For all of you climate change deniers:
CxHy + O2 --> CO2 + H20
CxHy (a hydrocarbon) like the one you fill up your gas tank with (octane) produces carbon dioxide and water when combusted in the presence of naturally-occurring oxygen.
The actual balanced chemical equation is here:
2 C8H18 + 25 O2 --> 16 CO2 + 18 H2O
As you can see, combusting two moles of octane actually produces 16 moles of carbon dioxide.
Okay, so we're producing the CO2, but how is it causing climate change?
CO2 is a larger molecule than the two major atmospheric gases, Nitrogen ~78% and Oxygen ~21%. And being very unreactive (does it blow up when you exhale?) the gas becomes settled in the atmosphere. Large amounts of CO2 form a 'blanket' that trap solar radiation that was once reradiated into outer space--this is known as the 'greenhouse effect.'
How does this affect sea levels rising?
From our old equation D=m/v we can solve for V: V=m/d. As we all know, as something heats up, it becomes less dense-->this DECREASING density INCREASES volume. So as planetary temperatures rise, ocean volume increases.
If you need more evidence, look to the dying coral of the ocean. Composed of calcium carbonate, coral is being destroyed by rapid ocean acidification. This same process takes place in our bodies:
CO2 + H2O -->H2CO3 (carbonic acid) carbonic acid kicks off two H+ protons in the process of forming carbonate. These acidic protons have contributed to overall ocean pH decreasing from ~8.25 --> ~8.17, which although measured on a logarithmic scale, is absolutely massive considering the sheer volume of ocean water.