Comment by lisa_henderson | Hacker News Reader

Comment by lisa_henderson | Hacker News Reader

The title says "All Our Fossil Fuels" but they really mean something like "all the fossil fuels we are likely to dig up given reasonable economic assumptions." If they really meant "all" the fossil fuel, the results would be worse than they suggest.

If you consider this:

"The climate of the Cretaceous is less certain and more widely disputed. Average temperatures were higher than today by about 18 degrees F (10 degrees C)."

http://what-when-how.com/global-warming/mesozoic-era-global-...

Then this seems a bit odd:

"an astonishing 16.2 degrees"

That sounds accurate if they mean Celsius but this is the New York Times, which I believe uses Fahrenheit as a matter of style, and they write: "Scientists predict global disaster at 3.6 degrees Fahrenheit over pre-industrial temperatures; there is enough fossil fuel extracted and within reach to raise temperatures 16.2 degrees" which confirms the use of Fahrenheit.

It's frightening to consider the impact it would have if we really did dig up all the fossil fuel, including the stuff that we probably won't be able to reach. It's worth thinking about, since technological breakthroughs now allow us to reach a great deal of fossil fuel that was considered uneconomic 30 years ago and, likewise, 30 years from now we might be able to reach fossil fuel that we now consider unreachable.

Assuming large concentrations of life, allowing the formation of fossil fuels, starts with the Cambrian, or a bit after, we can say that "all our fossil fuels" refers to the deposits that built up over the course of 500 million years. If we dug all of that up and burned all of it, then we should arrive at a temperature that is a bit hotter than anything that ever occurred before. If the Mesozoic saw average temperatures that were 10 degrees Celsius higher than today, then something like 16 degrees Celsius would be a reasonable guess. Or higher.

> The climate of the Cretaceous

The Cretaceous isn't when the fossil fuels were formed; that was much earlier, during the Carboniferous. Global temperatures don't actually correlate very well over geologic time scales with the amount of carbon sequestered in fossil fuels:

http://en.wikipedia.org/wiki/Geologic_temperature_record#Flu...

You misread the sentence. The comparison is being made to the Mesozoic. That is, the Mesozoic was much hotter than the Cretaceous. I can not imagine what you mean when you write "Global temperatures don't correlate ... with the amount of carbon sequestered in fossil fuels." I never suggested any such thing. But we do know that carbon can increase the temperature, and if we dig up an amount of carbon that was buried over 500 million years and we burn it all during a 200 or 300 year time span, then presumably we end up with more carbon in the air, at one time, than ever occurred before, and therefore we should expect the temperature to spike to a level never seen before.

> The comparison is being made to the Mesozoic. That is, the Mesozoic was much hotter than the Cretaceous.

Um, you do know that the Cretaceous is part of the Mesozoic, right? And that our fossil fuels were not formed during any part of the Mesozoic; they were formed during the Carboniferous, which is part of the Paleozoic, right?

> I can not imagine what you mean when you write "Global temperatures don't correlate ... with the amount of carbon sequestered in fossil fuels."

I mean just what I said: global temperatures don't correlate very well with the amount of carbon sequestered in fossil fuels. Even the amount of CO2 in the air, over the last 600 million years or so, does not correlate well with the amount of carbon sequestered in fossil fuels. If that were true, we would expect to see lots of CO2 before the Carboniferous, very little CO2 from then to now, then a lot now. That is not what we see when we look at the record. See, for example, here:

http://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atm...

> if we dig up an amount of carbon that was buried over 500 million years and we burn it all during a 200 or 300 year time span, then presumably we end up with more carbon in the air, at one time, than ever occurred before

And if you look up the actual levels of CO2 in the atmosphere over the last 600 million years or so, you will see that this is not even close to being true. CO2 levels have been in the thousands of PPM during the period between the Carboniferous and now, even though all that carbon was buried in fossil fuels. The current epoch is one of very low CO2 concentrations in geologic terms, even counting the recent increase due to our burning fossil fuels.

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