The GROI compares the probability of a climate change scenario against other scenarios, for example a plane crash or being struck by lightning.
For instance, at 400 parts per million of carbon, the IPCC computes a 22 percent probability we will see temperatures rise by 2 degrees Celsius (3.6°F). Scientists argue that 2 degrees Celsius is the threshold beyond which the world will careen into dangerous climate impacts. We are already hovering near 400 ppm of carbon.
To understand these numbers, consider fatal flight accidents. The probability of a plane crash is 0.0001 percent or about 30 accidents a year.
If the probability were to increase to 22 percent, there would be 6,648,000 accidents every year. That's 759 accidents every hour.
Global Warming: Why Only 95 Percent Certainty?
That's a really high risk few of us would be willing to accept when it comes to flying. So why are we okay with accepting the risk when it comes to the future livability of our planet?
The IPCC report states that we need to limit carbon emissions to 1000 gigatons (about 480 ppm) of carbon to have a 66 percent chance global temperatures will not rise beyond 2 degrees Celsius.