Climate Change Vocabulary: Probability

What are the odds your house will burn down? How about your chances at a blackjack table in Vegas? Or what about winning the lottery? From insurance to casinos, there are plenty of people trying to figure out the probability of certain events happening to get ahead. In the case of climate change, probabilities are also important to getting ahead. Yet people seem to care much less about those odds than the odds of hitting blackjack even though the ramifications are much bigger.

The Intergovernmental Panel on Climate Change (IPCC) reports all contain language based on probability. For example, the IPCC states,

“Where uncertainty in specific outcomes is assessed using expert judgment and statistical analysis of a body of evidence (e.g. observations or model results), then the following likelihood ranges are used to express the assessed probability of occurrence: virtually certain >99%; extremely likely >95%; very likely >90%; likely >66%...”

And so it keeps going down the line.

Here’s a statement from the IPCC using their wording:

“Most of the observed increase in global average temperature since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.”

That means there’s a greater than 90% certainty we’re causing the current climate changes.

Within the climate system, there are different probabilities for how carbon emissions will affect different events. For example, chances are good the likelihood of 100-year floods will increase in the southeastern US. Understanding these probabilities is important for businesses, governments, and individuals alike. With the flood example, agencies will have to remap floodplains and insurance companies will have to adjust rates.

Back to the Big Picture

So there’s a 90% chance human activities are changing the climate system. The probabilities are less certain about the exact effects. For example, in a discussion with filmmaker Laura David in the book Science is Culture, climate scientist Stephen Schneider put the chances of catastrophic climate change at 10% if nothing is done to curb emissions.

The odds your house will burn down are less than 10% yet many people buy homeowners’ insurance. Why aren’t we taking out a good climate change insurance policy by mitigating and adapting to it now when costs are comparatively low?

In the US, it seems like the government wants to please certain people and special interests. From the deteriorating war in Afghanistan to climate change, the government has put politics above the facts. Yet when the probabilities are so high that at least some things are going to change, and there’s a real chance of dramatic change, politics should take a backseat.

It’s time for governments to wise up and pay attention to the scientific community. The US government invaded a foreign country with less than 90% certainty that it had weapons of mass destruction. It's even more likely people are detrimentally altering the climate system. Political action should be a no-brainer.

Image Credit: Crystaljingsr