During at least the
time period when water vapor (WV) and carbon dioxide (CO2) have been
accurately measured worldwide, 1988-now, and apparently for centuries, WV
increase has been responsible for the human contribution to Global Warming with
no significant net contribution from CO2 or any other greenhouse
gases.
The words ‘water
vapor’ can be a bit misleading. WV is a transparent gas. If something is
visible, like steam or a cloud, it is not WV but is condensed liquid water
droplets or tiny bits of ice.
The term ‘vapor pressure’ has different meanings in different disciplines. In meteorology it means the partial pressure of WV in the atmosphere. In most other disciplines and general use, it means the pressure developed by the liquid as a result of its impetus to change phase and become a gas. This impetus depends only on the temperature of the liquid water. It is unambiguously called saturation vapor pressure. In this document, the saturation vapor pressure is sometimes referred to simply as vapor pressure (VP). The pressure of WV in the atmosphere might be identified as its partial pressure.
Another difference in term usage is the meaning of the word ‘feedback’. In engineering it usually refers to feedback factor, a dimensionless number which is the ratio minus one of response with feedback to the response if there were no feedback. In most science disciplines it refers to the magnitude of the response to a forcing which contributes to the cause of the forcing. In Climate Science it is measured in W/m2.
At a scale of
the size of atoms the atmosphere consists of spinning and vibrating gas
molecules, with empty space between them, bouncing elastically off surfaces and
each other. Activity of all of the gas molecules determines properties which
can be measured such as temperature and pressure. Only certain gas molecules
significantly contribute to radiation heat transfer. These are IR active in the
wavelength range of earth temperatures, are misleadingly called greenhouse
gasses (ghg) and include CO2 and WV. The radiation energy travels
from ghg molecule to ghg molecule (or between surface and ghg) at the speed of
light (in the atmosphere which is 99.97 % of the speed of light in a vacuum)
but effectively dwells in each molecule making the
molecule warmer. The increased cumulative dwell time from increased WV
molecules is what causes the increased Greenhouse Effect (GHE).
Approximately 99% of dry atmospheric molecules are non-ghg; nearly all nitrogen and oxygen with about 1% argon. Near the surface, they are substantially warmed by thermalization of the earth-source thermal radiation energy absorbed by the ghg molecules and, at higher altitudes (starting a few meters or less above the surface), cooled by pressure decline and reverse-thermalization back to the ghg molecules. Above about 2 km altitude, because of steep decline of the population of WV molecules, lower pressure, and wider spacing between ghg molecules, outward directed radiation from WV molecules can make it all the way to space.
All molecule
species are fairly well mixed throughout the atmosphere with the exception of
WV. WV molecule population declines with altitude from average of about 8,000
ppmv (parts per million by volume) at sea level [34, 35] to, because of the low
temperature (~ -50 °C, saturation vapor pressure of ice 3.94 Pa [28] and total
pressure at 12 km of 19,400 Pa), to a maximum of about 3.94/19,400 = 0.000203 =
203 ppmv at the tropopause. The 8,000 ppmv (0.8%) average increases to about 4%
in the tropics.
The tropopause altitude averages about 12 km (39,370 ft) with up to 16 km or so at the equator. In addition to the population decline of WV molecules due to temperature decline, is the decline due to average pressure decline of 19.4/101.3 = 0.19 from a sea level pressure of 101.3 kPa. The combination results in an overall average WV molecule population decline up to the tropopause of about 8,000/203 * 101.3/19.4 = 206 to 1.
2. Thermalization
Thermalization and/or reverse-thermalization (thermal conduction from surrounding molecules to replenish energy radiated by a ghg molecule) occur continuously throughout the atmosphere. Typical TOA emission spectra are shown in Figure 1. A black-body emission curve (emissivity 1) for an average global temperature of 288 K is a bit higher than a curve for the actual surface which has an emissivity about 0.99. The TOA flux is the black trace in Fig 1. The TOA and surface curves show radiation flux being slowed between the two locations (absorbed/emitted by all ghg). Prominently shown is the ‘notch’ associated with the CO2 absorb/emit band. The actual surface curve minus the TOA curve results in what is called the Greenhouse Effect (GHE).
A much more extensive description of thermalization is at Section 4 of [19].
Hitran [2] using
Quantum Mechanics and measurements determines, besides many other things, the relative
absorb/emit intensity of water vapor molecules vs CO2 molecules.
Comparison at zero altitude, when scaled by atmospheric abundance, is shown in
Figure 2. At sea level WV molecules outnumber CO2 molecules by about
8,000/330 ≈ 24 to one.
The relative
effectiveness of the increases of WV and CO2 over 30 years is
calculated as follows:
CO2
increase in 3 decades [3], 1988 to 2018: 407 - 348 = 59 ppmv
Average global water vapor increase trend from Figure 5, which is a graph of NASA/RSS TPW data, is 0.0416/29 * 100 * 10 = 1.43 % per decade.
The ground level population of WV molecules averaged about 8000 [34, 35]. Figure 3, at 30 degrees latitude (area to pole = area to equator) also averages global WV ≈ 8,000 ppmv. WV increase in 3 decades = 0.0143 * 8,000 * 3 = 343 ppmv.
Therefore, assuming
equivalent effectiveness per molecule, WV increase has been 343/59 ≈ 5.8 times
more effective at increasing ground level IR absorption than CO2
increase 1988-2018. (Much of the world human population has been falsely
indoctrinated)
Outward directed emission of WV below wavenumber 600 can make it all the way to space. Energy absorbed by CO2 molecules below the tropopause is redirected wrt wavenumber via thermalization to replenish energy radiated to space by WV molecules.
Well above the tropopause, radiation emitted from molecules there to space is primarily from CO2 molecules (indicated in Figure 1 by the spike at wavenumber 667). If you ignore the increase in water vapor (big mistake), near the surface, WV averages about 8,000 ppmv. The increase in absorbers at ground level since 1900 is then about 8,410/8,295 ≈ 1%. WV above the tropopause is limited to about 203 ppmv because of the low temperature (~ -50 °C) while the CO2 fraction remains essentially constant with altitude at (in 2019) about 410 ppmv; up from about 295 ppmv in 1900. The increase in emitters to space at high altitude (~> 20 km, 0.055 atm), and accounting for the lower atmospheric pressure, is (410 + 203)/(295 + 203) * 0.055 ≈ 0.068 = 6.8%. This (6.8%>1%) explains why CO2 increase does not cause significant warming (except near the poles). The result being that Climate Sensitivity (the temperature increase resulting from doubling the CO2 level) is not significantly different from zero.
More evidence that CO2 has no significant effect on climate is at Sect 2 of [19].
The exception at the poles is because it’s cold there at ground level so WV molecule count is already low. Therefore, transfer of energy to WV molecules which radiate it to space is negligible.
WV increase is a
cause of warming (average global temperature increasing) because it is a ghg. Part
of WV increase is a result of surface water warming because its saturation vapor
pressure increases with temperature. The saturation vapor pressure increase
causes an increase in the rate of WV molecules being forced into the atmosphere
(when the atmosphere at ground level is less than saturated with WV which is
usually the case). An additional source of WV increase is human activity,
especially irrigation. This is discussed further in Section 6.
In the atmosphere, condensed water can exist as water, ice or super-cooled water [26] (super-cooled water is liquid water below 0.0 °C). Accurate numerical values for saturation vapor pressure of liquid water [27] and ice [28] are graphed in Figure 4. Saturation vapor pressure for super-cooled water can be calculated using the Bolton equation [25]. The Bolton equation for saturation vapor pressure in kPa vs temperature in C is
p = 0.6112 * e^(17.67 * T /
(T+243.5)) (1)
As shown in Figure 4, saturation vapor pressure increases progressively with temperature. Of interest is the % increase in saturation vapor pressure per degree increase in temperature. This is readily calculated from the numerical data for both liquid water and ice from:
1/1 increase/Tave = (pj
– p(j-1)/(Tj – T(j-1))/Tave (2)
Where,
1/1 = %/100
j and (j – 1)
are adjacent values in the table
Tave = average
temperature of the adjacent values.
The same thing
for super-cooled water is obtained using the first derivative of the Bolton
equation which is
dp/dT = p * 17.67 * 243.5/(T+243.5)^2 (3).
This, divided by
p to get the 1/1 value curve, is shown in the bottom graph at Fig. 4.
Saturation vapor
pressure depends ONLY on the temperature of the ice or liquid water. The 1/1
change in saturation vapor pressure per Celsius degree for water, ice and
super-cooled water are shown in the lower graph of Figure 4.
Figure 4: Saturation vapor pressure of ice &water
and fractional rate of change per C degree change vs temperature.
The atmospheric temperature decreases with altitude so the accommodation for WV increases with altitude to about 12%/C° at the tropopause (°C is a temperature, C° is a temperature difference). This can result in the perhaps counterintuitive condition that as surface temperature increases, WV (specific humidity) increases but accommodation for WV in the atmosphere increases even more, so relative humidity decreases.
Based on ocean temperatures from [29], the area-weighted change in saturation vapor pressure per C degree at sea level is about 0.0633 / C°. The amount of compounding is unknown but cannot be greater than 0.0633+0.0633^2+0.0633^3+… = 0.0676/C°. It is conservatively estimated to be about 0.067/C° = 6.7%/C°
The accelerated
increase in WV, above that determined from just global temperature increase, is
expected from the surge in irrigation and has also been measured. Average
measured global atmospheric water vapor (total from surface to TOA) over the
years is provided here at Figure 5.
Worldwide about 86% of irrigated area is flood irrigated
[20]. To simplify calculation, assume all irrigation is flood irrigation
approximated as furrow type [16]. Optimum frequency is to flood the furrows
about every 10 days [17]. Thus about half the area is covered by water 10% of
the time where evaporation from the water is about one meter per year [18] and
the rest of the time, the additional evaporation is assumed to be according to
the calculated evapotranspiration. Evapotranspiration prior to irrigation must
have been low or irrigation would not be done. Evapotranspiration with
irrigation, to be cost effective, is most likely to be much more than
calculated. These two uncertainties are assumed to approximately cancel each
other. A further assumption is that, on average, irrigation is applied for
about 1/3 year. The total amount of WV resulting from irrigation is then
[(0.1 * (1 + 0.45)/2
+ 0.9 * 0.45) * 266E10]/3 = 42.3E10 m3 /y = 42.3E13 kg/y (k)
These calculations are summarized in Table 1
Water vapor source |
E13 kg/y |
% |
Irrigation |
42.3 |
90.0 % |
Transportation fuel |
0.4 |
0.8 % |
Fossil fuel for electricity generation |
0.3 |
0.7 % |
Cooling towers, etc. for electricity generation |
4.0 |
8.5% |
Total |
47.0 |
100 % |
Table 1: Summary of
contributions to atmospheric water vapor.
WV increase above that due to feedback from liquid water
temperature increase results about 90 % from irrigation. WV added by irrigation
is particularly influential because it is added at locations where natural WV
is low and because the liquid water is shallow, it is quickly and substantially
warmed by the sun.
The oceans, especially the warm tropical areas, produced the WV responsible for the basic GHE temperature increase of 33 K. Figure 6.1 shows typical WV distribution over the planet.
Figure 6.1: Typical WV distribution over the planet. [39]
Aquastat, a UN organization, has collected worldwide water use data in a massive document [36]. Their findings are summarized there graphically. A figure copied from their report is shown here as Fig 6. Numerical data for irrigation was obtained by measuring the graph. A parabola which fit nearly perfectly to the data was used to interpolate to get yearly values for the amounts used for agriculture. This equation is irrigation water = - 0.2880952*yr^2 + 1167.858 * yr - 1180741.3. It matches the reported values within approximately ±20km*3/yr.
Average global WV has been measured by NASA/RSS using satellite-based instrumentation. This data is reported as anomalies [5]. Annual data was obtained by averaging the monthly data for each year. Figure 6.3 shows annual water use for irrigation and year-average measured WV for the period of overlap. Pearson correlation coefficient for these two data sets is 0.789 [37] with probability of correlation occurring by chance (p-value) [38] of 0.00000031. Thus, it is shown with very high confidence that irrigation contributes significantly to measured WV increase.
Figure 6.3 Correlation shows that irrigation contributes
to WV.
The measured increased WV, which includes humanity’s contribution, mostly from irrigation in previously warm dry areas, has contributed an additional approximately 0.8 K [19] of the total average global temperature increase since 1895. Ref [19] identifies the three contributing factors considered, the data sources, and the algorithm which calculates the temperatures which match measured average global temperatures 96+% 1895-now (thru 2023).
The assessment here that irrigation accounts for 90% of humanity’s contribution to WV corroborates what Shiklomanov 1997 determined as mentioned by Doll in 2002 [33].
Given the earth area of 510E12 m^2 and average annual precipitation of about a meter or 1000 kg/m^2 the increased water use, mostly for irrigation, results in 47E13/5.1E17 = 0.0009 = 0.09 % equivalent increase in global precipitation.
7. Comparison of measured WV with WV increase calculated from feedback over a long time period.
Some people have asserted that WV content increases with air
temperature. That would be true if the air was all continuously at saturation.
Of course it is not. The driving factor for WV increase from temperature
increase is the saturation vapor pressure increase due to temperature increase
of the liquid water source. Increase of air temperature does add accommodation
for the added WV. The NET driving factor is the vapor pressure deficit which is
the difference between the saturation vapor pressure of the liquid surface
water and the partial pressure of WV in the atmosphere.
As described in Section 4, as the temperature of liquid surface water increases, its vapor pressure increases which, if it’s not already saturated, forces more WV molecules into the atmosphere. This contributes to a net feedback from all factors which caused the temperature to increase. A conservative value for WV increase (actual WV increase from feedback will be less than so calculated) was estimated in Sect 4 from available measured data to be 6.7% = 0.067 1/1. The large effective thermal capacitance of the planet is the main contributor to the conservatism. The temperature rise is in response to the time-integral of the forcing so it will lag the feedback forcing.
The file for calculated change in WV is generated in EXCEL
where each row contains:
WVn = WV(n-1) + (Tn – T(n-1))*
R * (WV(n-1) + F)
Where:
WVn = calculated WV in month n, kg/m^2
Tn = temperature anomaly in month n, C°
R = effective
rate of WV increase resulting from feedback of temperature increase, 0.067/C° (=
6.7 %/C°)
F = added to avoid circular reference of (WV(n-1)+WVn)/2.
For HadCRUT5 [31] as of Dec 2021, F = 0.029835/24 = 0.00124 kg/m^2/month.
Slope at F = 0 is 0.0298342. Effect over 34 yr = (0.0298355 - 0.0298342)*34 = 0.000044
kg/m^2
The starting calculated WV is adjusted to make the starting points of the trends the same.
The results of this algorithm are shown in Figure 7 along with the actual measured WV anomaly measured and reported by NASA/RSS [5] (plus 28.73). The measured WV is about 40.4% steeper than the calculated trend using HadCRUT5, Jan 1988 – Dec. 2023 temperature trend and 6.7%/K.
0.4161/0.3105 = 1.34
Figure 7: Measured WV
and calculated WV based on HadCRUT5 reported average global temperatures and
compounded feedback.
The GCMs calculate the WV within the models with the result that relative humidity is approximately constant. The linear trends assuming three different values for average relative humidity remaining constant with increasing air temperature are included on Figure 7.1.
The observation that the actual measured trend is steeper than calculated trends demonstrates that, on the long term, measured WV is increasing faster than possible from just temperature increase of the liquid water (feedback). The steepest slope calculated for the constant RH cases is (29.36 – 28.242)/34 = 0.0329 kg/m^2/y. The measured trend is then 0.0419/0.0329 = 1.27 or about 27% steeper than the estimated trend calculated within GCMs.
Figure 9: Scatter graph of WV vs HadCRUT5 measured
data.
This provides
fertile ground for those motivated to mislead to cherry-pick periods where the
increasing side of fluctuations drives both WV and outgoing-longwave-radiation
up.
26. Ice and mixed phase clouds: http://www.cas.manchester.ac.uk/resactivities/cloudphysics/background/ice/
27. Wexler, vapor pressure of
water: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5312760/
28. Wexler, thermodynamic
calculations for the vapor pressure of ice: https://nvlpubs.nist.gov/nistpubs/jres/81A/jresv81An1p5_A1b.pdf
30. HadCRUT4 data: http://www.metoffice.gov.uk/hadobs/hadcrut4/data/current/time_series/HadCRUT.4.6.0.0.monthly_ns_avg.txt
31. HadCRUT5 data: https://www.metoffice.gov.uk/hadobs/hadcrut5/data/current/download.html
32. Theory of Redirected energy: https://energyredirect3.blogspot.com
33. Water vapor generated by humanity is 90% from irrigation: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001WR000355
34. Ground level WV 5 g/kg ≈ 8000
ppmv in 1992: https://www.eso.org/gen-fac/pubs/astclim/espas/pwv/mockler.html Fig 1
35. Ground level WV 8,000 ppm WV
vs altitude Spectralcalc: https://www.spectralcalc.com/atmosphere_browser/modify_atmosphere.php
36. Water use: https://www.fao.org/aquastat/en/overview/methodology/water-use
37. Pearson coefficient
calculator: https://www.socscistatistics.com/tests/pearson/default2.aspx
38. p-value calculator: https://www.danielsoper.com/Statcalc/calculator.aspx?id=44
39. Ave global WV: https://www.labxchange.org/library/items/lb:LabXchange:328c385b:html:1
Very interesting paper and thanks for sharing it Dan.
ReplyDeleteWho is the author?
DeleteDan Pangburn, P.E. (ret), MSME, ASME life member
DeleteAgree, very important investigation.
ReplyDeleteThe key is to simplify.
We know the black body temperature steady state temperature of the earth which can easilly be calculated to -18 Celsius, meaning without atmosphere.
We know aveage earth temperature today which is + 14 C Celcius.
I am trying to corelate the two and need discussion about CO2 and WV H2O. Most important how many Watt -1 Tonn of each backscatter..
Without the Atmosphere as we know today, the black body steady state temperature of the earth would be different from -18 C due to Oceans.
ReplyDeleteThe -18 C assumes albedo of 0.3 which would not hold if no atmosphere. Also, if no atmosphere there would be no water vapor and no oceans.
DeleteSo what do we do about the irrigation problem?
ReplyDeleteWater vapor, and warming from increased WV, is limited by how much WV the atmosphere will hold. The amount of warming possible from increased WV appears to be less than a degree K and not a problem. Global cooling, portended by the quiet sun, is a far greater threat. The warming from increased WV is countering that, will slow and possibly prevent it
DeleteThis comment has been removed by the author.
DeleteGreat article (I'm a retired CEng). Nice statement re WV warming balancing quietening sun! Trying to convince youngsters they're not about to die through CO2 climate change is a challenge.
ReplyDeleteThanks. It seems a higher % of engineers figure it out than others.
ReplyDeleteChemical Engineer by training, now missionary to Haiti. In college Univ of Texas at Austin, one of my classes was a heat and material balance of the earth. It stretched my mind.
Deleteyes the engineer/scientist divide is often amusingly stark
Deletei like to joke that a scientist's job is to come up with a thousand ideas in hopes that one might move us a little closer to the truth, whereas an engineers' job is avoid a thousand fatal mistakes in one real-world application so that it works every time
In researching scientific data on climate after retirement from spending 40 years researching and designing jet engines, I discovered that the water vapor component of the atmosphere is about 75 times that of CO2 and became very suspicious of the IPCC claims about CO2. I am fascinated with this in -depth analysis, which shows the dominance of water vapor. Very gratifying!
ReplyDeleteHi Dan, I found your paper very interesting... do you have a rough idea how the total WV content of the atmosphere compare to human WV emissions?
ReplyDeletewondered a few years back how much human water usage would have to increase to affect sea levels and after some BOE calcs the answer there seems to be “by a few orders of magnitude” but then of course the hydrosphere masses about 300x what the atmosphere does so that seems like it might be in a relevant ballpark for WV
at any rate the idea human WV emissions might directly affect temp and thus CO2 levels is certainly intriguing... might help explain several discrepancies in the IPCC view... hope you are able to write more
Not much. In Section 6 it is calculated that humanity adds on average only about 0.00026% to the average precipitation.
Deletethanks, interesting
DeleteOops, I discovered a factor of 1000 error (Its been fixed). Humanity adds on average only about 0.26% to the average precipitation.
DeleteVery interesting. One large-scale climate effect of irrigation I know myself---for the past 30 years, the North India plains (including West Punjab and East Bengal) have seen far more winter fogs than were known previously. This coincides with a great increase in tube-well irrigation and consequent groundwater extraction on a massive scale.
ReplyDeleteI think that only the ground water extraction component of the irrigation should be included in your estimate of 3986 km3 of total irrigation. The surface water is merely being shifted from one place to another. Only the groundwater extraction adds to the surface water quantity.
Gyan, My argument for including surface water there is that the area where evaporation takes place is what matters and essentially all of the surface water would be spread out adding to the evaporation area without significantly diminishing the surface area of its source. Realize that this was just a sanity check and did not contribute to the findings shown in Table 1.
DeleteHow does water vapour account for regular abrupt climate changes of Dansgaard-Oeschger events during the glacial cycle?
ReplyDeleteIt doesn't. Human influence on WV was tiny prior to about 1800 and the rate increased dramatically around 1960.
DeleteDan, most interesting. However, I don't understand where you've gotten your extrapolation of water vapor back to the year 1600 ... what did I miss?
ReplyDeleteMy best to you,
w.
W,
DeleteYou didn't miss anything. I had developed the extrapolation in 2016 for use in http://globalclimatedrivers2.blogspot.com. The graph appears as Fig 3 there with very brief explanation (and wrong coefficient, I actually use 4.5247, not 4.5118). I used smoothed CO2 as a proxy and the resultant graph looks reasonable to me. I found these notes where I did it:
TPW = X (CO2 ppmv)^Y
π= (ln(πππ1−ln(πππ2)/(ln(πΆπ2,1)−ln(πΆπ2,2))
X = TPW1/CO2,1^Y
1. Linear eqn thru TPW data
2. Calc TPW1 & TPW2 from [linear regression] eqn
3. Select CO2,1 & CO2,2 frm [smothed] data [for same time interval?]
[That second equation should be: π= (ln(πππ1)−ln(πππ2))/(ln(πΆπ2,1)−ln(πΆπ2,2))
Thanks for the clarification, Dan. What I'm still not understanding is why you think that TPW varies linearly with the log of CO2 ... where is the observational evidence for that relationship?
Deletew.
The temperature varies with the log of CO2 or also with the log of WV (your work). Things proportional to the same thing are proportional to each other.
DeleteThanks so much for this illuminating analysis, Dan. Has anything like this been published in a peer-reviewed journal? I am not aware of anything that targets increased irrigation. You make a good case for the role of increased irrigation in the increase in global temperature in recent decades.
ReplyDeleteSee:
Deletehttps://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1195&context=natrespapers
w.
Thanks for the comments. IMO the key discovery is that water vapor has been increasing faster than possible from just planet warming (feedback) (Sect 7). This refutes the popular theory that CO2 with feedback caused the warming. The survey to find the source of the 'extra' water vapor was just out of curiosity. Later I found out that it corroborated an earlier study published by AGU. It is listed as Ref 33.
DeleteThanks for your response, Dan. Yes, I noted your strong point about the water vapor increasing faster than just planet warming would explain. I have not seen any other work that identifies the increase in global irrigation as a significant factor in recent global warming, but it makes sense. It would be nice to see your work get broader exposure through being published in a journal. Thanks again. Don
Delete@ Willis: thanks for the reference. I found several of these sorts of studies, but they are looking at local/regional effects, not global. It does raise the issue of advancing irrigation into semi-desert areas causing a decreased albedo, which of itself could cause warming, aside from the effect of raised humidity.
Delete