicators of climate.

Climate Classification Systems

Empirical Classification

  • Based on statistical and physical parameters (temperature, humidity, etc.).

  • Requires a minimum of 30 years of data.

Genetic Classification

  • Based on the causes of climate variation.

  • Factors include insolation, air masses, and topography.

  • Generalizes climate without describing the real-time weather situation.

Thornwaite System

  • Classifies climate locally, focusing on vegetation; useful for soil scientists and agriculture.

  • Determines Moisture Availability:

    • Potential Evapotranspiration (PET): Estimates water use under unlimited supply.

    • Actual Evapotranspiration (AET): Reflects real water use by plants and surface.

Köppen Climate Classification

  • Most widely adopted climate classification system.

  • Relies on regional temperature and precipitation patterns.

Tropical (A) Climates

  • Characteristics: High temperatures year-round, typically found near the equator; no winter (average cold month above 18°C / 64.4°F).

  • Influenced by the Intertropical Convergence Zone (ITCZ) and its seasonal movement.

  • Types:

    • Tropical Rainforest (Af): Located 5-10° of the equator, experiences year-round rainfall.

    • Dry Winter Tropical Savanna (Aw): Seasonal rainfall aligned with ITCZ migration.

    • Tropical Monsoon (Am): Exhibits distinct seasonal rainfall patterns.

Polar (E) Climates

  • Defined by having no month with average temperatures exceeding 10°C (50°F).

  • Includes Tundra (ET) and Ice-sheet (EF) climates.

Arid (B) Climates

  • Characterized by year-round moisture deficiency, with precipitation lower than potential evapotranspiration.

  • Locations typically between 15°N/S to 30°N/S, influenced by subtropical highs.

Highland (H) Climates

  • Change driven by air mass movements impacting microclimates related to elevation, clouds, and exposure.

  • Variability demonstrated on slopes, with leeward sides being drier.

Scale of Climate

  • Macro Climate: e.g., Sahara Desert.

  • Meso Climate: e.g., Coastal Southern California.

  • Micro Climate: e.g., Slopes of a single hill; effects influenced by slope aspect and human activities.

Weather vs. Climate

  • Understanding the differences between weather and climate in terms of time scales and current weather patterns.

Past Climatic Data

  • Evidence drawn from present-day data corroborating past and future climate changes.

Ice Ages

  • Historical Overview: Pre-Cambrian (600 million years ago); ice age cycles lasting millions of years.

  • During the current Pleistocene ice age, glaciers have retreated and advanced 20 times; currently in a warming interval.

Drivers of Climate Change

  • Influential factors include solar output, Earth's distance from the sun, continental positioning, ocean circulation, and atmospheric composition.

Recent Ice Ages

  • Marks periods of cold (glacial) and warmth (interglacial), primarily seen during the Pleistocene epoch (2.6 million years to present).

    • Last Glacial Maximum (LGM): Approximately 18,000 years ago.

Climate Research Techniques

  • Modern methodologies such as radiometric techniques and ocean sediment analysis (calcium carbonate, oxygen-isotope studies) provide insight into climate patterns.

Holocene Epoch

  • The last 10,000 years have exhibited trends indicating warming patterns.

Historical Climate Reconstructions

  • Methods employed include dendrochronology (tree rings), palynology (pollen analysis), and sedimentology.

Altithermal Period

  • Occurred 7,000 years ago; this period was warmer than today, opening questions about rapid temperature increases.

Causes of Climate Change

  • Various factors including orbital variations, oceanic circulation changes, landmass shifts, and celestial impacts (asteroids, comets).

    • Milankovitch Cycles: Include eccentricity (100,000 years), obliquity (41,000 years), and precession (21,000 years); affect Earth's climate and seasonality.

Modern Climate Change

  • Data on Global Warming: Directly linked to human activities; significant temperature increases recorded since 1995.

  • Global temperatures have risen between 0.5°C and 0.7°C.

  • Sea level rise of 15 to 30 cm over the past century.

The Issue of Global Warming

  • Scientific consensus exists regarding human impact on climate change.

  • Reports from the IPCC link greenhouse gas emissions from human activities to observed global temperature increases.

Recommendations for Future Actions

  • Global Strategies:

    • Develop alternative energy sources.

    • Improve energy management and recycling practices.

    • Mitigate deforestation.

    • Explore desalinization options.

  • Individual Actions:

    • Utilize public transport or carpooling.

    • Switch to energy-efficient appliances.

    • Regulate thermostat settings.

    • Engage in recycling initiatives.