All About Natural Disasters

[darksabre]

very true, regionally it can be more effective.

 

How much did it cost to install, and what incentives was he offered to install it, and to keep it going? Lets see his bill. Anecdotes are great, but evidence is better.

 

I wanted to cut NYSEG off and explored solar. I was approaching 30K to install a system. Where do solar panels come from - the ether? how much does it cost, and what is the environmental impact of manufacturing them? what about their disposal? Measuring the effectiveness of new technology isn't just about the numbers on your utility bill.

Solar panels are environmentally friendly to produce and nearly all of their components can be recycled including the silicon wafers. The used panel recycling industry is going to grow over the next 10-15 years as panels exceed their 20 year warranties or customers choose to upgrade. Silicon wafers can be melted down, re-grown, re-doped and turned into productive wafers again pretty much forever.

Interesting. I remember seeing a ton of windmills driving out to Buffalo on 20A (I think?), but would not have guessed solar would enjoy more widespread adoption!

Windmills are going to be popular when storage takes off. NYS has huge battery storage goals and the cost of batteries is decreasing. Storage of wind power is going to be a big deal in the near future.

[korab rules]

Solar panels are environmentally friendly to produce and nearly all of their components can be recycled including the silicon wafers. The used panel recycling industry is going to grow over the next 10-15 years as panels exceed their 20 year warranties or customers choose to upgrade. Silicon wafers can be melted down, re-grown, re-doped and turned into productive wafers again pretty much forever.

 

Windmills are going to be popular when storage takes off. NYS has huge battery storage goals and the cost of batteries is decreasing. Storage of wind power is going to be a big deal in the near future.

which solar company do you work for?

 

http://news.nationalgeographic.com/news/energy/2014/11/141111-solar-panel-manufacturing-sustainability-ranking/

 

I would put up a windmill in my back yard if I could.  I have yet to see the piles of dead birds under them predicted by the greenies, nor have I yet been struck by an ice chunk the size of a chevy truck when cruising past them on 20A.

Edited September 14, 2017 by korab rules

[SwampD]

very true, regionally it can be more effective.

 

How much did it cost to install, and what incentives was he offered to install it, and to keep it going?  Lets see his bill.  Anecdotes are great, but evidence is better.

 

I wanted to cut NYSEG off and explored solar.  I was approaching 30K to install a system.  Where do solar panels come from - the ether?  how much does it cost, and what is the environmental impact of manufacturing them?  what about their disposal?  Measuring the effectiveness of new technology isn't just about the numbers on your utility bill.  

All valid questions which we have covered on this board before. I think we are at an inflection point right now where they are finally producing more power than it took to create them. Ahead of schedule actually. It wouldn't have happened as fast without government intervention. I see that as a good thing.

 

are you being intentionally obtuse or do you really not understand that when people refer to the earths temperature they are referring to an average of data points, and that these same data points did not exist 100 years ago?

I understand that the data did not exist 100 years ago. And I also believe that the lines in that graph are most likely an average and that there were year to year and decade to decade swings. I still think that the current data is something to be concerned about and at least something to pay attention to, not just dismissed out of hand because "no one knows what the earth's temperature is - there isn't a temperature of a planet, something something,...Detroit."

Edited September 14, 2017 by SwampD

[darksabre]

which solar company do you work for?

 

http://news.nationalgeographic.com/news/energy/2014/11/141111-solar-panel-manufacturing-sustainability-ranking/

Chicken and egg is fun if you want to be obtuse. Solar has to have enough share of energy production before manufacturing is running on clean enough energy to really call itself truly Eco friendly. The same goes for electric cars. They still need grid power that is currently still largely polluting. But that's the same for anyone manufacturing anything anywhere.

 

Eventually the curves are going to cross and green energy will be truly green. But that takes time and yes dirty energy. But you can't get to the top of the hill if you don't start walking.

[korab rules]

All valid questions which we have covered on this board before. I think we are at an inflection point right now where they are finally producing more power than it took to create them. Ahead of schedule actually. It wouldn't have happened as fast without government intervention. I see that as a good thing.

 

I understand that the data did not exist 100 years ago. And I also believe that the lines in that graph are most likely an average and that there were year to year and decade to decade swings. I still think that the current data is something to be concerned about and at least something to pay attention to, not just dismissed out of hand because "no one knows what the earth's temperature is - there isn't a temperature of a planet, something something,...Detroit."

who is dismissing it?  it is something to watch - and people are.  To bring this full circle, as I stated in my first post in this thread way back at post #768, what I take issue with is people politicizing and monetizing the issue and the scientific community. 

 

People need to think for themselves, learn to analyze the they are fed every day, and stop thinking John Stewart is Walter Cronkite.

[qwksndmonster]

who is dismissing it? it is something to watch - and people are. To bring this full circle, as I stated in my first post in this thread way back at post #768, what I take issue with is people politicizing and monetizing the issue and the scientific community.

 

People need to think for themselves, learn to analyze the ###### they are fed every day, and stop thinking John Stewart is Walter Cronkite.

Politicizing it? It's a political issue no matter how you frame it.

 

Is this post from 2009? You're sposed to say John Olliver now.

[korab rules]

Chicken and egg is fun if you want to be obtuse. Solar has to have enough share of energy production before manufacturing is running on clean enough energy to really call itself truly Eco friendly. The same goes for electric cars. They still need grid power that is currently still largely polluting. But that's the same for anyone manufacturing anything anywhere.

 

Eventually the curves are going to cross and green energy will be truly green. But that takes time and yes dirty energy. But you can't get to the top of the hill if you don't start walking.

I'm a big believer in capitalism.  Forget green energy v brown energy - if it is economically feasible, it wont require propping up.  

 

So do you work in the solar industry or no?  i've been away for a couple years.   

[SwampD]

I'm a big believer in capitalism. Forget green energy v brown energy - if it is economically feasible, it wont require propping up.

 

So do you work in the solar industry or no? i've been away for a couple years.

Why do people assume that if you are pro Green you can't be pro capitalism? I'm pro capitalism. It absolutely has its place. But where it doesn't have its place, socialism has to step in.

[korab rules]

Why do people assume that if you are pro Green you can't be pro capitalism? I'm pro capitalism. It absolutely has its place. But where it doesn't have its place, socialism has to step in.

Who assumes that?  That is exactly where I fall!  Except for the socialism part - that .

[MattPie]

are you being intentionally obtuse or do you really not understand that when people refer to the earths temperature they are referring to an average of data points, and that these same data points did not exist 100 years ago?

 

You take the data from the last 100 years, compare it to parts of the 10000 year sample (ice, sediment, whatever) representing the last 100 years, and then you can apply that to the entire sample.

 

I'm a big believer in capitalism.  Forget green energy v brown energy - if it is economically feasible, it wont require propping up.  

 

So do you work in the solar industry or no?  i've been away for a couple years.   

 

Capitalism is really bad at long-term goals with short-term losses. This is exactly the situation that it fails to work. Safety is another, as most companies aren't going to sacrifice profits (or viability) to many sure their products are safe without nudging from an external watchdog.

Edited September 14, 2017 by MattPie

[SwampD]

Who assumes that? That is exactly where I fall! Except for the socialism part - ###### that ######.

Quick question. Is it better to put all the cans bottles and boxes that we use into landfills or recycle them?

 

Rehtorical, obviously, but I know for a fact the companies can not make money recycling and that unless it was municipally subsidized, they wouldn't do it. I have no problem paying taxes for that.

[korab rules]

You take the data from the last 100 years, compare it to parts of the 10000 year sample (ice, sediment, whatever) representing the last 100 years, and then you can apply that to the entire sample.

 

It doesn't work that way.  The historic data points we have available are so limited that you can never compare apples to apples.  For data concerning the last 1000 years, we are using tree rings and air bubbles inside of ice cores.  Ice cores are obviously only available in the arctic and antarctic region, so what is going on in the rest of world at that time has to surmised.  To understand the problems inherent in relying on ice core information, you have to understand ice cores, how and over what period of time air bubbles are created in glacial ice, and the ways in which the air in a bubble can be affected over time.  Most people think of ice cores like they do sedimentary rock - but it doesn't work that way at all.  For a taste of how it works, and the reasons why ice core air bubbles are of limited value, read this quote from a scientific article:

 

"The density of ice at the surface of an ice sheet is typically 0.3–0.35 g cm−3; the corresponding porosity is 62–67%. Settling and packing cause the density to rise rapidly to about 0.55 g cm−3 by a depth of 10–30 m. Below, recrystallization and other processes drive a somewhat slower increase in density, which continues until individual crystals are fused together into an impermeable mass of glacial ice. At the “bubble closeoff depth,” about 10–15% of the volume is air, and the density is about 0.81–0.84 g cm−3. The “firn” is the zone of porous snow and ice above the closeoff depth, and the depth interval in which bubbles close is termed the “firn–ice transition.” Below the transition, densification continues by the compression of bubbles due to hydrostatic pressure.

When the snow accumulation rate at the surface of an ice sheet is greater than about 4 cm yr−1 (expressed as the ice-equivalent thickness of annual layers), discrete seasonal layers of snow are preserved that have characteristic physical and chemical properties. Wintertime layers initially have higher densities than summertime layers. This density contrast is maintained during the densification process (Fig. 1). The firn-ice transition occurs at the same density for wintertime and summertime layers, but wintertime layers attain the closeoff density at a shallower depth. Consequently, there is an interval of about 10 m in which wintertime layers are more extensively sealed than summertime layers. In this interval, permeable and impermeable layers alternate in the ice sheet.

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Figure 1

(From Martinerie et al.,. (Upper) Closed porosity vs. density in the firn at Summit, Greenland. Note the monotonic relationship between the two properties. When density = 0.83, open porosity = 0. The decrease in closed porosity at higher densities is due to compression of bubbles. (Lower) Closed porosity vs. depth for maximum-density layers and minimum-density layers. Note how maximum-density layers are completely closed by 75-m depth, and minimum-density layers by 83-m depth. In the intervening depth interval, parts of the firn remain permeable but gases cannot migrate vertically.

 

There are three regimes of gas transport in the firn. The uppermost layer, which appears to extend down to about 10-m depth at some sites where firn air has been sampled and analyzed, is affected by convective mixing driven by surface wind stress. Underlying the convective zone is the “stagnant air column,” in which transport is by molecular and atomic diffusion only. Diffusivities of gases are typically about 1 m2 day−1 at 10-m depth. Below, they decrease with increasing density, due to a combination of lower porosity and higher tortuosity (the latter factor accounts for the extra distances gas atoms and molecules must travel as they wind their way through the ice crystals to move from one depth to another).

The diffusivity of the firn is such that air at the base of the stagnant column today has a “CO2 age” ranging from about 6 yr for the GISP2 core (central Greenland) to about 40 years at Vostok (East Antarctica). In point of fact, however, air in firn at a given depth is not of a single age. The composition of firn air is convoluted by a number of processes. Air in the convective zone responds instantaneously to changes in atmospheric chemistry. These changes then propagate down into the stagnant column by molecular or atomic diffusion. Schwander et al. (calculated that the age of maximum abundance at the base of the firn is about 0.65·zt2/D, where zt is the height of the stagnant column and D is the free air diffusivity of the gas at the ambient temperature and pressure of the site. A small fraction of the gas is younger, and there is a long tail to older ages.

The diffusivity of an element or compound decreases with increasing mass and increasing atomic or molecular diameter. Thus each element or compound diffuses at a different rate, and each isotope of a compound diffuses at a different rate. In consequence, the covariation between the composition of one gas and another (e.g., CO2 and CH4) in firn is different from their historical covariation in air. The isotopic composition of a gas (e.g., CO2) in firn air also varies with the concentration of that gas in a way that is different from the historical relationship. The concentrations of gases and isotopes that diffuse most rapidly will be closest to their current atmospheric concentrations. Because light isotopes diffuse more rapidly, the concentration of a gas in firn air will be more depleted in heavy isotopes than was the atmosphere at the time it had the same concentration as a firn air sample. Differential diffusivity is a first-order effect that must be taken into account when interpreting data on the concentration and isotopic composition of gases in firn air and ice cores.

Several additional factors influence the composition of air in the firn. Gravitational fractionation is one. The pressure of gases increases with depth below the surface of the firn according to the barometric equation:m = mass in units of g mol−1, g is the gravitational acceleration constant, z is depth, R is the ideal gas constant, and T is Kelvin temperature.

As Craig et al. and Schwander recognized, this equation applies not only to bulk air but to each individual constituent of air in that (dominant) depth interval of the firn where transport is essentially entirely by diffusion (the stagnant air column). The rate at which the enrichment-per-mass unit increases with depth, expressed in the δ notation, is (Δmg/RT −1)·1,000, or about 0.005‰/amu per meter at typical firn air temperatures. The relative enrichment with depth for different species is directly proportional to the mass difference. The firn air data for the GISP2 site, central Greenland, demonstrate the expected enrichment for the δ15N of N2 (Fig. 2). The enrichment or depletion is significant for nearly all species, corresponding to 3 ppmv of CO2 at the base of deep firn profiles, for example.

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Figure 2

δ15N (Left) and CH4 (Right) vs. depth in firn air from the GISP2 site at Summit, Greenland. The subsurface maximum in δ15N is due to thermal fractionation (15N is enriched at 5- and 10-m depth because the firn at these depths, which remains at the mean annual temperature, is colder than air at the surface during summertime, when sampling was done). The increase below 20-m depth is due to gravitational fractionation. CH4 decreases very slowly to the top of the bubble closeoff zone at 70-m depth. Below it decreases very rapidly because gases cannot migrate vertically and the age of the gas in the firn increases as rapidly as the age of the ice (about 4 yr/m).

 

Seasonal changes in the concentrations of gases in air cause seasonal variations in firn air chemistry. The magnitude of these variations relative to their secular trends depends on location and property. The effect is perhaps largest for O2, CO2, and δ13C of CO2 in Greenland. Seasonal variations are damped out with depth and become very small below 30–50 m.

Thermal fractionation also affects the isotopic and elemental composition of firn air. Severinghaus and Severinghaus et al. first recognized the importance of thermal fractionation in porous environmental media in their studies of the composition of air in sand dunes. Temperature gradients cause fractionation, with heavier gases or isotopes being enriched in colder regions. For 15N, the fractionation is about 0.025‰/°C. Thermal fractionation is large in firn because gases diffuse faster than heat. In consequence, steep seasonal temperature gradients occur in the upper ≈5 m of the firn and gases nearly equilibrate with these temperature gradients. This effect produces large seasonal variations in isotopic compositions and in the O2/N2 ratio in the top few meters of the firn. The seasonal anomalies decrease with depth, and for most species are insignificant below 30 m. O2 is an exception; the concentration of this gas in air is changing so slowly (on a percentage basis) that seasonal thermal gradients are significant down to 60-m depth.

These processes combine to influence the composition of gas throughout the firn, and at its base where gases are trapped as bubbles in impermeable ice. Here, two modes of trapping are possible. First, seasonal layering may be absent and air may be trapped throughout the bubble closeoff zone. In this case, the composition of the bulk trapped gases in ice cores will be further convoluted because of the finite closeoff interval. At Vostok, for example, the bubble closeoff zone is about 8 m thick. A single layer of ice traps bubbles throughout the ≈300 yr it moves through this zone. This process accounts for the largest share of the dispersion of gas ages in a single sample of ice. At Summit, Greenland, on the other hand, high-density layers are completely sealed as they pass through the top of the bubble closeoff zone. Sealing forms vertically impermeable layers that prevent additional diffusive mixing and “locks in” the composition of gas present in the open, intervening, low-density layers. In such a case, individual ice samples can resolve time periods as short as a decade. The influence of lock-in at Summit can be seen from the firn air data at GISP2 (Fig. 2). δ15N ceases to rise below 70 m depth. CH4 and CO2 concentrations fall rapidly below this depth; CO2 and CH4 “ages” of firn air increase about as rapidly as ice ages below 70 m (4 yr/m). These firn air results are similar to those of Schwander et al., who developed the method for firn air sampling and studied the composition of air in the firn at the nearby GRIP site.

The final process influencing the composition of gas in polar firn and ice cores is effusion. Craig et al. suggested this process to account for the depletion of O2 and Ar relative to N2 in polar ice samples, as measured first by Raynaud and Delmas and later by Craig et al. and Sowers et al. . Craig et al. pointed out that O2 and Ar, with diameters of about 3 Å, were smaller than N2 (diameter 3.3 Å). They suggested that cracks and imperfections in the ice of about 3 Å spacing would allow the effusive loss of O2and Ar while selectively retaining nitrogen. It is not clear whether effusion takes place in situ during bubble closeoff or after ice cores are retrieved. Some indications for the former possibility are that deep firn air samples are enriched in O2 and Ar relative to N2, and that the O2 and Ar depletions of ice core samples do not increase after cores have been on the surface for a few days.

The processes affecting gases in ice cores need to be taken into account in reconstructions of the composition of the past atmosphere. First, measured concentrations of gases in ice cores and firn air need to be corrected for effects of gravitational fractionation and, where appropriate, thermal fractionation. Second, gas records are useful only when dated absolutely or on a time scale common to other records. Because bubbles close at depths of 40–120 m, gases are younger than the ice enclosing them. The gas age–ice age difference (Δage) is as great as 7 kyr in glacial ice from Vostok; it is as low as 30 yr in the rapidly accumulating Antarctic core DE 08. There are substantial uncertainties associated with Δage, limiting our ability to interpret some records. This is not a problem when reconstructing the anthropogenic transient from ice core studies, because one can align the recent part of ice core records with direct observations and assume that Δage is constant below the interval of overlap.

Once trapped in bubbles, air in ice cores is subject to two additional processes. First, bubbles are compressed under hydrostatic pressure. Second, gases eventually begin to dissolve in the ice as air hydrates. Nucleation is kinetically limited, and at ambient temperatures and pressures occurs over order 104 yr. As a result, air hydrates form at depths of about 400–1,500 m; cold temperatures and slow accumulation favor formation at shallower depths.

Different gases form clathrates at different pressures. In the long zone over which air hydrates and bubbles coexist in ice cores, the composition of gases in bubbles must be different from the composition in bulk ice. When gas samples are extracted after crushing of ice for a sufficiently long period of time, as is done for CO2 analysis, individual compounds are apparently not fractionated despite the fact that overall extraction efficiency is <100%. The evidence for this statement is that coherent records of CO2 are obtained by analyzing different ice cores, despite the fact that the dissolution of gases occurs in samples of different ages."

Edited September 14, 2017 by korab rules

[SabresFanInRochester]

It doesn't work that way.  The historic data points we have available are so limited that you can never compare apples to apples.  For data concerning the last 1000 years, we are using tree rings and air bubbles inside of ice cores.  Ice cores are obviously only available in the arctic and antarctic region, so what is going on in the rest of world at that time has to surmised.  To understand the problems inherent in relying on ice core information, you have to understand ice cores, how and over what period of time air bubbles are created in glacial ice, and the ways in which the air in a bubble can be affected over time.  Most people think of ice cores like they do sedimentary rock - but it doesn't work that way at all.  For a taste of how it works, and the reasons why ice core air bubbles are of limited value, read this quote from a scientific article:

 

"The density of ice at the surface of an ice sheet is typically 0.3–0.35 g cm−3; the corresponding porosity is 62–67%. Settling and packing cause the density to rise rapidly to about 0.55 g cm−3 by a depth of 10–30 m. Below, recrystallization and other processes drive a somewhat slower increase in density, which continues until individual crystals are fused together into an impermeable mass of glacial ice (1). At the “bubble closeoff depth,” about 10–15% of the volume is air, and the density is about 0.81–0.84 g cm−3 (2, 3). The “firn” is the zone of porous snow and ice above the closeoff depth, and the depth interval in which bubbles close is termed the “firn–ice transition.” Below the transition, densification continues by the compression of bubbles due to hydrostatic pressure.

When the snow accumulation rate at the surface of an ice sheet is greater than about 4 cm yr−1 (expressed as the ice-equivalent thickness of annual layers), discrete seasonal layers of snow are preserved that have characteristic physical and chemical properties. Wintertime layers initially have higher densities than summertime layers. This density contrast is maintained during the densification process (Fig. 1). The firn-ice transition occurs at the same density for wintertime and summertime layers, but wintertime layers attain the closeoff density at a shallower depth. Consequently, there is an interval of about 10 m in which wintertime layers are more extensively sealed than summertime layers. In this interval, permeable and impermeable layers alternate in the ice sheet (3).

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Figure 1

(From Martinerie et al., ref. 3). (Upper) Closed porosity vs. density in the firn at Summit, Greenland. Note the monotonic relationship between the two properties. When density = 0.83, open porosity = 0. The decrease in closed porosity at higher densities is due to compression of bubbles. (Lower) Closed porosity vs. depth for maximum-density layers and minimum-density layers. Note how maximum-density layers are completely closed by 75-m depth, and minimum-density layers by 83-m depth. In the intervening depth interval, parts of the firn remain permeable but gases cannot migrate vertically.

 

There are three regimes of gas transport in the firn (4, 5). The uppermost layer, which appears to extend down to about 10-m depth at some sites where firn air has been sampled and analyzed, is affected by convective mixing driven by surface wind stress. Underlying the convective zone is the “stagnant air column,” in which transport is by molecular and atomic diffusion only. Diffusivities of gases are typically about 1 m2 day−1 at 10-m depth. Below, they decrease with increasing density (5), due to a combination of lower porosity and higher tortuosity (the latter factor accounts for the extra distances gas atoms and molecules must travel as they wind their way through the ice crystals to move from one depth to another).

The diffusivity of the firn is such that air at the base of the stagnant column today has a “CO2 age” ranging from about 6 yr for the GISP2 core (central Greenland) to about 40 years at Vostok (East Antarctica). In point of fact, however, air in firn at a given depth is not of a single age. The composition of firn air is convoluted by a number of processes. Air in the convective zone responds instantaneously to changes in atmospheric chemistry. These changes then propagate down into the stagnant column by molecular or atomic diffusion. Schwander et al. (6) calculated that the age of maximum abundance at the base of the firn is about 0.65·zt2/D, where zt is the height of the stagnant column and D is the free air diffusivity of the gas at the ambient temperature and pressure of the site. A small fraction of the gas is younger, and there is a long tail to older ages.

The diffusivity of an element or compound decreases with increasing mass and increasing atomic or molecular diameter. Thus each element or compound diffuses at a different rate, and each isotope of a compound diffuses at a different rate. In consequence, the covariation between the composition of one gas and another (e.g., CO2 and CH4) in firn is different from their historical covariation in air. The isotopic composition of a gas (e.g., CO2) in firn air also varies with the concentration of that gas in a way that is different from the historical relationship. The concentrations of gases and isotopes that diffuse most rapidly will be closest to their current atmospheric concentrations. Because light isotopes diffuse more rapidly, the concentration of a gas in firn air will be more depleted in heavy isotopes than was the atmosphere at the time it had the same concentration as a firn air sample. Differential diffusivity is a first-order effect that must be taken into account when interpreting data on the concentration and isotopic composition of gases in firn air and ice cores (7).

Several additional factors influence the composition of air in the firn. Gravitational fractionation is one (8–10). The pressure of gases increases with depth below the surface of the firn according to the barometric equation:m = mass in units of g mol−1, g is the gravitational acceleration constant, z is depth, R is the ideal gas constant, and T is Kelvin temperature.

As Craig et al. (8) and Schwander (10) recognized, this equation applies not only to bulk air but to each individual constituent of air in that (dominant) depth interval of the firn where transport is essentially entirely by diffusion (the stagnant air column). The rate at which the enrichment-per-mass unit increases with depth, expressed in the δ notation, is (Δmg/RT −1)·1,000, or about 0.005‰/amu per meter at typical firn air temperatures. The relative enrichment with depth for different species is directly proportional to the mass difference. The firn air data for the GISP2 site, central Greenland, demonstrate the expected enrichment for the δ15N of N2 (Fig. 2). The enrichment or depletion is significant for nearly all species, corresponding to 3 ppmv of CO2 at the base of deep firn profiles, for example.

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Figure 2

δ15N (Left) and CH4 (Right) vs. depth in firn air from the GISP2 site at Summit, Greenland. The subsurface maximum in δ15N is due to thermal fractionation (15N is enriched at 5- and 10-m depth because the firn at these depths, which remains at the mean annual temperature, is colder than air at the surface during summertime, when sampling was done). The increase below 20-m depth is due to gravitational fractionation. CH4 decreases very slowly to the top of the bubble closeoff zone at 70-m depth. Below it decreases very rapidly because gases cannot migrate vertically and the age of the gas in the firn increases as rapidly as the age of the ice (about 4 yr/m).

 

Seasonal changes in the concentrations of gases in air cause seasonal variations in firn air chemistry. The magnitude of these variations relative to their secular trends depends on location and property. The effect is perhaps largest for O2, CO2, and δ13C of CO2 in Greenland. Seasonal variations are damped out with depth and become very small below 30–50 m.

Thermal fractionation also affects the isotopic and elemental composition of firn air. Severinghaus (11) and Severinghaus et al. (12) first recognized the importance of thermal fractionation in porous environmental media in their studies of the composition of air in sand dunes. Temperature gradients cause fractionation, with heavier gases or isotopes being enriched in colder regions. For 15N, the fractionation is about 0.025‰/°C. Thermal fractionation is large in firn because gases diffuse faster than heat. In consequence, steep seasonal temperature gradients occur in the upper ≈5 m of the firn and gases nearly equilibrate with these temperature gradients. This effect produces large seasonal variations in isotopic compositions and in the O2/N2 ratio in the top few meters of the firn. The seasonal anomalies decrease with depth, and for most species are insignificant below 30 m. O2 is an exception; the concentration of this gas in air is changing so slowly (on a percentage basis) that seasonal thermal gradients are significant down to 60-m depth.

These processes combine to influence the composition of gas throughout the firn, and at its base where gases are trapped as bubbles in impermeable ice. Here, two modes of trapping are possible. First, seasonal layering may be absent and air may be trapped throughout the bubble closeoff zone. In this case, the composition of the bulk trapped gases in ice cores will be further convoluted because of the finite closeoff interval. At Vostok, for example, the bubble closeoff zone is about 8 m thick. A single layer of ice traps bubbles throughout the ≈300 yr it moves through this zone. This process accounts for the largest share of the dispersion of gas ages in a single sample of ice. At Summit, Greenland, on the other hand, high-density layers are completely sealed as they pass through the top of the bubble closeoff zone. Sealing forms vertically impermeable layers that prevent additional diffusive mixing and “locks in” the composition of gas present in the open, intervening, low-density layers. In such a case, individual ice samples can resolve time periods as short as a decade. The influence of lock-in at Summit can be seen from the firn air data at GISP2 (Fig. 2). δ15N ceases to rise below 70 m depth. CH4 and CO2 concentrations fall rapidly below this depth; CO2 and CH4 “ages” of firn air increase about as rapidly as ice ages below 70 m (4 yr/m). These firn air results are similar to those of Schwander et al.(4), who developed the method for firn air sampling and studied the composition of air in the firn at the nearby GRIP site.

The final process influencing the composition of gas in polar firn and ice cores is effusion. Craig et al. (8) suggested this process to account for the depletion of O2 and Ar relative to N2 in polar ice samples, as measured first by Raynaud and Delmas (13) and later by Craig et al. (8) and Sowers et al. (9). Craig et al. (8) pointed out that O2 and Ar, with diameters of about 3 Å, were smaller than N2 (diameter 3.3 Å). They suggested that cracks and imperfections in the ice of about 3 Å spacing would allow the effusive loss of O2and Ar while selectively retaining nitrogen. It is not clear whether effusion takes place in situ during bubble closeoff or after ice cores are retrieved. Some indications for the former possibility are that deep firn air samples are enriched in O2 and Ar relative to N2, and that the O2 and Ar depletions of ice core samples do not increase after cores have been on the surface for a few days.

The processes affecting gases in ice cores need to be taken into account in reconstructions of the composition of the past atmosphere. First, measured concentrations of gases in ice cores and firn air need to be corrected for effects of gravitational fractionation and, where appropriate, thermal fractionation. Second, gas records are useful only when dated absolutely or on a time scale common to other records. Because bubbles close at depths of 40–120 m, gases are younger than the ice enclosing them. The gas age–ice age difference (Δage) is as great as 7 kyr in glacial ice from Vostok; it is as low as 30 yr in the rapidly accumulating Antarctic core DE 08. There are substantial uncertainties associated with Δage, limiting our ability to interpret some records. This is not a problem when reconstructing the anthropogenic transient from ice core studies, because one can align the recent part of ice core records with direct observations and assume that Δage is constant below the interval of overlap.

Once trapped in bubbles, air in ice cores is subject to two additional processes. First, bubbles are compressed under hydrostatic pressure (14). Second, gases eventually begin to dissolve in the ice as air hydrates (14, 15). Nucleation is kinetically limited, and at ambient temperatures and pressures occurs over order 104 yr (15). As a result, air hydrates form at depths of about 400–1,500 m; cold temperatures and slow accumulation favor formation at shallower depths.

Different gases form clathrates at different pressures (16). In the long zone over which air hydrates and bubbles coexist in ice cores, the composition of gases in bubbles must be different from the composition in bulk ice. When gas samples are extracted after crushing of ice for a sufficiently long period of time, as is done for CO2 analysis, individual compounds are apparently not fractionated despite the fact that overall extraction efficiency is <100%. The evidence for this statement is that coherent records of CO2 are obtained by analyzing different ice cores, despite the fact that the dissolution of gases occurs in samples of different ages.  "

 

i

I don't know. That sounds scientific but Bill Nye didn't say it so I am going to have to just dismiss the validity.

[qwksndmonster]

I don't know. That sounds scientific but Bill Nye didn't say it so I am going to have to just dismiss the validity.

lol Bill Nye and Jon Stewart, we've got some good mid 2000s burns against millenials going on now

[korab rules]

lol Bill Nye and Jon Stewart, we've got some good mid 2000s burns against millenials going on now

Bill Nye is a champion of the global warning crowd and in the news constantly despite not having an advanced science degree. Jon Stewart continues to run his mouth despite officially retiring from the Comedy Central's the daily show 2 years ago.  Sorry that isn't a recent enough pop culture reference for you.  

 

Which pizza place are you delivering for?  no good 'za in Elmira that I am aware of.

Edited September 14, 2017 by korab rules

[qwksndmonster]

Bill Nye is a champion of the global warning crowd and in the news constantly despite not having an advanced science degree. Jon Stewart continues to run his mouth despite officially retiring from the Comedy Central's the daily show 2 years ago. Sorry that isn't a recent enough pop culture reference for you.

 

Which pizza place are you delivering for? no good 'za in Elmira that I am aware of.

And Nye has a new effin' show. Talk about a career kept alive through nostalgia.

 

Jon Stewart indeed needs to keep his mouth shut. He comes back out of nowhere lecturing tv hosts while remaining completely disconnected from the current political climate. Yeah, real easy to throw rocks when you don't have to steer the ship of a nightly show.

 

I'm not going to debate climate change with you. Just stop trying to conflate belief and concern in climate change with the liberal political echo chambers of TV shows. You're also at odds with an overwhelming majority of the scientific community.

 

(Despite my classification of Jon Stewart/John Oliver type shows as echo chambers, I think those guys have done a lot of great work, obvi)

[SwampD]

Global warming,... sorry, man made global warming may or may not be a thing, but I'll just say that after discarding my life into dumpster, I'm sure glad I moved 40 feet higher in elevation. Should gain me at least a couple of years.

Edited September 14, 2017 by SwampD

[MattPie]

Global warming,... sorry, man made global warming may or may not be a thing, but I'll just say that after discarding my life into dumpster, I'm sure glad I moved 40 feet higher in elevation. Should gain me at least a couple of years.

 

I live at 590 ft above sea level on top of a hill. Never can be too safe.

[korab rules]

Global warming,... sorry, man made global warming may or may not be a thing, but I'll just say that after discarding my life into dumpster, I'm sure glad I moved 40 feet higher in elevation. Should gain me at least a couple of years.

 

 

I live at 590 ft above sea level on top of a hill. Never can be too safe.

Way to look on the bright side, guys!  Global warming is the democratization of waterfront property!

[Huckleberry]

I live in Belgium, along with the Netherlands we are ###### lol.    When the nickname for both countries is the low lands you know global warming is a bad thing.

Edited September 14, 2017 by Huckleberry

[JJFIVEOH]

Again, you don't understand it so it can't be real.

 

I don't understand how my doctor measures my cholesterol, but when he tells me its high, I listen to him and change my diet.

 

And doctors are routinely prescribe people drugs they don't need to be on because they're bought off by pharmaceutical companies. 

 

Sorta like how college professors are paid for by US grants to "conclude" there is global warming.............. or sorta like petroleum companies paying for studies to "conclude" that they are clean and have no impact on the environment. 

[korab rules]

And Nye has a new effin' show. Talk about a career kept alive through nostalgia.

 

Jon Stewart indeed needs to keep his mouth shut. He comes back out of nowhere lecturing tv hosts while remaining completely disconnected from the current political climate. Yeah, real easy to throw rocks when you don't have to steer the ship of a nightly show.

 

I'm not going to debate climate change with you. Just stop trying to conflate belief and concern in climate change with the liberal political echo chambers of TV shows. You're also at odds with an overwhelming majority of the scientific community.

 

(Despite my classification of Jon Stewart/John Oliver type shows as echo chambers, I think those guys have done a lot of great work, obvi)

I recognize that there are free thinkers who have arrived at a belief in global warming, or man made global warming, of their own accord based on their own review of available evidence.  I also firmly believe that a majority of the country can't think their way out of a paper bag, and are perfectly content reading no further than the headlines of articles that show up in their facebook timeline, and get their "news" from the likes of Jon Stewart.  Even those moderately interested in politics and the environment are perpetually blasted by a lockstep media that won't tolerate freedom of thought.  The modern media has raised a generation of sycophants.  Google and facebook ensure contrary thoughts are never seen.  Confirmation bias takes care of the rest.

 

Many people have no idea why they believe in man made global warming - they just know that they do. 

[SwampD]

I recognize that there are free thinkers who have arrived at a belief in global warming, or man made global warming, of their own accord based on their own review of available evidence.  I also firmly believe that a majority of the country can't think their way out of a paper bag, and are perfectly content reading no further than the headlines of articles that show up in their facebook timeline, and get their "news" from the likes of Jon Stewart.  Even those moderately interested in politics and the environment are perpetually blasted by a lockstep media that won't tolerate freedom of thought.  The modern media has raised a generation of sycophants.  Google and facebook ensure contrary thoughts are never seen.  Confirmation bias takes care of the rest.

 

Many people have no idea why they believe in man made global warming - they just know that they do. 

Many people have no idea why they don't believe in man made global warming - they just know they don't. Actually they do, cuz their media told them so.

 

Ironic, no?

[rakish]

For those interested, this is the full paper that korab quotes

[SwampD]

For those interested, this is the full paper that korab quotes

So that's the one paper disputing MMGW. Nice work. You found it.

 

 

 

 

 

:devil: