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NEWSCIENCENEWSCIENCENEWSCIENCE surface global (land and sea) air temperatures suggest the planet has (1992) constructed a powerful argument that links Schumann's reso- been warming in recent decades. But satellite measurements of the nances to convection and ultimately to widespread tropical and/or planet's lower atmospheric temperature show no warming from 1979 global temperature. Williams concluded that a 1°C warming in the to 1998. tropics should result in a fourfold increase in lightning activity, and Temperature data from weather balloons launched throughout the __ he presented empirical data from several locations to support his con- world reveal variations and trends in global temperatures that corre- clusion. He noted that any measurable parameter nonlinearly related spond to those found in the satellite-based measurements. Analysis to temperature could be extremely useful in assessing the most subtle of pressure thickness measurements from these same balloons also changes in global temperature. Others have presented different sensi- shows no warming in recent decades. It's no wonder we have such an _ tivities: Price (1993) concluded that a 1°C warming would increase ongoing "heated debate" about the recent temperature history of the global lightning activity by 7%; Price and Rind (1994) found a 5-6% Earth! Yet most people recognise that their local weather is markedly _ increase per 1°C sensitivity; while Reeve and Toumi (1998) found the different than in past decades. sensitivity to be near 40% per 1°C. Regardless of the exact sensitivi- Scientists have suggested lately that another method may exist to __ ty, all these scientists conclude that lightning increases with even monitor planetary temperature accurately. The idea is simple, though moderate amounts of warming worldwide. More lightning would the underlying physics of the processes is complex. The method is generate a stronger SR, which may be useful in monitoring planetary based on the well-known fact that thunderstorms and lightning strikes _ temperatures. in many parts of the world are directly related to lower-atmospheric The link between SR and the number of lightning strikes is sup- air temperatures. Higher temperatures produce more lightning _ ported by a mean day/night temperature fluctuation pattern. A diur- strikes, while lower temperatures tend to depress lightning activity. nal pattern of worldwide lightning exists with three maxima recorded Lightning discharges occurring anywhere in the world produce elec- regularly due to the large number of mid- to late-afternoon thunder- tromagnetic pulses that spread away from storms in land areas of Africa, South the source. Much of the energy is quickly America, and Southeast Asia and degraded, but some of the energy the . . . Australia. (Storms are first generated in lightning produces falls in the extremely Lightning discharges Asia; later they form in Africa; and later kw frgevonevavelegh domain’ ggcurring anywhere inf 2, ws nSouh aren these long wavelengths, the energy from the world produce suspected rise in SR, and is a threat to its a lightning strike is able to circumnavi- H synchronisati ith brain waves. gate the Earth without serius | @f@Ctromagnetic pulses Small changes in temperature pump up degradation. This ow-Frequency/Tong- that spread away from into farge ens in extremely low fre- wavelength energy creates signals uenc resonances. Long-term which can be detected throughout the the source. toring ind study of global climate world. changes via measurements of ELF elec- Understanding SR waves requires a tromagnetic waves needs to be conducted basic appreciation of the vertical structure more closely. Monitoring the intensity of the atmosphere. In the upper reaches of the ionosphere, incoming and frequencies of the lightning-induced ELF SR could help monitor ultraviolet radiation and soft X-rays affect atoms or bonded groups of changes in the Earth's climate over time. atoms, causing gains or losses of negatively charged electrons. This One Israeli program proposed setting up two or three widely sepa- interaction creates an environment of positively and negatively rated ELF field sites. A suggested site for a permanent SR monitor- charged particles of the high atmosphere that, among other interesting ing station was in the Negev Desert in Israel. Members of this pro- qualities, can readily conduct electricity. posal want to develop, test and install the appropriate software for the The bulk of our insulating atmosphere lies between two conducting automatic electromagnetic monitoring and preliminary processing of layers of the Earth's surface and the lower boundary of the ionos- the incoming data. They suggested that simultaneous measurements phere. This spherically concentric cavity, the Earth/ionosphere cavi- could be made in Russia and Sweden to test the global nature of the ty, is bounded by those electrically conducting walls. Again, light- | ELF signals measured in Israel. The continuous ELF data measured ning discharges within the cavity produce electromagnetic pulses that in Israel could be compared with other ELF data sets from other loca- spread away from the source in the extremely low frequency domain, tions around the world, such as Hungary, USA or Japan. and the conductive walls of the cavity produce some interesting Furthermore, the relevant global climate data sets—such as surface effects for the low-frequency energy. temperature, satellite observations of the global distribution of deep For example, energy with a frequency near 7.5 Hz would have a__ convection, and global atmospheric water vapour measurements— wavelength of about 40,000 km (recall that wavelength = speed of __ could be used for comparisons with SR data to check the reliability of light / frequency). Because this wavelength equals the circumference _ the "global thermometer" hypothesis. of the Earth, the energy is able to circumnavigate the Earth/ionos- A systematic study of SR parameters during high-energy particle phere cavity without serious degradation. The 100 or so lightning _ precipitation events has shown that protons and electrons with ener- bolts occurring each second in the 1,000 lightning storms around the gies above 1 MeV ionise the upper boundary of the Earth/ionosphere world contribute to the energy in the 7.5 Hz portion of the spectrum, cavity. This leads to an increase in the resonance frequency and a which can be measured anywhere on the planet. It is these resonance _ decrease in the damping of the first Schumann's resonance, as derived properties of this global spherical capacitor or resonator) that from measurements at Arrival Heights, Antarctica. The study used Schumann predicted over 40 years ago. Continued on page 77 In an article published in Science, MIT scientist Earle Williams Lightning discharges occurring anywhere in the world produce electromagnetic pulses that spread away from the source. APRIL —- MAY 2003 NEXUS + 47 www. nexusmagazine.com