Measurements of solar occulation: the error in a naive retrieval if the constituent's concentration changes

The stratospheric concentrations of many minor constituents change rapidly at sunrise or sunset. If this happens, there is an inherent error when retrieving the vertical profiles of the constituents from measurements of their absorption of sunlight. For retrievals of NO at sunset the error can be estimated from in-situ measurements alone, without appeal to a model of stratospheric photochemistry. Below 20 km this error can approach 100% so that the retrieved NO is zero. But at 40 km, and at 25 km when the absorption is strong and Lorentzian, it can be less than 20%. Precise calculations of the error, even if small, require model calculations of the sunset and sunrise changes. With a model, we have calculated the error for NO, NO₂, OH and ClO.     

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Emissions control and reduction

A brief review of the information available on technological means for reducing anthropogenic emissions of greenhouse gases is provided. No assessment of economic or institutional difficulties for their implementation is attempted. A few cost figures are quoted where available, usually at the single-unit, microeconomic level, and further aggregation of the data is required to estimate global costs. Considerable additional analysis is required to do the latter, since simple summation of micro-level figures will in general not correctly yield macro level costs. It follows that no conclusions can be drawn from the information provided in this paper as to the preferred, most effective strategies for abating emission growths. The review should be viewed as providing a snap-shot picture of the data available as of today that is needed as input to an analysis of means and costs for achieving global scale reduction in emissions levels.