Chapter 21 Global Climate Change

Overview of Chapter 21  Introduction to Climate Change  Causes of Global Climate Change  Effects of Climate Change  Melting Ice and Rising Sea Level  Changes in Precipitation Patterns  Effects on Organisms  Effects on Human Health  Effects on Agriculture  Dealing with Global Climate Change

Climate Change Terminology  Greenhouse Gas  Gas that absorbs infrared radiation  Positive Feedback  Change in some condition triggers a response that intensifies the changed condition  Infrared Radiation  Radiation that has a wavelength that is longer than that of visible light, but shorter than that of radio waves  Greenhouse Effect  Increase of heat in a system where energy enters (often as light), is absorbed as heat, and released sometime later

Natural Physical Factors Affecting Climate: 1.Latitude: near equator is warm, near poles is cold, because at equator the Sun strikes Earth at a higher angle of insolation, at poles Sun strikes Earth at a lower angle of insolationnear equator is warm, near poles is cold, because at equator the Sun strikes Earth at a higher angle of insolation, at poles Sun strikes Earth at a lower angle of insolation

Natural Physical Factors Affecting Climate: 1.Latitude…continued: Seasons on Earth are determined by latitude and angle of insolation at various times throughout the year, and are caused by:Seasons on Earth are determined by latitude and angle of insolation at various times throughout the year, and are caused by: Tilt of Earth’s axis Tilt of Earth’s axis Earth’s revolution around the Sun Earth’s revolution around the Sun Parallelism of Earth’s axis Parallelism of Earth’s axis

Seasons on Earth…

Natural Physical Factors Affecting Climate: 2. Proximity to a large body of water (ocean or large lake): Water has a high specific heat, so the ocean does NOT heat up or cool down easily, and therefore helps to regulate temperatures of nearby coastal areas Water has a high specific heat, so the ocean does NOT heat up or cool down easily, and therefore helps to regulate temperatures of nearby coastal areas

Natural Physical Factors Affecting Climate: 3. Nearness to mountains: Higher elevations have colder avg. temperatures, longer snowpack, etc. Higher elevations have colder avg. temperatures, longer snowpack, etc. Orographic effect: (rainshadow) Orographic effect: (rainshadow) –Windward side of mountains force air to rise, expand, cool, and cause water vapor to condense, forming clouds and abundant rainfall –Leeward side of mountains experience dry conditions as air sinks…called the “rainshadow” side.

Orographic (Mountain) Effect:

Natural Physical Factors Affecting Climate: 4. Wind Circulation Patterns – caused by unequal heating of the Earth, which creates different temperature zones, which creates different pressure belts, which forces the major wind belts to occur, which determines major weather and climate patterns

Natural Physical Factors Affecting Climate: 5. Ocean Circulation Patterns: Prevailing wind belts create mass movements of ocean water (currents)Prevailing wind belts create mass movements of ocean water (currents) Circular ocean currents are called “gyres”Circular ocean currents are called “gyres” Ocean currents are also influenced by the Coriolis effect, and tend to circulate clockwise in the N. hemisphere, and counterclockwise in the S. hemisphereOcean currents are also influenced by the Coriolis effect, and tend to circulate clockwise in the N. hemisphere, and counterclockwise in the S. hemisphere Ocean currents are forced to move around major landmasses (continents and islands)Ocean currents are forced to move around major landmasses (continents and islands)

Earth’s Major Ocean Currents

Natural Physical Factors Affecting Climate: 6. Ocean-Atmosphere Interactions Ocean interacts with the atmosphere to dramatically influence climate patterns worldwideOcean interacts with the atmosphere to dramatically influence climate patterns worldwide El Nino & La Nina can impact global climate in any given yearEl Nino & La Nina can impact global climate in any given year

Long-Term Natural Factors Affecting Climate Paleoclimatology – the study of climate changes over the history of the Earth Paleoclimatology – the study of climate changes over the history of the Earth A variety of techniques and inferences are used to measure or infer atmospheric gas content, temperatures, dust particles, life forms, etc. A variety of techniques and inferences are used to measure or infer atmospheric gas content, temperatures, dust particles, life forms, etc. Methods Used to Determine Past Climate: Methods Used to Determine Past Climate: 1.Recorded Human Observations (only reliable for past 200 yrs.) 2.Ice Core Data 3.Tree Rings 4.Soil Sediments 5.Biological Fossils – Shells of aquatic organisms – Corals

Ice Core Data: Drilled from deep within the ground, ice cores can be used to measure increases and/or decreases in snowfall over time as well as changes in atmospheric gases as seen in trapped air bubbles, dust, and oxygen isotopes. Drilled from deep within the ground, ice cores can be used to measure increases and/or decreases in snowfall over time as well as changes in atmospheric gases as seen in trapped air bubbles, dust, and oxygen isotopes. Scientists drilling in the Greenland ice sheet have been able to piece together a climate record dating back approximately 110,000 years Scientists drilling in the Greenland ice sheet have been able to piece together a climate record dating back approximately 110,000 years Antarctic ice samples have yielded information as far back as 750,000 years. Antarctic ice samples have yielded information as far back as 750,000 years. Ice cores can provide vast amounts of information, including an annual record of temperature, precipitation, atmospheric composition, volcanic activity, and even wind patterns. Ice cores can provide vast amounts of information, including an annual record of temperature, precipitation, atmospheric composition, volcanic activity, and even wind patterns.

Ice Core Data: Specifically, CO 2 and CH 4 concentrations can be analyzed and used to infer past temperatures. Specifically, CO 2 and CH 4 concentrations can be analyzed and used to infer past temperatures. Thickness of ice layers also reflects temperature and precipitation in the past. Thickness of ice layers also reflects temperature and precipitation in the past. Atmospheric dust particles can also be analyzed from ice cores. Atmospheric dust particles can also be analyzed from ice cores.

Vostok Ice Core Data:

Long-term natural influences on climate…global changes There are several LONG-TERM changes that have influenced climate in a cyclic manner. There are several LONG-TERM changes that have influenced climate in a cyclic manner. Milankovitch Cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković Milankovitch Cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković Variations in the Earth's eccentricity, axial tilt, and precession comprise the three dominant cycles Variations in the Earth's eccentricity, axial tilt, and precession comprise the three dominant cycles

Milankovitch Cycles: Eccentricity Eccentricity is, simply, the shape of the Earth's orbit around the Sun. Eccentricity is, simply, the shape of the Earth's orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years. These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun's short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth's surface in different seasons. These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun's short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth's surface in different seasons. Animated sequence

Milankovitch Cycles: Axial Tilt Axial tilt is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Axial tilt is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees. A larger tilt will result in warmer summers and colder winters! A larger tilt will result in warmer summers and colder winters!

Milankovitch Cycles: Precession (wobble) Precession is the Earth's slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. Precession is the Earth's slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of about 23,000 years. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of about 23,000 years.

Milankovitch Cycles: Precession (wobble) Animated sequence

Milankovitch Cycles…overall effect:

Current Observations of Climate Today, a wide variety of instruments has been deployed to continuously measure a large number of climate factors including: Today, a wide variety of instruments has been deployed to continuously measure a large number of climate factors including: –Air temperature –Sea surface temperature –Greenhouse Trace Gas concentrations (CO 2, CH 4, O 3, NO, NO 2, etc. –Response of plants (budding times, size, etc.) –Response of animals (changes in range, timing of reproduction, etc.)

Introduction to Climate Change  Evidence for Climate Change  14 warmest years since mid-1800s have occurred since 1990  Phenological spring in N. hemisphere now begins 6 days earlier  Warming is not due to natural causes  Human produced greenhouse gases are most plausible explanation

Introduction to Climate Change: Mean Annual Global Temperature 1960–2007

Causes of Climate Change  Greenhouse gas concentrations increasing

Causes of Climate Change  Increased concentration of CO 2 (right)  Burning fossil fuels in cars, industry and homes  Deforestation  Burning of forests

Greenhouse Effect

Pollutants That Cool the Atmosphere  Atmospheric Aerosols  Both human and natural sources  Tiny particles that remain in troposphere for weeks or months  Often contain sulfur  Complicates models of climate change

Climate Models  Climate affected by:  winds, clouds, ocean currents, and albedo  Used to explore past climate events  Advanced models can project future warming events  Models are only as good as the data and law used to program them  They have limitations

Climate Models

Effects of Global Climate Change  Wildfire in California

Effects of Global Climate Change: Melting Ice and Rising Sea Levels  Sea level rise caused in 2 ways  Thermal Expansion  Melting of land ice  Melting has positive feedback  Increased melting decreases ice, which decreases albedo leading to further warming

Glacier National Park Melting Ice and Rising Sea Levels

Case-In-Point Impacts in Fragile Areas  Eskimo Inuit live traditional life dictated by freezing climate  Climate change is altering their existence  Wildlife displaced  Reduced snow cover and shorter river ice seasons  Thawing of permafrost (right)

Effects of Global Climate Change: Changing Precipitation Patterns  Some areas will get more water, some areas will have greater droughts

Effects of Global Climate Change: Effects on Organisms  Zooplankton in parts of California Current have decreased by 80% since 1951  Effecting entire food chain  Decline in krill around Antarctica  Species have shifted their geographic range  Migrating birds are returning to summer homes earlier

Effects on Organisms: Coral Reefs  Coral reefs can be bleached (right) due to increase in water temperature  Affects coral symbiotes and makes them more susceptible to diseases

Effect on Organisms: Vegetation

Effects on Human Health  Increased number of heat-related illnesses and deaths

Effects on Agriculture  Difficult to anticipate  Productivity will increase in some areas and decrease in others  Rise in sea level will inundate flood plains and river valleys (lush farmland)  Effect on pests is unknown  Warmer temperatures will decrease soil moisture- requiring more irrigation  Location (i.e. elevation and altitude) where certain crops can be grown may have to change

International Implications of Climate Change  Developed vs. Developing countries  Differing self- interests  Differing ability to meet the challenges of climate change

Dealing with Global Climate Change  Two ways to manage climate change  Mitigation: Limiting greenhouse gas emissions to moderate global climate change  Adaptation: Learning to live with environmental changes and societal consequences brought about by global climate change

Relationship Between Mitigation and Adaptation

Dealing with Global Climate Change: Mitigation  Locate/invent alternative fuels to fossil fuels  Increase efficiency of cars and trucks  Carbon Capture and Storage  Plant and Maintain trees to naturally sequester carbon

Dealing with Global Climate Change: Adaptation  Rising sea levels and coastal populations  Move inland  Construct dikes and levees  Adapt to shifting agricultural zones  NYC sewer line

International Efforts to Reduce Greenhouse Gas Emission  Kyoto Protocol  Legally binding  Provides operational rules on reducing greenhouse gases  US and Australia have not sign it - it will be difficult to implement without US backing