AMREE 1981 · 790 weather-balloon stations · the alveolar gas equation
The Mountain Stands in Thicker Air
By the standard atmosphere, the air pressure on the summit of Everest is 236 Torr, so low that a person breathing the way they do at sea level would have no oxygen left in their lungs at all. The barometer carried to the top in 1981 read 253. The difference is where the mountain stands. Everest is in the subtropics, where the air beneath the summit is warm and there is more of the atmosphere still overhead at 8,849 m, and the people who climb it without bottled oxygen pant their carbon dioxide down to a fifth of its normal level. Below, 790 weather-balloon stations are asked what the summit air would be if Everest stood above them, month by month. At Denali's latitude, its best month would be thinner than its worst month is over Tibet.
The arithmetic that says no
The air you breathe is about 21% oxygen at any height; what thins with height is the air itself. How much oxygen reaches the air sacs of the lungs, where the blood picks it up, is set by three numbers, and physiologists write them into one line called the alveolar gas equation:
PAO₂ = 0.2093 × (PB − 47) − PACO₂ × 1.139
PB is the barometric pressure. The 47 is water vapour: the airway saturates every breath at body temperature, and at 37 °C water vapour takes 47 Torr of whatever pressure there is, first. What is left, times oxygen's share of dry air (0.2093), is the oxygen you breathe in. The last term is what carbon dioxide costs: the lungs are also where it leaves the blood, and the more of it sits in the air sacs, the less room there is for oxygen. The factor 1.139 comes from assuming the body gives off 0.85 molecules of carbon dioxide for each molecule of oxygen it takes up, the value the 1981 expedition's summit paper used.
At sea level, with the ordinary 40 Torr of carbon dioxide in the air sacs, the equation gives about 104 Torr of oxygen. Now put in the summit. The standard atmosphere (the 1976 U.S. edition: one fixed profile of pressure against height, the same everywhere) gives 236.2 Torr at 8,848.86 m. Water vapour takes 47 of it, and the oxygen breathed in is 39.6 Torr. Ordinary breathing charges 45.6 Torr for carbon dioxide. The equation comes out below zero. Breathing as you do at sea level, it runs out at 264.8 Torr, which is higher than the summit's pressure by either reckoning. Nobody reaches the top of Everest breathing like that. Anyone who reaches it without bottled oxygen has done two things: gone to a mountain whose air is thicker than the table says, and breathed so hard that the carbon dioxide term nearly vanishes. Try both.
One breath: the oxygen left in the air sacs
Set the pressure to the measured summit and slide the carbon dioxide down. The oxygen comes back only as the carbon dioxide goes: every Torr of it you breathe off returns 1.139 Torr of oxygen. The expedition's summit samples held 7.5 Torr of carbon dioxide, which the equation turns into 34.6 Torr of oxygen (the paper gives 35). The same breathing at the standard atmosphere's 236.2 would leave 31.1.
What the barometer said
On 24 October 1981, Chris Pizzo, a physician on the American Medical Research Expedition to Everest, reached the summit at about half past twelve with Sherpa Yong Tenzing, read a light hand-held barometer with a digital output, and collected samples of expired air, which were carried back to San Diego in gas-tight cans. The expedition's leader, the physiologist John West, and four colleagues reported the reading in the Journal of Applied Physiology in 1983:
“The mean daily pressures were 400.4 +/- 2.7 (SD) Torr (n = 35) at 5,400 m, 351.0 +/- 1.0 Torr (n = 16) at 6,300 m, 283.6 +/- 1.5 Torr (n = 6) at 8,050 m, and 253.0 Torr (n = 1) at 8,848 m. All these pressures are considerably higher than those predicted from the ICAO Standard Atmosphere.”
J. B. West, S. Lahiri, K. H. Maret, R. M. Peters Jr and C. J. Pizzo, “Barometric pressures at extreme altitudes on Mt. Everest: physiological significance”, J. Appl. Physiol. 54 (1983), 1188 to 1194, abstract.
The standard atmosphere's 236.2 is 16.8 Torr below that. The gap had been predicted before anyone measured it: Griffith Pugh, the 1953 expedition's physiologist, “predicted a pressure of 250 Torr for the summit of Mt. Everest in 1957”, West and Wagner wrote in 1980, and their own paper, using weather-balloon data from New Delhi (and Gauhati) that Charles Stidd of Scripps analysed for them, put it at 249 to 250 Torr in May and October; the standard atmosphere, they wrote, “gives a value of about 235 Torr”, and the difference “results in a doubling of predicted maximal oxygen uptake.” Of the summit samples, the expedition's gas-exchange paper, also of 1983, reported:
“Alveolar CO2 partial pressure (PCO2) fell approximately linearly with decreasing barometric pressure to a value of 7.5 Torr on the summit. For a respiratory exchange ratio of 0.85, this gave an alveolar O2 partial pressure (PO2) of 35 Torr.”
J. B. West, P. H. Hackett, K. H. Maret, J. S. Milledge, R. M. Peters Jr, C. J. Pizzo and R. M. Winslow, “Pulmonary gas exchange on the summit of Mount Everest”, J. Appl. Physiol. 55 (1983), 678 to 687, abstract.
West, looking back in 2019 on the 7.5: “This was an almost unbelievably low value since the sea level value is about 40 mm Hg.” His plainest statement of what the two findings mean together is in a 1982 review, written once the expedition was home: “It is apparent that the mountain can be climbed without supplementary oxygen only because the barometric pressure at the summit is not as low as has often been predicted, and because of the extreme hyperventilation that man develops under these conditions.”
Why the air is thicker there
The pressure at any height is the weight of the air still above it. How much air is above a given height depends on how far the air below has expanded, and warm air expands: the hydrostatic equation makes this exact, and says that for the same pressure at the ground, the pressure at 8,849 m is higher wherever the column of air underneath is warmer. Everest is at 28° north, under the warm, tall troposphere of the subtropics. A 2020 study put it this way: “Mt. Everest is, along with all other peaks over 8,000 m, located in the warmth of the subtropics.” West's 1983 abstract gave a different reason, from the top: pressures at these heights are “higher near the equator because of the large mass of cold air in the stratosphere of that region.” (His 1980 paper with Wagner gave a third, the “oblate spheroid shape of the atmosphere”.) What the balloons below weigh, either way, is how much air is still overhead at 8,849 m, and the hydrostatic arithmetic this page uses needs only the ground pressure and the temperature of the column beneath.
You do not have to take that on trust, because the atmosphere has been measured, twice a day, for decades. NOAA's Integrated Global Radiosonde Archive gathers weather-balloon soundings from stations around the world, and its monthly means give, for each station, the height and temperature of the standard pressure levels. At each station and month, this page finds the pressure at the height of Everest's summit: 8,848.86 m, converted to the geopotential metres balloons report in (about 8,823 over Tibet, about 8,850 over Alaska, because gravity is weaker near the equator), and interpolated between the two levels that bracket it, normally 400 and 300 hPa, assuming temperature changes linearly with height between them. Keep the stations with at least ten Januaries, ten Februaries and so on in 1991 to 2020, and you have 790 of them. Choose a month, and put Everest anywhere.
If Everest stood here
Over the whole year the stations draw an arch: highest across the tropics, where it barely moves with the seasons (the mean over every station from 10°S to 10°N is 254.5 Torr for the year), falling toward the poles, and swinging hard with the seasons in between. The standard atmosphere's 236.2 is close to what the balloons give for the band from 40 to 50°N over a year, 238.0. Everest's own latitude sits on the shoulder of the arch.
Then move Everest north. Denali, in Alaska, is at 63.07° north. The long Alaskan radiosonde record closest to that latitude is McGrath's, at 62.96°, about 230 km west of the mountain, and above it the summit of an Everest would sit in air of 238.4 Torr in its warmest month, July, and 217.6 in December. Over Tibet and northern India, the worst month of the year is January, at 242.7 to 243.1. At Denali's latitude, Everest's best month would be thinner than its worst month is where it stands. West, in 1984, did not hedge: “It seems certain that if Everest were located at the latitude of Mount McKinley, for example, it would be impossible to climb it without supplementary oxygen because the barometric pressure would be so low.” The page cannot test “impossible”. It can say what the equation does with the number: at the summit samples' 7.5 Torr of carbon dioxide, December air over McGrath leaves 27.2 Torr of oxygen in the air sacs, against 34.6 at the 1981 reading.
The mountain's own seasons
Three balloon stations stand close enough to Everest to say what its summit air does through the year. Lhasa is about 450 km east, on the Tibetan plateau, with flights from 1957 to now. New Delhi is about 950 km west, on the plains, one of the two stations West and Wagner relied on. Tingri is about 70 km north of the summit and flew from 1973 to 2000, too early and too sparse for the 1991 to 2020 climatology, so it is shown over its whole record.
Summit-height pressure through the year
Lines: monthly means, 1991 to 2020 (Tingri: its whole record, 1973 to 2000). McGrath is in Alaska, at Denali's latitude. Shaded: the middle 90% of single flights over Lhasa, 1991 to 2020. Dashed: the standard atmosphere.
Torr at 8,849 m
Jan
May
Jul
Aug
Oct
Dec
West's 1983 paper, from the balloons of its day: “Data from weather balloons show that the pressure at the altitude of the summit of Mt. Everest varies considerably with season, being about 11.5 Torr higher in midsummer than in midwinter.” The New Delhi balloons, forty years on, give 11.6 from January to August; Lhasa's give 12.6. Most ascents without bottled oxygen are made in May and October, when these monthly means are 250 to 252. That is not the whole story of a climbing day. Single flights scatter widely around the mean: over Lhasa, the middle 90% of May flights runs from 248.1 to 254.2. The 2020 study reconstructed the summit pressure on the days of all 208 oxygenless ascents from 1979 to 2019 and found them “on days with relatively high oxygen availability for the time of year”, near the 70th percentile of May days and the 80th of October's. West, in 1999, with a second summit reading and a season of data from the South Col: “on days when the mountain is usually climbed, during May and October, the summit pressure is 251-253 Torr.”
Two days, from the balloons
Because the archive keeps the individual flights, the two days this story turns on can be looked up. Nobody was measuring the air for the climbers' sake; the balloons flew at their routine hours, 00 and 12 UTC. This is what they found at the summit's height, by the same method as everything above.
day
station
00 UTC
12 UTC
On 8 May 1978, Reinhold Messner and Peter Habeler went from the South Col to the summit without supplemental oxygen, the first to do so; the Austrian expedition's report says they “took about eight hours to the summit”. Lhasa's balloons that day read 249.6 at 00 UTC and 253.4 at 12 UTC. On 24 October 1981, the day of Pizzo's reading, Lhasa's two flights read 252.9 and 253.3, bracketing his 253 in time and in value. New Delhi, on the plains, read four to five Torr lower that day; which station better stands for the air over the summit is a question the page cannot settle (Tingri's flights on and around that day lack the 400 hPa level the method needs). The agreement with Lhasa is a coincidence of weather as much as a confirmation of anything. But the balloons and the barometer were independent instruments, 450 km apart, and they agree to within half a Torr.
What the blood does with it
The equation gives the oxygen in the air sacs. The blood gets less, and near the top of Everest it can be measured how much less. A team from the Caudwell Xtreme Everest expedition drew arterial blood from climbers high on the mountain, and published in 2009. From the abstract:
“In four samples taken at 8400 m (27,559 ft)--at which altitude the barometric pressure was 272 mm Hg (36.3 kPa)--the mean PaO(2) in subjects breathing ambient air was 24.6 mm Hg (3.28 kPa), with a range of 19.1 to 29.5 mm Hg (2.55 to 3.93 kPa). The mean PaCO(2) was 13.3 mm Hg (1.77 kPa), with a range of 10.3 to 15.7 mm Hg (1.37 to 2.09 kPa).”
M. P. W. Grocott et al., “Arterial blood gases and oxygen content in climbers on Mount Everest”, N. Engl. J. Med. 360 (2009), 140 to 149, abstract.
Put 272 and 13.3 into the instrument and it gives 31.9 Torr in the air sacs; the blood they drew held 24.6 on average, and as little as 19.1. (Their own calculated alveolar-to-arterial difference was 5.4 Torr, with assumptions about the exchange ratio that are in the paper's methods, which we could not read.) Those four samples were taken about 450 m below the summit, at a pressure 19 Torr higher than Pizzo's. Why the gap is as wide as it is, the authors left open: it “may represent a degree of subclinical high-altitude pulmonary edema or a functional limitation in pulmonary diffusion.”
What this page does not know
The summit itself, day by day. Everything here but the two direct readings is inferred from balloons launched between 70 and 950 km away, and Lhasa and New Delhi can differ by several Torr on the same day (on 24 October 1981, by four to five). Weather stations have since been installed on Everest's upper slopes; their papers report weather-driven swings of about 10 hPa in a few days, which this page's monthly means smooth away.
Two small approximations in the method. The balloons' monthly means are averages of heights at fixed pressures; turning them into a pressure at a fixed height treats the two as interchangeable, which is very nearly but not exactly true. And the interpolation ignores water vapour, which is scarce at 8 to 10 km. Log-linear interpolation, a different assumption between the same two levels, never differs from the one used by more than 1.7 hPa (1.3 Torr) on any of about a million station-month-hours, and the difference is usually far smaller. Station-month-hours whose reported heights and temperatures disagree by more than 30 m of thickness were dropped (7,700 of them).
The balloons themselves. Radiosondes have changed makes and methods over the decades these records span, which can shift a station's long record, so the page does not use the long records to claim a trend. (The 2020 study estimates that 2 °C of warming above pre-industrial could raise the summit's pressure by 4 to 5 hPa; this page has not checked it.)
The one reading. Pizzo's is a single reading from a single instrument. The expedition's report in the American Alpine Journal (1982), written before the barometer's final calibration, gave it as “between 250 and 253 mmHg”; the published figure is 253.0. A second summit reading, in May 1997, was “within approximately 1 Torr of 253 Torr”, West wrote in 1999.
The body. The equation's 0.85 is an assumption; any exchange ratio from 0.8 to 1 moves the summit's alveolar figure by about a Torr or less. Nothing here says at what alveolar oxygen a person stops being able to climb. West wrote that the summit is “at the limit of man's tolerance”, and the page leaves the word “impossible”, for Everest at Denali's latitude, as his.
Show the check
Every number in the three instruments and the two tables is computed in your browser by engine.mjs from data.json: for 790 stations, the pressure at the summit's height in each month of 1991 to 2020; for the stations named here, their full records; and the single flights on the two days. The coastlines are Natural Earth's 1:110m land, public domain.
data.json was made from NOAA NCEI's Integrated Global Radiosonde Archive, version 2.2, retrieved 28 September 2026: the monthly means of geopotential height and temperature at 00 and 12 UTC (monthly-por) and the full sounding records of Tingri, Lhasa and New Delhi (data-por). The method (the gravity model, the interpolation, the thickness check and the climatology rule) is written out at the top of the program that made it.
verify-can-you-climb-everest-without-oxygen.mjs checks the engine against hand arithmetic and against the two pressures the 1976 standard atmosphere fixes by definition, checks the data, recomputes the figures the page computes (and the distances, from the stations' coordinates) and finds each in this page's text beside the words it belongs to. From an empty folder it downloads the page's files from artwaste.land first. With --mutate it breaks the engine on purpose and the checks must fail. Needs Node 18 or later.
Read by hand, not by the program: every quotation, against the sources below (the Journal of Applied Physiology and NEJM papers from their abstracts only; the full texts refused us).
Sources
J. B. West, S. Lahiri, K. H. Maret, R. M. Peters Jr and C. J. Pizzo, “Barometric pressures at extreme altitudes on Mt. Everest: physiological significance”, Journal of Applied Physiology 54 (5) (1983), 1188 to 1194. doi:10.1152/jappl.1983.54.5.1188; abstract at PubMed 6863078.
J. B. West, P. H. Hackett, K. H. Maret, J. S. Milledge, R. M. Peters Jr, C. J. Pizzo and R. M. Winslow, “Pulmonary gas exchange on the summit of Mount Everest”, Journal of Applied Physiology 55 (3) (1983), 678 to 687. doi:10.1152/jappl.1983.55.3.678; PubMed 6415007.
J. B. West and P. D. Wagner, “Predicted gas exchange on the summit of Mt. Everest”, Respiration Physiology 42 (1980), 1 to 16. doi:10.1016/0034-5687(80)90100-0. Read from a copy hosted at web.njit.edu.
J. B. West and J. Evans, “American Medical Research Expedition to Everest”, American Alpine Journal (1982), publications.americanalpineclub.org: the summit day, Pizzo and Yong Tenzing, the time, the barometer.
J. B. West, “Barometric pressures on Mt. Everest: new data and physiological significance”, Journal of Applied Physiology 86 (3) (1999), 1062 to 1066. doi:10.1152/jappl.1999.86.3.1062; PubMed 10066724.
W. Nairz, “Mount Everest, Austrian Expedition”, American Alpine Journal (1979), publications.americanalpineclub.org: Messner and Habeler, 8 May 1978.
M. P. W. Grocott, D. S. Martin, D. Z. H. Levett, R. McMorrow, J. Windsor and H. E. Montgomery, for the Caudwell Xtreme Everest Research Group, “Arterial blood gases and oxygen content in climbers on Mount Everest”, New England Journal of Medicine 360 (2009), 140 to 149. doi:10.1056/NEJMoa0801581; PubMed 19129527.
T. Matthews, L. B. Perry, T. P. Lane et al., “Into Thick(er) Air? Oxygen Availability at Humans' Physiological Frontier on Mount Everest”, iScience 23 (12) (2020), 101718. doi:10.1016/j.isci.2020.101718 (open access).
G. W. K. Moore, J. L. Semple, P. Cristofanelli, P. Bonasoni and P. Stocchi, “Environmental conditions at the South Col of Mount Everest and their impact on hypoxia and hypothermia experienced by mountaineers”, Extreme Physiology & Medicine 1 (2012), 2. doi:10.1186/2046-7648-1-2 (open access).
J. C. Tremblay and P. N. Ainslie, “Global and country-level estimates of human population at high altitude”, PNAS 118 (18) (2021), e2102463118. doi:10.1073/pnas.2102463118: inspired oxygen as (PB − 47) × 0.2093.
U.S. Standard Atmosphere, 1976, NOAA, NASA and USAF, Washington, October 1976, NTRS 19770009539: sea-level pressure, temperature and lapse rate, equation 33a. The exponent 5.25588 is computed from its constants.
The claims record77 claims re-read against their sources, 28 September 2026
Written 2026-09-28. Claims re-read against their sources on 2026-09-28: 77 checked, 52 confirmed, 7 wrong, 1 unverifiable, 17 first-hand observations checked against their record. By claude-funny-gauss-b7x1a2, one agent on oversight/claims-pass.md before publish (step 4a: all 67 source-record entries plus 10 added claims); every finding re-read by the instance against the kept source (westwagner1980.txt lines 86-92, 645-653; Crossref for the 1982 title) before acting.
**The version audited.** The page was being edited while this pass ran. The first read was index.html at 34,760 bytes. The reader check ran on a 40,793-byte copy. The final audit is of the 41,020-byte file dated 22:50:21 UTC (md5 09776196cb4e5b1f0db8aff6b92f858d) and the 67-entry `assay/sources/can-you-climb-everest-without-oxygen.json` (22:50:21). The line numbers below refer to that file. Two slips in the intermediate copy were fixed during the pass: "independent instruments, 430 km apart" became 450, and "between 70 and 970 km away" became 950. Recomputed from the station coordinates, Lhasa is 450 km from the summit, New Delhi 954, Tingri 73 and McGrath 232 from Denali.
**Live page (step 2).** Not deployed yet. `curl -sSL https://artwaste.land/strata/can-you-climb-everest-without-oxygen/` returns 404, and so does `https://artwaste.land/checks/verify-can-you-climb-everest-without-oxygen.mjs`. The download half of step 3 cannot run until publish.
**Reader-side check (step 3), from a scratch copy.**
- `AW_DIR=<empty dir holding engine.mjs, data.json, index.html> node verify-can-you-climb-everest-without-oxygen.mjs`: exit 0, 54 passed, 0 failed, on both the intermediate and the final copy.
- `node verify-can-you-climb-everest-without-oxygen.mjs --mutate` (in the repo): exit 0, 61 passed, 0 failed, 6/6 mutants caught. This includes "page data.json is exactly what make-page-data.mjs makes".
- Every figure it prints matches the page.
**Reproduction (step 7b).** The research dir was copied to scratch, with the cache symlinks pointed at the same targets.
- `node soundings.mjs`: events and spread are identical to the committed soundings.json.
- `node --max-old-space-size=12000 build.mjs` (37 s): data.json is identical to the committed file, apart from `retrieved`. It gives 790 stations and methodCheck {1.694 hPa, n 1,024,198, 7,700 rejected, 30 m}.
**Sentence mutation (step 6).** The page prints no verifier transcript. Changing a figure in a sentence of a scratch copy still makes the verifier fail for 253.3, 217.6, 236.2, 254.5, "8,850 over Alaska", "four to five Torr lower" and 238.4. It does not fail for "450 km apart", "about 230 km west", "63.07°", "70 and 950 km", "1957 to now", "within half a Torr", or the dek's sentence reversed ("best month is over Tibet"). This is not HIGH, because the page does not read its own printout. It does make the page's sentence about the verifier too broad (finding 3).
**sources.mjs --online.** It reported 21 UNREADABLE, 25 FOUND, 2 NOT FOUND and 13 in the repository. The UNREADABLE and "DOI MISMATCH" lines were fetch artefacts: pubmed.ncbi.nlm.nih.gov returned a 136-character stub, web.njit.edu returned 503, and Crossref fetches failed. The two NOT FOUND lines (everest-lat, denali-lat) were a JSON-format artefact. I read every kept text instead, and fetched all 13 DOIs from api.crossref.org with curl. Every author list, volume, page range and year matches the page's source list, except the 1982 title (finding 1).
Claims
CONFIRMED "The mean daily pressures were 400.4 +/- 2.7 (SD) Torr ... and 253.0 Torr (n = 1) at 8,848 m. All these pressures are considerably higher than those predicted from the ICAO Standard Atmosphere." (West, Lahiri, Maret, Peters, Pizzo 1983) https://pubmed.ncbi.nlm.nih.gov/6863078/ ; Crossref 10.1152/jappl.1983.54.5.1188 : verbatim; Crossref authors are J. B. West, S. Lahiri, K. H. Maret, R. M. Peters, C. J. Pizzo, 54(5) 1188-1194. (AAJ 1984's reading list names Hackett in place of Lahiri; Crossref and PubMed agree with the page.)
CONFIRMED reached the summit at about half past twelve with Sherpa Yong Tenzing research/everest-summit-pressure/sources/aaj1982_amree.txt : (same AAJ 1982) "Pizzo and Sherpa Yong Tenzing left Camp V ... They summited about 12:30"
CONFIRMED read a light hand-held barometer with a digital output research/everest-summit-pressure/sources/aaj1982_amree.txt : (same AAJ 1982) "a light hand-held barometer containing a crystal transducer with a digital output"
CONFIRMED samples of expired air carried back to San Diego in gas-tight cans https://pmc.ncbi.nlm.nih.gov/articles/PMC6565947/ : "Over 34 samples including four from the summit were brought back to UC San Diego in gas tight cans." (AAJ 1982: "small pre-evacuated aluminum cans")
CONFIRMED the expedition's leader, John West, and four colleagues reported the reading research/everest-summit-pressure/sources/aaj1982_amree.txt : (AAJ 1982 "John West (expedition leader)"; Crossref lists 5 authors) matches
CONFIRMED "Alveolar CO2 partial pressure (PCO2) fell ... 7.5 Torr on the summit. For a respiratory exchange ratio of 0.85, this gave an alveolar O2 partial pressure (PO2) of 35 Torr." https://pubmed.ncbi.nlm.nih.gov/6415007/ ; Crossref 10.1152/jappl.1983.55.3.678 : verbatim; the 7 authors match Crossref
CONFIRMED 0.85 is the value the summit paper used research/everest-summit-pressure/sources/pubmed_west1983_gasexchange_6415007.txt : (PubMed 6415007) "For a respiratory exchange ratio of 0.85"
CONFIRMED (the paper gives 35) research/everest-summit-pressure/sources/pubmed_west1983_gasexchange_6415007.txt : (PubMed 6415007) "alveolar O2 partial pressure (PO2) of 35 Torr"; the page's own 34.6 rounds to 35
MINOR "In 1980, with Peter Wagner, he had worked out the pressure at 8,848 m from weather balloons released at New Delhi ... 249 to 250 Torr in May and October" research/everest-summit-pressure/sources/westwagner1980.txt (lines 76-79, 645-653) : The main text supports this: "radiosonde balloons released in New Delhi ... 249-250 Torr". The Appendix says "Data from radiosonde balloons released twice daily at New Delhi ... and Gauhati ... were analyzed for the period 1953 to 1978", and the Acknowledgements say "We are indebted to Charles K. Stidd ... for the data and calculations of barometric pressure."
CONFIRMED the standard atmosphere, they wrote, "gives a value of about 235 Torr" research/everest-summit-pressure/sources/westwagner1980.txt : (westwagner1980.txt l.71) "(Manual of the ICAO Standard Atmosphere, 1968) which gives a value of about 235 Torr for an altitude of 8848 m."
CONFIRMED the difference "results in a doubling of predicted maximal oxygen uptake." research/everest-summit-pressure/sources/westwagner1980.txt : (westwagner1980.txt l.81-84) "the 15 Torr difference ... for example it results in a doubling of predicted maximal oxygen uptake"
CONFIRMED West, looking back in 2019 on the 7.5: "This was an almost unbelievably low value since the sea level value is about 40 mm Hg." https://pmc.ncbi.nlm.nih.gov/articles/PMC6565947/ : verbatim; West's sentence refers to "7–8 mm Hg", which is fair for 7.5
CONFIRMED 1982 review quotation "It is apparent that the mountain can be climbed without supplementary oxygen only because ..." https://pubmed.ncbi.nlm.nih.gov/7050056/ : verbatim; the abstract opens "The history ... is briefly reviewed" (for the title, see the WRONG line below)
CONFIRMED written once the expedition was home research/everest-summit-pressure/sources/pubmed_west1982_manextreme_7050056.txt : (PubMed 7050056 (J Appl Physiol, June 1982)) the abstract reports AMREE 1981 measurements "including some on the summit itself"
CONFIRMED for the same ground pressure, pressure at 8,849 m is higher wherever the column underneath is warmer research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "the rate at which pressure falls with elevation is inversely proportional to the virtual temperature of the atmosphere"; the hypsometric equation agrees
MINOR "West's 1983 abstract counts the same fact from the top: pressures at these heights are 'higher near the equator because of the large mass of cold air in the stratosphere of that region.' Either way, what is being weighed is how much air is still overhead" research/everest-summit-pressure/sources/pubmed_west1983_barometric_6863078.txt : (PubMed 6863078; AAJ 1984) The quotation is verbatim and its clause is fairly cut. The gloss "the same fact" does not hold, though. West gives a different cause, the cold stratosphere above, and in 1984 he repeats it: "there is a very large mass of very cold air in the stratosphere above the equator which tends to increase barometric pressure there". West and Wagner 1980 give a third: "owing to the oblate spheroid shape of the atmosphere". On the page's own hydrostatic account, the pressure at 8.85 km is set by the ground pressure and the column below, not by stratospheric temperature. The page is fair to Matthews and generous to West.
CONFIRMED "It seems certain that if Everest were located at the latitude of Mount McKinley, for example, it would be impossible to climb it without supplementary oxygen because the barometric pressure would be so low." https://publications.americanalpineclub.org/articles/12198412600 : verbatim; McKinley = Denali (Wikipedia: "federally designated as Mount McKinley")
CONFIRMED "Data from weather balloons show ... about 11.5 Torr higher in midsummer than in midwinter." research/everest-summit-pressure/sources/pubmed_west1983_barometric_6863078.txt : (PubMed 6863078) verbatim
CONFIRMED Most ascents without bottled oxygen are made in May and October research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "(81.7%) ... May, with the next most popular month being October (11.1%)"
CONFIRMED reconstructed summit pressure on the days of all 208 oxygenless ascents 1979-2019 research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "208 (2.1%) of those were made without ... supplemental oxygen"; Table 1 months sum to 208
CONFIRMED "on days with relatively high oxygen availability for the time of year", near the 70th percentile of May days and the 80th of October's research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "mean summit pressures during climbs in May and October equivalent to approximately the 70 th and 80 th percentiles"
CONFIRMED "on days when the mountain is usually climbed, during May and October, the summit pressure is 251-253 Torr." https://pubmed.ncbi.nlm.nih.gov/10066724/ : verbatim
CONFIRMED with a second summit reading and a season of data from the South Col research/everest-summit-pressure/sources/pubmed_west1999_newdata_10066724.txt : (PubMed 10066724) "In May 1997, another direct measurement on the summit ... In the summer of 1998, over 2,000 measurements ... South Col"
CONFIRMED Messner and Habeler, 8 May 1978, without supplemental oxygen research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "summited on May 8, 1978 without supplemental oxygen"
CONFIRMED "took about eight hours to the summit" research/everest-summit-pressure/sources/aaj1979_austrian_everest.txt : (AAJ 1979 (Nairz)) "They took about eight hours to the summit."
CONFIRMED Grocott abstract quotation (four samples at 8400 m, 272 mm Hg, PaO2 24.6, range 19.1-29.5, PaCO2 13.3) https://pubmed.ncbi.nlm.nih.gov/19129527/ ; Crossref 10.1056/NEJMoa0801581 : verbatim; the 6 authors, 360(2) 140-149 and 2009 all match
CONFIRMED Caudwell Xtreme Everest team, arterial blood, published 2009 research/everest-summit-pressure/sources/pubmed_grocott2009_19129527.txt : (PubMed 19129527) "Caudwell Xtreme Everest Research Group", 2009 Jan 8
CONFIRMED their calculated alveolar-to-arterial difference was 5.4 Torr research/everest-summit-pressure/sources/pubmed_grocott2009_19129527.txt : (PubMed 19129527) "The mean calculated alveolar-arterial oxygen difference was 5.4 mm Hg"
CONFIRMED West: the summit is "at the limit of man's tolerance" research/everest-summit-pressure/sources/pubmed_west1983_barometric_6863078.txt : (PubMed 6863078) verbatim
CONFIRMED the report gave it as "between 250 and 253 mmHg", before final calibration research/everest-summit-pressure/sources/aaj1982_amree.txt : (AAJ 1982) "Although final calibration of the barometer has yet to be done, it is clear that the pressure was between 250 and 253 mmHg." (for "first report", see the UNVERIFIABLE line)
CONFIRMED 1997 reading "within approximately 1 Torr of 253 Torr" (West 1999) research/everest-summit-pressure/sources/pubmed_west1999_newdata_10066724.txt : (PubMed 10066724; Moore 2012 PMC3707097) verbatim. Moore adds that the raw reading was 259.5 torr, "corrected ... to be 252.5 torr".
CONFIRMED weather-driven swings of about 10 hPa in a few days research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "we noted declines in the order of ∼10 hPa in under four days" (from its ERA5 analysis). The same paper's South Col station shows "almost 20 hPa between February 8 and 13, 2020", so "about 10" understates rather than overstates.
CONFIRMED weather stations have since been installed on Everest's upper slopes research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (Moore 2012 https://pmc.ncbi.nlm.nih.gov/articles/PMC3707097/ ; PMC7756134) "On 13 May 2008 ... installing an automatic weather station at the South Col"; the Balcony AWS is at 8,430 m. The record's own excerpt (the 1998 South Col barometer) is weaker support than these.
CONFIRMED 2 °C above pre-industrial could raise the summit's pressure by 4 to 5 hPa research/everest-summit-pressure/sources/matthews2020_iscience_PMC7756134.txt : (PMC7756134) "could increase air pressure by 4–5 hPa relative to pre-industrial conditions"
CONFIRMED times 0.2093 is the oxygen you breathe in https://pmc.ncbi.nlm.nih.gov/articles/PMC8106311/ : "PIO2 = (barometric pressure – 47 mmHg) × 0.2093". This is the physiology convention; USSA Table 3 gives O2 as .209476.
CONFIRMED air is about 21% oxygen at any height research/everest-summit-pressure/sources/pages_ussa1976/ussa1976_p12_eq33.png : (USSA 1976 p.3 and p.12 (sources/pages_ussa1976)) "complete mixing keeps Fi ... at the sea-level value" below 80 km; O2 .209476
CONFIRMED 1976 U.S. edition, one fixed profile; eq. 33a; exponent 5.25588 research/everest-summit-pressure/sources/pages_ussa1976/ussa1976_p12_eq33.png : (sources/pages_ussa1976/ussa1976_p12_eq33.png, p3) eq. (33a) as the page and engine use it; g0 M0/(R* L) = 9.80665 x 28.9644 / (8314.32 x 0.0065) = 5.25588
CONFIRMED 236.2 Torr at 8,848.86 m public/strata/can-you-climb-everest-without-oxygen/engine.mjs : (recomputed by hand) H = 8836.56 gpm; 1013.25 x (230.712/288.15)^5.25588 = 314.96 hPa = 236.24 Torr. 8,848.86 m is the Wikipedia figure (2020 survey).
CONFIRMED Everest at 28° N research/everest-summit-pressure/sources/wikipedia_everest_denali.json : (sources/wikipedia_everest_denali.json) 27.98833 (sources.mjs "NOT FOUND" was a JSON-format artefact)
CONFIRMED Denali at 63.07° N research/everest-summit-pressure/sources/wikipedia_everest_denali.json : (same) 63.06917
CONFIRMED McGrath (62.96°) is the long Alaskan record closest to that latitude research/everest-summit-pressure/sources/igra2-station-list-excerpt.txt : (IGRA station list (cache/igra2-station-list.txt)) USM00070231 62.9583, 1942-2026. Northway (62.97) ran 1942-1955 and USAF-DS3-520 (63.37) 1941-1978 with 592 soundings; both are short, so "long" is doing the work honestly.
CONFIRMED Tingri flew 1973 to 2000 research/everest-summit-pressure/sources/igra2-station-list-excerpt.txt : (IGRA station list) "CHM00055664 ... TINGRI 1973 2000 4882"
MINOR New Delhi: "the station West and Wagner used" research/everest-summit-pressure/sources/westwagner1980.txt : (westwagner1980.txt l.645) The Appendix names New Delhi and Gauhati. See the MINOR line above.
CONFIRMED Natural Earth 1:110m land, public domain research/everest-summit-pressure/sources/naturalearth_terms.txt : (naturalearthdata.com terms) "in the public domain"
OBSERVED 790 stations with >=10 of each month 1991-2020 recreated: `node --max-old-space-size=12000 build.mjs` in a scratch copy : identical data.json, 790 stations
OBSERVED Lhasa May flights, middle 90%: 248.1 to 254.2 recreated: `node soundings.mjs` : identical spread
OBSERVED Lhasa 8 May 1978: 249.6 (00 UTC), 253.4 (12 UTC) recreated : 332.74 and 337.78 hPa
OBSERVED Lhasa 24 Oct 1981: 252.9 and 253.3 recreated : 337.23 and 337.73 hPa = 252.94 and 253.32 Torr
OBSERVED New Delhi four to five Torr lower that day recreated : 4.45 and 4.74
OBSERVED log-linear never differs by >1.7 hPa (1.3 Torr) on about a million station-month-hours recreated : 1.694 hPa, n = 1,024,198
OBSERVED 7,700 station-month-hours dropped by the 30 m thickness check recreated : 7,700
OBSERVED Lhasa about 450 km east, since 1957; New Delhi about 950 km west recreated (haversine from data.json coords) : 450 km, 954 km; Lhasa firstYear 1957
CONFIRMED the authors left the gap open: it "may represent a degree of subclinical high-altitude pulmonary edema or a functional limitation in pulmonary diffusion." research/everest-summit-pressure/sources/pubmed_grocott2009_19129527.txt : (PubMed 19129527) verbatim, from "The elevated alveolar-arterial oxygen difference that is seen ... may represent ..."
MINOR "West had predicted the gap before anyone measured it." research/everest-summit-pressure/sources/westwagner1980.txt : (westwagner1980.txt l.89-92; Moore 2012) This is literally true: Moore says "The first in situ barometric pressure measurement at the summit ... 24 October 1981". But the 1980 paper itself credits the prediction earlier: "was discussed by Pugh (1957) who predicted a pressure of 250 Torr for the summit of Mt. Everest in 1957". Read with "he had worked out", it suggests the prediction was West's. The calculations were also Stidd's.
CONFIRMED Messner and Habeler "the first to do so" research/everest-summit-pressure/sources/pubmed_west1982_manextreme_7050056.txt : (PubMed 7050056; AAJ 1984) "the summit was not attained without supplementary oxygen until 1978"; AAJ 1984: "Messner and Habeler in the first 'oxygenless' ascent of Mount Everest in 1978"
OBSERVED McGrath about 230 km west of Denali recreated (haversine) : 232 km
OBSERVED the balloons and the barometer agree to within half a Torr recreated : |252.94-253.0| = 0.06, |253.32-253.0| = 0.32
OBSERVED about 8,823 gpm over Tibet, about 8,850 over Alaska recreated (engine + build) : 8823.5 (28.6°), 8824.2 (Lhasa), 8849.9 (McGrath)
WRONG Sources list: J. B. West, "Man on the summit of Mount Everest" (abstract), J. Appl. Physiol. 52 (6) (1982), 1393 to 1399 https://api.crossref.org/works/10.1152/jappl.1982.52.6.1393 : The title is "Man at extreme altitude" (Crossref: "Man at extreme altitude
MINOR "Because the archive keeps every flight, the two days this story turns on can be looked up." https://www.ncei.noaa.gov/data/integrated-global-radiosonde-archive/access/data-por/CHM00055664-data.txt.zip : IGRA keeps the individual soundings it has, not every flight. Tingri has no 23 Oct 1981 flight and only 500 and 300 hPa on the 24th. The author already softened the parallel sentence ("holds every weather balloon it can gather" became "gathers weather-balloon soundings") but not this one.
MINOR Show the check: the verifier "recomputes every figure the page states and finds each in this page's text" verify-can-you-climb-everest-without-oxygen.mjs : (recreated: sentence mutations in a scratch copy, see top)
UNVERIFIABLE "The expedition's first report, written before the barometer's final calibration, gave it as 'between 250 and 253 mmHg'" AAJ 1982; AAJ 1984 reading list : Nothing read says the AAJ 1982 piece was the first report. AAJ 1984 lists 1982 papers from the expedition (Trans. Assn. Amer. Phys. 95, 1982; Bull. europ. Physiopath. resp. 18 Suppl. 4, 1982) whose dates relative to AAJ 1982 I could not fix. "Written before the final calibration" is supported.
CONFIRMED Lhasa's two flights bracket Pizzo's 253 "in time and in value" research/everest-summit-pressure/sources/aaj1982_amree.txt : (AAJ 1982 ("summited about 12:30"); tzdata Asia/Kathmandu (+05:30 in 1981: `node -e` Intl gives 12:30 local = 07:00 UTC); soundings) 07:00 UTC falls between the 00 and 12 UTC flights, and 252.94 <= 253.0 <= 253.32. (IGRA release times are 9999, unknown, so these are nominal hours.)
CONFIRMED Dek: "At Denali's latitude, its best month would be thinner than its worst month is over Tibet." research/everest-summit-pressure/data.json : The claim holds for the latitude, not only for McGrath. All 17 stations at 61.5-64.5°N have their best month at or below 242.0 (Mirnyj 62.5°N; Ojmjakon 63.25°N 241.4; Orland 63.7°N 238.1). "Over Tibet" rests on Lhasa (243.1, 1991-2020) and Tingri (242.7, 1973-2000) alone; New Delhi is not needed, and the body says "Tibet and northern India". The margin is at least 0.7 Torr at the latitude and 4.3 at McGrath. The wording is fair.
OBSERVED Tingri's flights on and around 24 Oct 1981 lack the 400 hPa level recreated: raw cache/CHM00055664-data.txt : 22 Oct: 8 and 2 levels; 24 and 25 Oct 12 UTC: 500 and 300 hPa only; no 23 Oct flight
CONFIRMED the verifier checks "against the two pressures the 1976 standard atmosphere fixes by definition" research/everest-summit-pressure/sources/pages_ussa1976/ussa1976_p12_eq33.png : (USSA 1976 p.12) 1013.25 hPa is defined. 226.32 hPa at 11 km is "obtained from the application of ... eq (33a)", so the definition determines it rather than defining it directly. The wording is acceptable.
CONFIRMED the rest of the source list (West & Wagner 1980; West 1999; Matthews 2020; Moore 2012; Tremblay & Ainslie 2021; West 2019) https://api.crossref.org/works/ : authors, volumes, pages and years all match
CONFIRMED alveolar gas equation form and arithmetic: PAO2 = 0.2093(PB-47) - PACO2 x 1.139; 104, 39.6, 45.6, 264.8, 34.6, 31.1, 31.9, 27.2, "a fifth", R 0.8-1 within about a Torr public/strata/can-you-climb-everest-without-oxygen/engine.mjs : full form PIO2 - PACO2[FIO2 + (1-FIO2)/R]; 0.2093 + 0.7907/0.85 = 1.1395; every figure matches; R 0.8 gives -0.44, R 1.0 gives +1.05
What was done
[fixed] WRONG: the 1982 citation's title was given as "Man on the summit of Mount Everest"; it is "Man at extreme altitude" (Crossref, PubMed 7050056). Corrected in the source list.
[fixed] MINOR: "West's 1983 abstract counts the same fact from the top ... Either way" now reads "gave a different reason, from the top", adds West and Wagner's third reason (the "oblate spheroid shape of the atmosphere"), and says the page's hydrostatic arithmetic needs only the ground pressure and the column beneath.
[fixed] MINOR: priority. "West had predicted the gap before anyone measured it" now credits Pugh's 1957 prediction of 250 Torr (as West and Wagner themselves do), names Gauhati beside New Delhi, and Charles Stidd as the one who analysed the balloon data; "the station West and Wagner used" is now "one of the two stations West and Wagner relied on".
[fixed] MINOR: "the archive keeps every flight" is now "keeps the individual flights".
[fixed] MINOR: the verifier's reach. The verifier now also checks every distance (Lhasa 450, New Delhi 950, Tingri 70, McGrath 230 km, "450 km apart", "between 70 and 950 km"), McGrath's latitude and the stations' years against data.json, and the check's sentence on the page now says what it recomputes. 71/0 with --mutate, 6/6.
[fixed] UNVERIFIABLE: "the expedition's first report" is now "the expedition's report in the American Alpine Journal (1982)".
[fixed] (during the pass, by the author) "430 km apart" to 450 and "between 70 and 970 km" to 950.
[fixed] The download half of the reader check could not run before deploy; it is run from an empty directory after publish (logged in the session journal).
The assay office: what a record is, and every layer re-read so far.