Measured increases of methane concentration in the Earth's atmosphere began approximately 18 000 years ago, and for the period of 10 000-12 000 years ago its concentration rose from 350up to 700ppbv. Coming nearer our time, 200-2000 years ago, methane in the atmosphere changed from 700 to 800ppbv. One hundred years ago, methane concentration was already at 900ppbv. During industrialization, methane emissions and atmospheric concentrations increased quickly up to 1500 ppbv. For example, measurements for 1978-88 showed that near-ground concentration increased from 1520 to 1690 ppbv. This growth rate slowed in the late 1980s and practically stopped in 1991-92, believed to be a result of the repair of Soviet gas pipelines. Most recently, methane concentration is rising again. Taking into account significant fluctuations of methane concentration in the atmosphere measured in different places of the globe and at various times, the average rate of its modern growth was 17 ± 1 ppbvyr-1, which corresponds to an increase of its contents in the atmosphere of 48 ± 3 million tons yr~ . For example, over the last 40 years, methane concentration has increased approximately by 30%, and it is now between 1720 and 1770 ppbv. The current total methane in the atmosphere equals 5000 million t and could double in the next 50 years at the current rate of increase.
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