Some things happen every year. A tree grows a bit and forms a new tree ring, snow falls in the arctic and creates a layer of ice, sediment settles in a lake, forming a layer of sediment called a varve.
Each of those things is in some ways a history record. Each encapsulates, in various ways, what happend that year. Ice cores contain tiny bubbles which contain a tiny sample of the atmosphere from hundreds and thousands of years ago. Tree rings vary in thickness. Varves contain whatever particulates settled into the lake that year.
We can look at these things and find a record of things like the metal smelting activities of the Roman Empire, but also of even of quite recent events. Examples:
http://www.nsf.gov/news/news_summ.jsp?cntn_id=112074
Here (from the above link) were see the history of lead in the deposits of four swedish lakes. A huge spike in the 20th Century is followed by rapid decline as leaded gasoline is phased out.
Although here's a slightly different story:
http://www.columbia.edu/cu/newrec/2417/tmpl/story.7.html
So could this be used to prove or disprove the covert-geoengineering hypothesis? Could the work already have been done?
Each of those things is in some ways a history record. Each encapsulates, in various ways, what happend that year. Ice cores contain tiny bubbles which contain a tiny sample of the atmosphere from hundreds and thousands of years ago. Tree rings vary in thickness. Varves contain whatever particulates settled into the lake that year.
We can look at these things and find a record of things like the metal smelting activities of the Roman Empire, but also of even of quite recent events. Examples:
http://www.nsf.gov/news/news_summ.jsp?cntn_id=112074
http://www.sciencedirect.com/science/article/pii/0013932775900555External Quote:Detailed measurements from a Greenland ice core showed pollutants from burning coal--the toxic heavy metals cadmium, thallium and lead--were much higher than expected. The catch, however, was the pollutants weren't higher at the times when researchers expected peaks."Conventional wisdom held that toxic heavy metals were higher in the 1960s and '70s, the peak of industrial activity in Europe and North America and certainly before implementation of Clean Air Act controls in the early 1970s," said Joe McConnell, lead researcher and director of DRI's Ultra-Trace Chemistry Laboratory.
"But it turns out pollution in southern Greenland was higher 100 years ago when North American and European economies ran on coal, before the advent of cleaner, more efficient coal burning technologies and the switch to oil and gas-based economies," McConnell said.
In fact, the research showed pollutants were two to five times higher at the beginning of the previous century than today. Pollution levels in the early 1900s also represented a 10-fold increase from preindustrial levels.
http://pubs.acs.org/doi/abs/10.1021/ba-1987-0216.ch012External Quote:The precise measurement of heavy metal levels within successive annual growth rings of trees presents, at first sight, an attractive and straightforward means for producing a detailed history of heavy metal pollution. However, before serious consideration is given to such a technique, many processes relating to the uptake, transport and deposition of heavy metals within trees must be understood.A brief survey of the pathways of metal uptake into trees is made, and consideration given to the external and internal factors which may operate in regulating metal entry. As the transport of metals within the tree is important, both pathways of metal transport, and the forms taken by metals during transport, are described.The regulation and patterns of metal deposition are fully considered, and emphasis is placed on internal factors which may regulate the rate of deposition, and the quantity of metal deposited, in a particular annual growth ring. The problem of possible lateral movement of metals between growth rings is also considered. Finally, conclusions are drawn regarding the potential of tree-ring analyses for producing pollution histories.
http://hero.epa.gov/index.cfm?action=reference.details&reference_id=364710External Quote:
Retrospective measurements of dated sediment cores can be used to determine the effect of regulations to control environmental inputs of hazardous chemicals. Sediment cores have been used to reconstruct histories of environmental contamination by mercury, lead, polycyclic aromatic hydrocarbons (PAHs), dioxins, polychlorinated biphenyls (PCBs), DDT, octachlorostyrene, pH, and carbon particles. These measurements have shown that most anthropogenic chemicals first appeared in sediments at the turn of the century at the time of the industrial revolution in most of North America. Industrial growth after World War II also resulted in inputs of pollutants such as PCBs and dioxins. Recent decreases in the levels of several contaminants may have occurred because of environmental awareness and the onset of environmental regulations. Inputs of banned pollutants continue, however, because of recycling of contaminants in the environment and long-range atmospheric transport.
http://www.sciencedirect.com/science/article/pii/S0048969702000323External Quote:
Laminated sediments from Bolterskardet Lake on Svalbard provide a new 150-year record of heavy metals in the Arctic. Independent data of 137Cs and 210Pb indicate that these laminations are annually deposited varves. The high sedimentation rate and varved sediments make Lake Bolterskardet a good site for studying history of heavy metal pollution in the region. A suite of heavy metals (Pb, As, Cd, Cu, Cr, Co, Ni, and Sn) were studied. The variations of Cu, Cr, Co, and Ni concentrations show an inverse pattern with the median grain size. It suggests that the particle size has a significant role in the accumulation and enrichment of heavy metals in the sediments. In the concentration profiles of studied heavy metals, only Pb concentrations show a significant increase from the lower parts to the upper parts of the core. Profiles of "total," "lithogenic," and "anthropogenic" Pb flux also show an increasing pattern. Anthropogenic Pb flux varies between 0.1 Ã'µg cm-2 yr-1 and 12.3 Ã'µg cm-2 yr-1, with a mean value of 2.4 Ã'µg cm-2 yr-1. The anthropogenic Pb fluxes were relatively low at around 0.7 Ã'µg cm-2 yr-1 prior to 1945, slowly increased after 1945, and reached a sidestep (between 1940s and 1970s) with mean value of 1.8 Ã'µg cm-2 yr-1. Second high value period was between 1980s and 1990s with mean value of 5.9 Ã'µg cm-2 yr-1.
Here (from the above link) were see the history of lead in the deposits of four swedish lakes. A huge spike in the 20th Century is followed by rapid decline as leaded gasoline is phased out.
Although here's a slightly different story:
http://www.columbia.edu/cu/newrec/2417/tmpl/story.7.html
External Quote:In sediment core samples taken from the lake, Columbia scientists have found evidence that incinerators-not leaded gasoline-were the main culprit in spewing lead into New York air.Because the lake has never been dredged, it holds a 130-year history of the city's heavy-metal emissions deposited in thin layers. By correlating the sediment layers to individual years, the scientists saw that the peaks in sediment lead levels did not match the pattern of leaded gasoline use, which was widely expected.
"Urban lakes act like big bucket collectors for atmospheric fallout," said Steve Chillrud, geochemist at Columbia's Lamont-Doherty Earth Observatory and principal author on the paper, which appears in the March 1 issue of Environmental Science and Technology. "As soon as we saw the lead data, we got really excited," said Chillrud. "The sediment record showed that the highest atmospheric lead levels occurred before the maximum use of leaded gasoline."
Despite the excitement, the scientists had a mystery on their hands. The sediment history, which started from the 1860s, showed that the lead levels were highest in the 1930s to early 1960s, after which levels tapered off. In contrast, the maximum use of leaded gasoline was in the late 1960s and early 1970s, until health concerns about smog and childhood lead poisoning resulted in the phase-out of leaded gasoline. This phase-out had previously been linked to a known decrease in human blood lead levels, but the environmental monitoring had only begun in the 1970s. The Columbia scientists began to think that the strong correlation between leaded gasoline and airborne lead in New York City was erroneous.
The scientists, looking for clues that would guide them to an earlier source of lead, measured other metal concentrations in the sediment, collected samples of Central park soil cores and learned about the history of the lake from Central Park Conservancy records. "We had really large amounts of heavy metals, so we were looking for something that could put a huge amount of pollution into the air," said Chillrud.
Chillrud was reluctant to let go of the leaded gasoline explanation, but when he also found high levels of tin in the sediment, he knew that he had to look elsewhere. "It was a big clue; automobiles just don't produce tin in large amounts," he said.
Chillrud and Lamont colleague Jim Simpson collaborated with Rensselaer Polytechnic Institute geochemist Richard Bopp, who had been at Lamont from 1971-1990. They considered smelters, but the main metal refining plants were in New Jersey and the scientists' previous work had shown that New Jersey smelter emissions decreased after the 1930s. Several pieces of the puzzle pointed toward incinerators, both municipal and residential/commercial, as another possible source. The incinerator record to support their ideas was the missing link. Bopp suggested calling a former graduate student of his, Dan Walsh, who had an interest in New York City's history of waste management and was currently the Department of Environmental Conservation's chief scientist at the Fresh Kills landfill on Staten Island.
"Steve called me up and told me that his results were surprising," remembers Walsh. "But as soon as he explained the pattern, it made great sense to me. It fit the incineration pattern, hand in glove."
Walsh sent Chillrud the incineration data he had collected for his Ph.D. from incinerators in New York, which were progressively closed in the 1960s, and the Lamont scientists were amazed how well his data matched theirs.
So could this be used to prove or disprove the covert-geoengineering hypothesis? Could the work already have been done?
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