Editing IPCC:AR6/WGI/Chapter-8 (section)

== 8.7 Final Remarks ==

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Despite the advances presented in this chapter, there are still many opportunities to improve the understanding and quantification of human influence on past, present and future water cycle changes:

* Extension and development of pre-instrumental data and paleoclimate records, particularly from the Southern Hemisphere, will improve estimates of the range of natural climate variability and extremes, and our knowledge of how the water cycle responded in past high CO <sub>2</sub> climates.
* Development of longer observational time series that will improve our understanding of physical processes and the analysis and simulation of natural modes of weather and climate variability.
* The use of large model ensembles will help better understand the interactions between climate change and internal variability and in the detection and attribution of observed water cycle changes.
* An improvement of the general circulation model (GCM)-simulated precipitation, latent heating and radiative effects of deep convective clouds would benefit from an improved representation of their interactions with aerosols.
* Further research on land surface processes, including groundwater recharge, the role of plant physiological changes, land use change, dams and irrigation, will improve future projections of key aspects of the terrestrial water cycle such as aridity and drought.
* Ongoing efforts to develop higher-resolution ‘convection permitting’ regional or global climate models will lead to an improved simulation of clouds and precipitation, their coupling with boundary layer and surface processes, their diurnal cycle and high-frequency variability, and their response to climate change, including extreme precipitation events.
* Further analysis of past and current climate variability alongside future climate change projections will provide physically understood constraints for improving the accuracy of regional water cycle simulations, adding value to the results obtained from global climate models.
* Increased understanding of internal variability and interactions with human-induced change will improve efforts to attribute changes in the water cycle and to understand and anticipate future non-linear change.

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