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

==== Atlas.2.4.2 Guidelines for the Interactive Atlas ====

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===== Atlas.2.4.2.1 Quantitative Support for Assessments =====

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Many assessment statements make use of evidence derived from observed changes, model projections, and process-oriented attribution of changes to human interventions. The Interactive Atlas shows a small subset of available observations that document climate change, namely surface air temperature and total precipitation (and thus not including observations of other atmospheric and Earth system components used as part of the evidence base for the report). Only datasets that have (near) global or large regional gridded spatial coverage and go back multiple decades are used. For each variable multiple datasets are included, but some of these have overlapping native ground-station observations and so are not independent ( [[#Atlas.1.4.1|Atlas.1.4.1]] ). The datasets show patterns of substantial spatial and temporal variability, and the empirical evidence of a non-stationary climatology needs to be filtered from this information. Issues with quality, representativity and mutual consistency lead to constraints on their use for attribution of causes of trends (see [[IPCC:Wg1:Chapter:Chapter-10#10.4.1.2|Section 10.4.1.2]] for examples). The practice of attributing trends and extreme events to human causes gives confidence that these trends are expected to continue in the (near) future, provided the human drivers of climate change remain unchanged. However, large internal variability at decadal time scales can be misinterpreted as an anthropogenic influence on the likelihood of extreme events, and in that case extrapolation of trends cannot be expected to be a reliable predictor for the future ( [[#Schiermeier--2018|Schiermeier, 2018]] ).

The Interactive Atlas gives access to a specific set of climate variables from a large number of climate model simulations, particularly the (global) CMIP5, CMIP6 and (regional) CORDEX archives. The global model outputs generally give a relatively coarse picture of climate change, which is an important line of evidence for the detection and attribution of climate change, but is rarely directly applicable for local climate change assessment or support of policy design ( [[#van%20den%20Hurk--2018|van den Hurk et al., 2018]] ). To provide additional detail, downscaling global projections with regional climate models (RCMs) or statistical downscaling can be undertaken but also adds a source of uncertainty as it involves additional modelling ( [[IPCC:Wg1:Chapter:Chapter-10#10.3|Section 10.3]] ).

The information displayed in the Interactive Atlas allows a number of sources of uncertainty to be quantified. ‘Observational uncertainty’ is represented by the use of multiple (albeit often not completely independent) observational datasets. ‘Uncertainty due to internal variability’ cannot be quantified directly since multiple realizations from historic and future projections are not accessible (the Interactive Atlas uses a single realization of each model). The use of a large collection of model systems allows for an elaborate quantification of ‘model uncertainty’. In addition, a comparison of CMIP5 and CMIP6 supports evidence of progress in model quality since AR5, while the evaluation of the added value of RCMs reveals model uncertainty related to spatial resolution ( [[IPCC:Wg1:Chapter:Chapter-10#10.3|Section 10.3]] ). Finally, the assessment of ‘scenario uncertainty’ is supported by the inclusion of multiple emissions scenarios for both CMIP5, CORDEX and CMIP6.

The communication of uncertainty has a profound influence on the perception of information that is exchanged during the communication process. An assessment of uncertainty communication and the barriers to climate information construction is given in [[IPCC:Wg1:Chapter:Chapter-10#10.5.4|Section 10.5.4]] .

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===== Atlas.2.4.2.2 Insights From Physical Understanding =====

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The detailed technical findings in IPCC reports also serve as an important benchmark resource for the research community. The Interactive Atlas complements the IPCC assessment report as a repository of scientific information on global and regional climate and its representation in coordinated model ensemble experiments. Regional climate is governed by a mixture of drivers, such as circulation patterns, seasonal monsoons, annual cycles of snow and regional land–atmosphere feedbacks. Global warming may affect regional climate characteristics by altering the dynamics of their drivers. The Interactive Atlas allows the comparison of different levels of global warming on specific regional climate features but is not designed for advanced analysis of the relationship between drivers and regional climate characteristics. For this, tailored analysis protocols need to be applied, such as the aggregation of climate change information from ensembles of regional climate projections, and stratification according to drivers of regional climate such as patterns of atmospheric circulation ( [[#Lenderink--2014|Lenderink et al., 2014]] ). The analysis of complex regional climate characteristics resulting from compound drivers also require additional expert knowledge and data processing ( [[#Thompson--2016|Thompson et al., 2016]] ). [[IPCC:Wg1:Chapter:Chapter-12#12.6.2|Section 12.6.2]] assesses various categories of climate services, including tailored analysis of regional climate processes.

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===== Atlas.2.4.2.3 Construction of Storylines =====

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Communicating the full extent of available information on future climate for a region, including a quantification of uncertainties, can act as a barrier to the uptake and use of such information ( [[#Lemos--2012|Lemos et al., 2012]] ; [[#Daron--2018|Daron et al., 2018]] ). To address the need to simplify and increase the relevance of information for specific contexts, recent studies have adopted narrative and storyline approaches (see Sections 1.4.4 and 10.5.3 for definitions and further discussion on these concepts; [[#Hazeleger--2015|Hazeleger et al., 2015]] ; [[#Shepherd--2018|Shepherd et al., 2018]] ). The use of region-specific climate storylines, including a role for local mechanisms, drivers and societal impacts generally requires detailed information that is typically not provided by the Interactive Atlas. However, background information and basic (scenario) assumptions can be derived from the Interactive Atlas which can be considered to provide an expert knowledge base from which to build targeted storylines and climate information.

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===== Atlas.2.4.2.4 Visual Information =====

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The visual communication of climate information can take many forms. Besides the standard visual products typically used for communicating global and regional climate information to practitioners (e.g., maps, time series or scatter plots), the Interactive Atlas incorporates new visuals, for example, ‘stripes’ ( [[#RMetS--2019|RMetS, 2019]] ), facilitating the communication of key messages (e.g., warming and consistency across models) to a less technical audience. The various tabular and graphical representation alternatives included as options in the Interactive Atlas (Figure Atlas.8) facilitate exploring the information interactively from different perspectives and in different levels of detail, thus favouring communication with the large and diverse audience of IPCC products.

To support the use of visuals provided in the Interactive Atlas for application to different audiences, new insights since AR5 have emerged from a range of scientific disciplines, including the cognitive and psychological sciences ( [[#Harold--2016|Harold et al., 2016]] ). Studies have used interviews and online surveys to assess interpretations of visuals used to communicate climate information and uncertainties ( [[#Daron--2015|Daron et al., 2015]] ; [[#Lorenz--2015|Lorenz et al., 2015]] ; [[#McMahon--2015|McMahon et al., 2015]] ; [[#Retchless--2016|Retchless and Brewer, 2016]] ). They commonly find wide-ranging interpretations and varied understandings of climate information amongst respondents due to the choice of visuals. In addition, [[#Taylor--2015|Taylor et al. (2015)]] found that preferences for a particular visualization approach do not always align with the approaches that achieve greatest accuracy in interpretation. Choosing appropriate visuals for a particular purpose and audience can be informed by testing and evaluation with target groups.

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===== Atlas.2.4.2.5 Dedicated Climate Change Assessment Programmes =====

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Communication aimed at informing the general public about assessed scientific findings on climate change have a different purpose and format than if intended to inform a specific target audience to support adaptation or mitigation policies ( [[#Whetton--2016|Whetton et al., 2016]] ). The growing societal engagement with climate change means IPCC reports are increasingly used directly by businesses, the financial sector, health practitioners, civil society, the media, and educators at all levels. The IPCC reports could effectively be considered a tiered set of products with information relevant to a range of audiences.

The Interactive Atlas does provide access to a collection of observational and modelling datasets, presented in a form that supports the distillation of information on observed and projected climate trends at the regional scale. Access to the repository of underlying datasets enables further processing for particular purposes. As noted above, it is not the intention nor the ambition of this IPCC assessment and the Interactive Atlas component to provide a climate service for supporting targeted policies. For this an increasing number of dedicated climate change assessment programmes have been carried out, aiming at mapping climate change information relevant for adaptation and mitigation decision support.

For instance, [[#EEA--2018|EEA (2018)]] provides an overview of European national climate change scenario programmes. Most of these use CMIP5 (or earlier) global climate change ensembles driven by an agreed set of greenhouse gas (GHG) emissions scenarios, followed by downscaling using RCMs and/or statistical methods, in order to generate regionally representative hydro-meteorological indicators of climate change. In some cases, output of selected downscaled global and regional models is provided to users ( [[#Whetton--2012|Whetton et al., 2012]] ; [[#Daron--2018|Daron et al., 2018]] ). Uptake by users is strongly dependent on providing justification of the selection or for the downscaling procedure and if further steps are needed to tailor the information to local scales ( [[#Lemos--2012|Lemos et al., 2012]] ). More comprehensive programmes provide probabilistic climate information by careful analysis and interpretation of ensembles of model outputs ( [[#Lowe--2018|Lowe et al., 2018]] ). The information is generally tailored to professional practitioners with expertise to interpret and process this probabilistic data. This top-down probabilistic information chain is not always able to highlight the essential climate change information for users, and alternative bottom-up approaches are encouraged ( [[#Frigg--2013|Frigg et al., 2013]] ). [[IPCC:Wg1:Chapter:Chapter-12#12.6.2|Section 12.6.2]] assesses climate services including the national climate assessments and user uptake.

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