Commentary & Opinion
12:05 pm
Tue April 10, 2012

Franz Litz: Loading the Dice for Warmer Weather

Today Dr. James Hansen, the well known American climate scientist, will accept the prestigious Edinburgh Medal for his work on climate change science. The Edinburgh Medal is awarded each year to a person of science whose professional achievements are judged to have made a significant contribution to the understanding and well-being of humanity.  Dr. Hansen will reportedly use the occasion to talk about climate change as a moral issue of unprecedented scale.

Hansen was one of the first climate scientists to step outside of the comfortable confines of academic science to seek the attention of politicians in Washington. Hansen says his grandchildren are what made him make this unusual choice for a serious scientist. His willingness to speak up in the face of political inaction makes Hansen seem more like an activist than a scientist.

Over the past 3 decades, Hanson has of course been joined by literally thousands of other scientists in his views about how human beings are altering the world’s climate system. The world’s Intergovernmental Panel on Climate Change has issued four comprehensive climate change assessment reports during this time, each report reaching stronger and stronger conclusions about the scientific community’s level of confidence in its findings.

When I read that Hansen will receive the Edinburgh Medal, I was reminded of his loaded dice analogy—a comparison he uses to explain how climate change alters our weather.  Filling the atmosphere with heat trapping gases is like loading the weather dice to favor warm extremes over cold extremes and neutral weather.

Picture a six-sided die with four of the sides painted red to correspond to warmer than normal weather. For the remaining two sides, imagine one is white for neutral weather and the other is blue for colder than normal weather.  Now imagine for any given season you roll that die to see what you’ll get.

The die I just described represents what is expected to happen under scientists’ “intermediate” climate change scenario, in which the rate of growth of global warming pollution is somewhat slowed from its current trajectory.  Think of it as a kind of middle-of-the-road global warming scenario in which we do some things to reduce our pollution levels, but not as much as the science is saying we need to do.

Under this middle-of-the-road scenario, we have a 4 in 6 chance of a warmer than normal season, a 1 in 6 chance of a normal season and a 1 in 6 chance that the season will be colder than normal.  So you can see that even if global warming runs its course with only moderate pollution reductions, we’ll still sometimes experience seasons that are colder than normal.  Cold seasons will just occur less frequently.

This past winter was warmer than normal for our part of North America. James Hansen might say that we rolled a red side of the die.  If next year we experience a normal winter or a colder than average winter, that won’t mean that global warming is not happening.  Rather, it will mean that we beat the slowly changing odds.

Global average temperatures are rising, making warmer-than-average seasons more and more likely. But our local meteorologists will still keep their jobs. Weather will always be more variable than climate.

Franz Litz is the Executive Director of the Pace Energy and Climate Center and Professor of Law at Pace Law School.

The views expressed by commentators are solely those of the authors, and do not reflect the views of this station or its management.

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