Post on 25-Dec-2015
Chapter 15Chapter 15
Human Influences on Climate
Human Influences on Climate
Figure CO: Chapter 15, Human Influences on Climate--Air pollution in New York City
© Dean D. Fetterolf/ShutterStock, Inc.
Feedback: change leads to change leads to more change
• Positive feedback mechanism: reinforces (enhances) the original trend (change)
• Negative feedback mechanism: damps out an existing trend (change)
• Example of a positive feedback mechanism: warming, evaporation, water vapor, warming
More climate feedback mechanisms
• Example of a negative feedback mechanism: warming, evaporation, water vapor, cloud, cooling
• Another positive feedback mechanism:– Called the ice/albedo feedback mechanism– Cooling, more ice, higher albedo, more cooling– Warming, less ice, lower albedo, more warming
Figure 01: Ice Albedo Feedback
Air Pollution
• Air pollutants are aerosol particles (liquids and solids) and gases that, in high concentrations, seriously affect the lives of people and animals, harm plants, or threaten ecosystems.
• Air pollutants can come from natural sources (volcanoes, forest fires, dust storms) or human activities (anthropogenic sources)
Figure 02: CO in lower troposphere – satellite image
Courtesy of NASA
Anthropogenic Sources of Air Pollution
• Transportation: motor vehicles, aircraft, ships• Energy generation: electricity generation• Industry: smelting, dry cleaning,
manufacturing• Home heatingCarbon dioxide can be considered a pollutant
Primary Air Pollutants
• Emitted directly by sources• Carbon monoxide, a gas, incomplete
combustion, can cause death in small concentrations, emitted by vehicles and defective heating devices
• Lead, a particulate, brain damage, in some paints and treated gasoline, outlawed now
More Primary Air Pollutants
• Oxides of sulfur, sulfur dioxide and sulfur trioxide, respiratory irritant, emitted in burning fossil fuels containing sulfur
• Oxides of nitrogen, nitric oxide and nitrogen dioxide, pulmonary problems, emitted by high-temperature combustion of fossil fuels in transportation and electric energy generation
More Primary Air Pollutants
• Hydrocarbons, also called volatile organic compounds, or VOCs– Some are carcinogens– Are made up of hydrogen and carbon– Emitted by motor vehicles, dry cleaning
• Particulates, small particles– Smallest are most dangerous to lungs
Figure T01: Trends in Air Pollutant Concentrations in the United States from 1990 to 2007
Figure B01: Lead and crime rate
Adapted from Nevin, Rick, Environmental Research 104 (2007): 315-336
Secondary Air Pollutants
• Are produced in chemical reactions with primary air pollutants
• Present harder-to-solve problems than primary air pollutants
• Include acid deposition and photochemical oxidants (smog)/ozone
Water Vapor, Clouds and Aerosol
• Warmer temperatures will lead to more water vapor in the atmosphere because saturation vapor pressure increases with temperature– Extra water vapor is more greenhouse gas– A positive feedback loop, more warming– Enhanced cloudiness complicates this scenario
• Human activity leads to changes in cloudiness– Contrails from aircraft– Aerosols from ships contribute to cloudiness– Aerosols from cities, ships act as CCN
Figure 03: Ship tracks
Courtesy of SSEC and CIMSS, University of Wisconsin-Madison
Figure 04: Contrails-- satellite
Courtesy of GeoEye and NASA. Copyright 2010. All rights reserved.
Figure 05: Saturation vapor pressure varies as a function of temperature
Acid Deposition
• Can be acid rain, snow, fog, dew, or dry• Formed when oxides of nitrogen and sulfur
combine with water vapor or liquid water to produce nitric acid and sulfuric acid
• In water, allows toxic heavy metals to leach out and contaminate drinking water
• Damage to structures, make lakes toxic
Figure 06: pH scale
Courtesy of EPA
Figure 07: pH of rain
Photochemical Oxidants/Smog/Ozone
• Irritates eyes, nose, throat; causes coughing chest pain, and shortness of breath, aggravates asthma and bronchitis
• Forms when sunlight acts on a combination of hydrocarbons, oxides of nitrogen, and oxygen
• Ozone is the main component, with PAN and formaldehyde
The Stratospheric Ozone Hole
• Is reduced amounts of ozone over the Antarctic in the decades since 1955
• Occurs in the Antarctic spring• Is the result of the chlorine in CFCs• Occurs because
• The Antarctic atmosphere is very cold • Has polar stratospheric clouds• The polar vortex prevents mixing
• Should improve in the next 50-100 years
Figure 08: The observed ozone minimum over Antarctica between 1955 and 2009
Modified from: GSFC/NASA
Figure 09: The daily minimum ozone values between 40°S and the South Pole
Modified from: GSFC/NASA
Figure 10: The annual average size of the ozone hole
Modified from: GSFC/NASA
Desertification
• Is a spread of a desert region• Is due to climate change• Is due to human impacts on the land
– Overgrazing– Deforestation without reforestation– Diversion of water from a fertile region– Farming on unsuitable land (terrain, soil)
• Vulnerable areas include fringes of Sahara desert, the Aral Sea, Lake Chad (West Africa)
Figure 11: Aral Sea, 1989 to 2008
Courtesy of the University of Maryland Global Land Cover Facility/Landsat and MODIS/NASA
Urban Heat Islands
• Increased temperatures compared to rural surroundings
• Greatest effect in summer and during the night
• Due to human activities– Industrial activity– Thermal properties of buildings and roads– Evaporation of water– Air conditioning and heating– Transportation
Figure 12: Urban heat island – conceptual model
Figure 13A: Urban heat Island – satellite
Courtesy of Robert Simmon, based on data from the National Land Cover Database and Landsat 7/NASA
Figure 13B: Urban heat Island – satellite
Courtesy of Robert Simmon, based on data from the National Land Cover Database and Landsat 7/NASA
Figure 14: Heat island – LondonAdapted Chandler T.J. The Climate of London. Hutchinson, 1965
Figure 15: Magnitude of urban heat island
Courtesy of T. R. Oke, The University of British Columbia
Figure B02: Urban Heat Island and precipitation
Adapted from Shepherd, J.M., et al., Agronomy Monograph 55, (2010): 1-29 and J. Aitkenhead-Peterson and A. Volder (ed.). Urban Ecosystem Ecology. American Society of Agronomy, 2010
Global Warming is a Fact!!!
• Over the past 2 decades the global average surface temperature has increased noticeably.
• A trend involves a steady change in one direction—upward for global average temperature.
• Not every location and/or every region shows the identical pattern.
Figure 16: Temperature departures from the global mean temperature over land since 1880
Source: NASA/GISS
Figure 17: The annual temperature changes of the past 50 years
Courtesy of GISS/NASA
More Observations of Global Warming
• Widespread retreat of nonpolar glaciers• Thinning of arctic sea ice • Decreased N Hemisphere snow cover• Increase of global mean sea level• Longer growing season in NH• Shortened duration of ice cover on NH lakes
Figure 18: Sea level rise
Source: Intergovernmental Panel on Climate Change, "Climate Change 2007,” The Fourth Assessment Report, Working Group 1, Figure 5.13; Red curve from: Church and White, 2006; Blue curve from: Holgate and Woodworth, 2004; Black curve from: Leuliette et al., 2004
Figure 19: SeaWiFS Ocean biology
Courtesy of GeoEye and NASA. Copyright 2010. All rights reserved.
Figure 20: Sea Ice change
Source: National Snow and Ice Data Center
Figure 21: Snow cover change
Courtesy of Riccardo Pravettoni, UNEP/GRID-Arendal
Figure 22: Lake Mendota ice cover
Source: Wisconsin State Climatology Office
Figure 23: Winter Temperature changes
Courtesy of NOAA/NCDC
Greenhouse Gases and Global Warming
• Greenhouse gases include carbon dioxide, water vapor, methane, CFCs and others
• Concentrations of carbon dioxide have increased by 25% since the 19th century, and increase by 0.5% per year
• More energy is trapped in Earth’s atmosphere• Feedbacks are very important• Scientists rely on complex computer models
of climate
Global Warming and the Oceans
• Oceans absorb energy trapped by increased amounts of greenhouse gases
• Vertical motions in the atmosphere are very sensitive to temperature– Climate change can accelerate rapidly if global warming affects
convection in the oceans
• Oceans are full of life, which will be affected by global warming
• Sea level is rising due to thermal expansion and melting of ice sheets over land
Global Warming and the Cryosphere
• Cryosphere is the portion of Earth’s surface covered by ice
• The cryosphere is shrinking– Mountain glaciers are shrinking– Arctic ice has thinned and covers a shrinking area at the end of
summer– The Greenland ice sheet is melting rapidly
• Earlier snowmelt inhibits storage of water• Lakes freeze/melt later/sooner and lose water
through evaporation
Global Warming and the Biosphere
• Biosphere comprises all of Earth’s living organisms
• Tundra plants/animals are very sensitive to changes in snow cover and temperature
• Gardeners notice changes in hardy zones related to global warming
The IPCC
• IPCC is the Intergovernmental Panel on Climate Change (over 1000 scientist)– Formed by the United Nations’ World
Meteorological Organization (WMO) and the Environment Programme (UNEP) in 1988
• Writes reports that describe our current knowledge about climate change, based on published scientific literature
• Has 90% confidence that observed temperature rises are due to humans