We developed the Greenhouse Gamble™ wheels to convey uncertainty in climate change prediction. The roulette-style spinning wheels show the estimated probability of potential change in global average surface temperature over the next 100 years. Each wheel represents a different set of greenhouse gas policies, and the face of each wheel is divided into colored slices. Each slice represents the likelihood of temperature change in that range by the year 2100.
The "No Policy" wheel assumes no attempt is made to curb the global emissions of greenhouse gases. The median warming level of the "No Policy" wheel is 5.2 °C, which means there are even odds of a result falling either above or below that level. The most likely result is in the 5-6°C range. The tiny blue slice is a one-in-100 chance of constraining global temperature change under 3°C.
The "With Policy" wheel assumes that policies are enacted to limit cumulative emissions of greenhouse gases over the century to 3.4 trillion metric tons (measured in CO2-equivalent). The median warming level of the "With Policy" wheel is just 2.3 °C, with the most likely result falling in the 2-2.5°C range.
Humankind will be spinning the "No Policy" roulette wheel as long as we allow global emissions to increase. However, if policies to reduce emissions are enacted, we will get to spin the "With Policy" wheel, which gives us a 9/10 chance of constraining global temperature change to below 3°C in 2100.
On May 1, 2001, The Greenhouse Gamble wheel premiered with an auspicious whirl by (then) President of MIT, Charles M. Vest, at the 25th Anniversary Symposium of the Office of Science and Technology Policy.
President Vest's sure-handed tug launched a twirl spanning several seconds, while the auditorium filled with former Presidential Science Advisors anxiously awaited a result. When the revolutions finally slowed, the pointer came to rest on an optimistically cool slice: an increase of only 2-3°. With a facetious grin and a triumphant thrust of both fists upward, Chuck exclaimed: "I saved the world!" The crowd cheered.