

While much of Europe has been denied a white Christmas, many of us were still having a white snow cover while the clocks went forward for ‘summer’ time this weekend. But although it appears that this winter is never-ending, it mainly comes very late this year. The coldest of temperatures and the main snowfall arrived in February and March, while the early winter months were even above average in some areas of central Europe.

Regular observations are collected regularly by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, which records data about the land surface temperature (i.e. “how hot the ‘surface’ of the Earth would feel to the touch in a particular location“, a different measure than the air temperature we see on the weather reports every day). This map shows the land surface temperature anomaly this March compared to the average temperatures from 1951 to 1980 projected on a gridded population cartogram where every grid cell is resized according to its total population. The projection used in this visualisation shows, how the world’s population was exposed to the temperature anomalies in the late spell of winter last month:



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The picture of the late winter started emerging in February which is shown in the following map. Here it can be seen that the comparably warm February land surface temperatures in large parts of Russia were not only in the remote areas that disappear in such a map, but were also affecting larger parts of the population that lives in the western parts of the country, with Moscow being the ‘dark red’ blob just east of the already freezing people in Eastern Europe:



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In contrast to the recent cold months, the picture in January provided a much more mixed impression, where parts of the densely populated Eastern seaboard of the United States was warmer than average – before the February blizzard brought the memories of winter back into people’s minds:



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What we perceive as a very cold winter in the northern hemisphere is not only an effect of the very late arrival of cold temperatures and snow, but also a result of our perspective on the weather patterns. The gridded population cartogram reflects a lot of how many of us in the northern hemisphere experiences the conditions this winter, while a conventional map of the data (shown in the inset reference image on the bottom left) shows that considerable regions in the Arctic – which are sparsely populated – had above average land surface temperatures in February: Large parts of Greenland and the Arctic regions in North America showed much warmer than average land surface temperatures, but affect very few people (and hence do not appear in these map projections).

The full picture of changing land surface temperatures during this winter season can be seen in the following cartogram animation that starts with the conditions as observed in October 2012 and goes until the most recent image of March 2013. It confirms, that we were far from a long-cold winter, but experienced a rather late arrival with a bitterly cold ending in March that sticks most in our minds now as our image of this winter:



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Climate change, or indeed global warming is far from off the table just because some of us experienced a rare ‘white Easter’ instead of an equally rare white Christmas. In other parts of the world, the maps and animation also show that despite above average land surface temperatures in Australia on many parts of the continent, most of the population faced below average values in February and March. Changing climates are more complicated than what we see in front of our doorstep, but also more complex than current weather phenomena. This image is a snapshot which together with many other snapshots can give us more insights into how the global weather patterns chance and contribute to a changing climate.

As explained on NASA’s Earth Observatory website: “Some land surface temperature anomalies are simply random weather phenomena, not part of a specific pattern or trend. Others anomalies are more meaningful. Widespread cold anomalies may be an indication of a harsh winter with lots of snow on the ground. Small, patchy warm anomalies that appear in forests or other natural ecosystems may indicate deforestation or insect damage. Many urban areas also show up as hot spots in these maps because developed areas are often hotter in the daytime than surrounding natural ecosystems or farmland. Warm anomalies that persist over large parts of the globe for many years can be signs of global warming.”

The maps on this page have been created by Benjamin D. Hennig using data by NASA (temperatures) and SEDAC (population). Please contact me for further details on the terms of use.