In March 1991 a claim was filed at the US patent office by David Chang und I-Fu Shih for the stratospheric use of the Welsbach effect for reducing global warming. The beneficiary of this patent was the Hughes Aerospace Corp in Los Angeles. The patent stated that minute particles of barium, aluminium, cadmium, and other substances could be sprayed into the atmosphere to reflect solar and other radiations back into space. Some such particles could be stored in suspension in aircraft fuels, burnt with them in their engines, and pass out into the atmosphere in the combustion gasses. Others substances could be kept in canisters attached to aircraft wings or bodies and sprayed into the atmosphere as required [w23], [w10], [w17].

Many people have seen white trails that lingered much longer in the sky than ordinary aircraft vapour-trails do. These trails are often released by several craft flying in formation and smear together slowly until much of the sky is milky white. These "chemtrails" ostensibly protect the planet from global warming. They are often spread without the knowledge of the people below who are supposed to benefit from them, and without the approval of their authorities - hence illegally.

Chemtrails can be used for Perfect weather control technology [that] will enable the military to withhold rain, cause floods, droughts and storms, withhold sunshine, damage food crops, and bring any country to its knees without firing a shot [w13]. During the Kosovo attack in the spring of 1999, weather patterns over most of Europe were normal - except over Serbia. It was wrapped under a white haze for several months that fit almost exactly inside its frontiers. This caused an unprecedented drought there. Similar effects were noticed over North Korea and Zimbabwe [w17].

It is believed that barium salts, polymer fibers and other chemicals in the atmosphere are physical irritants that may be directly or indirectly responsible for unexplained nose bleeds, asthma, allergies, pneumonia, upper respiratory ailments and arthritis-like symptoms. Chemicals sprayed into the atmosphere are producing air and ground conditions that may be harmful to humans and animals, while stimulating the growth of molds and bacteria. Barium salts... are toxins that are readily absorbed into the gastrointestinal tract which are deposited into muscles and other tissue. No case data is available on the long-term effects of barium in humans. Aluminium may cause Alzheimer's disease [w23]. Cadmium is a well-known poison, like arsenic. Elsewhere [w15], it is stated that liver ailments and SARs are unusually prevalent in regions where chemtrails were seen often. People sitting in passenger aircraft that leave chemtrails may be paying to poison their loved ones below without being aware of it [w12], [w16].