Scientists have worked hard to retain integrity while making their work more relevant and accessible to society. One outcome has been the following in the Summary-for-Policymakers of the Climate Change 2001 Synthesis Report by the Intergovernmental Panel on Climate Change (IPCC).
"Confidence and likelihood statements"
"Where appropriate, the authors [of working group 1]... assigned confidence levels that represent their collective judgment in the validity of a conclusion....
virtually certain (greater than 99% chance that a result is true);
very likely (90-99% chance);
likely (66-90% chance);
medium likelihood (33-66% chance);
unlikely (10-33% chance);
very unlikely (1-10% chance); and
exceptionally unlikely (less than 1% chance)."
It is worth reviewing the statements considered to be virtually certain. There are VERY few cases in our lives and societies where we are that certain. Typically, we are very happy making decisions based on what the IPCC considers "very likely" understanding.
What would you do if your car mechanic told you it was "very likely" that your brakes would fail if you did not fix them? More accurately, what would you do if you took your car to ten mechanics and they all agreed it was "very likely" that this was the case? These hypothetical mechanics might not be willing to say to the minute when your brakes would fail--they're not certain about the exact timing. But they might say it's "very likely" to occur within six weeks.