Editing IPCC:AR6/WGI/Chapter-10 (section)

== 10.7 Final remarks ==

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The assessments in this chapter are based on a rapidly growing body of evidence from the peer-reviewed literature, most of which was not previously considered by IPCC reports. Several challenges in the construction of regional climate change information have been identified:

* Limited climate monitoring in some regions impedes the full understanding of the relevant climate processes, an appropriate validation of model simulations, and the formulation of trustworthy regional climate information. Beyond temperature and precipitation, there is a shortage of observed variables needed for regional process understanding, attribution, and model development and validation, among others. Examples include surface evapotranspiration, soil moisture, radiation, wind and relative humidity, among many others identified by sectors sensitive to climate (Sections 10.2, 10.3 and 10.6).
* Compared to the increasing number of large-scale evaluations, there is a shortage of process-based model evaluations at regional scales to assess the fitness of the chosen models for specific purposes (Sections 10.3 and 10.4).
* There is a general lack of studies of the simulation of large-scale, downscaling-relevant processes in global models to support the design of global/regional model matrices that both span a sufficiently large range of projection uncertainty and realistically represent the regional climate of interest. The fitness of statistical methods for regional climate change studies has received limited attention by the scientific community, while as in the case of global models, process-based evaluation has proven useful ( [[#Soares--2019b|Soares et al., 2019b]] ). Studies of past changes and pseudo-reality studies to assess the predictors and model structures required for downscaling in a future climate are promising avenues ( [[#10.3|Section 10.3]] ).
* Internal variability is a large contributor to climate uncertainty at regional scales, especially for extreme events. Further study of the processes governing regional internal variability, such as the modes of variability and the teleconnections that connect them to the regional variability, but also of the local processes and drivers involved, will help improve its understanding. The same applies to the validation of the simulated internal variability that underpins the trustworthiness of model-based climate information (Sections 10.3, 10.4 and 10.6, and Cross-Chapter Box 10.1).
* Methodologies on how to propagate climate uncertainties from global and regional scales down to the human settlement scale are still under development. In some cases, bias-adjustment methods are used with substantial neglect of the physical processes involved ( [[#10.3|Section 10.3]] and Cross-Chapter Box 10.2).
* The production of regional climate information relies mainly on global and regional models that often do not incorporate human-controlled surface processes (urban parametrizations is one example) in their land surface components. This limits the representation of uncertainties for climate information at the urban scale ( [[#10.3|Section 10.3]] , Box 10.2, and Cross-Chapter Box 10.2).
* Literature plays a central role as a source for constructing regional climate change information. The amount of climate change literature available is unevenly distributed across the world, and large bodies of literature (e.g., local and regional reports) are often overlooked in the construction of climate information. Furthermore, research tends to focus on regions that attract the attention of the Global North so that climate aspects relevant to other regions may not receive sufficient attention for generating appropriate regional climate information (Sections 10.2, 10.3, 10.5 and 10.6).
* Governmental institutions producing regional and local climate information often use diverging approaches that are not necessarily coherent with each other. Coherency could be improved by implementing a quality control system and a traceability solution for the sources of the information. Collective work with the social sciences and humanities will improve the communication, perception and response to regional climate information and help translate user requirements (Sections 10.5 and 10.6).
* There is a shortage of regional climate change studies distilling multiple lines of evidence. Most studies rely on either global models or downscaled global models, with an increasing number of studies focusing on the use of emulators and the selection and combination of models. However, there are limited studies distilling this information with a wider range of lines of evidence that includes observations, process understanding, attribution, and hierarchies of models (Sections 10.3, 10.5 and 10.6).

Addressing these challenges could facilitate the assessment of both sources and methodologies that lead to an increased fitness and usefulness of regional climate information for a wide range of purposes.

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