title: Identifying the molecular origin of global warming.
abstract: We have investigated the physical characteristics of greenhouse gases (GHGs) to assess which properties are most important in determining the efficiency of a GHG. Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrogen fluorides, and various other known atmospheric trace molecules have been included in this study. Compounds containing the halogens F or Cl have in common very polar X-F or X-Cl bonds, particularly the X-F bonds. It is shown that as more F atoms bond to the same central atom the bond dipoles become larger as a result of the central atom becoming more positive. This leads to a linear increase in the total or integrated X-F bond dipole derivatives for the molecule, which leads to a nonlinear (quadratic) increase in infrared (IR) intensity. Moreover, virtually all of the X-F bond stretches occur in the atmospheric IR window as opposed to X-H stretches, which do not occur in the atmospheric window. It is concluded that molecules possessing several F atoms will always have a large radiative forcing parameter in the calculation of their global warming potential. Some of the implications for global warming and climate change are discussed.
authors.affiliation: NASA Ames Research Center, Space Science and Astrobiology Division, Moffett Field, California 94035, USA.
authors.forename: Partha P
authors.initials: PP
authors.lastname: Bera
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Francisco
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Lee
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D002980:Climate; D005459:Fluorides / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry*; D057232:Global Warming; D009584:Nitrogen / Q000737:chemistry*
chemical_list: D005466:Fluorocarbons; D009584:Nitrogen; D005459:Fluorides