19 years

19 years on this planet,
Do you not feel like your life has ran its
Course and filled the earth with your joy
Not sure there’s really much room left
That’s more likely why there is a whole in the ozone layer
Not greenhouse gasses it was your excessively large smile!

19 years on this planet,
Not sure your life has really ran its
Course. I think there is much more left to give,
Your smile can grow and get much more big
So god help us! This ozone hole might kill us all
But it is well worth it if your having a ball!
Ayways. HAPPY BIRTHDAY my dear.

I like the idea behind this, and also that it's a birthday poem. Just a few nitpicks:

19 years on this planet, ["19" should technically be spelled out.]
Do you not feel like your life has ran its [it should be "has RUN"]
Course and filled the earth with your joy
Not sure there’s really much room left
That’s more likely why there is a whole in the ozone layer [I'd get rid of "more." Also, "whole" should be "hole".]
Not greenhouse gasses it was your excessively large smile! [I like this line, but you should have a hyphen or semicolon or something between "gasses" and "it".]

19 years on this planet, [again, spell out nineteen]
Not sure your life has really ran its [again, "has run"]
Course. I think there is much more left to give,
Your smile can grow and get much more big [should be "bigger," not "much more big"]
So god help us! This ozone hole might kill us all
But it is well worth it if your having a ball! [it feels obvious that you were trying to rhyme here, and rhymes should not feel forced. Also, you didn't rhyme at all in the first stanza, so it feels weird and Hallmark-y that you start rhyming here.]
Ayways. HAPPY BIRTHDAY my dear. [eh. I like that this is a birthday poem, and you can end on a "happy birthday," but the way this line is written doesn't sound as powerful as the rest of the poem - I would suggest getting rid of "anyways" and "my dear" and just say "happy birthday," not in capital letters.]

Overall, I did like this piece, especially the line "not greenhouse gasses it was your excessively large smile." Not sure why, I just really liked that line... Anyways, hopefully my nit-picking was helpful.

~Blue

I liked this poem. it was really good. I liked the idea of it. Keep writing.