# Did climate cool down when underground hydrocarbons stocks formed?

As far as I understand, the dominant theory of modern climate change says that recent warming is mainly caused by the massive burning of hydrocarbons that used to be stored in solid form mostly underground as petroleum, coal, etc.

This suggests that the reverse process should contribute to a cooling of the climate (or to a slowed down warming if other processes are at play at the same time).

In particular, a cooling should have occurred throughout the period when the stocks of underground hydrocarbons were formed by the "pilling" of organic remains.

My questions:

1. Is this roughly what climate theory would predict or am I omitting some things?
2. Was such an effect observed during the formation of the underground stocks of hydrocarbons?
3. Can this reasoning be extended to say that a world where no solid hydrocarbons are burnt and the concentration of atmospheric hydrocarbons keeps falling (as it is captured by organism and transformed into solid hydrocarbons) would experience a continuous (if slow) cooling? Or are there some non-linearities by which the stock of solid hydrocarbons would "max out" or the effect of removing carbon from the atmosphere fade away?
• Bro, you have to understand an increase in any other stable form of carbon not in the atmospheric reservoir result in a reduction of greenhouse gas (The total amount of carbon on Earth is relatively constant as far as I know since exchange with space is minimal). It does not have to be hydrocarbon underground, it can be trees (lignin) aboveground and humus at undisturbed soil surface or even a wooden building etc. – y chung Apr 13 '17 at 18:17

Possibly

One thing you have to understand is that natural carbon sequestration via the formation of fossil fuel is VERY slow, it can take millions of years to build up the coal we burn in a day. In addition, one of the more dominant effects on the climate is solar radiance and continental position which changes over such long stretches of time, making matching such slow changes to carbon with climate change more difficult. Continent position also affects carbon sequestration and CO2 concentration directly making it even more confusing. Things like seaways and deserts can have huge effects on CO2.

The real problem is matching coal formation to changes in CO2 concentration. Most coal comes from the carboniferous and the permian time periods (along with the evolution of land plants that make it), the carboniferous saw severe cooling and severe drops in CO2. How much of this is CO2 lost to coal versus how much is just the formation of forests and other terrestrial ecosystems combined with changes in contingent positions is still up for debate.

The permian however saw severe warming near its end and a rapid rise in CO2 at the same time, but most of it was relatively stable and unchanging both in CO2 and temp. It also included one of the largest volcanic events in earth's history, and again changing tectonic position. So although the link between CO2 and temprature is really well established we can't even say for sure such slow coal formation actually reduces atmospheric CO2 concentrations.

source

Compare CO2 above to temp (red line) below. Note that just three variables together predict temprature amazing well.

source

The carboniferous period was 350-270 million years ago. The content of C02 at that time was close to 3000 ppm, but this fell to 200-300 ppm by the end of this period. The average temperature of earth during this period was 20-25 $^{\circ}$C this fell to an average of 12 $^{\circ}$C by the end of the carboniferous period. So, the answer to your question is this, the carboniferous period ended because of climate change, the drop in CO2 was the main reason for this. a lot of CO2 was also used in the creation of calsium carbonate(limestone) there was also heavy volcanic activity during this period this do lower the temparature atleast in the short time during the eruption and a few years there after.

the last part of your question is basicaly can the co2 level get too low. the level of co2 are regulated by plants if it falls, several things will happen,plants will grow slower the temparature on the earth will go down making plants grow even slower. but this is higly unlikely to happen as long as the suply of co2 is continued.

• Source for 3000 ppm please, becasue I have never seen an estimate above 1000 ppm at the highest. – John Apr 13 '17 at 19:05
• Not a great source since it doesn't tell you were it gets the number, but it is consistent with newer works. I was thinking average for the carboniferous not maximum. totally my fault. – John Apr 13 '17 at 21:04
• @trondhansen If you add one or two peer-reviewed references to the 3000 ppm and the temperature range 20-25 C I will be happy to give a +1. – daniel.neumann Apr 14 '17 at 17:34
• I think this answer could be fleshed out a bit as it's basically just 2 data-points, beginning and end, but it's still essentially correct. – userLTK Apr 14 '17 at 21:35
• i did use the numbers on wikipedia,if anybody want feel free to add more information to my answer,feel free to alter it too.johns answer is way better then mine. – trond hansen Apr 15 '17 at 7:05

At the instant any atom of carbon is taken out of the atmosphere by a plant or animal and incorporated into its structure then that atom is "off the list" as it were with respect to having an effect in the atmosphere. Once in the animal/plant it may be there for eons until it becomes oil, coal,or whatever. So it is not the ultra slow conversion of organic matter to hydrocarbons that is relevant but the amount taken up by living matter on a daily basis which is sequestered into its structure.

Looking at the historical record we would therefore need to think about the amount of animal and plant activity on the planet and, to some extent, its type. This is quite difficult as we only have proxy records. however as we know that CO2 is effectively plant food it seems reasonable to assume that if the proxy record shows high levels of atmospheric CO2 we might expect that fairly quickly, a few year/decade timescale, that plant life on earth would respond quickly and become very lush indeed.

This is of course only one factor with respect to CO2. Past volcanic activity is likely to also be relevant.

• It sounds to me like you're describing primary production and missing the outgoing decomposition/respiration terms. The net flux is a relatively small difference between the large input/output terms, and the atmosphere responds to that rather than the gross terrestrial uptake. – Deditos Apr 18 '17 at 10:06
• An observation of any natural forest, woodland, scrub or indeed any bit of "left to nature" land with plants on it shows that the decaying bits do not all decompose but that the level of the soil builds up. This is why archeologists have to dig down to find old buildings, the surface has risen due to tons of soil i.e. decayed plants. Soil typically is 10% carbon by weight. Therefore a big increase in "lushness" will "trap" significantly more carbon in the very slow (sometimes static) decomposition cycle. Some never decomposes of course- e.g. coal. – user7733 Apr 19 '17 at 19:48
• @Deditos. You other comment about me ignoring respiration is wrong as I specifically said carbon atoms "incorporated into its structure". i.e. not carbon atoms used in regular in/out processes like respiration. It is the carbon atoms "trapped" in the plant that are of interest here. – user7733 Apr 19 '17 at 19:50
• Bit slow replying, sorry. Okay, so I can see you're saying that the vegetation+soil pools form a buffer between the atmosphere and the fossilized pool, and that buffer could potentially expand quickly. But that would need a similarly quick forcing of some sort - what are you saying that forcing is? Atmos CO2 was already high, and globally the veg+soil pool was more or less in balance with it. It was the slight tipping of that balance by changing veg strategies that allowed the slow accumulation of carbon in the buffer. – Deditos Apr 24 '17 at 16:31