17. januar 2017

The Climate Change story in one image

The online climate change debate is an exhausting place to navigate: From doomsday-preppers to conservative-ostriches all fighting for a few seconds of attention. Here is my contribution to global warming today:

The climate change story in one image

UAH LT 1979 thru December 2016 v6

In this post I thought I'd just look at the power of data visualisation in telling the story about global warming, or trying to obfuscate that story with exactly the same data. I made the above chart using the same dataset as the below chart which is a visualisation of global temperature data often linked to by skeptics. These charts are created from the exact same published data set called UAH LT v6 (See bottom of post for additional details).

The noisy chart by Roy Spencer
Raw data: http://www.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt  

In the context of the climate change skeptic viewpoint I have often seen this chart used to flag that 2016 is within statistical margin of error no warmer than 1998 and that December 2016 was cold and thus "There is no warming trend!"

While the chart shows the published data it uses at least these methods to obfuscate the Global Warming trend in the data:
  • Large visual weight on individual monthly averages as blue dots
    • Adds to the impression that there is a lot of noise in the data and confuses the picture as global warming is discussed in yearly averages over decades. 
  • Annotates a 13-month running average with red
    • Climate change is normally discussed as 30 year or longer trends.
  • Plots every gridline label
    • Adds to the noisy and detailed ("sciency") impression and hides the yearly average.
  • A wide aspect and long x-axis range
    • Reduces the visual impact of the temperature trend.
  • Annotates the month of December 2016
    • The average of December 2016 does not say anything about the average of 2016 nor the climate trend. It appears as a decoy to re-frame the discussion away from the trend and over to the peaks in '98 & '16 that are El Niño events. 
The author of the noisy chart is the co-author of the actual dataset, yet his University presents the very same data with a clear visual emphasis on the increasing trend using a different chart:

Global temperature trend


Climate change is the story of the year
For me the climate change theme provides an abundance of interesting and challenging topics to explore: How to use data visualisations to tell the climate story, citizen science projects contributing data, the challenge of linking global policy with everyones daily life, how to handle impossible So-Me discussions and much more ...




UAH LT v6 dataset
University of Alabama in Huntsville Lower Troposphere v6 dataset

Global temperature datasets
The UAH satellite based global temperature data set is derived from measurements of  microwave emissions from oxygen in the atmosphere conducted by many different satellites over the years. There are several other global temperature datasets, some based on satellite data and several based on ground (land/ocean) measurements. 

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