Monday, August 18, 2014

Global Warming...

...5% of CO2 is the problem?

//The IPCC estimates that, since the Industrial Revolution, humans have released 365 billion tons of carbon from burning fossil fuels. Annual emissions, including those from deforestation and cement production, are less than 9 billion tons. Yet natural carbon cycles involve annual exchanges of carbon between the atmosphere, the land, and the oceans many times greater than emissions from human activities. The IPCC estimates that 118.7 billion tons of carbon per year is emitted from land and 78.4 billion tons from oceans. Thus, the human contribution of 9 billion tons annually accounts for less than 5 percent of the total gross emissions. The AGW hypothesis, as well as all the climate-change policies that depend on it, assumes that the human 5 percent drives the overall change in the amount of CO2 in the atmosphere—and that the other 95 percent, comprising natural emissions, is counterbalanced by absorption of CO2 from the atmosphere by natural processes. Summing it up, the IPCC declared in its fourth assessment report, in 2007: “The increase in atmospheric CO2 is known to be caused by human activities.”

Salby contends that the IPCC’s claim isn’t supported by observations. Scientists’ understanding of the complex climate dynamics is undeveloped, not least because the ocean’s heat capacity is a thousand times greater than that of the atmosphere and relevant physical observations of the oceans are so sparse. Until this is remedied, the science cannot be settled. In Salby’s view, the evidence actually suggests that the causality underlying AGW should be reversed. Rather than increased levels of CO2 in the atmosphere triggering global temperatures to rise, rising global temperatures come first—and account for the great majority of changes in net emissions of CO2, with changes in soil-moisture conditions explaining most of the rest. Furthermore, these two factors also explain changes in net methane emission, the second-most important “human” greenhouse gas. As for what causes global temperatures to rise, Salby says that one of the most important factors influencing temperature is heat exchange between the atmosphere and the ocean.

Why is the IPCC so certain that the 5 percent human contribution is responsible for annual increases in carbon dioxide levels? Without examining other possible hypotheses, the IPCC argues that the proportion of heavy to light carbon atoms in the atmosphere has “changed in a way that can be attributed to addition of fossil fuel carbon”—with light carbon on the rise. Fossil fuels, of course, were formed from plants and animals that lived hundreds of millions of years ago; the IPCC reasons that, since plants tend to absorb more light carbon than heavy carbon, CO2 emissions from burning fossil fuels reduce the share of heavy carbon in the atmosphere. But Salby points to much larger natural processes, such as emissions from decaying vegetation, that also reduce the proportion of heavy carbon. Temperature heavily influences the rate of microbial activity inherent in these natural processes, and Salby notes that the share of heavy carbon emissions falls whenever temperatures are warm. Once again, temperature appears more likely to be the cause, rather than the effect, of observed atmospheric changes.//


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