CLIMATE: A BRIEF INTRODUCTION Weather is a local area’s short-term physical conditions such as temperature and precipitation. Climate is a region’s average weather conditions over a long time. Latitude and elevation help determine climate.

Earth’s Current Climate Zones Figure 5-2

Solar Energy and Global Air Circulation: Distributing Heat Global air circulation is affected by the uneven heating of the earth’s surface by solar energy, seasonal changes in temperature and precipitation. Figure 5-3

(sun aims directly at equator) Winter (northern hemisphere tilts away from sun) Spring (sun aims directly at equator) 23.5 ° Solar radiation Summer (northern hemisphere tilts toward sun) Figure 5.3 Natural capital: as the planet makes its annual revolution around the sun on an axis tilted about 23.5°, various regions are tipped toward or away from the sun. The resulting variations in the amount of solar energy reaching the earth create the seasons in the northern and southern hemispheres. Fall (sun aims directly at equator) Fig. 5-3, p. 102

Coriolis Effect Global air circulation is affected by the rotation of the earth on its axis. Figure 5-4

Cold deserts Westerlies Forests Northeast trades Hot deserts Forests Equator Figure 5.4 Natural capital: because of the Coriolis effect the earth’s rotation deflects the movement of the air over different parts of the earth, creating global patterns of prevailing winds that help distribute heat and moisture in the troposphere. Southeast trades Hot deserts Forests Westerlies Cold deserts Fig. 5-4, p. 102

Convection Currents Global air circulation is affected by the properties of air water, and land. Figure 5-5

Heat released radiates to space Moist surface warmed by sun LOW PRESSURE HIGH PRESSURE Heat released radiates to space Condensation and precipitation Cool, dry air Falls, is compressed, warms Rises, expands, cools Warm, dry air Hot, wet air Figure 5.5 Natural capital: transfer of energy by convection in the troposphere. Convection occurs when hot and wet warm air rises, cools, and releases moisture as precipitation and heat (right side). Then the more dense cool and dry air sinks, gets warmer, and picks up moisture as it flows across the earth’s surface to begin the cycle again. Flows toward low pressure, picks up moisture and heat HIGH PRESSURE Moist surface warmed by sun LOW PRESSURE Fig. 5-5, p. 103

Convection Cells Heat and moisture are distributed over the earth’s surface by vertical currents, which form six giant convection cells at different latitudes. Figure 5-6

Tropical deciduous forest Cold, dry air falls Cell 3 North Moist air rises — rain Polar cap Cell 2 North Arctic tundra Evergreen coniferous forest 60° Cool, dry air falls Temperate deciduous forest and grassland 30° Desert Cell 1 North Tropical deciduous forest Moist air rises, cools, and releases Moisture as rain 0° Equator Tropical rain forest Tropical deciduous forest 30° Desert Figure 5.6 Natural capital: global air circulation and biomes. Heat and moisture are distributed over the earth’s surface by vertical currents, which form six giant convection cells at different latitudes. The resulting uneven distribution of heat and moisture over the planet’s surface leads to the forests, grasslands, and deserts that make up the earth’s biomes. Cell 1 South Temperate deciduous forest and grassland Cool, dry air falls 60° Cell 2 South Polar cap Cold, dry air falls Moist air rises — rain Cell 3 South Fig. 5-6, p. 103

Ocean Currents: Distributing Heat and Nutrients Ocean currents influence climate by distributing heat from place to place and mixing and distributing nutrients. Figure 5-7

(b) The earth's surface absorbs much of the incoming solar radiation (a) Rays of sunlight penetrate the lower atmosphere and warm the earth's surface. (b) The earth's surface absorbs much of the incoming solar radiation and degrades it to longer-wavelength infrared (IR) radiation, which rises into the lower atmosphere. Some of this IR radiation escapes into space as heat, and some is absorbed by molecules of greenhouse gases and emitted as even longer-wavelength IR radiation, which warms the lower atmosphere. (c) As concentrations of greenhouse gases rise, their molecules absorb and emit more infrared radiation, which adds more heat to the lower atmosphere. Figure 5.7 Natural capital: the natural greenhouse effect. When concentrations of greenhouse gases in the atmosphere rise, the average temperature of the troposphere rises. (Modified by permission from Cecie Starr, Biology: Concepts and Applications, 4th ed., Pacific Grove, Calif.: Brooks/Cole, 2000) Fig. 5-7, p. 104

Ocean Currents: Distributing Heat and Nutrients Global warming: Considerable scientific evidence and climate models indicate that large inputs of greenhouse gases from anthropogenic activities into the troposphere can enhance the natural greenhouse effect and change the earth’s climate in your lifetime.

Global Warming and Climate Change Climatic records indicate over past 160,000 years, a correlation between greenhouse gas concentration and global temperatures. UN established Intergovernmental Panel on Climate Change (IPCC) 1996 Assessment - Concluded climate change is occurring and it is highly probable human activity is importance cause of the change.

Global Warming and Climate Change IPCC Conclusions Average temperature of the earth increased .5 to 1.0 degrees Fahrenheit over the last 100 years. Strong correlation between temperature increase and amount of greenhouse gases in the atmosphere. Human activity greatly increases amounts of greenhouse gases in atmosphere.

Changes in Average Global Temperature

Causes of Global Warming and Climate Change Greenhouse Effect Greenhouse gases allow sunlight to penetrate the atmosphere. Absorbed by earth’s surface. Reradiated as infrared energy (heat). Absorbed by gases.

Greenhouse Effect

Greenhouse Effect Carbon Dioxide Chlorofluorocarbons Methane Fossil fuel burning, deforestation. Chlorofluorocarbons Refrigerants, cleaning solvents, propellants. Methane Breakdown of organic material by anaerobic material. Nitrous Oxide Biomass burning - Breakdown of nitrogen-rich products.

Potential Consequences of Global Warming Rising Sea Level Beach and coastal wetland erosion. Disruption of Water Cycle Navigation Hydropower Water Supply and Demand Flood Control Environmental Quality and Recreation Political Issues

Potential Consequences of Global Warming Health Effects Most direct effect of climate change would be impacts of hotter temperatures. Hot temperatures force cardiovascular system to work harder to cool the body. Heat exhaustion and some respiratory problems increase. Aggravate air quality problems. Ozone

Potential Consequences of Global Warming Changing Forests Geographic distributions of vegetation. Challenges to Agriculture Increased CO2 concentration likely to increase crop yields in some areas and decrease yields in other areas. Pest range expansion could increase vulnerability. Unanticipated Changes Greatest risks may be those yet to be discovered.

Effects of Global Warming

Addressing Climate Change Energy Efficiency Increase efficiency of energy utilization. Reduce carbon dioxide production. Carbon Tax Role of Biomass Increase amount of carbon dioxide removed from the atmosphere. Increased vegetation growth. Short-term benefit.

Addressing Climate Change Political and Economic Forces Will be difficult to achieve global consensus to reduce CO2 emissions, as CO2 is released as a result of energy consumption which affects all sections of the economy. Resources and policies to increase investment in renewables and other long-term technologies will be needed.