There are several knowledge gaps in our understanding of the global- scale sensitivity of groundwater systems to climate change and resulting feedbacks . There are process uncertainties in groundwater recharge simulation due to the potential impact of atmospheric CO2 on vegetation and resulting changes in ET . There are uncertainties in impact models due to poor representation of recharge pathways  and inability to adequately capture feedbacks among climate, land use and groundwater systems . Finally, there are gaps in long-term observational data, especially in less-developed countries , making it challenging to evaluate the performance of impact models .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report