Ozone went poof in one year
It starts with crops, deforestation and perhaps even Bitcoin mining (read this post and its comments before starting a conversation about the Bitcoin bit, pun intended), which lead to global warming. The world heats up a few degrees every year, until winds around the North Pole's polar vortex manage to heat it up.
So far, it was all about rising temperatures, but harsh winters come from that polar vortex monster. It's usually a very cold, high-altitude cyclone. In fact, its temperatures are so cold, wind currents don't even affect them. It's like when two seas of different colors meet, but never mix. In the case of air, it has to do with pressure.
But then global warming came, heating up winds enough to mix with the polar vortex, reducing pressure differences. The polar vortex mixes with the surrounding air, spreading out all the way into the continents, causing extremely harsh winter in places like New York City. Up until this point, most people can easily access this knowledge.
In 2020, humankind witnesses a new event never before seen: South Pole's ozone hole is Huge. Gargantuan. Humongous. Absolutely gigantic. But this is extremely unexpected, because in 2019, the ozone hole had basically closed completely. The question is: what the heck happened? I'm glad you ask.
South Pole's polar vortex is a completely different beast. There is nothing capable of warming it up like in the Northern Hemisphere, because wind currents don't travel in similar paths. This polar vortex has a much lower temperature compared to its northern cousin, ranging from -50 °C to -90 °C.
Both last year and now in 2021, South Pole's polar vortex didn't increase when it should, during November and December, when it's summer. In fact, temperatures remained as low as -80 °C when it's usually brought up to -60 °C. A difference as great as 20 °C is terrible, because it helps shape up high-altitude (stratospheric) clouds.
Oh no, clouds! What are we going to do!? Uh, these clouds don't do anything harmful by themselves, but when Earth is tilted just right - during summer - the Sun really lights up the South Pole. Sun radiation interacts with these clouds. The chemical reaction liberates chlorine, which then interacts with the ozone layer, effectively destroying it.
The ozone layer haunts us yet again
So we have this really big hole, a lack of the greenhouse gas called Ozone. It usually helps heat remain within the planet. Now that it's gone, a lot more heat than usual is slipping away from Earth through the ozone hole. Less heat equals even more time under a low enough temperature to keep creating more of these clouds, which are also eaten up by Sun radiation and then destroying even more of the ozone layer, letting even more heat slip out, prolonging the cold, so more clouds form, destroy more of the ozone, and then...! Repeat.
This means a cold enough temperature sustains the problem for many months all on its own. That's why I'm freezing here in Brazil, where the winter is 10 °C degrees colder than usual. (Help!)
Where do we go from here? No one knows. Will this lower temperature help stop the next year's global warming, stabilizing our world, or is this cyclical temperature madness here to stay for good? Time will tell. I bet you, though, no one would have guessed that healing the ozone hole too much would create a new problem.
Maybe planting some forests would help fight the spark of global warming though, as it all starts with excessive heat. Getting rid of the root of all problems often fixes everything.