@newtboy,

I also noticed my point on CO2 forcing was missed earlier in thread still, I'll try one last time to express this.

In 1900 CO2 concentrations were under 300ppm, today they are nearly 400ppm. Climate model estimates place the impact of that extra 100ppm of CO2 as increasing the TOA energy imbalance by 3W/m-2. Observations of TOA energy imbalance are well agreed that the net imbalance is 0.5W/m-2. That means that natural processes(likely largely the 0.8C warming we've already had) have already cancelled out 2.5W/m-2 of that 3W/m-2. That is to say, 83% of the impact of increased CO2 concentrations has already been balanced out to date. How long it takes to get that all the way to 100% is part of the problems that climate models are trying to solve, but regrettably it's tied to TOA energy so models still don't have a great deal of veracity yet on that for us. Still, it's reason for a lot less gloom and doom than so many are calling for.

@newtboy

#1 and #2, fine, if you won't go there to read it's now pasted in full for you:
Arctic tundra soils serve as potentially important but poorly understood sinks of atmospheric methane (CH4), a powerful greenhouse gas1, 2, 3, 4, 5. Numerical simulations project a net increase in methane consumption in soils in high northern latitudes as a consequence of warming in the past few decades3, 6. Advances have been made in quantifying hotspots of methane emissions in Arctic wetlands7, 8, 9, 10, 11, 12, 13, but the drivers, magnitude, timing and location of methane consumption rates in High Arctic ecosystems are unclear. Here, we present measurements of rates of methane consumption in different vegetation types within the Zackenberg Valley in northeast Greenland over a full growing season. Field measurements show methane uptake in all non-water-saturated landforms studied, with seasonal averages of − 8.3 ± 3.7 μmol CH4 m−2 h−1 in dry tundra and − 3.1 ± 1.6 μmol CH4 m−2 h−1 in moist tundra. The fluxes were sensitive to temperature, with methane uptake increasing with increasing temperatures. We extrapolate our measurements and published measurements from wetlands with the help of remote-sensing land-cover classification using nine Landsat scenes. We conclude that the ice-free area of northeast Greenland acts as a net sink of atmospheric methane, and suggest that this sink will probably be enhanced under future warmer climatic conditions.

#3, regardless of if it make's sense to you, and regardless of if it means a 10C warming by 2100, the IPCC scientists collaborative summary says it anyways. If you want to claim otherwise it's you opposing the science to make things seem worse than they are, not me.

#4, To tell them those things would sound like this. The IPCC current best estimates from climate models project 2100 to be 1.5C warmer than 2000. This has already resulted in 2000 being 0.8C warmer than 1900. Summer arctic sea ice extent has retreating significantly is the biggest current impact. By 2100 it is deemed extremely unlikely that the Greenland and Antarctic iccesheets will have meaningfully reduced and there is medium confidence that the warming will actually expand Antarctic ice cover owing to increased precipitation from the region. That's the results and expectations to be passed on from the 5th report from an international collaboration of scientists. Whether that fits your world view or not doesn't matter to the scientific evidence those views are founded on and supported by.

You said the ocean's may be unfishable in 20 years, and the best support you came up with was a news article quote claiming that by 2040 most of the Arctic would be too acidic for Shell forming fish. Cherry picked by the news article that also earlier noted that was dependent on CO2 concentrations exceeding 1000ppm in 2100, and even that some forms of plankton under study actually faired better in higher acidity in some case. In a news article that also noted that the uneven distribution of acidity makes predicting the effects very challenging. If news articles count as evidence I then want to claim we'll have working fusion power to convert to in 5 years time from Lockheed Martin. I'll agree with your news post on one count, the world they talk about, where CO2 emissions continue accelerating year on year, even by 2100, is bad. It's also a bit hard to fathom with electric cars just around the corner, and if not solar and wind, fusion sometime before then too, that we'll still be using anywhere near today's emissions let alone still accelerating our use.

by 2025 it's estimated that 2/3 of people worldwide will live in a water shortage.
And you link to a blog, and a blog that provides exactly zero references to any scientific sources for the claim. Better yet, even the blog does NOT claim that the access to water will be limited because of climate change, the blog even mentions multiple times how other forms of pollution are destroying huge amounts of fresh water(again with zero attributions).

Here's the IPCC best estimates for 2100 impacts regionally:
http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter14_FINAL.pdf

You'll find it's a largely mixed bag if you can be bothered to read what the actual scientists are predicting. Just bare in mind they regularly note that climate models still have a lot of challenges with accurate regional estimates. I guess your blogger isn't hindered by such problems though. If you don't want to bother I'll summarize for you and note they observe a mixed bag of increased precipitation in some regions, notably monsoons generally increasing, and other areas lowering, but it's all no higher than at medium confidences. But hey, why should uncertainty about 2100 prevent us from panicking today about more than half the world losing their drinking water in 10 years. I'll make you a deal, in ten years we can come back to this thread and see whether or not climate change has cause 2/3 of the world to lose their drinking water already or not. I'm pretty confident on this one.

Northern India/Southern China is nearly 100% dependent on glacial melt water, glaciers that have lost 50% in the last decade
Lost 50% since 2005? That'd be scary, oh wait, you heard that from the same blog you say? I've got a hunch maybe they aren't being straight with you...
Here are a pair of links I found in google scholar to scientific articles on the Himalaya's glaciers:
http://cires1.colorado.edu/~braup/himalaya/Science13Nov2009.pdf
I you can't be bothered to read:
Claims reported in the popular press that Siachin has shrunk as much as 50% are simply wrong, says Riana, whose report notes that the glacier has "not shown any remarkable retreat in the last 50 years" Which looks likely that your blogger found a popular press piece about that single glacier and then went off as though it were fact, and across the entire mountain range .

http://indiaenvironmentportal.org.in/files/glaciers%20and%20climate.pdf
Here's another article noting that since 1962 Himalayan glacier reduction is actually about 21%.

If you go back and read the IPCC links I gave earlier you can also find many of the regional rivers and glaciers in India/East China are very dependent on monsoons and will persist as long as monsoons do. Which the IPCC additionally notes are expected to, on the whole, actually increase through 2100 warming.

I've stated before up thread that things are warming and we are the major contribution, but merely differed from your position be also observing the best evidence science has for predictions isn't catastrophic. That is compounded by high uncertainties, notably that TOA energy levels are still not able to be predicted well. The good news there is the latest IPCC estimated temps exceed the observed trends of both temperature and TOA imbalance, so there's reason for optimism. That's obviously not license for recklessly carrying on our merry way, as I've noted a couple times already about roads away from emissions that we are going to adopt one way or another long before 2100.

@newtboy,
as the ice on land disappears, it exposes permafrost that, as it melts, also emits methane.

More from charliem's article's abstract:
Arctic tundra soils serve as potentially important but poorly understood sinks of atmospheric methane (CH4), a powerful greenhouse gas1, 2, 3, 4, 5. Numerical simulations project a net increase in methane consumption in soils in high northern latitudes as a consequence of warming in the past few decades3, 6. Advances have been made in quantifying hotspots of methane emissions in Arctic wetlands7, 8, 9, 10, 11, 12, 13, but the drivers, magnitude, timing and location of methane consumption rates in High Arctic ecosystems are unclear.

The article he linked IS saying that they've identified regions up north where the soil absorbs more methane the warmer it gets. They note this is a relatively unknown area as opposed to northern regions that emit methane. Charliem just didn't read the reference he pulled out at is it is counter evidence to his and your own statements.

As for your point:
As for your misunderstanding of CO2, removing all CO2 production tomorrow
I never said anything about that, I said:
if we could magically remove all the CO2 we've added to the atmosphere
As in I was talking about not merely ending our emissions, but also sequestering and pulling out of the atmosphere all the CO2 lingering there from us over the last century as well. That's pushing CO2 concentrations back down from nearly 400 to under 300. Re-read my statements in the correct context and they'll make more sense.
As for people "thriving", that's just ridiculous. There's been a food shortage world wide for quite some time now.
Again, context matters doesn't it? I'm describing how a person from 1915 would not look at our world today and wish they could go back to their time, end all CO2 emissions and avoid the catastrophic consequences we're suffering in 2015. If you want to talk about food distribution, your right and we've had problems with it forever. If you want to talk food production though, it's never been higher, if you go look at global agriculture output it's a steady increasing line as surely as the instrumental temperature record.

For the record, I absolutely state that the evidence throughout the entire instrumental record is a warming planet since records began in 1900. I absolutely state that the evidence is irrefutable that CO2 contributes to warming. I absolutely state the the evidence is irrefutable that we are raising global CO2 concentrations with our actions. Where I diverge from those like you is I do NOT see the scientific evidence declaring the results are catastrophic. It's simply not there to be found, in many cases it is in fact contrary to the limited evidence we DO have on it as well.

@charliem,

Energy is absolutely a better measure and marker of climate change than temperature. I started there since the video did. In reality though, everything in climate change is solely about the energy balance at the Top Of Atmosphere. More TOA energy in and temps go up in the long term, less and temps go down. It's the very foundation of climate change.

The climate models that your links look to for projections of things like methane thresholds are based on modelled temperature predictions. The IPCC notes the following on the state of the art in climate models:
For instance, maintaining the global mean top of the atmosphere (TOA) energy balance in a simulation of pre-industrial climate is essential to prevent the climate system from drifting to an unrealistic state. The Models used in this report almost universally contain adjustments to parameters in their treatment of clouds to fulfil this important constraint of the climate system (Watanabe et al., 2010; Donner et al., 2011; Gent et al., 2011; Golaz et al., 2011; Martin et al., 2011; Hazeleger et al., 2012; Mauritsen et al., 2012; Hourdin et al., 2013).
http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter09_FINAL.pdf
It's in Box 9.1

So, climate models currently FAIL to predict TOA energy accurately and hand tuning is required for modelling temperatures into the known past in order to avoid unrealistic states because the TOA energy is wrong. Maybe we aught not panic just yet on extrapolations from that base. I'm not calling climate models garbage, rather they are a learning tool for climate processes and one lesson is that we have a long ways to go in understanding the central component of TOA energy balance. If you go to google scholar and lookup the references from the IPCC assertions you'll find that the modellers acknowledge that most models still either leak or create energy from nothing. As in, even conservation of energy is imperfect in them still.

Your cursory glance approach is a problem, the devil is in the details.

Looking at energy further from NASA's numbers also tells us that the net contribution to TOA energy trapping from the CO2 we've added in the last 100 years is about 3W/m-2 globally. The global TOA energy imbalance is about 0.5W/M-2. In other words, if we could magically remove all the CO2 we've added to the atmosphere, we'd suddenly have a global energy imbalance at TOA of -2.5W/M-2. That brings two things to mind.
1.The enormous energy imbalance you want to call a catastrophe is 0.5W/M-2, but merely rolling back to 1900 CO2 concentrations today would yield a negative energy imbalance 5 times as large.
2.Of the 3W/M-2 that our actions have pushed on the planet, natural factors(warming and other unknowns) have already balance out 2.5W/M-2 of the imbalance, today.

You also might wanna check how much energy is in the oceans on the whole. If you take the increase in energy as a percentage of OCH instead of straight joules you'll find the trend is << than 1% annually.

@dannym3141, I understand that you are "stepping out of the debate," but, for your edification, I'll respond here... And, for the record, I am not "funded" by Big Oil, Big Coal, Big Solar, or Big Green. Nor am I a professor of climate or environmental science at a State University (and don't have a political agenda around this issue other than to help promote sound reasoning and critical thinking). I do, however, hold a doctorate and can read the scientific literature critically. So, in response to what climate change "believers" say, it's worth noting that no one is actually taking the temperature of the seas. They simply see sea levels rising and say "global warming," but how do they know? It's a model they came up with. But far from certain, just a theory. Like Antarctica melting, but then someone finds out that it's due to volcanic activity underneath, and so on.

And also, why is the heat then staying in the water and not going into the atmosphere? So, they then have to come up with a theory on top of the other theory... So the heat is supposedly being stored deep below where the sensors cannot detect it. Great. And this is happening because...some other theory or another that can't be proven either. And then they have to somehow come up with a theory as to how they know that the deep sea warming is due to human activity and not to other causes. I'm not denying that any of this happens, just expressing skepticism, meaning that no one really knows for sure. That folks would "bet the house on it" does not serve as any proof, at all.

The discussion on the sift pivots from "global warming" to vilifying skeptics, not about the original skepticism discussed, that there is catastrophic man-caused global warming going on. Three issues yet to be proven beyond skepticism: 1) that there is global warming; 2) that it is caused by human activity; 3) that it's a big problem.

When I ask about one, they dance around to another one of these points, rather than responding. And all they have in response to the research is the IPCC "report" on which all their science is based. And most if not all published "believers" say that the heat "may be hiding" in the deep ocean, not that they "certainly know it is" like they seem to claim.

They don't have knowledge that the scientists who are actively working on this do not have, do they? It's like the IRS saying, "My computer crashed." The IPCC says, "The ocean ate my global warming!"

Here are some links worth reading:

http://online.wsj.com/news/articles/SB10001424052702304636404577291352882984274

And, from a different rebuttal: "Referring to the 17 year ‘pause,’ the IPCC allows for two possibilities: that the sensitivity of the climate to increasing greenhouse gases is less than models project and that the heat added by increasing CO2 is ‘hiding’ in the deep ocean. Both possibilities contradict alarming claims."

Here's the entire piece from emeritus Alfred P. Sloan Professor of Meteorology, Department of Earth, Atmospheric and Planetary Sciences at MIT, Dr. Richard Lindzen: http://www.thegwpf.org/richard-lindzen-understanding-ipcc-climate-assessment/

And take your pick from all of the short pieces listed here: http://www.drroyspencer.com/2011/08/is-gores-missing-heat-really-hiding-in-the-deep-ocean/

And http://joannenova.com.au/2013/09/ipcc-in-denial-just-so-excuses-use-mystery-ocean-heat-to-hide-their-failure/

"Just where the heat is and how much there is seems to depend on who is doing the modeling. The U.S. National Oceanographic Data Center ARGO data shows a slight rise in global ocean heat content, while the British Met Office, presumably using the same data shows a slight decline in global ocean heat content."

http://www.arizonadailyindependent.com/2013/10/03/the-ocean-ate-my-global-warming-part-2/#sthash.idQttama.dpuf

Dr. Lindzen had this to say about the IPCC report: "I think that the latest IPCC report has truly sunk to a level of hilarious incoherence. They are proclaiming increased confidence in their models as the discrepancies between their models and observations increase."

http://www.arizonadailyindependent.com/2013/10/01/the-ocean-ate-my-global-warming-part-1/#sthash.oMO3oy6X.dpuf

So just as "believers" can ask "Why believe Heartland [financier for much of the NPCC], but not the IPCC," I can just as easily ask "Why should I believe you and not Richard Lindzen?"

"CCR-II cites more than 1,000 peer-reviewed scientific papers to show that the IPCC has ignored or misinterpreted much of the research that challenges the need for carbon dioxide controls."

And from the same author's series:

"Human carbon dioxide emissions are 3% to 5% of total carbon dioxide emissions into the atmosphere, and about 98% of all carbon dioxide emissions are reabsorbed through the carbon cycle.

http://www.eia.gov/oiaf/1605/archive/gg04rpt/pdf/tbl3.pdf

"Using data from the Department of Energy and the IPCC we can calculate the impact of our carbon dioxide emissions. The results of that calculation shows that if we stopped all U.S. emissions it could theoretically prevent a temperature rise of 0.003 C per year. If every country totally stopped human emissions, we might forestall 0.01 C of warming."

http://www.arizonadailyindependent.com/2013/08/01/climate-change-in-perspective/#sthash.Dboz3dC5.dpuf

Again, I have asked, repeatedly, where's the evidence of human impact on global warming? "Consensus" is not evidence. I ask for evidence and instead I get statements about the consensus that global warming happening. These are two different issues.

"Although Earth’s atmosphere does have a “greenhouse effect” and carbon dioxide does have a limited hypothetical capacity to warm the atmosphere, there is no physical evidence showing that human carbon dioxide emissions actually produce any significant warming."

Or Roger Pielke, Sr: http://wattsupwiththat.com/2011/09/20/pielke-sr-on-that-hide-and-seek-ocean-heat/

Or Lennart Bengtsoon (good interview): "Yes, the scientific report does this but, at least in my view, not critically enough. It does not bring up the large difference between observational results and model simulations. I have full respect for the scientific work behind the IPCC reports but I do not appreciate the need for consensus. It is important, and I will say essential, that society and the political community is also made aware of areas where consensus does not exist. To aim for a simplistic course of action in an area that is as complex and as incompletely understood as the climate system does not make sense at all in my opinion."

http://www.spiegel.de/international/world/meteorologist-lennart-bengtsson-joins-climate-skeptic-think-tank-a-968856.html

Bengtsson: "I have always been a skeptic and I believe this is what most scientists really are."

What Michael Crichton said about "consensus": "Let’s be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science, consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus."

Will Happer on the irrelevancy of more CO2 now: "The earth's climate really is strongly affected by the greenhouse effect, although the physics is not the same as that which makes real, glassed-in greenhouses work. Without greenhouse warming, the earth would be much too cold to sustain its current abundance of life. However, at least 90% of greenhouse warming is due to water vapor and clouds. Carbon dioxide is a bit player. There is little argument in the scientific community that a direct effect of doubling the CO2 concentration will be a small increase of the earth's temperature -- on the order of one degree. Additional increments of CO2 will cause relatively less direct warming because we already have so much CO2 in the atmosphere that it has blocked most of the infrared radiation that it can. It is like putting an additional ski hat on your head when you already have a nice warm one below it, but your are only wearing a windbreaker. To really get warmer, you need to add a warmer jacket. The IPCC thinks that this extra jacket is water vapor and clouds."

Ivar Giaever, not a climate scientist per se, but a notable scientist and also a skeptic challenging "consensus": http://www.telegraph.co.uk/earth/environment/climatechange/8786565/War-of-words-over-global-warming-as-Nobel-laureate-resigns-in-protest.html

Even prominent IPCC scientists are skeptics, even within the IPCC there is not agreement: http://www.climatedepot.com/2013/08/21/un-scientists-who-have-turned-on-unipcc-man-made-climate-fears-a-climate-depot-flashback-report/

And for your research, it may be worth checking out: http://www.amazon.com/The-Skeptical-Environmentalist-Measuring-State/dp/0521010683

Perfectly good explanation. Thanks for clarifying your stance for me.

In reply to this comment by Psychologic:
^ Posting a video is not an endorsement of its contents unless stated as such. This was posted as a point of discussion. I'm also not concerned with the methodologies of a particular video, but of those used to construct conclusions within the general realm of climate change.

The Cassiopeia Project contains a wealth of wonderful resources on various scientific subjects (physics, chemistry, evolution, etc), but this particular video struck me as unusual. Something about it doesn't sit right with me, but it isn't because of any specific data point it contains.

Here are some random reactions I have to the video:
-If most of the recent warming happened toward the end of the last hundred years then the "average increase per century" isn't very relevant.
-Focusing on "the last few years" in a statistical analysis is not all that useful.
-Regardless of the cause, the general trend has been one of warming. Saying it isn't something to worry about can, at best, only apply to increases up to this point.

My main questions:
-What is the mathematical relationship between CO2 concentration and temperature due to the greenhouse effect? Is it linear, logarithmic, or something else?
-What effect has water vapor concentration had on historical temperature trends? Does a large increase in water vapor continue trapping heat, or can it be offset due to more cloud formation?


I'm not advocating for any side of the debate. The problem is that my fascination with the subject far outstrips the available free time I have to invest in researching it.

When I look into this stuff I find mostly crap from people who start with a conclusion and then find evidence to support it... sorting through that becomes very time consuming. I know there are people on the Sift that have put far more time into researching this topic, so my hope is that I can benefit from their endeavors.

I also happen to enjoy controversial subjects, so this video seems to fit. =)


>> ^Stormsinger:

Then why are you promoting a video that says nothing about its methodology? If you want to understand the methodology shouldn't you actually be -looking- for methodologies?
Actions really do speak louder than words...and your actions and words aren't saying the same things.>

^ Posting a video is not an endorsement of its contents unless stated as such. This was posted as a point of discussion. I'm also not concerned with the methodologies of a particular video, but of those used to construct conclusions within the general realm of climate change.

The Cassiopeia Project contains a wealth of wonderful resources on various scientific subjects (physics, chemistry, evolution, etc), but this particular video struck me as unusual. Something about it doesn't sit right with me, but it isn't because of any specific data point it contains.

Here are some random reactions I have to the video:
-If most of the recent warming happened toward the end of the last hundred years then the "average increase per century" isn't very relevant.
-Focusing on "the last few years" in a statistical analysis is not all that useful.
-Regardless of the cause, the general trend has been one of warming. Saying it isn't something to worry about can, at best, only apply to increases up to this point.

My main questions:
-What is the mathematical relationship between CO2 concentration and temperature due to the greenhouse effect? Is it linear, logarithmic, or something else?
-What effect has water vapor concentration had on historical temperature trends? Does a large increase in water vapor continue trapping heat, or can it be offset due to more cloud formation?


I'm not advocating for any side of the debate. The problem is that my fascination with the subject far outstrips the available free time I have to invest in researching it.

When I look into this stuff I find mostly crap from people who start with a conclusion and then find evidence to support it... sorting through that becomes very time consuming. I know there are people on the Sift that have put far more time into researching this topic, so my hope is that I can benefit from their endeavors.

I also happen to enjoy controversial subjects, so this video seems to fit. =)


>> ^Stormsinger:

Then why are you promoting a video that says nothing about its methodology? If you want to understand the methodology shouldn't you actually be -looking- for methodologies?
Actions really do speak louder than words...and your actions and words aren't saying the same things.>

This man, fox news, and all his "scientists" are fucking lunatics.
CO2 concentrations have only breached normal nominal ranges from nature alone within the past 20 years.

How can he say stuff like this ? Hes a fucking climatologist, youd think the guy would bloody well know better.

Australia is facing the LARGEST drought we have ever seen, and it is persisting.
That is to say, that previous lakes and river/estuary systems that went close to being dry, still had recoveries due to late rain seasons, and the ecosystems would survive...thats not happening now, the rivers and estuaries are literally dieing, and have no chance of recovery if it continues along this path.

Our farming industry has been decimated, they have been forced to sell off all their cattle / sheep, and destroy all non-essential plants, and trim back to the stalks those that arnt in flower / spawn cycles. If this was the US, and we had a similar system with FEMA, this would of been declared a national emergency and been ongoing for the past 10 years.

I honestly can't remember the last time it rained here, theres this huge water resivour that was built behind my house estate about 70 years back to prevent flooding, because this area was prone to it back then...and now, no rain.

Global warming is a crock ?

What about the berring straight being OPEN for the first time, EVER during the summer months!! ?

Or the perma-frost in the outer rim of the atlantic region (norway, iceland, greenland etc.) thawing out ?

This isnt fairytale shit made up just to scare people, it is actually fucking happening. That this guy has the audacity to pool together 30000 willing idiots with pHD's is a scorn on his curriculm vitae`, im amazed he even manages to keep the weather channel running.

Australia is having to invest in massive scale water infrastructure upgrades, billions and billions of dollars is being pumped into desalination plants and new pipelines to help prevent the death of this country. It is serious, and it has nothing to do with population, the country has had a steady population for quite some time, and increases due to immigration do nothing to dint the overall size of the populus.

Geez ladybug, I can't believe your virtually harmless comment. I almost dropped this, but the more I think about it.. the crazier it is.

From wikipedia:

Carbon dioxide content in fresh air varies and is between 0.03% (300 ppm) to 0.06% (600 ppm), depending on location and in exhaled air approximately 4.5%. When inhaled in high concentrations (greater than 5% by volume), it is immediately dangerous to the life and health of plants, humans and other animals. The current threshold limit value (TLV) or maximum level that is considered safe for healthy adults for an 8-hour work day is 0.5% (5000 ppm). The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues would be significantly less.

These figures are valid for carbon dioxide supplied in "pure" form. In indoor spaces occupied by humans the carbon dioxide concentration will also reach a level higher than in pure outdoor air. Concentrations higher than 1000 ppm will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration. The discomfort will be caused by various gases coming from human respiration and perspiration, and not by CO2 itself. At 2000 ppm will the majority of occupants feel a significant degree of discomfort, and many will develop nausea and headache. The CO2 concentration between 300 and 2500 ppm is used as an indicator of indoor air quality in spaces polluted by human occupation.

Acute carbon dioxide toxicity is sometimes known as choke damp, an old mining industry term, and was the cause of death at Lake Nyos in Cameroon, where an upwelling of CO2-laden lake water in 1986 covered a wide area in a blanket of the gas, killing nearly 2000.

From MSDS

>4% by volume in the atmosphere produces labored breathing and is dangerous for even a few minutes of exposure; >12% causes rapid unconsciousness; a few hours exposure at 25% results in death.

Maybe liquid Nitrogen or helium would only be equivalent to holding your breathe.. but CO2 is toxic. So I realize one lb of dry ice in a 20ft x 20ft room is relatively harmless, but you are talking about inhaling it directly over the course of however long you are hitting the hookah. That is going to be way over an average intake of 3000ppm. Now you might argue that when breathing normal air in between hitting the hookah, you are dispelling a lot of excess CO2, but I think your blood is getting elevated toxic levels during the hose sucking parts.