Accurate Estimation of CO2 Background Level from Near Ground Measurements at Non-Mixed Environments

Abstract

Atmospheric CO2 background levels are sampled and processed according to the standards of the NOAA (National Oceanic and Atmospheric Administration) Earth System Research Laboratory mostly at marine environments to minimize the local influence of vegetation, ground or anthropogenic sources. Continental measurements usually show large diurnal and seasonal variations, which makes it difficult to estimate well mixed CO2 levels. Historical CO2 measurements are usually derived from proxies, with ice cores being the favourite. Those done by chemical methods prior to 1960 are often rejected as being inadequate due to poor siting, timing, or method. The CO2 versus wind speed plot represents a simple but valuable tool for validating modern and historic continental data. It is shown that either a visual or a mathematical fit can give data that are close to the regional CO2 background, even if the average local mixing ratio is very different.