When you're young, you often have to depend on adults to help you understand how the world works. Grown-ups seem to know everything or sometimes nothing. What does a smart, rational person (yes, kids, that means you!) do when someone in authority, older or with more experience tells you something works a certain way or is a scientific fact?
Sometimes teachers and parents know important things--like you need to wash your hands to keep from getting sick. Then you look around and Derrick over there never washes his hands and is perfectly healthy. What's up with that? Why isn't Derrick sick? Don't parents and teachers know anything?
It will always be true that there are exceptions to general rules--like hand-washing. It's believed that over the long run, hand washing helps prevent the spread of disease. It's based on past experience and observations. Does this mean everyone who washes their hands will stay well? No, but based on the way diseases are spread, it is more likely people who wash hand will be sick less often than those who don't.
What about more complicated ideas--for example, are we changing our climate by burning fossil fuels and we are going to cause a very severe temperature rise on the planet? Your teacher may have told you "everyone agrees" this is happening. That is not true. There are many climate scientists who do not agree that our burning oil and coal and natural gas are threatening our planet. These things do have an effect, just as everything on the planet affects everything else. Climate is very complicated. Wait, though, our president said it's important. Yes, President Obama did say global warming is real. He also said "We don't have time for a meeting of the Flat Earth society" which was meant to insult those who do not agree (we know the earth is not flat so he wanted to make people who disagreed look foolish). However, it turns out some members of the Flat Earth society do believe we are changing our climate with fossil fuels. That shows clearly that there is not agreement on this and trying to insult others is not really a good way to convince people you are right.
Studying the climate and global warming also got mixed in with politics, which is a very bad thing. Science is based on evidence, politics is mostly based on emotions. So politics is what is out there trying to make people feel guilty about driving cars and living a modern life. That's not science.
How, then, can you know what is science and what is politics? Asking questions can help. Ask why the fossil fuels hurt the planet. You may get and answer such as "It's physics". Part of it is, part of it is computer models and mathematics which are not always accurate. If when you ask about why fossil fuel burning is bad the person calls you names (like denier or says you're just stupid) it's probably because this is something they believe but they don't know why. Or it could be that the person just doesn't want to be asked questions on their beliefs--which means this is politics. Science loves questions and will always take the time to explain.
Global warming is important we are told and very dangerous. There are all kinds of scary predictions. Shouldn't we DO something? Shouldn't we be worried? These are important questions. If fossil fuels really are hurting the earth, shouldn't we stop using them?
What if we did stop using fossil fuels? We would have to give up full-time electricity, cars, and go back to the old way people lived, without lights, cell phones, television, computers, etc. It would be very, very difficult and would harm a lot of people. We know this harm will happen, while we don't know for sure if CO2 and fossil fuels are actually going to cause something bad.
Wait--how about wind and solar? Can't we use those? They have free fuel. Yes, the fuel is free. The electricity is part-time and only when nature delivers it, not necessarily when we need it. Making the turbines and solar panels takes fossil fuels and mining. Then there's installation and we change the landscape. Plus, both forms of energy are very damaging to bird and bats. Neither energy source is practical today--it's why we stopped using such things and went to fossil fuels.
You're a young person who has heard all the scary stories about climate. How can you know what is true and what is fiction? Honest answer--you can't. What you can do is sensible things to keep the earth livable, like not littering, not wasting energy, reuse things and so forth. There are energy efficient lights, recycling, fuel efficient cars all of which are fine things to do if it's what you want to do. Will it save the planet? It's doubtful, both because these things are very small cuts in usage in the big picture and because we really don't know the planet is in need of saving. These are just ideas that make people feel good and do save on clutter and landfills. Keeping the planet reasonably clean is just a good idea.
Should you be worried the planet is dying--no. The science is not complete on what is involved in climate regulation on earth and whether we humans can really cause massive changes in the climate. It may not be understood before you have grandchildren. Maybe not ever. Panic and fear are the wrong responses to changes on the planet. It's also wrong to burden children with this and very wrong to try and frighten children into believing that global warming is absolutely true for political gain. Sadly, that is very often done as you can see in the news with all the name-calling and insults about those who do not agree with the global warming science.
How should you deal with this? You can be the person who finds a new efficient power source--one that truly revolutionizes things. You could be the one that does what Henry Ford did and takes us to a new way of traveling (I still want flying cars! Maybe you could be the one that creates one!) Maybe you could do like Edison and find a new way to make light (LEDs are a good start). What the planet needs is smart, curious people who try to make life better, not someone preaching fear and doom while demanding people go backward in their living conditions. Ask questions, study science and math. Learn how things work and take us to a better future. That's what you can do!