Warming stripes — visualisations of annual temperature series from the Nordic countries

Nina Kirchner

Ongoing climate change is a complex problem and communicating it to a general audience often requires short and simple explanations. Warming stripes refer to figures that resemble the black-and-white barcodes which uniquely identify almost every product we buy when it is scanned at the cashier check-out.

Warming stripes can be seen as a barcode describing changes in mean annual air temperature at a specific place over a long period of time. For each year where measurements are available, a stripe is drawn — in shades of blue if the year was cold, in shades of red if the year was warm. Warming stripes are to be read from left to right — the leftmost stripe denoting the first year of measured temperature, the rightmost stripe denoting the year before present. When blue colors dominate the leftmost part of the Warming stripes, and red colors do so in their rightmost part, the Warmings stripes visualize the ongoing warming — one of the changing climates' main indicator, in the instant the observer is looking at them.

Sweden Stockholm, Sweden Uppsala, Sweden Longyearbyen, Svalbard

Citation

Nina Kirchner (2019) Warming stripes — visualisations of annual temperature series from the Nordic countries. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/kirchner-warming-stripes-1

Data description

The dataset includes annual mean temperature data for each site provided as comma separated value (csv) files having two columns (year, data). The Warming stripe for each site is available as a png file. One m-file with matlab (R2017a) code, that reads a data file and produces a Warming stripe, is also included.

Comments

This kind of data presentation is inspired by a larger set of visualisations of climate records in the online Climate Lab Book by Prof. Ed Hawkins, National Centre for Atmospheric Science at the University of Reading.

The warming stripes presented here are derived from instrumental records of annual mean air temperature data for Sweden (1860–2018), Stockholm (1756–2018), Uppsala (1722–2018), and Longyearbyen, Svalbard (1898–2018). They are based on data from the following sources:

Sweden: SMHI. This data series is a composite of 35 stations from Sweden having homogenized temperature records.

Stockholm: Stockholm Historical Weather Observations – Monthly mean air temperatures since 1756. The version of the Stockholm temperature series used here is adjusted for the urban heat island effect. The data series is discussed in: Moberg A, Bergström H, Ruiz Krigsman J, Svanered O. (2002): Daily air temperature and pressure series for Stockholm (1756–1998). Climatic Change, 53, 171–212, doi:10.1023/A:1014966724670.

Uppsala: SMHI. The version of the Uppsala temperature series use here is adjusted for the urban heat island effect. The data series is discussed in: Bergström H, Moberg A. (2002): Daily air temperature and pressure series for Uppsala (1722–1998). Climatic Change 53, 213–252, doi:10.1023/A:1014983229213.

Longyearbyen, Svalbard: Data were obtained by personal communication with Øyvind Nordli at the Norwegian Meteorological Institute. The data series is discussed in: Nordli Ø, Przybylak R, Ogilvie AEJ, Isaksen K. (2014): Long-term temperature trends and variability on Spitsbergen: the extended Svalbard Airport temperature series, 1898–2012. Polar Research, 33:1, doi:10.3402/polar.v33.21349.

The following persons provided various kinds of help with putting together and updating this dataset: Frederik Schenk and Anders Moberg at Stockholm University; Erik Kjellström at the Swedish Meteorological and Hydrological Institute; Veijo Pohjola, Ward van Pelt and Erik Sahlée at the Uppsala University; and Øyvind Nordli at the Norwegian Meteorological Institute.