Screenshot of a frame of a <a href="https://en.wikipedia.org/wiki/Climate_spiral" class="extiw" title="w:Climate spiral">Climate spiral</a> <a href="https://en.wikipedia.org/wiki/Data_visualization" class="extiw" title="w:Data visualization">Data visualization</a> of Earth's Arctic sea ice volume from 1979 to 2017.
<ul><li>Independent variable is time:</li></ul><dl><dd><ul><li>Months are represented by angles about a center point</li>
<li>Years are represented by evolving colors as the years pass</li></ul></dd></dl><ul><li>Dependent variable is Earth's arctic sea ice volume, represented by distance from the center point, which generally becomes smaller as time progresses due to shrinkage of polar sea ice volume. Curve is "lopsided" due to seasonal (winter-summer) variations.</li></ul><ul><li>May 2017 publication date is estimated, based on content of graph and first Wayback Machine archive of 6 June 2017.</li></ul><ul><li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20190819055209/http://www.climate-lab-book.ac.uk/spirals/">Footnote in source</a> states: "LICENSE Creative Commons License These blog pages &amp; images are licensed under a Creative Commons Attribution-ShareAlike 4.0 International License."</li></ul>
Ed Hawkins, climate scientists at the <a href="https://en.wikipedia.org/wiki/University_of_Reading" class="extiw" title="w:University of Reading">University of Reading</a>
CC BY-SA 4.0
Hawkins, Ed, <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190819055209/http://www.climate-lab-book.ac.uk/spirals/">Climate spirals</a>. <i>Climate Lab Book</i> (May 2017). Archived from <a rel="nofollow" class="external text" href="http://www.climate-lab-book.ac.uk/spirals/">the original</a> on <span class="mw-formatted-date" title="2019-08-19">19 August 2019</span>. (<a rel="nofollow" class="external text" href="http://www.climate-lab-book.ac.uk/files/2016/06/icevol_2017.gif">Direct link to GIF for "Arctic Sea Ice Volume"</a>)