AF - AIS terminology proposal: standardize terms for probability ranges by Egg Syntax

Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: AIS terminology proposal: standardize terms for probability ranges, published by Egg Syntax on August 30, 2024 on The AI Alignment Forum.
Summary: The AI safety research community should adopt standardized terms for probability ranges, especially in public-facing communication and especially when discussing risk estimates. The terms used by the IPCC are a reasonable default.
Science communication is notoriously hard. It's hard for a lot of reasons, but one is that laypeople aren't used to thinking in numerical probabilities or probability ranges. One field that's had to deal with this more than most is climatology; climate change has been rather controversial, and a non-trivial aspect of that has been lay confusion about what climatologists are actually saying[1].
As a result, the well-known climate assessment reports from the UN's Intergovernmental Panel on Climate Change (IPCC) have, since the 1990s, used explicitly defined terms for probability ranges[2]:
(see below for full figure[3])
Like climatology, AI safety research has become a topic of controversy. In both cases, the controversy includes a mix of genuine scientific disagreement, good-faith confusion, and bad-faith opposition. Scientific disagreement comes from people who can deal with numerical probability ranges. Those who are arguing in bad faith from ulterior motives generally don't care about factual details.
But I suspect that the large majority of those who disagree, especially laypeople, are coming from a place of genuine, good-faith confusion. For those people, anything we as practitioners can do to communicate more clearly is quite valuable.
Also like climatology, AI safety research, especially assessments of risk, fundamentally involves communicating about probabilities and probability ranges. Therefore I propose that the AIS community follow climatologists in adopting standard terms for probability ranges, especially in position papers and public-facing communication.
In less formal and less public-facing contexts, using standard terminology still adds some value but is less important; in sufficiently informal contexts it's probably not worth the hassle of looking up the standard terminology.
Of course, in many cases it's better to just give the actual numerical range! But especially in public-facing communication it can be more natural to use natural language terms, and in fact this is already often done. I'm only proposing that when we do use natural language terms for probability ranges, we use them in a consistent and interpretable way (feel free to link to this post as a reference for interpretation, or point to the climatology papers cited below[2]).
Should the AIS community use the same terms? That's a slightly harder question. The obvious first-pass answer is 'yes'; it's a natural Schelling point, and terminological consistency across fields is generally preferable when practically possible. The IPCC terms also have the significant advantage of being battle-tested; they've been used over a thirty-year period in a highly controversial field, and terms have been refined when they were found to be insufficiently clear.
The strongest argument I see against using the same terms is that the AIS community sometimes needs to deal with more extreme (high or low) risk estimates than these. If we use 'virtually certain' to mean 99 - 100%, what terms can we use for 99.9 - 100.0%, or 99.99 - 100.00%? On the other hand, plausibly once we're dealing with such extreme risk estimates, it's increasingly important to communicate them with actual numeric ranges.
My initial proposal is to adopt the IPCC terms, but I'm very open to feedback, and if someone has an argument I find compelling (or which gets strong agreement in votes) for a different or extended set of terms, I'll add it to the proposal. If no su...