memes

Well nothing really "happens", but more trends we see now will continue and intensify. Think drought, extreme weather including flooding, harsh growing conditions in general. Fires, deforestation, loss of animal life in general, warmer oceans and rising seas.

Uhh not sure what else, theres a lot of questions on how our society will be able to respond to the changes to our understanding of the entire global landscape. Wars may be fought over resources like water. Immigrants fleeing from places now too hot/inhospitable to realistically make a life. How will we respond to life as we know it changing drastically in real time all around us?

When ice forms, it traps small airpockets in it, so we take samples of ice from the polar circles kilometres deep, date it, crush it to release the air pockets and measure the air contents. Then we can see how different the CO2 amounts were to now.

Source: there's a fuck ton of different articles that talk about this, and this is the first one I found of Google, search yourself for more.

Its ice core data, this nature article describes it if you can access it somehow. "Air bubbles in ancient ice cores" is what NASA says

Maybe spend a few minutes googling this stuff because it's been answered many times over and it just looks like you're deliberately trying to poke holes in what is ultimately very well established scientific fact.

To give you a TLDR though it's ice cores. You look at the air trapped in ice cores, the deeper you drill the further back in time you go because the ice and therefore the air trapped inside is older.