Atmosphere and Climate Change Chapter 13

Section 1: Climate and Climate Change

Weather and Climate Weather – the state of the atmosphere in one area at one time. What is the weather today here? What is the weather in Anchorage, Alaska? Climate - the long term prevailing weather at a particular place What is the climate for here? What is the climate for Anchorage, Alaska? Two places can have the same weather on the same day But they can have VERY different climates Weather: Seattle and Phoenix might both have rain today Climate : Seattle is wet and cool, Phoenix is dry and hot **It depends on their proximity top the equator.

What Determines Climate Climate is determined by: Atmospheric Circulation Patterns Oceanic Circulation Patterns Local geography Solar activity Volcanic Activity Which is most important? Latitude (How far above/below you are from the equator)

Latitude is the distance north or south of the equator Latitude is the distance north or south of the equator. Measured in degrees. Equator is 0 degrees, the poles are 90 degrees Low Latitudes – get the strongest, most concentrated sunlight. Night and Day are 12 hours, all year round High temps all year round High Latitudes – sunlight is spread over a greater area, weaker, less energy Daylight hours vary At the poles the sun sets for only a few hours during the summer Dark almost all day during winter Average annual temperatures lower than at equator. Latitude

Atmospheric Circulation Three basic rules: 1. Cold air sinks – but pressure is stronger at lower levels so cold air gets compressed and thus warms. 2. Warm Air Rises – lower pressure lets it expand and it cools down 3. Warm Air holds more water vapor than cold air – so as it rises the water vapor cools and condenses How do we get wind? 1. Sun heats the earth surface. 2. Hot Air Rises 3.Cold Air replaces it………wind!

Earth gets heated differently More heat at equator, more air rising Rising air cools making lots of clouds! And rain!.(think where are our jungles?) Cool air can’t sink back down because of continuous rising hot air Has to spread north and south until it eventually cools enough that it begins to sink…and warm Dry warm air sinks at 30 North and 30 South What do we find at 30 North and South around the globe?

Prevailing winds – winds that blow predominantly in one direction most of the year. From what direction does our prevailing wind come from? (They are deflected to the right in the Northern Hemisphere) Trade Winds – the prevailing winds between 30° and equator.

Ocean Circulation Patterns Water holds a lot of heat (think how much heat it takes to boil water!) Ocean currents are caused by winds and the movement of the earth The ocean currents move heat around the globe. In the summer where would you rather swim? Off California coast in LA or off the South Carolina coast Colder water flows south from Alaska, warm water flows north from the Caribbean

EL Nino VS La Nina Some ocean currents change the way they flow: Pacific Ocean water near Americas warms – leads to increased clouds and rainfall in SW US La Nina Opposite of El Nino, cooler waters in Pacific near Americas, droughts in the SW US Pacific Decadal Oscillation Similar to El Nino but the switching occurs every 20 – 30 years

Topography Rain Shadow Topography is a broad term used to describe the detailed study of the earth's surface. Where is Mt Kilimanjaro? (Tanzania) It has snow all year round! That’s due to its height (colder as you go up in atmosphere!) Rain Shadow Dry area on the eastern side of mountains

Sun’s Impact Solar Cycle – 11 year cycle of the sun. http://www.nasa.gov/mov/143924main_AmazChangeSun_QT%20big%20progre.mov Solar Cycle – 11 year cycle of the sun. At the maximum – the sun emits UV radiation This can warm the lower atmosphere and Earth. On earth the Northern Lights can be seen as far south as Mexico on occasion. Increased radiation from the sun can cause warming of the atmosphere Seasons – Why do we have them? All due to the tilt of the earth – 23.5° relative to the plane of its orbit. (Angle of the sun’s rays striking the Earth)

That’s all for 13.1 Time for a reading quiz

Section 2: The Ozone Shield

Ozone Layer Ozone is the chemical compound O3 Large concentration is found in the stratosphere Ozone Layer absorbs most UV radiation coming from the sun UV radiation can damage organisms cells Chemicals Can Destroy Ozone CFCs – chlorofluorocarbons CFCs are non flammable, non poisonous, and non reactive at the Earth’s surface CFCs used as propellants in spray cans and coolants in fridges/air conditioners It takes 10 -20 years for CFCs to reach the stratosphere from the Earth's surface

High energy of the UV radiation breaks it down CFCs are broken apart in the stratosphere High energy of the UV radiation breaks it down The single chlorine from CFC can react with O3 and changes it, depleting the O3 Scientists estimate that a single chlorine atom can break down 100,000 ozone molecules.

Ozone Hole First noticed in 1970 from satellite photos over the South Pole What Causes it? During the cold polar winters, dry stratospheric air over the pole is isolated. Air becomes so cold that it condenses and forms clouds (Polar Stratospheric clouds: high-altitude clouds made of water and nitric acid at - 80° C) Chlorine from CFCs builds up on the surface of the clouds When the pole begins to warm the chlorine goes back to depleting ozone.

Video on Ozone Depletion http://video.nationalgeographic.com/video/news/environment- news/antarctica-ozone-vin/

Why Care About Ozone? Ever have a bad sunburn? UV radiation can damage organisms DNA Can lead to skin and other cancers Notable impact to amphibian eggs (death/mutations) Phytoplankton can be killed by UV Phytoplankton is the producer for most ocean food chains Phytoplankton loss would also effect atmospheric CO2 levels Montreal Protocol Many nations banned the use of CFCs in 1992 (US stopped production by 2000) CFCs still a problem….Why? CFCs molecules remain in the stratosphere for 60 – 120 years

That’s all for 13.2 Time for a reading quiz

Section 3: Global Warming

Greenhouse Effect The earth is like a greenhouse The atmosphere acts like the glass – which lets the sun’s rays pass through. The earth absorbs this as heat energy and keeps it in, only letting a little heat out The gases in the atmosphere absorb the radiation keeping it from escaping out to space This absorption of radiation by gases is called the greenhouse effect

Greenhouse gases Water Vapor, CO2, CFCs, Methane and NOx all absorb radiation Water vapor and CO2 are the primary greenhouse gases Since 1958 (in Hawaii) CO2 levels have been measured – reflective of the entire earth (the gases have traveled across the entire Pacific Ocean) Levels are higher in the winter: fewer leaves on the trees (dying grasses and leaves release carbon) General increase because of burning fossil fuels(not just in winter)

Global Warming Where does all the CO2 come from? Why be concerned? Power plants and cars that burn fossil fuels and deforestation Why be concerned? CO2 is a greenhouse gas Scientists believe the increase will warm earth more than normal Direct correlation between CO2 levels and global warming

What Happens If The Earth Warms? Melting Ice and Rising Sea Levels Coastal areas flooded Nearly 3 billion people live within 100 km of a coast Excess sea water can change freshwater aquifers near coasts Changing Weather Patterns Warming the oceans could change currents that influence weather today Human Health Problems Deaths due to heat waves Longer growing seasons, more pollen, more asthma Warmer weather allow mosquitoes and other disease carrying organisms to live longer

Heat leads to droughts, severe impact to crops Agriculture Heat leads to droughts, severe impact to crops May change where plants and animals live Kyoto Protocol Nations met and laid out timelines for reducing CO2 emissions Decrease emissions by 5% from 1990 levels by 2012. Reducing CO2 is difficult for developing countries Need industry using cheap fossil fuel to improve economies

That’s all for 13.3 Time for a reading quiz