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Earth’s Climate. Factors That Determine Climate. The Earth is cold at the poles and warm at the equator. Sunlight falling at an angle is spread out over a greater area and therefore causes less heating at steeper angles in polar regions. Tilt of the Earth’s axis
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Factors That Determine Climate The Earth is cold at the poles and warm at the equator Sunlight falling at an angle is spread out over a greater area and therefore causes less heating at steeper angles in polar regions.
Tilt of the Earth’s axis • 23.5 towards the sun in summer • 23.5 away from the sun in winter Polar regions become extremely cold in winter. Even though the poles get constant sun in summer, the solar angle is so low that the heating is small. Also, polar ice reflects sunlight, further reducing the effect of constant sun. Factors That Determine Climate Solar energy absorption Solar energy reflection
Equinox Solstice Equinox Solstice
Also Watch!!!! http://www.youtube.com/watch?v=WLRA87TKXLM&safety_mode=true&persist_safety_mode=1&safe=active Seasonal Changes
Weather and Climate What is weather? Weather is the state of atmospheric conditions that exist over relatively short periods of time, from a few hours to a couple of days). Weather includes the passing of a thunderstorm, hurricane, or blizzard, and the persistence of a heat wave, or a cold snap. What is Climate? Climate is the weather we expect over the period of a month, a season, a decade, or a century. It is often described in terms of "climate norms" or average weather conditions. Climographs are graph of monthly average temperature plotted against average precipitation. The temperature points are joined by a line.
Reading a Climograph Location at the top Dotted Line Graph = average monthly temp. Temperature Scale Watch Fº vs. Cº!! Bar Graph = Average Monthly Rainfall…think of a glass filling up w/ water Months at the bottom JFMAMJJASOND Precipitation Scale, Watch inches or mm!!
Factors That Determine Climate Latitude: Warm and moist at the equator, cold and dry at the poles Altitude/Elevation: Higher altitudes are colder and dryer Proximity to landforms: (mtns., deserts, plains, valley) Mountains can cause clouds an precipitation on the windward side, and dry conditions on the leeward side Proximity to oceans: Oceans moderate temperature and increase humidity Polar or Tropical water currents can influence temperatures
Elevation/altitude For every 1,000 ft of elevation change, we calculate 3.5°of temperature change As we rise in elevation, temperature….? As we drop in elevation, temperature….?
Coastal vs. Inland • Precipitation: • Receive more rain, than snow • Humidity acts to insulate temperatures • Sun goes down, the moisture retains heat • Temperatures: • Remain more constant throughout the year • Cooler Summers, Warmer Winters • Less variation in yearly averages than inland • Precipitation: • Typically receive more snow, than rain • Little humidity, daytime heat is lost • Sun goes down it gets cold • Temperatures: • Have more variation throughout the year • Cooler winters, Warmer Summers • Lots of variation in yearly averages
This is how distance from water can influence a location’s climate Red= Inland Blue= Coastal
How do scientists know what the weather was like in the past?
Climate Data Direct Measurements: Observations of air & water temperature, precipitation amount, etc… have been made routinely with accurate instruments for about 150 years Historical Records: Clues left in written documents from the past Paleoclimate: Properties of the Earth and Atmosphere are determined from clues hidden in the Earth, a kind of forensic science. Sources of paleoclimate information: • Ice Cores • Tree Rings • Ocean Sediment
Ice Cores • Ice cores are samples of ice taken from glaciers . • Air bubbles, dust, and oxygen isotopes get trapped in glacial ice, and can be used to analyze past climate. • Glaciers become thicker over time, so the deeper you drill the older the ice is. Glaciers obtain one layer each year, so counting layers is like counting years. Ice core data can extend back hundreds of thousands of years • Ice cores can reveal temperature, precipitation, and gas composition of the lower atmosphere • They also can indicate volcanic eruptions, solar variability, sea-surface productivity and a variety of other climate indicators.
Tree Rings In temperate regions where there is a distinct growing season, trees generally produce one ring a year Since tree growth is influenced by climatic conditions, patterns in tree-ring widths, density, and isotopic composition reflect variations in climate. Trees can grow to be hundreds to thousands of years old and can contain annually-resolved records of climate for centuries to millennia. If a tree is fossilized, the age of the tree (how long ago it died) can be determined by examining isotopes. Isotope ratios are also indicative of temperature change.
Ocean Sediments Billions of tons of sediment accumulate in the ocean and lake basins each year. Scientist drill cores of sediment from ocean and lake floors. Ocean and lake sediments include tiny fossils and chemicals that are used to interpret past climates.
The Greenhouse Effect The Earth receives ultraviolet (UV) radiation from the sun, absorbs it, and then radiates the energy out as infrared radiation If the Earth behaved as a simple blackbody then the Earth’s average temperature would be –18 C However, the Earth’s average temperature is 15 C. The Earth is warmer because our atmosphere traps some of the outgoing IR radiation. This is a natural process known as the greenhouse effect. The greenhouse effect is a good thing, without it the Earth would become too cold for life to exist. However, man’s activities appear to be altering the natural balance.
