if global warming was real then it would be pretty trivial to just write a breakdown of the concept for laypeople to understand but instead i have to deal with ivory tower faggots smugly vagueposting about this every time it comes up as if it was as self evident as the rotation of the earth
When the sun shines on the Earth, it sends us lots of heat. That heat bounces off into space. However, some gases absorb that heat and keep it trapped on Earth. This is good because otherwise we'd all freeze to death.
A very long time ago, the Earth had a lot more of these gases in the atmosphere and was a lot hotter. Various things meant these gases got trapped in different forms, including fossil fuels. A long time ago the cycle of decay didn't work the same way so lots more got trapped. This meant the Earth got cooler. It still happens today, plants do it when they grow.
When we burn fossil fuels (among other things) we release lots of those gases, a lot more than our plants can recapture. That means the Earth traps more heat. That doesn't happen straight away. It also does not mean the Earth warms up evenly. Having more heat means the atmosphere has more heat energy, which can mean more extremes - in the same way that if you turn up the burner under a simmering pot, it starts bubbling more violently.
There are also really complicated other things. White things reflect more light, so ice bounces more light and heat out into space. When that ice goes away, it means heating can speed up. There is also something called methane clathrate, which is a fancy way of saying ice that has trapped a lot of a greenhouse gas. When that melts from getting too warm, it can speed up heating too. Some things, like the warm air and water that goes to Europe, could stop working if the saltiness of the sea gets diluted by melting ice. All sorts of things could result in the weather you normally have being very different.
This all doesn't mean the Earth will turn into Venus. But it does mean the world could look very different. The climate has varied lots and lots over history, but generally changes very slowly. The concern is that it is changing very very fast now. Too fast for plants and animals to adapt. Also our society is very complicated, and if our food can't grow like it used to in the same places, or our rain patterns change, or it gets too hot to live in certain places, it could cause big issues for all of us. Although we have lots of clever technology, the supply chains are very complicated, and this sort of disruption could mean we can't easily use our technology. Things like drought or famine could kill lots of people and also lead to wars over resources, or many refugees trying to get into countries where things are still ok.
How's that?