Wow! Did you know that climate change isn't created by humans at all? Nah. That's wrong. It so happens, that it's scientifically proven that it's humans who have caused climate change!
Not at all! That's just a theory! Well yes, Tommy, it's right that the greenhouse effect and the global climate change that it causes is a theory. But it's not just any old theory, it's a scientific theory. And that means something different from the everyday use of the word 'theory'.
Like this: All over the world there are scientists, researching all kinds of things. In many cases several different researchers are working on the same issues, trying to answer the same questions. Often they cooperate with each other. But, most researchers also want to be the first one to find and present the next big discovery in their field. So, there is also quite a bit of competition between researchers.
Here's a group that does research on the climate. They have a hypothesis: they suspect that the amount of carbon dioxide that the oceans can take up, is affected by how hot it is in the air. Now they have tested their hypothesis by carrying out an experiment, and reached the conclusion that, "Yes, higher temperatures lead to reduced carbon dioxide uptake." Good job! They have created new knowledge! A new piece to the giant jigsaw puzzle of knowledge, that can explain how the earth's climate changes.
The researchers write an article, where they describe their investigation. They describe what it is they have been studying... ... and exactly how they have gone about doing it -- what method they have used. And they explain what conclusions they have been able to draw from their work. Now, other researchers can read the article, and see if the conclusions agree with their research.
Because the article clearly states exactly how the experiment was carried out -- what method was being used -- these other researchers can try doing the experiment again themselves. And see if they get the same results. They replicate the experiment. If several teams of researchers replicate an experiment, and reach the same results, then it is more probable that the conclusions are correct. The piece of the puzzle gets better and better.
But sometimes things can go wrong, and researchers reach conclusions that are not correct. Maybe they weren't careful enough with the measurements. Or perhaps they wanted to be successful and famous, and falsified the results. Maybe the researchers received money from someone, who then pressured them to reach certain conclusions. When these things happen, researchers produce false pieces to the puzzle that don't add any real knowledge.
Such faulty pieces are normally not spread around very much. They might be detected so soon, that nobody wants to publish the article. Or, it might turn out that the experiment can't be replicated with the same result. In that case, researchers will find out that the conclusions weren't right. Meanwhile, a lot of other researchers keep working, experimenting and finding support for -- or disproving -- their hypotheses.
Researchers keep adding more and more pieces to the puzzle. In time, the pieces form a whole, coherent, image: a scientific theory. A scientific theory is something bigger than a single result from a single experiment. It is a coherent description of an area within science, that is supported by several different experiments, observations, and inquiries. Such as the theory describing gravity, Plate tectonics, Evolution, Or the climate!
But you have to be aware! Because, those bad pieces of the puzzle, the faulty conclusions, they are still out there. And sometimes they are used as proof for things that are not true at all. So, a single piece of the puzzle, a single scientific report or article, can sometimes be incorrect. But an entire puzzle that fits together - a scientific theory - is something you can usually trust.