Black carbon is known as potential agent for global warming because it directly heat up the atmosphere by absorbing solar radiation energy. The black carbon heats not only the ambient air but also indirectly affects the global warming or cooling by acting as cloud condensation nuclei. More recently, it is suggested that the black carbon can semi-directly increase the atmospheric temperature by vaporizing the air surrounding the black carbon, resulting in the loss of water contents in the cloud, so that the amount of cloud is reduced. Then, the solar energy easily penetrates the stratosphere. Since 1980, many researchers who drew attention to carbon dioxide are changing their research objectives into the black carbon. In this situation, the most frequently used technique for measuring the light absorption is a filter-based technique. However, previous studies raise issues associated with the overestimation of the black carbon concentration when it is measured using filter-based instruments. In addition to this issue, the limitation of the filter-based technique is discussed from the view point of non-linearity and negative signals at zero level.