I doubt that it's possible to be certain of anything.
I don't want to say I know it's not possible to be certain of anything, of course, because in that case I can be accused of claiming I'm certain that we can't be certain of anything, thus contradicting my own claim through the magic of language. And, in fact, I'm not certain it's not possible to be certain of anything. Unfortunately, I'm certain that I'm not certain it's not possible to be certain.
There are problems in the use of the word "certain," then. There are also problems in the use of the word "true." For that matter, there are problems with the use of the word "know." These problems may be usefully addressed by philosophers--I'm not certain that's the case, however. John Dewey, as we know, maintained that "truth" was problematic and so, being inclined to awkwardness in the use of language, substituted for it "warranted assertability."
The problems caused by the word "certain" and its synonyms are not merely those which may befuddle philosophers, because the problems of philosophers can also be problems in what certain of them delight in calling "ordinary, day-to-day life (or existence)." At least they can if we let them. And to a certain extent I think we have, as we have come to accept that it's desirable to be certain, and even that we must be certain.
Certain of what?--you might ask, and I do ask, rhetorically. Certain of anything of importance to us or to others.
Dewey wrote of the difficulties resulting from the desire or need for certainty in The Quest for Certainty. One of those difficulties is that we convince ourselves that only what is certain can be considered true, or good. Having done so, we necessarily despair of or denigrate what takes place in our lives, because very little of what does or will take place is absolutely certain. So, we come to believe that we, and the world, are defective in some way, and true certainty lies elsewhere. Or we come to doubt our senses, our judgments, our actions.
Even in ancient times, there were skeptics (who are, unsurprisingly, called "the skeptics" or sometimes "sophists") and they apparently would wander about Greece annoying people with their skepticism. They were so annoying that certain philosophers, such as Plato, felt it necessary to rebut them. In Plato's case, he did so through his character called "Socrates" who may or may not have espoused arguments which were similar to those of the actual Socrates. It was, and probably is, thought necessary to do so because certainty is thought essential by many.
Speaking only for myself (which is all that I can do in this case) skepticism doesn't trouble me. I'm unimpressed by the fact that we cannot know most anything with absolute certainty. I see no reason why we should. And, I'm quite content to make judgments based on the best available evidence, even if that means I cannot be certain those judgments are absolutely true.
In fact, I question whether any of us really doubt when we're not absolutely certain. If our conduct is any guide, I don't think we can reasonably maintain that we do. Though it's true we don't know with absolute certainty the sun will rise tomorrow, we don't harbor any doubt that it will; the possibility that it won't rise doesn't cause any worry or concern. There are many things we take for granted even when we know there is a possibility they won't take place. It's how we live, and we have no reason to doubt unless something arises which causes us actual concern or worry, or creates a problem. We don't normally require certainty in "ordinary day-to-day life."
So certainty as Dewey addressed it isn't quite the issue it is in life as it is in philosophy. We like being certain of things in life as well, of course. But we like to be uncertain, especially as far as people we dislike or positions with which we disagree are concerned. That is to say, we're selective in our demand for certainty.
The controversy, such as it is, regarding climate change is an example of the demand for certainty. The questioning of the theory of evolution is another. Those who deny climate change face a problem in doing so, because it appears that the vast majority of those knowledgeable in the area believe it exists. There are, however, a handy few who disagree. Thus, it can be claimed there is uncertainty--it isn't absolutely certain that climate change is taking place, or that humanity has caused or exacerbated it, so it may be discounted. It may as well be claimed to be a hoax, a kind of fraud being perpetrated for some reason by someone (what would motivate the hoax is unclear to me).
As to the theory of evolution, merely because it is overwhelming accepted by those knowledgeable and there is ample evidence for it, it can't be established with certainty. So, it can't be said to be true; therefore, it's appropriate for other theories to be taught, such as creationism. Uncertainty can have its benefits, for creationists in any case.
There may well be a quest for certainty, as Dewey proposed. However, the demand for certainty is something which doesn't universally apply. We don't need certainty to live, we disregard it in most cases. We demand it when we find it useful to do so. We find it useful to do so when we disagree with each other.
In that manner, the fact that people we disagree with can't establish their claims with certainty, and positions with which we disagree with can't be established with certainty, is a benefit for some of us. It allows them to hold untenable opinions and make unreasonable decisions serenely, secure in the knowledge (so to speak) that it doesn't matter whether they can't be certain of them because nobody can be absolutely certain of anything.
The idea that no belief can be criticized because nothing is certain can be reassuring, in some cases.