
Indoor CO2 may reach levels harmful to cognition by the end of this century - beefield
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GH000237
======
awb
A good deal is spent explaining rising CO2 levels in the atmosphere and the
effects of CO2 on cognition, but it wasn't immediately obvious to me how
indoor CO2 levels would be rising. Towards the end, here is their explanation:

> in steady state, indoor CO2 concentration is always at least as high as the
> outdoor concentration (as neither generation nor ventilation rate can be
> negative) and simply scales with the ratio of generation to ventilation. For
> reasonable values of G and Q for elementary school students (0.004 L/s per
> student) and classrooms (10 L/s per student), respectively, a ratio G/Q
> equates to 400 ppm (Persily, 2018; Persily & de Jonge, 2017). Under such
> assumptions, then, an outdoor CO2 concentration of 477 ppm (411 ppm as in
> 2019, plus a 66‐ppm urban enhancement) would equate to 877 ppm inside the
> classroom upon reaching equilibrium.

The equation and explanation can be found about 60% of the way down.

~~~
formerly_proven
Most classrooms (at least here) aren't well-ventilated (windows are generally
kept closed because of "draft" or alternatively "we aren't heating for the air
force!", and buildings generally don't have AC/air exchange), CO2 levels are
often far beyond 1000 ppm in classrooms anyway, which is obviously not good
(there may be debate if going from 450 ppm to 600 pm leads to worse outcomes,
but it's pretty obvious that nausea-inducing levels of CO2 and air so stale it
feels like breathing water most definitely lead to worse outcomes).

~~~
wiz21c
If climate becomes warmer, then we'll open the windows more often :-)

~~~
klipt
Not if you're running AC.

~~~
grishka
I'm from a place where you only need AC one week per year so naturally no one
has it except in cars, but I've heard that decent systems, especially central
ones, don't recirculate the same air over and over again but take it from the
outside.

~~~
Tempest1981
Check out HRVs: (air exchangers)

[https://www.popularmechanics.com/home/interior-
projects/how-...](https://www.popularmechanics.com/home/interior-projects/how-
to/a149/1275121/)

------
hyperpape
Gwern raised some cautions about the studies indicating that these moderate
levels of CO2 have cognitive impacts. I haven’t read enough to have an
opinion, but any HN readers interested in this should probably follow up on
the studies he references:
[https://news.ycombinator.com/item?id=21569947](https://news.ycombinator.com/item?id=21569947).

------
GuB-42
Their conclusion is that we should emit less CO2. Certainly a good idea, but
their data clearly point to better ventilation.

Better ventilation is something we can do right now, that will improve things
immediately and 100 years from now.

Maybe the best thing would be the mandatory installation of powerful
ventilation systems with heat exchangers for new buildings, and incentives to
upgrade existing installations. That would help with both problems: getting
more fresh air and limiting energy expenditures which can, in turn, reduce CO2
emissions.

~~~
fyfy18
> mandatory installation of powerful ventilation systems

In my country that's already been a thing for the last few years. The HRV
system is around €1000, so it isn't a major cost for the benefits you get.
From this year all newly installed units need to be 90% efficient.

Also "powerful" is probably not needed, the system I have at the lowest speed
changes the air in my entire apartment every 3 hours, and is basically the
same noise level as a barely audible computer fan.

~~~
zdragnar
The difference in scale between your apartment and most schools is no trivial
matter.

At my high school, our one building, with tall ceilings, large cafeteria and
so forth, housed around 1300 people every day. Some are smaller, some much
bigger.

Moving all of that air at least once a day would require powerful exchangers
indeed. If nothing else, it would probably be cheaper and better for students
to have plants everywhere. One of my teachers' classrooms was like a tiny
jungle. I can't say that it made a significant difference, but it was pleasant
at least.

~~~
baskire
Plants sadly don’t make a significant impact to indoor co2.

I see a future indoor co2 sequestration device being incredibly popular

~~~
londons_explore
> indoor co2 sequestration device

If you're happy for it to have rechargeable cartridges, you could easily build
one with a once/week cartridge change. The cartridge needs to be ~the same
weight as all the food eaten by all the people in the building.

The material the cartridge is made from is dirt cheap (literally limestone!),
and recharging is a simple matter of heating it up.

With a pipe to the outdoors and some vents on a servo, the machine could even
auto-refresh its cartridge every day, making it almost maintenance free.

~~~
ActionPlankton
I'm curious about this cartridge idea. I'm picturing a pipe with quicklime
inside and coffee filters on the ends, with a blower to force air through. How
tightly would the contents be packed?

This is a little different from what I'd been thinking before your message,
which would be more of a fluidized bed reactor -- like quicklime swirling
around in air in a garbage can. I think that's closer to how some powerplants
treat exhaust.

I've read that there are microscopic changes to the quicklime particles after
a couple absorbtion/heating cycles (their pores fill up or something), after
which you need to do something to further refresh it, maybe by dissolving it
and precipitating it back out of solution.

This led me to considering whether aqueous chemistry might be better.

The simplest would be to react air with calcium hydroxide (would you use a
bubbler? Or a packed counterflow tower? Or a spray tower?) and collect the
calcium carbonate that precipitates out.

But, based on my shaky chemistry, I understand solubility of calcium hydroxide
is low, so you do better with a two-stage process like the Kraft Process:

1\. Absorb CO2 in contactor:

2NaOH + CO2 -> Na2CO3 + H2O

2\. Regenerate solution in causticizer:

\- CaO + H2O -> Ca(OH)2

\- Na2CO3 + Ca(OH)2 -> 2 NaOH + CaCO3

3\. Decompose calcium carbonate:

CaCO3 -> CaO + CO2

The concentrated NaOH solution would be very caustic, so you'd have to be
careful with that, but apart from that none of this seems too terribly scary?

Some parts of the above are endothermic, others exothermic, so maybe this
could even let you shift energy from the summer (solar furnace?) to the winter
when you need it, as part of the deal.

Or maybe this is all too complicated and you should just use a canister of
soda lime granules, like an anesthesia machine? (
[https://en.m.wikipedia.org/wiki/Soda_lime](https://en.m.wikipedia.org/wiki/Soda_lime)
)

I'd be interested to hear more from people whose chemistry is better than
mine.

~~~
ActionPlankton
Let's do the thermodynamics:

First, some enthalpies of formation (at 298 K and 1 atm, in kJ/mol) (from [1]
unless otherwise indicated):

    
    
      H2O(l)       -285.8
      
      CO2(g)       -393.509
      CO2(aq)      -419.26
      
      NaOH(g)      -425.93 
      NaOH(aq)     -469.15
      
      Na2CO3(s)   -1130.77
      Na2CO3(l)   -1108.51  (from [2])
      Na2CO3(aq)  -1157.34  (from [3])
      
      CaO(s)       -635.09 
      CaCO3(s)    -1206.9
      Ca(OH)2(s)   -986.09
      Ca(OH)2(aq) -1002.82 
    

The reactions:

1\. 2NaOH(aq) + CO2(g) -> Na2CO3(aq) + H2O(l) ... -111.33 kJ/mol (exothermic)

Here I assume that the gas has to dissolve as part of the reaction so use
CO2(g) instead of CO2(aq) on the left hand side. I get an enthalpy delta of
-111.33 kJ/mol. This differs from some homework answers I find online like [4]
because I use NaOH(aq) while they use NaOH(s), etc; I hope I'm right for this
application.

2a. CaO(s) + H2O(l) -> Ca(OH)2(aq) .... -81.93 kJ/mol (exothermic)

2b. Na2CO3(aq) + Ca(OH)2(aq) -> 2 NaOH(aq) + CaCO3(s) .... 14.96 kJ/mol
(endothermic)

3\. CaCO3(s) -> CaO(s) + CO2(g) ... 178.30 kJ/mol (endothermic)

Energy issues:

The easy thing would be to run at least (2b) (causticization) concurrently
with (1) so you're always precipitating out CaCO3 and don't accumulate any
Na2CO3 solution. It would also be easiest to combine (2a) with (2b) in a
single causticization chamber. And it'd be simplest to skip (3) entirely, just
treat CaO as a consumable, and be happy that you've sequestered carbon as
CaCO3.

However, in a temperate climate, you can imagine doing the following to shift
energy around the year (how realistic this is I don't know):

\- Only run (2a) during the winter, to heat your home; you'd accumulate
Ca(OH)2 solution to be used during the summer in (2b).

\- Only run (2b) during the summer, to cool your home. During the winter you'd
accumulate Na2CO3 solution from (1), which you'd need to store.

\- If you're doing (3), do it during the summer, when a solar furnace can be
operated. This gives you a reagent that you'll use in (2a) during the winter.

\- You'd want to run (1) all year round, to scrub the CO2.

The main inefficiency this is trying to make useful is that you need to go
down in energy with (2a) and back up in (3). And down in energy with (1) and
back up in (2b).

I'll next need to understand the soda lime method to compare.

[1]
[https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation](https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation)
[2]
[https://webbook.nist.gov/cgi/cbook.cgi?ID=C497198&Mask=2](https://webbook.nist.gov/cgi/cbook.cgi?ID=C497198&Mask=2)
[3] [http://chemistry-reference.com/reaction.asp?rxnnum=454](http://chemistry-
reference.com/reaction.asp?rxnnum=454) [4]
[https://answers.yahoo.com/question/index?qid=20131119075117A...](https://answers.yahoo.com/question/index?qid=20131119075117AA4IPZU)

------
derefr
Is there any practical way to have less indoor CO2 than outdoor CO2, _without_
needing to buy expensive single-use scrubber chemicals? Maybe presuming you
live somewhere with cheap electricity and/or a cheap fresh water supply?

Basically I’m asking whether there’s a Maxwell’s Daemon-like device for
separating the CO2 from the air, and venting the CO2 back outside, while
bringing in the rest of the air. Like a CO2 scrubber, but without any need for
CO2 _sequestration_ , since you exist inside an open system instead of in a
space station/bunker/submarine.

~~~
beefield
There are these things called plants that do that kind of stuff, so maybe if
you have enough of them inside your house, they eat the CO2 away... :)

~~~
derefr
I don’t think there’s any _practical_ level of plant-having that would result
in there being _less_ CO2 in the house than in the atmosphere.

IIRC, there’s some point in running an indoor grow-ops where you start needing
to worry about spraying CO2-enriched air on the plants; but that’s just to
accelerate growth, like a fertilizer. Or, sometimes, it’s because OPSEC
requires you to not vent your smelly waste air — and because no human or
animal lives in the grow-op house to convert O2 to CO2, the air becomes
gradually CO2-poor. But that wouldn’t happen if even one human lived there;
humans convert metabolize a lot faster than plants do.

------
dreamcompiler
Yes, better ventilation is part of the solution. But the authors point out
that in many urban areas a "dome" of increased CO2 hangs over the city.
Ventilation won't solve that problem. Only reducing fossil fuel burning will.

------
MichaelZuo
My recommendation is to get an indoor CO2 monitor for your bedroom that can
alarm whenever levels go above 1000 ppm. From what I understand high end
office are being equipped with such systems with direct control of the
ventilation systems for exactly this reason.

For home use a mid-range unit is sufficiently accurate, precise, and reliable.
I use the Extech CO200 personally. Don’t but a cheap unit because those have
calibration drift after a few months. And recalibration is not trivial.

~~~
beefield
I did some quick search end the very cheapest sensors seem to calculate
something called eCO2. Like e.g.

[https://www.adafruit.com/product/3566](https://www.adafruit.com/product/3566)

What I was not able quickly to figure out is:

\- What this eCO2 actually is?

\- What is the real world accuracy I can expect from this kind of sensor, with
and without calibration?

\- is it enough for calibration just to go outside and assume some number
between 400 and 500 (assuming outside means not just next to industrial
chimney)? If not, what would be better calibration process?

~~~
gsich
Why not use a real one? MH-Z19 or Z14.

~~~
beefield
because my google-fu was not good enough to find those.... Regardless, I would
be curious on the same questions about real world accuracy on those as well.

~~~
acidburnNSA
I have two of them, one inside and one outside. They both go down to roughly
400 ppm and the indoor one goes very high when it's all cooped up inside. The
outdoor one fluctuates since I'm in an urban area. I believe they are accurate
to within about 10%.

During the smoke event, they combined with my indoor/outdoor pm2.5 sensors
have been extremely useful.

~~~
throwaway3neu94
They should go down to 400ppm because the periodic autocalibration which is on
by default assumes the lowest level seen in 24 hours is 400ppm.

------
offsky
A regenerative CO2 scrubber that people could install inline with existing
whole house AC systems would be a big success. I would buy it in a heartbeat.

------
salex89
So, we're burning fossil fuels, increasing CO2 output, don't have an idea
which will reliably improve the situation and are getting stupider by the day,
decreasing our chance to ever getting one. Yay...

~~~
cbmuser
We do. It’s called nuclear power and it‘s fought by those who claim they are
fighting for the environment.

>
> [https://www.giss.nasa.gov/research/briefs/kharecha_02/](https://www.giss.nasa.gov/research/briefs/kharecha_02/)

~~~
hhjinks
Honest and good faith question here: assuming all electricity on the grid was
nuclear, how much CO2 emission would remain? You can't just swap massive cargo
ships to nuclear overnight. Would "just" making the power grid green be
enough?

~~~
whatisthiseven
No, power generation is about a quarter:
[https://www.epa.gov/ghgemissions/sources-greenhouse-gas-
emis...](https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions)

Transportation could push that total to 50% if all ICE cars were converted or
destroyed and only electric vehicles were used (ignoring ships and trains).
"Industry" includes CO2 waste byproducts which are much harder to reduce as
many processes may struggle to eliminate that byproduct. Instead capture and
sequestration would be needed. This is another 25%

The rest are small, but since we need virtually all CO2 emissions to be zero,
we are left with nearly another 25% that isn't tied to electric production and
is difficult to replace.

So, 50% of all CO2 isn't power generation related.

------
kev009
Has anyone experimented with supplemental oxygen for cognitive benefit?

~~~
frank2
Increasing O2 has physiological effects different from the effects of
decreasing CO2. It is not just the ratio or difference between the
concentrations that matter.

For example, a major effect of increasing CO2 is to make the blood more acidic
(or to put more stress on the homeostatic mechanisms that maintain a target
pH), and my guess is that no amount of increasing O2 will cancel that out.

~~~
matheusmoreira
> a major effect of increasing CO2 is to make the blood more acidic (or to put
> more stress on the homeostatic mechanisms that maintain a target pH), and my
> guess is that no amount of increasing O2 will cancel that out

True. More details on this mechanism:

The body uses buffer systems in order to minimize blood pH changes. For
example, the bicarbonate buffer system which is catalazyed by carbonic
anhydrase.

    
    
      CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃- + H+
    

It is converted back to carbon dioxide in the lungs and exhaled. The rate at
which this process occurs is mainly influenced by respiratory rate. Oxygen
doesn't directly influence it. O₂ enables aerobic cellular respiration, the
process which produces carbon dioxide.

The hydrogen ions are buffered by proteins such as hemoglobin. They are also
excreted by the kidneys.

[https://en.wikipedia.org/wiki/Buffer_solution](https://en.wikipedia.org/wiki/Buffer_solution)

[https://en.wikipedia.org/wiki/Bicarbonate_buffer_system](https://en.wikipedia.org/wiki/Bicarbonate_buffer_system)

[https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis](https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis)

[https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid...](https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid-
base-balance/)

------
jug
This is already a problem in classrooms etc, and shows itself by tiredness and
headaches. As I understand it, this will only push harder towards better
ventilation.

------
bjoli
Not just indoor. Just google what a 400ppm increase does and look at
projections. The IPCC predicts that major cities might reach 1000ppm outdoors.

~~~
trhway
Looks like in a few decades the AC units will be coming with CO2 scrubbers
standard. Just a one more way the global warming is going to tax our
economy/society.

~~~
calcifer
Wouldn't home CO2 scrubbers need fairly frequent filter replacement? I can
easily imagine units being sold with a subscription, e.g $14.99/month and you
get a new filter every month.

------
rkwasny
Just get one of this:
[https://www.amazon.co.uk/gp/product/B01DY30PG8/](https://www.amazon.co.uk/gp/product/B01DY30PG8/)

~~~
LargoLasskhyfv
So. What are you going to do when it shows you levels of CO2 too high? Opening
a can of _Perry Air_ , search for
[https://duckduckgo.com/?q=air+quality+improvement+with+plant...](https://duckduckgo.com/?q=air+quality+improvement+with+plants)
, or what? Using it as an indicator of when to finally move elsewhere?

~~~
sandworm101
Plants + grow lamps. Get something easy to grow quickly indoors, say some
random type of _weed_ , and start letting it absorbing co2.

~~~
belltaco
Don't plants take oxygen and release CO2 at night?

~~~
sandworm101
They do and they don't. The net result of a growing plant is the absorption of
CO2 and H2O to create O2 and various hydrocarbons, oxygen and plant matter.
The carbon is fixed in the body of the plant. But i did mention grow lamps.
Keep them lit and there is no night.

~~~
vitus
Plants still need to use the glucose, though. It's misleading to say that
plants produce CO2 at night (since they produce it all the time); rather, they
become a net CO2 producer at night because they're not offsetting it with
photosynthesis.

I'm not convinced that grow lamps are an effective way to offset that, since
photosynthetic efficiency is fairly low (3-4%), and the electricity for the
lamp has to come from somewhere. Not to mention that lamps (even LEDs) are
also fairly lossy. I'm also not convinced that's even worth optimizing.

~~~
sandworm101
This is about indoor air pollution. I assume the coal-fired power plant is at
least not in the same building.

------
mrfusion
I’m definitely on team climate change but this just feels alarmist to me.

~~~
tpmx
Yeah, what happened to being solution-oriented?

It's odd how on HN you're not supposed to be negative of anything technical
even if it's flaming crap, but also at the same time you're also supposed be
assuming certain doom when it comes to climate change. How about we try to
solve the technical problem at hand?

~~~
adrianN
I don't understand what you're trying to say. The paper just observes that
outdoor and indoor CO2 concentrations are related, and that high CO2 impacts
cognition. Therefore increasing CO2 in the atmosphere has an impact on indoor
cognition. What is the problem with that? Why is it "flaming crap"?

~~~
tpmx
> Why is it "flaming crap"?

You 100% misread my post. I did not claim the article was "flaming crap".
Please re-read it, this time reading _every_ word.

~~~
adrianN
I'm sorry, English is not my first language. I did in fact read every word in
your post, but still don't understand it. Can you maybe rephrase it? I am
pretty sure that this discussion here is not about climate change, but about
the effects of higher CO2 concentrations in the atmosphere, on CO2
concentrations indoors.

------
ThomPete
Correct me if I'm wrong but that graph they show compares averaged numbers
over hundreds of years or even thousands of years, with year over year numbers
once we started measuring this regularly the last +100 years.

This seems just straight out disingenuous to say the least unless I am missing
something or is this kind of misrepresentation the new standard for research
papers today?

~~~
petermcneeley
Perhaps but that graph has little to do with their argument. Their argument is
simple. If CO2 levels go up its going to make indoor CO2 levels worse. At some
point this causes cognitive impairment.

~~~
ThomPete
It actually has a lot given that they are saying IF CO2 levels goes up to a
certain level at the end of the century. They are using that graph as one of
the reasons for why it's likely to go up.

This is their conclusion

"We conclude that indoor CO2 levels may indeed reach levels harmful to
cognition by the end of this century, and the best way to prevent this hidden
consequence of climate change is to reduce fossil fuel emissions. Finally, we
offer recommendations for a broad, interdisciplinary approach to improving
such understanding and prediction."

That's a big if especially since one of the reasons they believe it might
increase to those levels is exactly this mix of averaged measurements and year
over year.

Keep in mind the IPCC models range for nothing to worry about to the world is
going under.

With regards to the CO2 levels having an impact on our cognitive abilities at
the end of the century thats also a lot of speculation and a lot of
assumptions.

This is not science this is speculation. Interesting but so filled with
assumptions and guesses and speculation about what might happen in 2100.

And if that wasn't enough they just straight out claim the have the solution
which is hindering fossil fuel.

This is just activism put into research format from what I can see.

~~~
adrianN
You're confusing the effects of CO2 on climate (which you _might_ argue are
not too bad if you enjoy playing russian roulette), with the concentration of
CO2, which we can measure extremely accurately and for whose increase the
mechanism is very well understood: We burn carbon, it ends up in the
atmosphere as CO2, increasing the concentration there for a long time. We also
understand the impact of CO2 on cognition very well, because we can simply run
experiments.

~~~
ThomPete
I don't think I am.

The causality of the article is.

Outdoor CO2 might be rising dramatically > dramatically rising outdoor CO2
leads to dramatically rising indoor CO2 > too high a concentration of indoor
CO2 might have an impact on our cognitive abilities.

That's not the worst part of that paper the worst part is that they then just
throw in things like this:

"The best way to prevent indoor CO2 levels from reaching levels harmful to
cognition is through reduced fossil fuel emissions."

What about better ventilation? Just like we do with a lot of other things
today. But no instead they just go for the most extreme recommendation based
on absolutely nothing.

Keep in mind we are talking at the end of the century.

I don't understand how anyone can read this and think this is quality
research.

~~~
beefield
> Outdoor CO2 might be rising dramatically > dramatically rising outdoor CO2
> leads to dramatically rising indoor CO2 > too high a concentration of indoor
> CO2 might have an impact on our cognitive abilities.

Are you really claiming there is some uncertainty whether the burning of
fossil fuels will actually raise CO2 levels of the atmosphere? I have thought
that the discussion is whether the rising CO2 causes global warming or not.

And if we agree that burning the fossil fuels increases CO2 in atmosphere
(forget the damn global warming, we are not talking about that) Do you claim
that there is no reason to believe that the indoor CO2 will also rise? I hope
you understand that kind of claim to be so weird that I would expect you to
elaborate a bit more why you think that would not be the case.

Finally, whether the increased CO2 actually has any effect on cognitive
capabilities, that is of course the main topic in the discussion here. I have
no further comments on that one.

~~~
ThomPete
I am claiming that the research paper is not about cognitive capabilities (as
that is taken for granted in the headline) but about fossil fuels effect on
CO2 hence the title of the paper.

"Fossil Fuel Combustion Is Driving Indoor CO2 Toward Levels Harmful to Human
Cognition"

If it was just about CO2 there would be no need to include fossil fuel
combustion unless of course they know exactly how much CO2 is caused by fossil
fuel combustion and how much is natural variation. There is no conclusion on
that which is why you don't find an actual number of how much humans affect.

It's one thing to talk about CO2 levels and it's affect on human cognition,
even that is not conclusive as is also obvious when you read the paper. But
they go way way further to conclude that if we want to avoid that we should
decrease fossil fuel use.

On what basis do they do that? No one knows how much is driven by humans and
how much is natural

Do they have any evidence that; 1) that's without consequences, 2) it's the
only way to deal with increasing CO2 if if it is harmful.

This is not research this is mixing together a bunch of different assumptions
and using CO2 effect on cognitive abilities to talk about fossil fuel.

~~~
adrianN
It doesn't seem hard to me to get at least a good ballpark estimate on the
amount of CO2 we put into the atmosphere, say in the last 50 years. We know
roughly how much coal and oil and gas we've burnt so far. Calculating how much
the atmospheric concentration changed from that amount is easy enough. I'm
sure someone did the math and would've published a paper about it if it turned
out that human activities don't account for most of the CO2 concentration
change. That would be kind of a big deal.

~~~
ThomPete
yet we dont have a ballpark number that says how much is human made and how
much is natural. It doesent exist even in the IPCC report. You are welcome to
prove me wrong.

~~~
imtringued
I think this satisfies your desire for a "ballpark number"

[https://ourworldindata.org/contributed-most-global-
co2](https://ourworldindata.org/contributed-most-global-co2)

Come on. You're just putting your head in the sand and pretending the sand is
the real world.

~~~
ThomPete
That talks about countries contributing relative to each other NOT relative to
natural. Please point to the number. It's not there because it doesn't exist
because we don't know.

And let me put it like this. If you know the number send it to the nobel
committee and you would be getting one.

~~~
martinpw
It is pretty uncontroversial that CO2 increase in the atmosphere is almost all
from human activity, and that a large part of that comes from burning fossil
fuels. For example the US EPA website says:

[https://www.epa.gov/ghgemissions/sources-greenhouse-gas-
emis...](https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions)

 _Human activities are responsible for almost all of the increase in
greenhouse gases in the atmosphere over the last 150 years. The largest source
of greenhouse gas emissions from human activities in the United States is from
burning fossil fuels for electricity, heat, and transportation._

and there is a link right on that paragraph to the IPCC report. Given the
current EPA director, you might expect that to have been removed if there was
any controversy about it.

And there are multiple lines of evidence to indicate fossil fuels are the
major source, including carbon isotope ratios:

[http://www.realclimate.org/index.php/archives/2005/06/how-
mu...](http://www.realclimate.org/index.php/archives/2005/06/how-much-of-the-
recent-cosub2sub-increase-is-due-to-human-activities/)

Finally, if there was any doubt about it you could be sure the oil companies
would be trumpeting it.

~~~
ThomPete
So in other words. You can't give me a number, not even a ballpark number. Why
do you think that is? Why isn't it important to you if it's 10% or 51% or 99%?

~~~
martinpw
The EPA quote clearly implies that for the US it is > 50%.

The realclimate article says: "the rise in atmospheric CO2 is entirely caused
by fossil fuel burning and deforestation". So then the question is what is the
ratio between those two sources. Quote here says ~10% of total is from
tropical deforestation:

[https://www.climatecouncil.org.au/deforestation/](https://www.climatecouncil.org.au/deforestation/)

So ballpark figure is 90% from fossil fuels? The exact number doesn't matter
for the basic argument of the paper though, as long as it is the vast majority
of the source.

~~~
ThomPete
ask yourself why they cant be precise

~~~
adrianN
Just by following references in the Wikipedia about the carbon cycle I found
this book chapter
[https://scihub.wikicn.top/https://doi.org/10.1016%2FS0070-45...](https://scihub.wikicn.top/https://doi.org/10.1016%2FS0070-4571%2808%2970338-8)
that contains numbers (and error bars), alas from 1985. I'm confident that our
knowledge about the carbon cycle has improved since then, given the amount of
research climate change has gotten in the last thirty years.

~~~
ThomPete
Yes it's from 1985 and no it doesn't actually give a number either.

The fact that you can't find it and have to go to 1 article which isn't even
giving you that number, should tell you that maybe you haven't gotten all the
facts here.

This is exactly what started my journey from worrying about the climate to
understanding it to realizing the base for all this is much much much fragile
and much much much more politisized.

~~~
adrianN
I spent about 20 minutes looking for that reference. I'm sure an actual
climate scientist could provide you with a better reference.

Page 450 has a table. Historic CO2 concentration: 280ppm, "current"
concentration 341ppm: a 21% increase. From that and the 60 * 10^15 moles C in
the atmosphere in 1982 we can deduce around 50 * 10^15 moles C in 1800 in the
atmosphere. That seems to be in the right ballpark of 14 * 10^15 moles of
emissions from fossil fuels: not all of the carbon ends up in the atmosphere,
e.g. some is dissolved in the ocean. Certainly the difference is not large
enough (and doesn't have the right sign!) to support the theory that man made
carbon dioxide didn't contribute the majority of the extra carbon in the
atmosphere.

