Unit 6 Climate and Global Climate Change

Climate The LONG TERM weather patterns for an area. Describes monthly or annual variations in: Temperature Precipitation Wind Other weather variables

What Affects Climate? 1. Latitude:

Equator receives more direct sunlight → Warmer Climates North & South of equator sunlight is indirect → Cooler Climates

Climate Zones: Tropical Zone: Equator to 23.5° N & S Temperate zone: 23.5° - 66.5° N & S Polar zone: 66.5° to N & S poles Polar Zone Temperate Zone Tropical Zone Temperate Zone Polar Zone

2. Topography Water heats & cools more slowly than land: Earth’s Oceans moderate coasts → coastal climates

↑ altitude, ↓ temp Leeward side of mountains → drier air

3. Air Masses Continental (dry) vs Maritime (wet) Tropical (warm) vs Polar (cold)

4. Circulation Cells Cells of air circulation are driven by solar energy & earth’s rotation These cells transport energy & heat from equator to poles

Climate Classification Köppen classification system Divides climates based on average temperatures, precipitation & vegetation

Global Climate change A pattern of change that occurs over many years (NOT seasonal variations from year to year) Global warming: the increase in average global temperature that has occurred over MANY years

Greenhouse Gases Heat trapping gases in the atmosphere: Carbon Dioxide Methane Nitrous Oxide Water vapor Effects on the climate depend on: How much is produced How long it stays in the atmosphere How much heat it can trap

Water Vapor Water vapor increases as the Earth’s surface warms Water vapor leads to climate warming Climate warming leads to more evaporation of water & more water vapor – a positive feedback loop

Natural Causes of Climate Change

Earth’s Climate in the Past

Earth’s Wobble: the 26,000 year precession cycle affects Earth’s seasons Earth’s Orbit: changes from circular to elliptical over a 100,000 year cycle

Volcanic Activity: volcanic ash in the atmosphere blocks the Sun and cools Earth’s climate

Solar Activity: sunspot cycles affect temperatures on Earth

Sunspots and Sunspots Cycles: Occur ~every 11 years Dark spots up to 50,000 miles wide Move across the surface of the sun Give off more energy

Photosynthesis Plants take in CO2 (a greenhouse gas) and put out O2. This reduces greenhouse gases

El Nino Southern Oscillation (ENSO) Cycles of El Nino, warmer waters, and La Nina, cooler waters, off South America. Causes cycles of wet & dry weather

Microclimates A localized pocket with a climate different from the surrounding area. Example:

Using ice cores, scientists found there is more CO2 in atmosphere today than in past

The level of the greenhouse gases methane, CO2, and nitrous oxide are increasing.

Carbon Dioxide (CO2) 55% of human produced greenhouse gas Comes from: Fossil fuel combustion for power Cutting down or burning trees Industrial processes (making cement or chemicals) Can stay thousands of years

Methane (CH4) 30% of human produced greenhouse gas Comes from: Livestock (cows and sheep) Landfills Natural gas Mining coal Stays ~12 years Traps 20 times more heat than CO2

Nitrous Oxide (N2O) 5% of human produced greenhouse gas Comes from: Farming (fertilizer) Fossil fuel combustion Industrial processes Stays ~114 years Traps 298 times more heat than CO2

Sources of Greenhouse Gas emissions in US Electricity production (32%) Fuel combustion for transportation (20%) Industrial processes (20%) Agriculture(10%) Residential (10%)

Heat Islands Cities and urban centers with many concrete buildings and asphalt have a warmer climate than surrounding rural areas