Assuming.

Assuming that happened: what happen with the CO2 created at that time?  Where did it go?

No, it wasn't Co2 that killed most living creature long ago, neither dinosaurs; what killed most creatures then was the position of the solar system in respect to our Milky Way galaxy, it took a few hundred million years for Planet Earth to move into a position different than that of its original position that permitted some variety of creatures to exist ...planet earth moved further into another position around our Black Hole in such a way that it permitted new life to take hold in the planet, so by accident (mutation) the amino acids precursor for Human DNA via RNA, was created, not Dinosaurs again on the reason that the Nebula which the earth passed through contained less O2 and more of the mixtures of other element; life started again, the ingredient for dinosaurs were there, but with poor amount of O2 in comparison to the huge amount of O2 needed for the amino acids to evolve into huge (chicken-like) creature with enormous sizes as known today it existed.  Man was created of the rich emulsion of gases well abundance on the surface of the planet: evolution took a different route to yield: Homo sapiens, now turning into Homo sapiens-sapiens (recently).

This Homo sapiens-sapiens is still evolving, from Earth to the moon.

On reference to our Earth moon this is this: http://www.foxnews.com/science/2017/10/19/caves-discovered-on-moon-raise-hope-for-human-colonization.html

Colonizing the moon via its caves was a secret I guarded for long time with the hope that once US decide to go back, my message would be: "HARRY!" The first that start using any cave would be the first "MoonOwner" no matter what we tell here on Earth: United Nations.  And now that a crazy guy, millionaire and incredible person got that idea, I felt happy I was not the only one who was crazy, so I am not alone.  And that was why in my private designs of what to colonize first (Mars or the moon), I wrote in my personal scrape notes: the moon, then Mars almost at the same time (with 10 to 20 years differences).

If US succeeds colonizing the moon, Mars is a sweet banana to colonize, for it would be easier to travel from the moon to Mars by 3D-ish devices fabricate on the surface of Earth moon due to gravity (less mass energy storage and stronger dynamo in its engines, this is, stronger push to abandon the moon surface and advance to Mars.

It was my secret, now known, for someone else with a phenomenal dynamism in science is helping to give it a push to extra celestial bodies.

This step must and shall be done now at the very beginning of our 21st. Century or else US will lose all its investment in celestial exploration on the reason that someone else (other nations), will use all our energy already known around the corner of Plannet Earth (scientific advances) for their own benefit and harvesting ...the time is now or else!

Humans are not sedentary, Humans are gregarious animals, this is the way how they could evolve into a higher class as is today the Homo sapiens-sapiens they are as of now.  Evolution doesn’t stop as humans will keep evolving on the moon and Mars in such a way that even though they will look a little different in phenotype, their genotype will be the same.

Humans group into nations in accordance to the niche where they live; so, we have Russians, Chinees and Latinos with slit differences by same genotype as humans.  At the moon and Mars, the same will happen.

Now, one of the problems that humans have is that sometimes they want to keep its ethnicity and transport that into different regions as eliminating the ones already in existence over that region.  But in the case of the United State, this Nation State is not looking for that, but its existence at which it includes all regions.  In term to China, Russia, Spain and England, there is a littler variant in that thinking for they look for their root in nationality and that is why the US doesn’t look, for it wants to exist as a multi-national Culture where there is abundance of open-minded people contributing to the Science-technological development of the nation …a great problem is been born from old practice of old centuries habitat: Extreme Capitalism.

With extreme capitalism, science would advance in small steps as opposite to just capitalism at which everyone is a player for the existence of US based on Science/tech advances in giant steps.

US would melt within it any Russian or Chinese culture at which it would make US culture still greater (just as a reference, for any culture is valid here).

The existence of Humans from the Democratic point of view is better guarantee than from any other point.  Humans commit crimes in order to satisfy its need.  In a modern Democracy, crimes still will exist, but it would be in a lesser magnitude as compare as in mass killing of not long ago and still more to happen.

By conquering outer planets be them moons or planets such as Mars, Human would rapidly evolve to near a true Democracy because they all would need each other for their own survival.

Humans to exist need H2O from where they could extract most of its living material.  Now, as humans evolve there are some of them, just individuals, that interfere with that human advance.  This are the so known spies in tech.  This spies in tech work to benefit just a human culture, not all together, US call them Traitors to Democracy such as Eduard Snowden and a lot of Whistler blowers that don’t see on the future of all humans.  True it is that some governmental department had committed some form of crimes, but those crimes are selective against some humans that intend to destroy Democracy as is in the case of some humans called: terrorist; not crimes committed by Democracy against whole population.  Humans have to exist, so selective crimes have to be used to destroy those that intend to destroy humanity in the nave of abnormal believes after death.  Too many whistle blowers don’t know of this concept described above.

To understand evolution, humans must be understood from its point of origen, continuing from its biological point and seen all the lags in its social habitat: history, its created physic as well as its philosophy, which is too complex.  Yet humans are just starting to understand itself once it has the intent to travel outer space.

On Climate Change.

Why I disagree with Climate Change: there are active volcanoes every day of the week, mostly; as the earth spin on itself and around the Sun, it also spins around our galaxy the milky way almost in the same manner.  Being that, some million years the climate for billions of things around in a section as planet earth, change too. It causes that all life on earth extinguishes creating new generation millions of years after.  That's why archeologist could see different layers on the surface of Earth with different creatures that existed.  Dinosaurs were the last ones.  Also, assuming that a meteor landed in what's today Golf of Mexico, and all of planet earth were set on fire, there would be burned Dinosaurs bones, of which in reality there are none. There would be burn ground of which there are none.

Yes, the Climate is changing on the said above: "spinning". Humans are to be gone (die all) in the future unless Human learn to live in a subzero climate change using fusion energy as some many others intelligence things had done too. Later, I will tell how the Solar system was formed.

Note: it is very good to correct things that pollute the Climate, for it improve humans living condition, health and existence but the so call "Climate Change"