Climate monitoring under SAI

For many of SAI's impacts, neither small- nor large-scale experiments would resolve uncertainties. In these cases, model- and theory-based predictions can be validated only against the climate response to deployment itself. Sufficient, continuous monitoring of the relevant elements of the climate system is therefore essential: it allows estimates of SAI's impacts to be revised as soon as possible in light of incoming data, and equips decision makers to respond if observations differ from predictions or if unexpected or undesired consequences are detected. The elements needing monitoring are diverse, including surface climate changes, changes in sunlight reaching humans and ecosystems, and large-scale ocean circulation. 

The pre-requisites to this research activity include defining the observational requirements for measurements, and ensuring continuity of said capabilities. Climate variables are already well measured, so no large system-development program is anticipated (unlike stratospheric process monitoring systems).

Not all important impacts can be constrained by observations on policy-relevant timescales, since some will have a low signal relative to the noise of natural variability. For example, a change in regional rainfall may be statistically significant across many model simulations, yet remain undetectable in an actual deployment for decades.

This activity involves regular analysis and interpretation of climate observations during deployment. Distributed teams of researchers will analyze incoming data across the elements of the climate system identified by prior research activities — including the surface climate (temperature, precipitation, air quality), changes in sunlight reaching the surface (UV, diffuse/direct fraction), polar change (particularly sea-ice extent), and large-scale ocean circulation (particularly the Atlantic meridional overturning circulation, AMOC). Researchers will compare observations to model- and theory-based predictions in near real time and communicate findings to inform decision making. This activity has no fixed end date: it will begin ahead of deployment to establish baselines and their variability, and continue throughout any deployment phase, requiring sustained resources.