Defining Climate
• Climate = long term weather patterns… – Averages and variations in temp., precip., wind,
etc.
• Normals: – 30+ year averages of daily high and low temp,
rainfall, wind speed and wind direction, measured at a specific location
– Normals are not necessarily usual weather conditions
Factors that Influence Climate
• Latitude (north or south of the equator)• Topography (rain shadow effect)• Air masses
Climate Classification
• Köppen’s classification system—based on temperature, precipitation, and vegetation– Tropical (high temp. year round)– Dry—largest area (low precipitation)– Mild (warm summers, cool winters)– Continental (warm summers, cold winters)– Polar—also highlands (low temp. year round)
Short-Term Climate Changes
• El-Niño—changes in southern Pacific Ocean with global effects
• Volcanoes tend to decrease global temperatures
Natural Causes of Climate Change
• Solar/sunspot activity—11 year cycle• Maunder minimum: low sunspot activity from
1645 to 1716 corresponds to “Little Ice Age.”• Long-term changes in Earth’s orbit, tilt, and
wobble cause cycles in temperature (ice ages)