English: w:Warming stripes w:data visualization diagram that represents temperature deviations above (in red stripes) and below (in blue stripes) a 1961-1990 average value.

General notes:

• Credit for general concept of w:warming stripes: climate scientist Ed Hawkins, w:University of Reading, U.K.
• Data values are visualized using color rather than locations of points on a graph.
• The average temperature in reference period 1961-1990 determines boundary between blue and red.
• Horizontal scale is time, from 1850 (left) to 2018 (right).
• Each hue (up to 8 blue and 8 red) covers a temperature range of 0.1 degrees Celsius.
• Data is global (not for a locality).

Source documentation re the underlying data:
https://www.metoffice.gov.uk/hadobs/hadcrut4/index.html
https://web.archive.org/web/20190102231319/https://www.metoffice.gov.uk/hadobs/hadcrut4/index.html

"HadCRUT4 is a gridded dataset of global historical surface temperature anomalies relative to a 1961-1990 reference period. Data are available for each month since January 1850, on a 5 degree grid. The dataset is a collaborative product of the Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia.

"The gridded data are a blend of the CRUTEM4 land-surface air temperature dataset and the HadSST3 sea-surface temperature (SST) dataset. The dataset is presented as an ensemble of 100 dataset realisations that sample the distribution of uncertainty in the global temperature record given current understanding of non-climatic factors affecting near-surface temperature observations. This ensemble approach allows characterisation of spatially and temporally correlated uncertainty structure in the gridded data, for example arising from uncertainties in methods used to account for changes in SST measurement practices, homogenisation of land station records and the potential impacts of urbanisation.

"The HadCRUT4 data are neither interpolated nor variance adjusted."

Recommended source citation for the data:

• Morice, C. P., J. J. Kennedy, N. A. Rayner, and P. D. Jones (2012), Quantifying uncertainties in global and regional temperature change using an ensemble of observational estimates: The HadCRUT4 dataset, J. Geophys. Res., 117, D08101, doi:10.1029/2011JD017187.
• From wikitext, with link: (April 17, 2012). "Quantifying uncertainties in global and regional temperature change using an ensemble of observational estimates: The HadCRUT4 dataset". J. Geophys. Res. 117 (D8). DOI:10.1029/2011JD017187.

FAQ re the datasets:
https://www.metoffice.gov.uk/hadobs/hadcrut4/faq.html
https://web.archive.org/web/20190119092400/https://www.metoffice.gov.uk/hadobs/hadcrut4/faq.html

Actual download page:
https://www.metoffice.gov.uk/hadobs/hadcrut4/data/current/download.html
https://web.archive.org/web/20190619234924/https://www.metoffice.gov.uk/hadobs/hadcrut4/data/current/download.html

Creator/Uploader's remarks:

• I averaged only datasets 1-10 from the 100 HadCRUT4 "Global (NH+SH)/2" datasets, since the standard deviation among each of the 170 year-wise averaged values was small (only 0.01 - 0.02 degrees). That is, the datasets substantially agreed.
• I averaged the datasets year-wise in Microsoft Excel, and separated the averaged values into categories with "cutoff" (boundary) temperature deviations being multiples of 0.1 degrees (a simple linear relation). I assembled color-coded rectangles in Microsoft Powerpoint, exported, and re-sized using Photoshop.
• My resulting warming stripes diagram differs from that published by Ed Hawkins because he used different dataset than I did. Mine is based on deviation from a 1961-1990 reference period average, whereas Hawkins' data used a 1971-2000 reference period (separating blue from red). Mine includes data for 2019, whereas Hawkins' June 2019 warming diagram ended with 2018 data. My "cutoff" temperatures (which determine boundaries between adjacent color bands) is probably different, and less sophisticated. I used a different color scheme.
• I made a typo in the remarks for uploading Version 3: it is 3200x1800 (not 2100x1800).