A Theoretical Analysis of the Uncertainty of Climate Elasticity Method on the Attribution of Climate Change and Human Activity on Streamflow

In the attribution analysis of the impact of climate change and human activities, the climate elasticity method is the most used one. It normally calculates the streamflow change caused by the climate changes between two periods from the observed average precipitation and potential evapotranspiration, which uses elasticity coefficients to reflect the impact of precipitation and potential evapotranspiration on streamflow. The elasticity coefficients are usually calculated from the annual actual evapotranspiration equations under Budyko Hypothesis. In this paper, the attribution uncertainty of the climate elasticity method is proposed by six commonly used annual actual evapotranspiration equations based on the Budyko framework, and the potential evapotranspiration is calculated from Penman equations. The serial of streamflow is calculated using the precipitation minus actual evapotranspiration, and in the impact period, additional streamflow reduction is deduced as the impact of human activities. So, the theoretical contribution of the climate change could be calculated from the constructed data. The results show that the calculated relative error of contribution of climate change varies from +200% to -500%, and most of them are underestimation. It indicates that the attribution results of the climate elasticity method has a trend of underestimate the impact of the climate change and overestimate the impact of human activity.