I'm not sure who to believe on this subject
I'm not a scientist and I'm not sure either.
From the layperson's perspective it's basically an argument from authority, a demand that we have faith in what the elites tell us. How successful that kind of rhetoric will be depends on how much confidence we have in the elites. Given how passionate and politicized this subject has become, and how linked it is to grand social-change agendas, and I have to say that my own confidence is limited.
I've heard that the climate has changed before and that the ice caps have even melted before
If we look at the Earth's whole geological history, there have been tremendous climactic changes that had nothing to do with human beings and whose causes remain poorly understood. There apparently have been periods when the Earth didn't have any polar icecaps at all, and researchers have suggested that there might have been a period long ago when all of the Earth's seas were frozen, even at the equator. (The 'snowball Earth hypothesis.) That's the range of natural variation seen on this planet and we seem to be well within it today. Certainly it's well established that the last ice-age lasted until comparatively recently, about 12,000 years ago, and that its end was a global warming event that dwarfs anything seen today in magnitude (though perhaps not in rate).
but global warming is still being mentioned
I'm inclined to believe that it's been happening over the period in which good measurements have been taken, the last 150 years or so. Obviously a lot of the rhetoric that laypeople are subjected to is total hyperbole, such as the hysterical talk of this being an extinction-level event. But I'm reasonably confident that some changes have been observed.
and governments are even trying to take action against it
Within reason, some of those actions are probably good ideas even if global warming wasn't a concern. We are going to have to start weaning ourselves off fossil-fuels at some point, since their supply is limited. It's advisable that the West not be dependent on the Middle East for its energy supplies. And China has a terrible air-pollution problem that it really needs to get a grip on.
there are people who say that it's a scam
It's a highly politicized cause, whatever else it might be. It's probably well past the point where we can expect dispassionate objectivity from anyone. Hiring and tenure decisions depend in part upon people expressing the 'correct' opinions on this. Authors' access to journals depends on it. So outsiders start to wonder whether the conclusions are being driven by the data, or whether the data is being driven by the conclusions.
I'm certainly in no position to know precisely what the truth is. But people are demanding my faith nevertheless and I'm just not prepared to give it.