Climate
- Climate is more than "the average state of the atmosphere" because a complete climate description should also include variations and extremes to accurately portray the total character of an area.
- The most important elements in climate descriptions are temperature and precipitation inasmuch as they have the greatest influence on people and their activities and also have as important impact on the distribution of vegetation and the development of soils.
- Perhaps the first attempt at climate classification was made by the ancient Greeks, who divided each hemisphere into three zones: torrid, temperate, and frigid.
- Since the beginning of the twentieth century, many climate-classification schemes have been devised.
- The classification of climates is the product of human ingenuity and its value is determined largely by its intended use.
- For decades, a climate classification devised by Wladimir Köppen (1846–1940) has been the best-known and most used tool for presenting the world pattern of climates.
- The Köppen classification uses easily obtained data: mean monthly and annual values of temperature and precipitation.
- Furthermore, the criteria are unambiguous, simple to apply, and divide the world into climate regions in a realistic way.
- Köppen believed that the distribution of natural vegetation was the best expression of an overall climate.
- Consequently, the boundaries he chose were largely based on the limits of certain plant associations.
- Köppen recognized five principal climate groups, each designated with a capital letter:
- A (humid tropical),
- B (dry),
- C (humid middle-latitude, mild winters),
- D (humid middle-latitude, severe winters), and
- E (polar).
- Four groups (A, C, D, E) are defined by temperature.
- The fifth, the B group, has precipitation as its primary criterion.
- Order exists in the distribution of climate elements and the pattern of climates is not by chance.
- The world's climate pattern reflects a regular and dependable operation of the major climate controls.
- he major controls of climate are:
- (1) latitude (variations in the receipt of solar energy and temperature differences are largely a function of latitude),
- (2) land/water influence (marine climates are generally mild, while continental climates are typically much more extreme),
- (3) geographic position and prevailing winds (the moderating effect of water is more pronounced along the windward side of a continent),
- (4) mountains and highlands (mountain barriers prevent maritime air masses from reaching far inland, trigger orographic rainfall, and where they are extensive, create their own climatic regions),
- (5) ocean currents (poleward-moving currents cause air temperatures to be warmer than would be expected), and
- (6) pressure and wind systems (the world distribution of precipitation is closely related to the distribution of Earth's major pressure and wind systems).
- Situated along the equator, the wet tropics (Af, Am) constant high temperatures and year-round rainfall combine to produce the most luxuriant vegetation in climatic realm—the tropical rain forest.
- Temperatures in these regions usually average 25°C (77°F) or more each month and the daily temperature variations characteristically greatly exceed seasonal differences.
- Precipitation in Af and Am climates is normally from 175 to 250 centimeters (68 to 98 inches) per year and is more variable than temperature, both seasonally and from place to place.
- Thermally induced convection coupled with convergence along the intertropical convergence zone (ITCZ) leads to widespread ascent of the warm, humid, unstable air and ideal conditions for precipitation.
- Dry regions of the world cover about 30 percent of Earth's land area.
- Other than their meager yearly rainfall, the most characteristic feature of dry climates is that precipitation is very unreliable.
- Climatologists define a “dry climate” as one in which the yearly precipitation is less than the potential water loss by evaporation.
- To define the boundary between dry and humid climates, the Köppen classification uses formulas that involve three variables:
- (1) average annual precipitation,
- (2) average annual temperature, and
- (3) seasonal distribution of precipitation.
- Humid middle-latitude climates with mild winters (C climates) occur where the average temperature of the coldest month is less than 18°C (64°F) but above -3°C (27°F).
- Several C climate subgroups exist.
- Humid continental climates with severe winters (D climates) experience severe winters.
- The average temperature of the coldest month is -3°C (27°F) or below and the average temperature of the warmest month exceeds 10°C (50°F).
- The greatest annual temperature ranges on Earth occur here.
- Polar climates (ET, EF) are those in which the mean temperature of the warmest month is below 10°C (50°F).
- Annual temperature ranges are extreme, with the lowest annual means on the planet.
- Although polar climates are classified as humid, precipitation is generally meager, with many nonmarine stations receiving less than 25 centimeters (10 inches) annually.
- Two types of polar climates are recognized.
- Found almost exclusively in North America, the tundra climate (ET), marked by the 10°C (50°F) summer isotherm at its equatorward limit, is a treeless region of grasses, sedges, mosses, and lichens with permanently frozen subsoil, called permafrost.
- The ice cap climate (EF) does not have a single monthly mean above 0°C. Consequently, the growth of vegetation is prohibited, and the landscape is one of permanent ice and snow.
- Highland climates are characterized by a great diversity of climatic conditions over a small area.
- In North America, highland climates characterize the Rockies, Sierra Nevada, Cascades, and the mountains and interior plateaus of Mexico.
- Although the best known climatic effects of an increased altitude are lower temperatures, greater precipitation due to orographic lifting is also common.
- Variety and changeability best describe highland climates.
- Because atmospheric conditions fluctuate with altitude and exposure to the Sun's rays, a nearly limitless variety of local climates occur in mountainous regions.
Climate Change Notes
Climate Change
Consequences to living organisms
- Global change- any chemical, biological or physical property change of the planet. Examples include cold temperatures causing ice ages.
- Global climate change- changes in the climate of the Earth.
- Global warming- one aspect of climate change, the warming of the oceans, land masses and atmosphere of the Earth.
- When radiation from the sun hits the atmosphere, 1/3 is reflected back.
- Some of the UV radiation is absorbed by the ozone layer and strikes the Earth where it is converted into low-energy infrared radiation.
- The infrared radiation then goes back toward the atmosphere where it is absorbed by greenhouse gasses that radiate most of it back to the Earth.
- Water vapor
- Carbon dioxide
- Methane
- Nitrous oxide
- Ozone
- Volcanic eruptions- mainly carbon dioxide
- Methane – from decomposition
- Nitrous oxide- from denitrification
- Water vapor
- Burning of fossil fuels
- Agricultural practices
- Deforestation
- Landfills
- Industrial production- CFC’s are an example
- no one was around thousands of years ago to measure temperatures so we use other indirect measurements. Some of these are
- Changes in species compositions
- Chemical analyses of ice
- We know that an increase in CO2 in the atmosphere causes a greater capacity for warming through the greenhouse effect.
- When the Earth experiences higher temperatures, the oceans warm and cannot contain as much CO2 gas and, as a result, they release CO2 into the atmosphere.
- Melting of polar ice caps, Greenland and Antarctica
- Melting of many glaciers around the world
- Melting of permafrost
- Rising of sea levels due to the melting of glaciers and ice sheets and as water warms it expands
- Heat waves
- Cold spells
- Change in precipitation patterns
- Increase in storm intensity
- Shift in ocean currents
Consequences to living organisms
- Wild plants and animals can be affected. The growing season for plants has changed and animals have the potential to be harmed if they can’t move to better climates.
- Humans may have to relocate, some diseases like those carried by mosquitoes could increase and there could be economic consequences.
- The fundamental basis of climate change- that greenhouse gas concentrations are increasing and that this will lead to global warming is not in dispute among the vast majority of scientists.
- What is unclear is how much world temperatures will increase for a given change in greenhouse gases, because that depends on the different feedback loops.
- In 1997, representatives of the nations of the world went to Kyoto, Japan to discuss how best to control the emissions contributing to global warming.
- The agreement was that emissions of greenhouse gases from all industrialized countries will be reduced to 5.2% below their 1990 levels by 2012.
- Developing nations did not have emission limits imposed by the protocol.
- An approach involving taking CO2 out of the atmosphere.
- Some methods include storing carbon in agricultural soils or retiring agricultural land and allowing it to become pasture or forest.
- Researchers are looking at cost-effective ways of capturing CO2 from the air, from coal-burning power stations, and from other emission sources.
- This captured CO2 would be compressed and pumped into abandoned oil wells or the deep ocean.