Do coal and oil burn? Does money corrupt? Have scientists ever learned anything? Is water wet?
If "only" 97% of scientists agreed DDT was toxic, would we still spray it everywhere? WHAT?!? If only 5% of them thought it was, we'd stop spraying and investigate. How many scientists thought DDT was harmful? More than 50%? More than 90%? More than 10%? That never was an issue, nor should it be. And remember: the impacts of Climate Change are inconceivably greater than those of DDT.
Climate Change Deniers (no, they're not "sceptics") are saying that we should continue to pour these pollutants into the environment because a few people think there's nothing wrong with it. That's rather bizarre. The only reason we hear them is because some people make lots of money from burning oil & coal, these people influence the press, and to some extent the governments. And lots of people can be bamboozled for a while, if you control where they get their information. (This is how it works)
Yes, Climate Change exists. Some scientists worked this out over 100 years ago, and clear evidence was available 50 years back.
How can you know? If you're a Climate Scientist then read the IPCC reports. If you're not, but you are a technical scientist then read the "summary for policymakers", otherwise, ask a few Climate Scientists. Just like you ask a car mechanic what's wrong with your car. Just like you know smoking is harmful, and you know the earth orbits the sun, and you know your phone works, even if you don't fully understanding the scientific detail. You rely on the experts.
For simplified (but not trivialised) physics try Richard W Erskine's essay: Demystifying Global Warming.
If you've heard the arguments from "deniers" about wobbles, ice shelves, etc, have a look at the facts relating to these specific issues here at Reality Drop.
Here's a lighter look at the question: (one instance of bad languange..)
or a slightly more explicit explanation from the Union of Concerned Scientists below...