2.4A Climate Notes

1. Climate and weather are fundamental to understanding how ecosystems are distributed across the Earth.
2. Both describe atmospheric conditions but differ in timescale, variability, and application.
3. Climate determines long-term environmental patterns that influence vegetation, animal life, and biome formation, while weather governs short-term fluctuations experienced in daily life.

Weather

1. Weather is the short-term state of the atmosphere, observed over hours or days.
2. It reflects daily fluctuations driven by changing air masses, pressure systems, and local energy exchanges.
3. Key weather variables:
   1. Temperature: How hot or cold the air is.
   2. Humidity: The amount of moisture in the air.
   3. Precipitation: Rain, snow, sleet, or hail.
   4. Wind Speed and Direction: How fast the wind is blowing and where it's coming from.
   5. Cloud Cover: The amount and type of clouds in the sky.

Climate

1. Describes long-term patterns and extremes of atmospheric conditions in a specific region.
2. Measured over an average period of approximately 30 years (standard climatological baseline).
3. Determined by global systems such as solar radiation, Earth’s tilt, ocean currents, and atmospheric circulation.
4. It helps us understand what to expect in a given area, such as:
   1. Tropical Climates: Hot and humid, with heavy rainfall (e.g., the Amazon Rainforest).
   2. Arid Climates: Dry with minimal precipitation (e.g., the Sahara Desert).
   3. Temperate Climates: Moderate temperatures with distinct seasons (e.g., Western Europe).

The 30-Year Reference Period

1. The 30-year averaging period was chosen to capture natural variability while minimizing the influence of short-term anomalies.
2. Until 2020, the official climate baseline was 1981–2010.
3. However, this approach has limitations:
   1. The database is too short to reflect century-scale variability.
   2. The 1981–2010 period includes rapid global warming, making it non-representative of long-term “normal” conditions.
   3. A 30-year record cannot estimate rare, extreme events, such as 50-year or 100-year floods or droughts.

Factors Influencing Climate and Weather

1. Latitude

1. Controls the intensity and angle of incoming solar radiation.
2. Equatorial regions receive direct sunlight year-round (warmer, wetter climates).
3. Polar regions receive oblique sunlight (colder, drier climates).

2. Altitude

1. Temperature decreases with height (≈ 6.5°C per 1000 m).
2. High-altitude ecosystems like alpine tundra resemble polar biomes.

3. Ocean Currents

1. Warm currents (e.g., Gulf Stream) raise coastal temperatures.
2. Cold currents (e.g., Humboldt Current) lower them, often creating deserts near coastlines.

4. Distance from the Sea

1. Maritime climates (coastal) have mild temperatures and high rainfall.
2. Continental climates (inland) show greater seasonal extremes.

5. Prevailing Winds

1. Determine the direction of moist or dry air masses.
2. Westerlies and trade winds redistribute heat and moisture globally.

6. Aspect

1. The orientation of slopes affects sunlight exposure.
2. North-facing slopes in the Northern Hemisphere receive less sunlight and are cooler.

7. Human Activities

1. Urbanization (urban heat islands), deforestation, and fossil fuel combustion modify local and global climates through greenhouse gas emissions and albedo changes.

Ecological Importance of Climate

1. Determines biome distribution (tropical rainforests, tundra, deserts).
2. Controls soil formation, nutrient cycling, and hydrological processes.
3. Influences adaptations of organisms - physiological, structural, and behavioural.
4. Affects human activities such as agriculture, settlement, and energy use.