So, what could "1430x climate damage" reasonably mean? Note that it isn't just "climate change".

There are basically two methods used to create these numbers:

1. Someone creates a score, that has no inherent meaning, based on a bunch of different properties. In that case, the precise values aren't meaningful, but higher and lower can be useful for categorizing different compounds.
2. A climate model with very large known flaws and wide standard errors is used to create an estimate that is then fed into an economic model that is known to be severely flawed. The reported number in this case is the estimated economic damage, but the confidence intervals are so large that you can't rule out that there's no effect.