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It has become a virtually undisputed fact that the root cause of global warming is emissions of CO2 and other greenhouse gases, resulting from human activity dating back to the dawn of the industrial revolution. Measurements have been made of CO2 concentration in the atmosphere contained in ice cores excavated from the Antarctic, which has accumulated over a period of 420,000 years. Findings show that CO2 concentration in these ice cores repeatedly fluctuates between 180 - 290 ppm, with cyclical changes coinciding exactly with those of glacial/interglacial periods. In addition, it has been shown that, over the short period from the advent of the industrial revolution to the present time, CO2 content in the earth's atmosphere has increased from 280 ppm to 355 ppm (in 1980s).
While this sort of scientific validation is of very recent vintage, it should be noted that, in 1896, the Swedish scientist, Svante A. Arrhenius, found that, based on calculation of the infrared absorption rate of CO2, with a doubling of the CO2 atmospheric concentration, surface temperatures rise 5-6 degrees C. However, until about 1950, it was believed that almost all of the CO2 released into the atmosphere through human activity was ultimately absorbed by the ocean. Since seawater contains CO2 in quantities about 50 times that of the atmosphere, if this CO2 had not been absorbed by the oceans, then, based on the estimated volume of CO2 artificially released since the 19th century, the atmospheric concentration of this substance would surely have been far higher than the then known level.
However, starting in 1956, upon analyzing fluctuations of carbon isotope abundance ratio in 14C/12C contained in annual tree rings, it was discovered that only about 40-50% of the increase in CO2 believed to have been absorbed by the oceans was actually absorbed therein. But where, then, did the remaining CO2 go that had not been absorbed by the ocean? While considering this dilemma, we learned that the earth is made up of elements with complex interaction and that the ocean plays an important role in global climatic change, but that there are still far too many unknowns as to what actually takes place in the marine environment.
There is, accordingly, an urgent need to understand the oceanic process on a global scale, along with a growing awareness of the importance of global observations in this research. Today, many international programs have already begun to operate, designed to trace and predict the nature of global environmental changes appearing in the world's oceans, based on the use of research vessels, buoys, satellites, and other means.
In order to understand the mechanism of complex oceanic changes, it is necessary to conduct observations on a long-term basis over a wide geographic range, surveying both present conditions and process of changes in the marine environment. Although observation data, when using a private vessel, can cover the limited phenomena that can be grasped from the upper layer of water on a voyage route, if the same waters are repeatedly covered on a long-term basis, high-density temporal and spatial observations are quite feasible.
Furthermore, Vos observations do not require a huge input, while their routes can cover virtually every area of the world's oceans. Generally, observation work at sea is far more laborious than that on shore, as the survey areas are, by definition, uninhabited. In this connection, commercial vessels, which place high priority in keeping regularity of service on a fixed route, are quite suitable as a platform for a variety of observations.
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