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fyi - greenhouse warming - Q & A

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  • npat1@juno.com
    fyi Here is one website on greenhouse warming with Q & A. http://www.cmdl.noaa.gov/ccgg/faq.html#7 Frequently Asked Questions What is the carbon cycle? What is
    Message 1 of 1 , Feb 27, 2003
      fyi

      Here is one website on greenhouse warming with Q & A.
      http://www.cmdl.noaa.gov/ccgg/faq.html#7

      Frequently Asked Questions

      What is the carbon cycle?
      What is the greenhouse effect?
      What is global warming?
      What is a climate model?
      What greenhouse gases does CMDL/CCGG measure?
      Where are these gases measured?
      What are isotopes of greenhouse gases?
      Why are isotopes of greenhouse gases important?
      How are the amounts of greenhouse gases measured?
      How much CO2 is in the atmosphere?
      How much has the amount of greenhouse gases changed in history?
      How do I get the CCGG data?

      What is the carbon cycle?

      The Carbon Cycle is a complex series of
      processes through which all of the carbon atoms in existence rotate. The
      same carbon atoms in your body today have been used in countless other
      molecules since time began. The wood burned just a few decades ago could
      have produced carbon dioxide which through photosynthesis became part of
      a plant. When you eat that plant, the same carbon from the wood which was
      burnt can become part of you. The carbon cycle is the great natural
      recycler of carbon atoms. Unfortunately, the extent of its importance is
      rarely stressed enough. Without the proper functioning of the carbon
      cycle, every aspect of life could be changed dramatically.

      What is the greenhouse effect?

      The Sun, which is the Earth's only
      external form of heat, emits solar radiation mainly in the form of
      shortwave visible and ultraviolet (UV) energy. As this radiation travels
      toward the Earth, the atmosphere absorbs 25% of it, and 25% is reflected
      by the clouds back into space. The remaining radiation travels unimpeded
      to the Earth and heats its surface. The Earth releases a lot of energy it
      has received from the Sun back to space. However, the Earth is much
      cooler than the Sun, so the energy re-emitted from the Earth's surface is
      much weaker, in the form of invisible longwave infrared (IR) radiation,
      sometimes called heat.

      Gases that absorb and trap this IR radiation, such as water vapor (H2O),
      carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are known as
      "greenhouse gases". The atmosphere acts like the glass in a greenhouse,
      allowing much of the shortwave solar radiation to travel through
      unimpeded, but trapping a lot of the longwave heat energy trying to
      escape back to space. This process makes the temperature rise in the
      atmosphere just as it does in the greenhouse. This is the Earth's natural
      greenhouse effect and keeps the Earth 33 � C warmer than it would be
      without an atmosphere, at an average 15 � C.

      What is global warming?

      The term Global Warming refers to the observation
      that the atmosphere near the Earth's surface is warming. This warming is
      one of many kinds of climate change that the Earth has gone through in
      the past and will continue to go through in the future. It is reasonable
      to expect that the Earth should warm as the amount of greenhouse gases in
      the atmosphere increases. It is known for certain that atmospheric
      concentrations of greenhouse gases are rising dramatically due to human
      activity. It is less well known exactly how the increases in these
      greenhouse gases factor in the observed changes of the Earth's climate
      and global temperatures.

      What is a climate model?

      The major components of the climate system that
      are important for climatic change and its consequences, such as sea level
      rise, during the next century are: the atmosphere, oceans, terrestrial
      biosphere, glaciers and ice sheets and land surface. In order to project
      the impact of human perturbations on the climate system, it is necessary
      to calculate the effects of all the key processes operating in these
      climate system components and the interactions between them. These
      climate processes can be represented in mathematical terms based on
      physical laws such as the conservation of mass, momentum, and energy.
      However, the complexity of the system means that the calculations from
      these mathematical equations can be performed in practice only by using a
      computer. The mathematical formulation is therefore implemented in a
      computer program, which we refer to as a 'model'. If the model includes
      enough of the components of the climate system to be useful for
      simulating the climate, it is commonly called a 'climate model'."

      From the Intergovernmental Panel on Climate Change (IPCC) document An
      Introduction to Simple Climate Models used in the IPCC Second Assessment
      Report - IPCC Technical Paper II available at:
      http://www.ipcc.ch/pub/techrep.htm

      Which greenhouse gases does CMDL/CCGG measure?

      Carbon Dioxide (CO2) is a colorless, odorless gas consisting of
      molecules of two oxygen atoms and one carbon atom. Carbon dioxide is
      produced when any form of carbon or almost any carbon compound is burned
      in an excess of oxygen. For example, it is released into the atmosphere
      by man-made combustion of fossil fuels. Carbon dioxide is removed from
      the atmosphere by carbon dioxide "sinks" such as absorption by seawater,
      and photosynthesis by ocean-dwelling plankton and land-dwelling biomass,
      including forests and grasslands.

      Methane (CH4) is a colorless, odorless non-toxic gas consisting of
      molecules of four hydrogen atoms and one carbon atom. Methane is
      combustible, and mixtures of about 5 to 15% in air are explosive. It is
      the main constituent of natural gas, a fossil fuel. It is released into
      the atmosphere when organic matter decomposes in environments lacking
      sufficient oxygen. Natural sources include wetlands, swamps and marshes,
      termites, and oceans. Man-made sources include the mining and burning of
      fossil fuels, digestive processes in ruminant animals such as cattle,
      rice paddies and the burying of waste in landfills. Most methane is
      broken down in the atmosphere by reacting with hydroxyl (OH) radicals.

      Carbon monoxide (CO) is a colorless, odorless gas that is formed when
      carbon in fuel is not burned completely. It is a component of motor
      vehicle exhaust, which contributes about 56 percent of all CO emissions
      nationwide. Other sources of CO emissions include industrial processes
      (such as metals processing and chemical manufacturing), residential wood
      burning, and natural sources such as forest fires. Although CO is not
      itself an important greenhouse gas, it is an important component of the
      oxidising capacity of the troposphere, and is an important tracer for
      urban pollution. It's main sink is chemical reactions with the hydroxl
      (OH) radical.

      Molecular Hydrogen (H2) like CO, is not a direct greenhouse gas. But it
      can reduce OH and so indirectly increase CH4 and HFCs. H2 is produced in
      many of the same processes that produce CO (e.g., combustion of fossil
      fuel and atmospheric oxidation of CH4), and its atmospheric measurements
      can be used to constrain CO and CH4 budgets. About one third of
      atmospheric H2 is removed by reaction with tropospheric OH, and the
      remainder, by microbial uptake in soils.

      Nitrous oxide (N2O) is a colorless, non-flammable gas with a sweetish
      odour, commonly known as "laughing gas", and sometimes used as an
      anaesthetic. Nitrous oxide is naturally produced by oceans and
      rainforests. Man-made sources of nitrous oxide include nylon and nitric
      acid production, the use of fertilizers in agriculture, cars with
      catalytic converters and the burning of organic matter. Nitrous oxide is
      broken down in the atmosphere by chemical reactions that involve
      sunlight.

      Sulfur hexafluoride (SF6) is an extremely potent greenhouse gas. SF6 is
      very persistent, with an atmospheric lifetime of 3,200 years. Thus, a
      relatively small amount of SF6 can have a significant impact on global
      climate change. The primary user of SF6 is the electric power industry.
      Because of its inertness and dielectric properties, it is the industry's
      preferred gas for electrical insulation, current interruption, and arc
      quenching in the transmission and distribution of electricity. SF6 is
      used extensively in circuit breakers, gas-insulated substations, and
      switchgear.

      CCGG also measures the common isotopes of CO2 and CH4, in collaboration
      with the Stable Isotope Laboratory at the University of Colorado.

      What are isotopes of greenhouse gases?

      Atoms having the same number of protons, but different numbers of
      neutrons, represent the same element, but are known as different isotopes
      of that element. The isotope for an element is specified by the sum of
      the number of protons and neutrons. Isotopes of interest in the carbon
      cycle are carbon 12, which makes up about %98.9, and carbon 13, making up
      about %1.1. Oxygen isotopes of interest are oxygen 16, the most common,
      and oxygen 18.

      Why are isotopes of greenhouse gases important?

      Chemical and biological processes in nature, such as respiration,
      photosynthesis and atmospheric chemical reactions, often show very slight
      preferences for one isotope over another. For example, photosynthesis
      discriminates against the heavy 13C isotope, and plant matter and
      respired CO2 is therefore depleted in 13C relative to the atmosphere.
      Careful analysis of the isotopic composition of atmospheric trace gases
      can provide valuable information on the sources and sinks of the gases
      concerned because each natural process leaves its isotopic "signature" in
      the gases it produces.

      How are the amounts of greenhouse gases measured?

      Non-isotopic measurements of greenhouse gases are generally made
      with two techniques: Non-Dispersive Infrared (NDIR) analysis, or by gas
      chromatography.

      The amount of CO2 in the atmosphere is large enough that the NDIR method
      of measurement works well. An NDIR analyzer relies on the same principle
      of IR absorption that makes greenhouse gases important in the first
      place. An infrared analyzer consists of an infrared source at one end,
      and an infrared detector separated by a gas cell. The gas of interest is
      passed through this cell, and absorbs some of the infrared radiation
      coming from the source. The detector converts the amount of IR reaching
      it to a usable signal, such as a voltage. So as the concentration of CO2
      changes in the sample, the signal from the detector changes. By flowing a
      gas with a known amount of CO2 through the cell, we can calibrate the
      analyzer so that the voltage output from the detector can be converted
      into amounts of CO2.

      Gas Chromatography is a separation method in which gas mixtures flow over
      a material that retains some components more than others, so different
      components flow over the material at different speeds. The gas is
      separated into individual chemical components which can then pass through
      a detector, which varies in output for each component in the mixture.
      This is called a chromatogram. By measuring the height of each peak in a
      chromatogram, the amount of a component (such as CH4) can be calculated.
      Chromatography is the preferred method for gases other than CO2 since it
      is well suited for small samples with small amounts of the gas of
      interest.

      Example chromatogram showing a methane (CH4) peak.
      These types of measurements are relative, that is, a gas with known
      amounts of the species in question (a 'standard' or 'reference' gas)
      needs to be measured by the system as well, so that the samples with
      unknown quantities can be calculated relative to the known amount.
      Because of this, CCGG has an extensive program dealing with standard
      gases.

      Where are these gases measured?

      CGGG makes continuous and discrete measurements of greenhouse gases at
      numerous worldwide surface sites, towers, aircraft, and ships of
      opportunity. There is a world map of the many different sampling sites.

      Air samples are collected in glass flasks from sampling sites of the NOAA
      CMDL CCGG Cooperative Air Sampling Network and returned to the CCGG
      laboratory in Boulder, Colorado for analysis. In-Situ, continuous
      measurements are made at the 4 baseline CMDL Observatories, and at 2 tall
      tower sites in the United States.

      The table below summarizes where and how measurements are made for the
      different gases.

      Measurement Species
      Location CO2 CH4 CO H2 N2O SF6 13CO2 CO18O 13CH4
      CCGG Cooperative Flask Sampling Network
      CMDL Observatory - Barrow, Alaska
      CMDL Observatory - Mauna Loa, Hawaii
      CMDL Observatory - American Samoa
      CMDL Observatory - South Pole, Antarctica
      Tall Tower - WLEF, Park Falls, Wisconsin
      Tall Tower - KETK, Moody, Texas
      Aircraft
      Measurements made by CMDL/CCGG group.
      Measurements made by CMDL/HATS group.
      Measurements made by CU/INSTAAR.

      How much CO2 is in the atmosphere?

      For the year 2001, the estimated global average CO2 amount was about 375
      parts per million (ppm). If we use a value of 5.137 x 108 kilograms for
      the mass of the atmosphere, then 1 ppmv of CO2 = 2.13 Gt (billions of
      tons) of carbon. This gives us a value of almost 800 Gt of carbon in the
      atmosphere.

      How much has the amount of greenhouse gases changed in history?

      Ice cores have been collected from Antarctica and Greenland which contain
      information stored in the ice that can be used to reconstruct climates
      thousands of years ago. As snow accumulates on ice caps and sheets where
      temperatures usually remain below freezing year round, it lays down a
      record of the environmental conditions at the time of its formation. Over
      time the snow, buried under further accumulations, is compacted to ice,
      preserving the climatic information. Air bubbles trapped in the ice can
      be analyzed to reconstruct the atmospheric composition at the time when
      the ice formed.

      Measurements of the amount of greenhouse gases in these bubbles show that
      the "pre-industrial" amount of CO2 in the atmosphere was about 280 parts
      per million (ppm), almost 100 ppm below todays value. The figure below
      show results of CO2 measurements of air trapped in ice cores taken at the
      Law Dome site in Antarctica, along with present day measurements at the
      CMDL Mauna Loa Observatory in Hawaii. CO2 amounts have increased about
      35% in the last 200 years.

      Law Dome Ice Core data source:
      D.M. Etheridge, L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M.
      Barnola and V.I. Morgan. 1998. Historical CO2 records from the Law Dome
      DE08, DE08-2, and DSS ice cores. In Trends: A Compendium of Data on
      Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge
      National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A

      How do I get the CCGG data?

      Data is available at the CMDL anonymous ftp site at ftp.cmdl.noaa.gov.
      Data from the CCGG Globalview project is available online.

      To suggest other questions for this page, email the CMDL Webmaster.

      Disclaimer
      Privacy Notice
      Climate Monitoring & Diagnostics Laboratory
      Carbon Cycle Greenhouse Gases
      325 Broadway R/CMDL1
      Boulder, CO 80305

      Source: http://www.cmdl.noaa.gov/ccgg/faq.html#7

      Posted by:
      Pat Neuman
      npat1@...
      Chanhassen, Minnesota
      ___


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