Insights Regarding Observational Requirements For Climate Change Signal Detection

Climate change signals must be detected against both the noise of internal natural variability as well as a wide range of uncertainties in the observing system. Observing system uncertainties include SI traceable accuracy, instrument stability over a decade or longer, calibration across data gaps, changing instrument designs, changing sampling of the earth, and changing data analysis methods. Most current observations used for climate change signals were not designed with climate change uncertainties in mind (National Academy of Sciences Continuity Report for NASA, Nov. 2015). Examples are given of how to set requirements for climate change observations relative to anticipated climate change signals and climate system natural variability. Given that we currently lack an observing system designed specifically for climate change, what would such a system look like? Design principles are provided, and examples are given of how more accurate observations can narrow key scientific uncertainties in climate change. Examples will also be presented of observations that can meet these much more challenging climate change requirements. The lack of a designed climate observing system naturally raises the question of the societal return on investment of providing such a system. Recent published estimates using state of the art economic integrated assessment models (IAMs) suggest a return of ~ $50 per $1 invested. Society will be managing the Earth’s Climate System actively or passively, wisely or unwisely, for the indefinite future. The world has had an internationally designed, committed, and shared weather observing system for many decades. It is time to begin an equivalent international climate change observing system. The motivation for such systems are the same: a better future for society.