Mapping the climate: guidance on appropriate techniques to map climate variables and their uncertainty
Maps are a crucial asset in communicating climate science to a diverse audience, and there is a wealth of software available to analyse and visualise climate information. However, this availability makes it easy to create poor maps as users often lack an underlying cartographic knowledge. Furthermore, communicating and visualising uncertainties in climate data and climate change projections, using for example ensemble based approaches, presents additional challenges for mapping that require careful consideration.
This paper assesses a range of techniques for mapping uncertainties, comparing "intrinsic" approaches that use colour in much the same way as conventional thematic maps, and "extrinsic" approaches that incorporate additional geometry such as points or features. We proposes that, unlike traditional cartography, where many known standards allow maps to be interpreted easily, there is no standard mapping approach used to represent uncertainty (in climate or other information). Consequently, a wide range of techniques have been applied for this purpose, and users may spend unnecessary time trying to understand the mapping approach rather than interpreting the information presented.
We use cartographic knowledge and lessons learned from mapping other information to propose a suitable mapping technique that represents both magnitude and uncertainty in climate data. This technique adjusts the hue of a small palette of colours to show the mean or median of a climate variable, and the saturation of the colour to illustrate a measure of uncertainty. It is designed to be easy to replicate, visible to colour blind people and intuitive to understand. This technique may be utilised to map a wide range of climate data, and it is proposed that it would provide a consistent approach suitable for mapping information for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5).