The New Climate Dice

During the extreme heat waves and droughts of the early 1980s, climatologist James Hansen noticed coincident public discussions about the possible link of extreme events to climate change. He says discussion cooled, however, when natural variability turned up a season with average or cold temperatures. In 1988, another heat wave and drought wiped out crops in the U.S. Midwest, and resulted in more than 5,000 deaths, according to NOAA’s National Climatic Data Center. That same year, Hansen introduced the analogy of loaded dice to demonstrate variability and the growing frequency of extreme temperature events.

On one of the six-sided dice, Hansen painted two sides blue, two sides white, and two sides red to represent the chance of a cold, average, or warm summer season, respectively. That’s how the dice would have rolled from 1951 to 1980, when climate was relatively stable. On the other die – this one loaded – Hansen painted one side blue, one side white, and four sides red. That’s how climate models suggested the dice would roll by the first decade of the 21st century, should the increase of greenhouse gases in the atmosphere play out as it did.

“If you keep track for several seasons you notice the frequency of the anomalies has now changed, and you’re getting much more of those on the warm side than on the cool side,” Hansen says.

The changes that Hansen and colleagues calculated in 1988 turned out to be close to reality, as far as how many sides of the dice would now be red as opposed to blue to represent today’s climate. But a key difference between the 1988 dice and the new climate dice is the addition of an entirely new color. Almost one full side previously red is now brown, representing a new category of extreme hot events.

“I didn’t think about adding another color in 1988,” Hansen says. “Since then I have realized that the extreme cases are the most interesting and hold the most potential for impact, such as we’re seeing this summer in the case of the drought and devastated corn crop.”

The division between warm and cool will continue to change in the future, Hansen says. “But it’s still a crapshoot and you shouldn’t take one cool season as an indication that there’s something wrong with our understanding of global temperature and warming.”

Hansen and colleagues continue to use the dice for communication purposes, but they now employ a different statistical tool – the bell curve – that they say better demonstrates the change in temperature anomalies, particularly at the extremes.

Text by Kathryn Hansen. Top image: James Hansen of NASA’s Goddard Institute for Space Studies. Credit: NASA

6 thoughts on “The New Climate Dice”

  1. >> During the extreme heat waves and droughts of the early 1980s, climatologist James Hansen noticed coincident public discussions about the possible link of extreme events to climate change.

    That seems a strange claim. The only discussions I recall of climate change from that time was the possibility of the then noted cooling presaging a new (incorrectly named) “ice age”. Also “extreme events” was not in the vocabulary of this period.

    The gaussian bell analysis is interesting and is probably more informative than the usual “global mean temp”. It is unfortunate that this analysis did not include earlier data. Excluding warmer periods of the 1930’s that would provide more context of climate variation means the animation is misleading.

    This is so obvious to anyone with a knowledge of climate it is hard to see why earlier data was excluded from Dice. It could give the impression that Dr Hansen is once again trying to load the dice.

  2. Thank you; I was never happy with the “loaded dice” analogy because it kind of implies that there is some kind of intelligent force working to increase global average temperature and the number of extreme weather events (fair dice are the default when properly made: it makes a brain to “load” them)— something only an insane homicidal sociopath would think a good thing to do.

    The bell curve is vastly better at showing how the probabilities have shifted towards more extreme events.

    Where I live (Northern New Mexico) we have had two “fifty-year floods” in the past two years; this is a major problem because many of the dams on Rio Chama and other rivers are made out of dirt and rocks: while down-stream it is relatively sparsely population compared to a very large number of other places, human lives are still at risk from extreme weather events such as flooding.

    It took Rio Arriba County several days and an impressive sum of money to open the roads closed by the unusual flooding. The county has been updating its disaster preparedness handbook (with meetings where anyone interested may attend). We know more extreme weather events is already a reality; we know it must get worse because the laws of physics dictate it must; but the money to mitigate the damage still is not available, and no one holds any hope at all that the funds necessary will ever be available.

  3. Excellent idea to know the weather report.

    I was wondered with this climate dice.

    Thanks for posting this.



  5. Do you this this “new color” is an effect of global warming? Should we be that scared ? Can the situation possibly be THIS wrong? Thank you

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