So I did this math for an ELI5 and was floored with the results. Everything after this is a copy-paste of my post there except for an added comparison to d&d that hit me after and I was too lazy to go back and add it to the ELI5. This was done on my phone late at night, so I welcome any and all corrections.
Let's start with what is familiar in your home. The energy required to heat 1kg of water 1C is 4,200 joules. How much is that? It's enough to power an average LED bulb for about 10 seconds.
How much water is 1kg? Not much, so let's bring that number up a bit. 1 cubic meter of water weighs 1000kg! So about 1 Minecraft block of water is 1000kg. Heating that 1 Minecraft block of water takes enough energy to power a bulb in your house for 10,000 seconds, or over 2.75 hours.
So that's a respectable amount of power for 1 cubic meter. Your next question should be, "how many cubic meters of water are in the ocean?" We'll, it's a stupidly huge number, so let's scale up again, to 1 cubic kilometer. Now, your first instinct might say "that's easy, 1 cubic km is 1,000 cubic meters" but you'd be wrong. We're working with volume, so 2 cubic meters is 4 times as much water as 1. So that means 1 cubic km, is 1,000,000,000 cubic meters! That's 1 billion! You want to know how long you could power that bulb for? Over 300,000 years! Holy shit! That's a lot of power!
And we're not even done yet. Now do you still want to know how much water is in the ocean? Are you sure? We'll ok then. 1.332 BILLION cubic kilometers! That's 400,000,000,000,000,000 years of LED power! The life of the universe is a drop in the ocean compared to how long you could power a light bulb with the energy it takes to raise the ocean 1C!
That lightbulb just isn't working for an understandable scale anymore. Let's try something else.
So raising the ocean 1 degree takes 5,594,400,000,000,000,000,000,000 joules. The atomic bomb, dropped on Hiroshima produced 1,000,000,000,000 joules of energy. Raising the ocean by 1 degree. Takes 5,594,400,000,000 as much energy as was dropped on Hiroshima. 5.5 trillion times. If we had 5.5 trillion bombs, and sold them for $4 a piece. We could pay off the national debt.
The tsar bomba, the largest nuclear device ever detonated, produced 1,500,000,000,000,000 joules of energy. Raising the ocean 1 degree, takes as much energy as 3,729,600,000 tsar bombas. Give every other person on the planet the largest nuclear device ever detonated and we could raise the ocean 1 degree.
NOAA shows that the surface temperature of the ocean has risen .13C over the last 100 years. Let's make an incredibly cautious assumption that that is the only part of the ocean that has warmed, and that that amount accounts for only 1% of the ocean. That's 51,643.8 tsar bombas every year. That's 1 tsar bomba every 6 seconds. If you play D&D, That's 1 tsar bomba per round. Humanity is casting level 5000 fireballs every round and really needs to stop.
That is how much our planet is warming. That is how much extra energy is being trapped by greenhouse gasses. That is why this is an emergency.
Edit: clarification of 1C and first paragraph to explain what is going on.