Often events with a 2-3% chance of happening are basically ignored. A 2-3% risk that any restaurant will get your order wrong? No big deal, you will still go out to eat. But Grand Forks City Engineer Al Grasser very well summarized why 2-3% is not always disregarded in describing the odds of a 60+ feet flood as
low probability of a high-consequence event.
High-consequence event. If there is a 2-3% you will be run over if you try to run across the street without looking, you take that seriously. Likewise, Grand Forks does not just let slide a 2-3% chance of a 60-foot flood (and about 1% chance of a 63-foot flood). It may be a rather unlikely event, but the costs if something happens that overcomes the local permanent flood protection is so immense that the only sensible option is to take precautions to try to avoid or ameliorate the consequences. That is reasonable risk management.
Now imagine you are in some fictional town along the Red River. The experts have explained that flooding to some degree is imminent. There is a slight chance it may not be so terrible, and those chances improve if serious preparatory action is taken. But on the other end of the spectrum it may be catastrophic, especially if nothing is done in preparation to minimize impacts. However, this town is making no serious effort at all to avoid any consequences - no sandbags, no levees, no diversions, no anything. In fact there is much more action being taken, like diverting even more water into the river, that would lead to worsening rather than to avoiding or minimizing the impacts of flooding.
As inconceivable as that seems with regard to flooding around a town, that exemplifies our action (or inaction, as the case may be) pertaining to climate change. Not only are we avoiding significant effort to deal with the problem, we are causing it ourselves and continuing to stack the odds and consequences against ourselves.
A couple years ago the MIT Joint Program on the Science and Policy of Climate Change performed a new analysis that is analogous to the local peak flood forecasts. They estimated the odds of what the global average temperature increase over essentially the 21st century would be and expressed it like a roulette wheel or a "wheel of misfortune":
By that estimate where we continue recklessly dumping immense quantities of greenhouse gases into the atmosphere there is a roughly 2-3% chance of the temperature increase being 15+ degrees Fahrenheit. A more median projection is 9-10 degree Fahrenheit warming. We have already committed to non-trivial warming, but we could keep things from being that bad. If we enacted and followed serious policy to cut greenhouse gas emissions, the worst case for the year 2100 may be only 6+ degrees warming with a median of about 4 degrees warming.
Will we try to minimize the risk of dire consequences, or will we continue with the business as usual and maximize the risk?