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<br />than industry emissions into thc atmosphere in many parts of the country or individual exposure <br />from tooth fillings. Accumulations in the soil, vegetation, and surface runoff have not been large <br />enough to measure above natural background45. A 2004 sludy for Snowy Hydro Limited in <br />Australia confirmed these earlier findings. The expansion of liquid propane (LP) as a gas is <br />another possible seeding method. Regarding the l1ammability of propane released from <br />dispensers';l>, it was shown that it was necessary to bring the ignition source to ,vithin four feet of <br />the dispenser nozzle to cause the propane plume to bum under very light winds. A modest <br />increase in ,'...ind speed would blowout the l1ame. It was further noted that, "Propane is a <br />colorless, odorless, hydrocarbon that is harmless to plant and animal life. The quantities used in <br />seeding arc so small, 0.75 Ib per minute from each dispenser, that there is no accumulation <br />leading to a pollution problem." Another study41 noted that "There is a great deal of propane <br />(CJlIg) and butane (C4111O), another hydrocarbon, being released by human activities al a scale <br />far larger than for propane seeding. Propane docs not present an cnvironmental ha7.ard bccausc <br />of its rapid oxidative degradation. Although technically a greenhouse gas, its approximate one <br />month lifetime in the atmosphere is too short 10 function in this manner. In contrast, CFCs have <br />atmospheric lifetimes in the range of60 - 500 yrs." <br /> <br />As for concern 3), the SCPP Environmental Assessmcnt report4J investigated thc impacts of an <br />assumed ,,,'cather moditication-induccd precipitation increasc of 5 - 7.5% on weathcr elements, <br />hydrologic and physiographic phenomena, plant and animal communities, the human <br />environment, and land and ,,'ater rcsource use. The report concluded that there would be no <br />significant impact on these environmental sectors, The perccntage increases from '....eather <br />modification are much smaller than inter~annual variability of natural precipitation. <br />Furthermore. all California operating projects have suspension criteria dcsigned to stop cloud <br />seeding anytime there is a 1100d threat. All projects employ metcorologists who monitor current <br />and projected weather conditions. Additionally. water management personnel from sponsoring <br />companies mnnitor streamflow and reservoir storage. The combined interdisciplinary inputs <br />about flood potential are considered. and conditions are compared against suspension criteria in <br />advance of any potcntial l1ood-producing storms. Moreover. the types of stonns that produce <br />floods in Califomia are almost always too warnl for effective silver iodide seeding (Byron <br />l\.larler, personal communication), Although weather modification increases are small compared <br />to natural precipitation variability, one can anticipate some concerns about snow removal from <br />roads and snow loading on roofs. <br /> <br />Finally, some have questioned the notion of "interfering with nature" through weather <br />modification. These questions onen ignore the fact that human acti,itles have caused <br />inadl'ertenl weather modification for many centuries. The NRC reportl2 states that "there is <br />ample evidence that inadvertent wcather and global climate moditication (e,g.. greenhollse gases <br />alTccting global temperatures and anthropogcnic aerosols afTecting cloud properties) is a reality." <br />Evcn the simple act of cultivating a farm lield will alter local climate. 111Ienliona! weather <br />modification, particularly of the fornl practiced in winter seeding, alters the environment tar less <br />than the accumulated etlccts of inad\'erlem weather moditication. Indeed. cloud seeding in <br />C'a\lfornia m~y h~ve been partially c.ompen~ti~f for precipitation losses from the inadvcrtcnt <br />weather modification brought on by aIr pollutlonh. <br /> <br />17 <br />