97% of all climate scientists agree on what is happening. Temperature is rising overall right now - about 0.8C/1.4F over the last 100 years and most of that in the last 35 years, and there are reasons for why it is not linear - the sun's output varies, we have volcanic eruptions which put up ash which temporarily cools things, and as I have said, there is a 30-40 year lag because it is the accumulation of more heat over time. There is a lot of "momentum" in the system.
There have been many climate changes in the past, and they were caused by different things in different combination. The temperature increase we are currently in now is being caused by a new and different thing that has never happened before - and that is we humans burning fossil fuel.
These past changes only matter because of what we can learn from them. This current very rapid change (rapid in the geological sense of the word) is not like those previous events, and yes that means that we can't know *precisely* what will happen in the future - but we *do* know generally what will happen.
There is massive amount of data from all around the globe - keeping each and every one of them all through the data set is not required. We have new methods of collecting data being developed all the time - we now know how to date when an ancient glacier melted.
All science keeps finding more questions than it answers, and the more we learn, the more intelligent questions we can ask. But, we know enough about what is happening now to be very concerned. We are causing most of the increase in carbon dioxide, which is the main driver of the current warming climate - and that means we can do things differently and begin to mitigate the worst of what could happen.
I seek to learn as much as I can, all the time. I learned several new things watching these: