atmosphere and climate changesection 1 bellringer

Atmosphere and Climate Change Section 1

Bellringer


Objectives

• Explain the difference between weather and climate.

• Identify four factors that determine climate.

• Explain why different parts of the Earth have different climates.

• Explain what causes the seasons


Climate

• I. Climate and Climate Change

• Weather – the state of the atmosphere at a particular place at a particular moment

• Climate – the long-term prevailing weather conditions at a particular place based upon records taken

• A. What Factors Determine Climate?

• Climate is determined by latitude, atmospheric circulation patterns, oceanic circulation patterns, the local geography of an area, solar activity, and volcanic activity.

• the most important factor is latitude – or distance from the equator


Latitude

• B. Latitude

• Latitude is the distance from the equator is measured in degrees north or south of the equator

• -equator is 0 deg latitude

• -most northerly is 90 deg north – the North Pole

• -most southerly is 90 deg south – the South Pole


Low Latitudes

• latitude influences climate because the amount of solar energy an area of Earth receives depends on its latitude

• More solar energy falls on areas near the equator than on areas closer to the poles.

• The incoming solar energy is concentrated on a small surface at the equator.

• In regions near the equator, night and day are both about 12 hours long throughout the year.

• In addition, temperatures are high year-round, and there are no summers or winters.


High Latitudes

• in regions closer to the poles, the amount of solar energy arriving at the surface is reduced

• In regions closer the poles, the sun is lower in the sky, reducing the amount of energy arriving at the surface.

• In the northern and southern latitudes, sunlight hits the Earth at an oblique angle and spreads over a larger surface area than it does at the equator.

• Yearly average temperatures near the poles are therefore lower than they are at the equator, and the hours of daylight vary


Low and High Latitudes


Atmospheric Circulation

• Three important properties of air illustrate how air circulation affects climate.

• Cold air sinks because it is denser than warm air. As the air sinks, it compresses and warms.

• Warm air rises. It expands and cools as it rises.

• Warm air can hold more water vapor than cold air can. Therefore, when warm air cools, the water vapor it contains may condense into liquid water to form rain, snow, or fog.



• Solar energy heats the ground, which warms the air above it. This warm air rises, and cooler air moves in to replace it. This movement of air within the atmosphere is called wind.

• Because the Earth rotates, and because different latitudes receive different amounts of solar energy, a pattern of global atmospheric circulation results.

• This circulation pattern determines Earth’s precipitation patterns.



• Solar energy heats the ground which warms the air above it

– the warm air rises and cooler air moves in to replace it this is called convection current

– this air exchange produces wind

• Because the Earth rotates, and because different latitudes receive different amounts of solar energy, the pattern of global atmospheric circulation results


Global Circulation Patterns

• circulation pattern determines precipitation pattern

– -solar energy at the equator causes surface to warm and evaporate – as it rises, it cools and \ precipitates – this is why there is large amounts of rain at the equator


Global Circulation Patters

• cool air normally sinks, but since warm air is rising right over the equator, the cool air is forced away from the equator

• the cool air sinks, and warms, and the warm, dry air moves across the surface of the Earth creating dry conditions-this pattern continues up towards the poles

• Air descending at the 30º north and 30º south latitude either moves toward the equator or flows toward the poles. Air moving toward the equator warms while it is near the Earth’s surface.

• At about 60º north and 60º south latitudes, this air collides with cold air traveling from the poles.

• The warm air rises, and most of this uplifted air is forced toward the poles. Cold, dry air descends at the poles, which are essentially very cold deserts.


Prevailing Winds

• Winds that blow predominantly in one direction throughout the year are called prevailing winds.

• Because of the rotation of the Earth, these winds do not blow directly northward or southward.

• Instead, they are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

• belts of prevailing winds blow most of the time in both hemispheres – called trade winds


Prevailing Winds• Prevailing winds are produced in both hemispheres

between 30º north and south latitude and the equator.

• The trade winds blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere.

• Prevailing winds known as the westerlies are produced between 30º and 60º north latitude and 30º and 60º south latitude.

• In the Northern Hemisphere, these westerlies are southwest winds, and in the Southern Hemisphere, these winds are northwest winds.

• The polar easterlies blow from the poles to 60º north and south latitude.


Quick LAB


Oceanic Circulation

• Ocean currents have a great effect on climate because water holds large amounts of heat.

• The movement of surface ocean currents is caused mostly by winds and the rotation of the Earth.

• These surface currents redistribute warm and cool masses of water around the world and in doing so, they affect the climate in many parts of the world. which can warm or cool coastal areas year-round

• El Nino – Southern Oscillation (ENSO)


El Niño–Southern Oscillation

• El Niño is the name given to the short-term (6-18 month) periodic change in the location of warm and cold water masses in the Pacific Ocean

• during El Nino, winds in the western Pacific Ocean which are usually weak, strengthen and push warm water eastward

• this causes increased rainfall in the Southern half of the US and in equatorial South America causes drought in Indonesia and Australia



• La Niña when water in the eastern Pacific Ocean is cooler than normal

• -rainfall in rainforests of Indonesia and in Australia

• -dry conditions in the Southern half of the US


Pacific Decadal Oscillation

• Pacific Decadal Oscillation (PDO)– a long-term 20-30 year change in the location of warm and cold water masses in the Pacific Ocean

• Influences the climate in the northern Pacific Ocean and North America

• It affects ocean surface temperatures, air temperatures, and precipitation patterns.


Topography• Elevation or Altitude – height above sea level has an important effect

on climate

• temperatures fall by about 6deg Celsius for every 1,000 m increase in elevation

• Mountain ranges also influence the distribution of precipitation. For example, warm air from the ocean blows east, hits the mountains, and rises. As the air rises, it cools, causing it to rain on the western side of the mountain. When the air reaches the eastern side of the mountain it is dry. This effect is known as a rain shadow.

• Height above sea level (elevation) has an important effect on climate. Temperatures fall by about 6°C (about 11°F) for every 1,000 m increase in elevation.


Topography


• At a solar maximum, the sun emits an increased amount of ultraviolet (UV) radiation. UV radiation produces more ozone, which warms the stratosphere.

• The increased solar radiation produces more ozone warming the stratosphere and can warm the troposphere and surface of the Earth a little

• Both the sun and volcanic eruptions influence Earth’s climate.

Other Influences on Earth’s Climate


• In large scale volcanic eruptions – sulfur dioxide gas is released and can reach the upper atmosphere

• The sulfur dioxide, which can remain in the atmosphere for up to 3 years, reacts with smaller amounts of water vapor and dust in the stratosphere.

• This reaction forms a bright layer of haze that reflects enough sunlight to cause the global temperature to decrease.

Other Influences on Earth’s Climate


G. Seasonal Changes in Climate

• Temperature and precipitation change with the seasons

• The seasons are caused by the tilt of the Earth’s axis

-because of the tilt the angle at which the sun’s rays strike the Earth changes as the Earth moves around the sun

• It is summer when the particular hemisphere is tilted towards the sun and winter when it is tilted away from the sun

• It is opposite for the northern and southern hemisphere


Seasonal Changes in Climate


Seasonal Changes in Climate

• During summer in the Northern Hemisphere, the Northern Hemisphere tilts toward the sun and receives direct sunlight. The number of hours of daylight is greatest in the summer. Therefore, the amount of time available for the sun to heat the Earth becomes greater.

• During summer in the Northern Hemisphere, the Southern Hemisphere tilts away from the sun and receives less direct sunlight. But, during the summer in the Southern Hemisphere, the situation is reversed.


Math Practice


Bellringer


Objectives

• Explain how the ozone layer shields the Earth from much of the sun’s harmful radiation.

• Explain how chlorofluorocarbons damage the ozone layer.

• Explain the process by which the ozone hole forms.

• Describe the damaging effects of ultraviolet radiation.

• Explain why the threat to the ozone layer is still continuing today.


II. The Ozone Shield

• Ozone layer – an area in the stratosphere where ozone is highly concentrated

• -ozone is a molecule made of three oxygen atoms

• -the ozone layer absorbs most of the ultraviolet (UV) light from the sun

• -UV light is harmful to living things because it can damage genetic material in living cells

• -the ozone acts like a sunscreen for the Earth’s inhabitants


• Each CFC molecule contains from one to four chlorine atoms, and scientists have estimated that a single chlorine atom in the CFC structure can destroy 100,000 ozone molecule.

Chemicals That Cause Ozone Depletion


A. Chemicals That Cause Ozone Depletion

• During the 1970s, scientist began to worry that a class of chemicals called chlorofluorocarbons (CFCs)

• might be damaging the ozone layer.


CFC

• -they were once considered the miracle chemicals because they were nonpoisonous, nonflammable, and they don’t corrode metals

• -used as coolants in refrigerators and air conditioners, used as a gassy “fizz” for making plastic foams, and as a propellant in spray cans of products like deodorant, insecticides, and paint

• At the Earth’s surface, CFCs are chemically stable, but in the stratosphere CFC molecules break apart by UV radiation’s energy

• -once broken, parts of the CFC molecule destroy protective

• -over a period of 10-20 years CFCs released at the surface make their way to the stratosphere

• -each CFC molecule can contain 1-4 chlorine atoms, an single chlorine atom can destroy 100,000 ozone molecules


B. The Ozone Hole

• In 1985, scientists reported that the ozone layer above the South Pole had thinned by 50-98% - this was the

• first news of the ozone hole – a thinning of stratospheric ozone that occurs over the poles during the spring

• NASA scientists reviewed the data sent by a weather satellite and they were able to see the first signs ofthinning as early as 1979

• The concentration of ozone fluctuates during the year, the data showed a growing ozone hole – over the Arctic as well


The Ozone Hole


How does the ozone hole form?

• -during the dark polar winter, strong circulating winds over Antarctica called the polar vortex isolate cold air from surrounding warmer air

• -the air within the vortex grows extremely cold and high altitude clouds made of water and nitric acid polar stratospheric clouds begin to form

• on the surfaces of polar stratospheric clouds the products of CFCs are converted to molecular chlorine

• -when sunlight returns to the South Pole in the spring, molecular chlorine is split into two chlorine atoms by ultraviolet radiation


Ozone

• -the chlorine atoms rapidly destroy ozone causing a thin spot, or hole, which lasts for several months

• Ozone produced as pollution in the troposphere is a pollutant and harmful – plus it is chemically reactive and cannot reach the stratosphere

– Ozone Movie Clip


Effects of Ozone Thinning on Humans• -As the amount of ozone in the stratosphere decreases,

more UV light is able to pass through the atmosphere and reach Earth’s surface

• -UV light is dangerous to living things because it damages DNA

• -more susceptible to skin cancer and other damaging effects

• -See Table 1


Effects of Ozone Thinning on Humans


Effects of Ozone Thinning on Animals and Plants

• -High levels of UV light can kill phytoplankton that live near the surface of the ocean – phytoplankton forms the basis of the marine food chains

• -reduction of phytoplankton can also reduce fish harvests and cause an increase in the CO2 in the atmosphere


Effects of Ozone Thinning on Animals and Plants

• -UV light can be especially damaging for amphibians – they lay eggs that lack shells and high UV light kills more eggs and puts amphibian populations at risk

• -ecologists use the health of amphibian populations as an indicator of environmental change due to the sensitivity of these creatures

• -UV light can damage plants by interfering with photosynthesis – this damage can result in lower crop yields


Effects of Ozone Thinning of Animals and Plants


C. Protecting the Ozone Layer• In 1987, a group of nations met in Canada and agreed to take action

against ozone depletion.

• -under an agreement called the Montreal Protocol, these nations agreed to sharply limit their production of

• CFCs, and a second conference in 1992 developed countries agreed to eliminate most CFCs by 1995, the

• US pledged to ban all substances that pose a significant damage to the ozone layer by 2000

• -chemical companies developed CFC replacement

• -ozone protection is considered and international environmental success story

• -battle to protect the ozone layer is not over, CFC molecules remain active in the stratosphere for 60-120 years


Protecting the Ozone Layer


Bellringer


Objectives

• Explain why Earth’s atmosphere is like the glass in a greenhouse.

• Explain why carbon dioxide in the atmosphere appears to be increasing.

• Explain why many scientists think that the Earth’s climate may be becoming increasingly warmer.

• Describe what a warmer Earth might be like.


III. Global Warming

• A. The Greenhouse Effect

• The Earth is similar to a greenhouse. The Earth’s atmosphere acts like the glass in a greenhouse

• -sunlight streams through the atmosphere and heats the Earth

• -this heat radiates up from the Earth’s surface and some escapes and the rest is absorbed by gases in the troposphere and warms the air


The Greenhouse Effect


The Greenhouse Effect

• This is called the greenhouse effect – this is good for life on earth and keeps it livable

• -the gases that absorb and radiate heat are called greenhouse gases

• -major greenhouse gases are water vapor, carbon dioxide, chlorofluorocarbons, methane, and nitrous oxide

• -of these, water vapor and carbon dioxide account for most absorption of the heat that occurs in the atmosphere


Measuring carbon dioxide in the atmosphere

• -in 1958, Charles Keeling began monitoring CO2 on the top of the Mauna Loa volcano in Hawaii

• -he found the levels of CO2 varied with the seasons – high CO2 in the winters because there is less

• photosynthesis, and lower CO2 in spring and summer because photosynthesis removes it


Rising carbon dioxide levels

• -After a few years of monitoring it was obvious they were changing in ways other than seasonal fluctuations

• -see figure 15

• -increase is due largely to the CO2 released into the air when fossil fuels are burned

• -levels of CO2 in the atmosphere thousands of years ago can be determined by analyzing ice cores drilled from ice sheets

• -shows that CO2 levels are higher today than they have been for the last 420,000 years and probably for the last 20 million years


Rising Carbon Dioxide Levels


Greenhouse Gases and the Earth’s Temperature• -many scientists think that because greenhouse gases

trap heat near the Earth’s surface, the more greenhouse

• gases there are, the more the global temperature will increase

• -a comparison of carbon dioxide in the atmosphere and global temperatures supports this view

• -today we are releasing more carbon dioxide into the atmosphere than any other greenhouse gas


Greenhouse Gases


Rising Temperatures

• -caused by burning coal, oil, and from cars that burn gasoline

-burning trees in the tropical rain forest for farming

-we are releasing other greenhouse gases in significant amounts

• table 2


B. Global Warming

• Global warming – the increase in average temperature at the Earth’s surface during the 20th Century

• -because the temperature is raising at a similar rate to the increase in greenhouse gases, many scientists

• believed the increase in greenhouse gases have caused the increase in temperature

• -thousands of experiments and computer models support this hypothesis


How Certain is Global Warming


Modeling global warming

• -the increase in temperature is predicted to continue throughout the 21st century

• -it’s not possible to rule out natural climatic variability but not likely

• -predictions about future changes in climate are based on computer models

• -scientists write equations that represent the atmosphere and oceans then they enter data about CO2 levels, prevailing winds, and many other variables

• -weather forecasters use similar programs

• Models are not always accurate, but are becoming more reliable as more data is available and additional variables are included


C. Consequences of a Warmer Earth

• In North America, birds are nesting about 11 days earlier than they did 50 years ago, in Britain 200 species of plants are flowering up to 55 days earlier

• -birds nesting and plants flowering are strongly influenced by temperature

• -scientists are not sure how quickly the Earth will warm or how severe the effects will be

• -different computer models give different predictions


Melting ice and rising sea levels

• possible serious effects – changes in weather patterns, rising sea levels

• -effects will be different in different areas

• -ice melts as global temperatures increase

• -causes sea levels to rise around the world

• -affects coastal areas – could be flooded and people who live near coastlines could lose their homes, beaches become eroded, salinity of bays and estuaries might increase which can effect marine fisheries


• -coastal freshwater aquifers could become too salty to use for drinking


Global weather patterns• if the Earth warms up significantly, the surface of the

oceans will absorb more heat which may make hurricanes and typhoons more common

• -change in ocean current patterns such as shutting off the Gulf Stream – this can significantly affect the world’s weather

• -some regions might have more rainfall than normal while other regions might have less

• -severe flooding in some areas and drought in others


Human health problems

• -heat-related deaths can increase

• -trees and flowering plants would bloom earlier and for longer and so people with allergies would suffer longer

• -enable mosquitoes which are vectors of diseases such as malaria, dengue fever, encephalitis, West Nile to

• establish themselves in areas where it is too cold for them at the moment


Agriculture

• -most severely impacted

• -decreased crop yields

• -increased irrigation would further deplete freshwater supplies

• -decreased food for humans increasing famine


Effects on plants and animals

• -alter the range of plant species and the composition of plant communities

• -trees could colonize cooler areas and forests could shrink in the warmer part of their range and lose diversity

• -shift in the geographical range of some animals

• -birds might not have to migrate as far south for the winter

• -zooplankton in the ocean might be depleted which many marine animals depend on for food

• -warming in the tropics can kill the algae that nourish corals – destroying coral reefs


D. Recent Findings

• The Intergovernmental Panel on Climate Change (IPCC) is a network of approximately 2,500 of the world’s leading climatologists

• In 2001 they gave their 3rd assessment report (TAR) which describes what is currently know about the global climate system

• -during the 20th Century, average temps increased by 0.6 deg, snow cover and ice have decreased

• average sea level has risen, concentrations of greenhouse gases have continued to rise


E. Reducing the Risk• In 1997, representatives from 160 countries met and set

timetables for reducing emissions of greenhouse gases

• -treaty called the Kyoto Protocol


Kyoto Protocol • treaty requires developed nations to decrease emissions of carbon

dioxide and other greenhouse gases by an average of 5% below their 1990 levels by 2012

• -in March of 2001, the US decided not to ratify the Kyoto Protocol

• -most developed nations are going ahead with the treaty

• -need to slow global warming has been recognized by the global community

• -some nations and organization have engaged in reforestation projects to reduce the CO2

• -effort to slow global warming is made difficult by the economic, political, and social factors faced by different countries

• -conflict has already arisen between developed and developing countries over future CO2 emissions


Copenhagen 2009• In 2012 the Kyoto Protocol to prevent climate changes and global

warming runs out. To keep the process on the line there is an urgent need for a new climate protocol.

• The Copenhagen Accord was drafted by the US, China, India, Brazil and South Africa on December 18, and judged a "meaningful agreement" by the United States government. It was "taken note of", but not "adopted", in a debate of all the participating countries the next day, and it was not passed unanimously.

• The document recognized that climate change is one of the greatest challenges of the present day and that actions should be taken to keep any temperature increases to below 2°C. The document is not legally binding and does not contain any legally binding commitments for reducing CO2 emissions. Many countries and non-governmental organizations were opposed to this agreement

atmosphere and climate changesection 1 bellringer

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