Both poles, annual mean
−58,213km² / year
About Croatia of ice each year. 20.736 million km² remains in 2025 — about Russia and India together.
360 yearsstraight line to zero
Dark tick = one year at this rate. 360 of those ticks empty the 2025 bar.
NSIDC Sea Ice Index v4.0 · G02135
Arctic and Antarctic ice and temperature vs the 1988 estimates
Hansen named both poles as the first unambiguous warming. NOAA 60°–90°S did not follow. High-end 1980s sea-level paper ran to metres; the gauges show centimetres. The split that holds is Arctic-only air warming plus a measured drop in Earth’s reflectance — albedo, not a well-mixed gas at both ends of the planet.
Daily satellite observations of ocean area with ice concentration of at least 15%, both hemispheres, same plot style. Record begins 26 October 1978. Values are from the NSIDC Sea Ice Index, not from a climate model.
Observational summary
Findings from the record, not from a climate model
Abstract
sea-ice extent (1978–present), 60°–90° air temperature (1880–present), polar daily 2 m temperature, zonal annual means, satellite altimetry, and published /earthshine reflectance are examined as observations. Four results follow. (1) has risen ~20 cm since 1900; the altimeter since 1993 is 3.3 mm yr⁻¹ (NASA, 100.1 mm on 7 July 2026). Half of 1971–2018 was thermal expansion of seawater already in the ocean — volume, not melt ( AR6). That is faster than the 20th-century tide-gauge rate, and an order of magnitude slower than high-end 1980s inundation scenarios. At the measured rate a metre takes ~300 years. Floating Arctic sea ice does not raise sea level. (2) Hansen et al. (1988) named both poles as the first unambiguous greenhouse warming. NOAA 60°–90°N 1988–2020 rose +2.17 °C; NOAA 60°–90°S changed −0.01 °C. A well-mixed must warm both. Ice and cloud need not. (3) Arctic air was already warming at +0.45 °C/decade in 1910–1940, before fossil-fuel CO2 was large; Antarctic piecewise windows have r² ≤ 0.08. Earthshine and CERES measure a decline in planetary reflectance since ~2000. The geographic split is Northern-Hemisphere ice and cloud, not a well-mixed greenhouse gas at both ends of the planet. (4) The 1988 both-poles claim missed the south. High-end 1980s sea-level tails missed the altimeter by a factor of ~10. Models that treat albedo as a small feedback on greenhouse forcing underestimate a term the satellites measure as a first-order change in .
1. Sea level
Tide gauges: ~1.4–1.7 mm yr⁻¹ through most of the 20th century, ~20 cm from 1900 to now. NASA altimeter 7 July 2026: 100.1 mm above 1993 (~3.3 mm yr⁻¹). AR6: of seawater already in the ocean was 50% of 1971–2018 rise (47.5 mm) — volume, not melt. land-ice mass (Greenland −264 Gt/year, Antarctica −135 Gt/year) is ~1.1 mm yr⁻¹ of added water, a minority of the altimeter. Acceleration relative to the 20th century is in the record. The height is not unusual in paleoclimate (last interglacial +6–9 m; last glacial −125 m). See Sea level splice. The acceleration implied by Hoffman et al. (EPA 1983) high-end cases (2–3.5 m by 2100, ~32 mm yr⁻¹) is not. The altimeter is about ten times slower. At 3.3 mm yr⁻¹ the ocean rises 3.3 cm per decade. Arctic sea ice already floats; its melt is ~0 mm. 88% of land-ice sits on Antarctica.
2. Both-poles claim
Hansen et al. (1988) wrote that an unambiguous warming would appear first in “ocean areas near Antarctica and the north pole,” from well-mixed greenhouse forcing, high latitudes more than low. The red line on the 1988–2020 charts is that model’s high-latitude Scenario A rate: 0.35 °C/decade global (Hansen 2006) × ~2 = 0.70 °C/decade. NOAA Arctic 60°–90°N ran with it (+2.17 °C in 32 years). NOAA Antarctic 60°–90°S did not (−0.01 °C). GISS 64°–90° zonal annual means give the same split (+2.27 °C north, −0.09 °C south). The fingerprint those papers published is not the pattern in the thermometers.
3. Northern-Hemisphere albedo
NOAA Arctic annual: 1910–1940 +0.45 °C/decade (r² = 0.66), while fossil-fuel CO2 was still small against later decades; 1940–1970 −0.35 °C/decade (r² = 0.40); 1970–2025 +0.56 °C/decade (r² = 0.85). The same three windows on NOAA Antarctic have r² = 0.08, 0.03, and 0.02 — not a rate. That 1910 climb is in the thermometers; the hockey-stick reconstruction that flattened it did so by overweighting one bristlecone site (see Related observational labs). VEI 4–5 eruptions inside 1940–1970 (Agung 1963 is the tropical stratospheric event) do not time the 1940 start of the Arctic dip. Goode, Pallé et al. (2021) and CERES both show Earth’s reflectance falling since ~2000: less reflected shortwave is more absorbed sunlight. Nikolov and Zeller (2024) and Goessling, Rackow and Jung (2024) agree on that CERES fact over the last ~26 years: GSAT tracks absorbed sunlight, not a leftover energy-imbalance ledger. NZ Equation 16 has no greenhouse term. Polar ice is only a sliver of the ASR rise; low cloud did most of it (see NZ Atlas). Raise albedo (sulfate, low cloud, ice) and the surface cools; lower it and the surface warms. That sign works in both directions without a greenhouse-forcing calculation. Ice-albedo and cloud albedo are geographic. They concentrate in the north, where the ice lid and the air temperature actually moved.
4. What the models missed
The 1988 both-poles claim was not a small miss on the south; it was the wrong spatial pattern. High-end 1980s sea-level paper was not a small miss on the altimeter; it was the wrong order of magnitude. Those calculations treated well-mixed greenhouse radiative forcing as the leading term and albedo as a feedback that follows it. CERES and earthshine measure a drop in reflected sunlight — an albedo change — as a leading term in absorbed solar. Models that fold that term into a residual feedback underestimate it. This page does not run a radiative-forcing budget and does not claim greenhouse gases have no effect. It shows that the mechanism Hansen published (well-mixed, both poles) is not the observed split, and that the absorbed-solar term the 1988 framing did not lead with is the one the satellites moved.
Significance
The practical reading of these series is narrow. Sea-level rise at the measured rate is centimetres per decade, not metres; Arctic sea-ice melt does not add to it; the ice that could add to it is mostly East Antarctic ice sheet, which is not the NSIDC sea-ice record. Temperature and sea ice moved in the Arctic and did not follow in the Antarctic. That is the pattern of Northern-Hemisphere albedo (ice, cloud), not of a well-mixed anthropogenic greenhouse gas acting equally at both poles. Less summer Arctic ice than the satellite era is documented in Holocene proxies (Funder et al. 2011). The significance is not a forecast. It is that the estimates that named both poles, and the high-end sea-level tails, were not confirmed by the instruments, and that albedo — a change in how much sunlight the planet keeps — is the observational term those estimates treated as secondary.
Series, CSVs, and papers: Sources and methods. Companion labs on the hockey-stick weighting, CERES albedo (Nikolov & Zeller / Goessling), the δ¹³C fingerprint, and stomata vs ice-core CO2: Related observational labs.
Arctic
4.674
million km² · 2 Sep 2026
−1.932
vs 1981–2010 median 6.606
10 of 44 years on this date (1 = lowest)
Antarctic
17.362
million km² · 2 Sep 2026
−0.955
vs 1981–2010 median 18.317
3 of 44 years on this date (1 = lowest)
Straight-line rate, 1979–last complete year
Ordinary least-squares through complete calendar years in the Sea Ice Index. No climate model, no forcing, no feedback. Ice does not have to go to zero on a line. A year count is shown only when the fit is consistent (r² ≥ 0.40).
Arctic September
−76,064km² / year
About Czechia of ice each year. 4.750 million km² remains in 2025 — about the European Union.
62 yearsstraight line to zero
Dark tick = one year at this rate. 62 of those ticks empty the 2025 bar.
The last 15 Septembers (2011–2025) do not continue that slope (r² = 0.00). The 62-year figure is the full-record line, not the recent decade.
Antarctic annual mean
−7,366km² / year
The 1979–2025 line is not a usable rate (r² = 0.04). A near-zero slope can be written as thousands of years; that number is the scatter, not a clock.
No tick: the fit does not pick a year.
A thousand years, drawn to scale
now1,000 years
- 62 yArctic September
- 360 yBoth poles, annual
Antarctic annual mean has no mark: r² = 0.04 over 1979–2025, so a “thousands of years” figure from that slope is not supported by the series.
Where the ice is, and what sea ice does to sea level
extent in this app is the ocean’s ice lid, not the ice sheets. Almost all of Earth’s ice volume sits on land in Antarctica. Floating sea ice already displaces its own weight; when it melts, the water level does not rise. Most of the measured rise is expansion of water already in the ocean. The splice of proxies, gauges and satellites is under Sea level.
Land ice, as sea-level equivalent if it all melted
East Antarctica 53.3 m · 81%West + Peninsula 4.5 m · 7%Greenland 7.42 m · 11%Other glaciers 0.32 m · <1%
BedMachine: Antarctic ice sheet 57.8 m sea-level equivalent (88% of land ice), Greenland 7.42 m. Total land ice ≈ 65.5 m. Arctic sea ice is not on this bar. PIOMAS mean September volume is about 11,500 km³ — if that ice sat on land it would be ~3 cm of sea level; because it floats, the contribution is ~0.
Antarctic share of land ice
88%by SLE
57.8 m of 65.5 m. The ice that could move the ocean is in the south, mostly East Antarctica.
Arctic sea ice → sea level
~0mm
Floating ice. The Arctic already melts ~16,000 km³ every summer and grows it back. That seasonal swing is larger than the satellite-era trend.
Ocean since 1900
~20cm
Tide gauges: about 1.4–1.7 mm/year through most of the 20th century. NASA altimeter 7 July 2026: 100.1 mm above 1993. A paperback, not a storey.
Satellite-era rate
3.3mm / year
One inch in about eight years. At that rate, a metre of global mean rise takes ~300 years. Not a forecast — the measured rate.
Thermal expansion of seawater — volume, not melt
Water already in the ocean expands when it warms. That is a change in volume of existing seawater (thermosteric, or steric, sea level). It does not require ice to melt, and it is not the Arctic sea-ice series on this page. Fresh water has a density maximum near 4 °C; seawater at ocean temperature and salinity expands with heat. The thermal expansion coefficient α is about 1.5–2.5 × 10⁻⁴ per °C (TEOS-10). Mean ocean depth is ~3,700 m: a uniform 0.1 °C through the full column at α = 2 × 10⁻⁴ °C⁻¹ would raise the surface ~7 cm. Heat actually sits mostly in the upper ocean, so the measured steric rise is smaller than that uniform-column sketch.
IPCC AR6 (SPM A.4.3, Table 9.5): thermal expansion was 50% of global mean sea-level rise in 1971–2018 — 47.5 mm, 1.01 mm/year. Glaciers 22%, ice sheets 20%, land-water storage 8%. Over 1901–2018 expansion was 38% of the total (63 mm). Over 1993–2018 it was 46% (1.31 mm/year). The ocean took 91% of the extra heat in the climate system over 1971–2018. Expansion of water already there, not melt of the ice lid, is the largest single term in that 1971–2018 budget.
Thermal expansion 50%Glaciers 22%Ice sheets 20%Land water 8%1971–2018, IPCC AR6
GRACE land-ice mass
−264 / −135Gt/year
NASA GRACE/GRACE-FO, 2002–2025: Greenland −264 Gt/year, Antarctica −135 Gt/year (the 2025-03 map). 360 Gt ≈ 1 mm sea level, so the two sheets together are ~1.1 mm/year of added mass. That is barystatic — melt of ice on land. It is not “stopped.” It is also not most of the altimeter: 1.1 mm/year against ~3.3 mm/year total. Expansion plus glaciers make up the rest.
Greenland interior vs margin
Interior ~flat
Andersen et al., EGUsphere 2025-5015 (CryoSat-2, 2011–2025): Greenland mean elevation still falling, driven by the ablation zone below 1,500 m. The interior above 1,500 m is near-stable. Polar Portal surface mass balance is a seasonal map (e.g. 25 Jul 2026), not a stopped ice sheet. Loss is at the edges; the high plateau is not the GRACE average.
Why expansion matters here
50%of 1971–2018
If half the measured rise is seawater getting slightly warmer and occupying more volume, then Arctic sea-ice melt is the wrong picture of the ocean going up. Floating ice was already in the water. Land-ice melt adds mass; expansion adds volume without that mass. Both are centimetres per decade at the rates above — not the 1983 high-end metres.
IPCC AR6 SPM A.4.3 and Table 9.5; NASA GRACE ice-sheet indicator; NASA Sea Level Change Portal (100.1 mm since 1993 on 7 Jul 2026); Polar Portal; Andersen et al. doi:10.5194/egusphere-2025-5015. NASA ice sheets · sealevel.nasa.gov · IPCC AR6 WGI.
Holocene Arctic summer ice
The NSIDC record starts in 1978, after the Little Ice Age. It is not a Holocene baseline. Funder et al. (2011), northern Greenland — the sector expected to hold summer ice last — found substantially less Arctic Ocean summer ice during the Holocene Thermal Maximum (~8,000–5,000 years ago), probably less than 50% of the 2007 September cover. Other cores show summers between the Pole and Siberia periodically near ice-free in that same window.
The Roman Warm Period (~250 BCE–400 CE) and the Medieval Warm Period are regional in the proxies (North Atlantic, Svalbard, driftwood). They sit inside Holocene variability. A pan-Arctic “ice-free September” map is not measured for year 0; it is documented for parts of the early-to-mid Holocene and for the last interglacial. Less summer ice than the satellite era is not new in this interglacial.
Funder et al., Science 333, 747–750 (2011). doi:10.1126/science.1205345
Sea level, measured vs high-end 1980s paper
Observed global mean: ~20 cm from 1900 to now. Satellite era ~3.3 mm/year. Half of 1971–2018 was expansion of water already in the ocean. That is the record. It is small next to a 2 m tide, and small next to 58 m of Antarctic ice.
Not every 50-year-old calculation missed. IPCC 1996’s most likely 30-year rise was ~8 cm; about 9 cm arrived (Church and colleagues). IPCC 1990’s 2100 best estimate was 66 cm (range 31–110 cm). Thirty-six years in, ~12 cm have accumulated — below a linear 66 cm path.
High-end 1983 EPA/Hoffman scenarios ran to 2–3.5 m by 2100. At 3.5 m/110 years that is ~32 mm/year. The altimeter is 3.3 mm/year — about ten times slower. Hansen 2016’s multi-metre-in-50–100-years case has not shown up in the gauges. Those high tails are what failed, not every central estimate.
NOAA/CU altimetry; Church & White tide-gauge series; IPCC FAR 1990 ch. 9; Hoffman et al. EPA 1983; IPCC SAR 1996; IPCC AR6 Table 9.5. NOAA sea level
Sea level: proxies spliced onto gauges spliced onto satellites
The height of the ocean is not the scare in paleoclimate. The last ice age sat ~125 m lower; the last interglacial sat 6–9 m higher. What papers claim as unusual is acceleration versus the late Holocene, not the +236 mm since 1900. Hover the 1993 join: that is a splice of two instruments, the same class of join as tree rings onto thermometers. Dotted acronyms have a textbook note and a note from this record.
Common Era — Kopp rates spliced onto the instrumental series
Dashed: piecewise from (salt-marsh foraminifera, coral microatolls, 24 localities + gauges). Teal: CSIRO/Church & White tide-gauge reconstruction. Dark: , offset to the 1993 gauge value. mm vs EPA 1880.
Kopp 2016 ratesCSIRO / Church & White gaugesNOAA STAR altimeter
Instrumental close-up — the 1993 splice
How the series were obtained: gauges are a staff on a harbour wall, corrected for and reconstructed globally with satellite-era spatial patterns. Satellites are radar range to the sea surface, 66°S–66°N in the STAR file (trend on the file: 3.17 mm/year, no GIA). Hover 1993 for the join.
Last Glacial Maximum
−125 to −130 m
~21,000 years ago
Lambeck et al. 2014. Almost the whole ice-sheet SLE was on land. Today’s +20 cm is a rounding error on that axis.
ice age lowstand
Meltwater Pulse 1A
still tens of metres below now
~14,600 years ago
Fairbanks / Deschamps et al. The satellite era is ~3.3 mm/year — an order of magnitude slower than a deglacial pulse.
40–60 mm/year for centuries
Last interglacial (Eemian)
+6 to +9 m vs now
~125,000 years ago
Dutton et al. 2015. Hippos in the Thames, coral above today’s high-water. Current GMSL is not high in this light.
higher stand, not a 20 cm wiggle
Late Holocene (Kopp)
± ~8 cm
0–1700 CE
Kopp et al. 2016. Centimetres over millennia. The 20th century (13.8 cm) is faster than those centuries — that is a rate claim, not a height claim.
~0.1 mm/year, then a fall 1000–1400
Acceleration is the claim. Height is not.
since 1900 is ~236 mm on this splice (~23.6 cm). That is a paperback on end, not a storey, and it is trivial next to the glacial cycle. Kopp et al. (2016) argue the 20th-century rate (1.4 mm/year) was faster than any century in the previous ~27. The satellite era is ~3.3 mm/year. That is acceleration versus the late Holocene. It is not acceleration versus Meltwater Pulse 1A (40–60 mm/year). High-end 1980s paper ran at ~32 mm/year to 2100; the altimeter is ten times slower.
Half of 1971–2018 rise was of water already in the ocean — volume from heat, and ocean heat comes from the sun. shows the planet absorbing more sunlight because albedo fell. Treating that drop as a “feedback” on forcing is an interpretation. The splice on this chart does not measure a forcing ledger; it measures millimetres.
Salt-marsh foraminifera, coral microatolls, and other geological RSL indicators from 24 localities, plus tide gauges, in a Gaussian-process model. This snapshot is a piecewise line from the paper’s published rates, aligned to EPA 1900 — a splice of proxies onto gauges. Tide gauges: Coastal and island tide gauges, reduced-space reconstruction with satellite-era spatial patterns (Church & White 2011). Inches converted to mm. 1880 = 0. Altimeter: Radar range from TOPEX/Poseidon, Jason-1/2/3, Sentinel-6MF. Annual mean of available missions. Offset so 1993 matches EPA CSIRO 1993 (the splice).
Extent by day of year
Arctic and Antarctic use the same layout. Each faint line is one year. Hover to read a date; click a line to pin that year. Bands are the NSIDC 1981–2010 10th–90th and 25th–75th percentiles; dashed line is the median.
Arctic
million km²
Antarctic
million km²
Annual mean extent
Bars are the observations. The dashed line is an ordinary least-squares fit through complete years in the selected window. Incomplete years are drawn fainter and left out of the slope. The line describes the plotted points; it is not a physical model.
Arctic
−0.508 million km²/decade · 1979–2025 · n=45 · r²=0.90
million km²
Antarctic
−0.074 million km²/decade · 1979–2025 · n=45 · r²=0.04
million km²
2 Sep, each year
Same calendar date across the satellite record. Bar height is extent that day. Click a year to pin it on the seasonal plots.
Arctic
19812026
Antarctic
19812026
Arctic lowest daily extent
3.340 million km² on 16 Sep 2012
Arctic highest daily extent
16.635 million km² on 1 Mar 1979
Antarctic lowest daily extent
1.848 million km² on 21 Feb 2023
Antarctic highest daily extent
20.201 million km² on 20 Sep 2014
Sources and methods
Every series plotted on this page can be downloaded as the snapshot used here, and opened at the publisher. Papers and data products cited in the notes are listed below. Retrieved 2026-09-04.
Data in this snapshot
NSIDC Arctic daily extent
G02135 v4.0 · last 2026-09-02
NSIDC Arctic monthly extent
Fetterer, F
NSIDC Arctic 1981–2010 climatology
Percentiles by day of year
NSIDC Antarctic daily extent
G02135 v4.0 · last 2026-09-02
NSIDC Antarctic monthly extent
Antarctic (Southern Hemisphere)
NSIDC Antarctic 1981–2010 climatology
Percentiles by day of year
NSIDC Arctic annual mean extent
Complete years only in the OLS
NSIDC Antarctic annual mean extent
Complete years only in the OLS
NOAA Arctic monthly temperature
NOAA CAG Arctic region (land+ocean). Monthly surface temperature departure from the 1901–2000 mean.
NOAA Antarctic monthly temperature
NOAA CAG Antarctic region (land+ocean). Monthly surface temperature departure from the 1901–2000 mean.
NOAA Arctic annual temperature
Mean of months; complete = 12 months
NOAA Antarctic annual temperature
Mean of months; complete = 12 months
GISS Arctic zonal annual
64N–90N · vs 1951–1980
GISS Antarctic zonal annual
90S–64S · vs 1951–1980
ERA5 Arctic daily 2 m air temperature
66.5°–90°N, area-weighted · last 2026-08-28
ERA5 Antarctic daily 2 m air temperature
66.5°–90°S, area-weighted · last 2026-08-28
CSIRO / Church & White tide-gauge GMSL
1880–2013 · mm vs 1880
NOAA STAR satellite GMSL (spliced to 1993 gauge)
1993–2025 · 3.17 mm/year, no GIA correction
Kopp 2016 Common Era rates (piecewise)
Published century rates aligned to EPA 1900 — not the GP posterior
Papers and referenced material
- Hansen et al. 1988, J. Geophys. Res.
Both-poles claim; Scenario A/B/C; 4.2 °C 2×CO2 sensitivity.
- Hansen 2006, PNAS
Restated 1988–2005 Scenario A/B/C global rates: 0.35 / 0.19 / 0.24 °C per decade.
- Hansen Senate testimony, 23 June 1988
“More warming at high latitudes than at low latitudes.”
- Robock 2000, volcanic eruptions and climate
Stratospheric sulfate raises albedo; tropical VEI 5+ cools 1–3 years.
- Sato et al., GISS volcanic aerosol optical depth
Agung 1963 is the SAOD spike inside 1940–1970.
- Goode, Pallé et al. 2021, earthshine albedo
Earthshine and CERES: Earth’s reflectance falling 1998–2017.
- CERES, NASA Langley
Top-of-atmosphere reflected shortwave. A drop is an albedo drop, measured.
- Nikolov & Zeller 2024
CERES albedo + TSI fit to 21st-century global surface air. No greenhouse term in Equation 16.
- Goessling, Rackow & Jung 2024, Science
2023 record-low albedo; ASR +1.82 W m⁻² vs 2001–2022. Same CERES darkness NZ plot.
- NZ Atlas — reanalysis of Nikolov & Zeller and Goessling et al.
GSAT tracks ASR (R² 0.84) not EEI (R² 0.45). Shared 26-year CERES albedo fact; the fork is forcing language.
- Funder et al. 2011, Science
Holocene Thermal Maximum: northern Greenland summer ice probably <50% of 2007.
- BedMachine Antarctica / Greenland
Land-ice sea-level equivalent: Antarctic 57.8 m, Greenland 7.42 m.
- PIOMAS Arctic sea ice volume
September mean volume ~11,500 km³. Floating ice; not in NSIDC extent.
- NOAA Climate.gov, global sea level
20th-century tide gauges ~1.4–1.7 mm/year; satellite era ~3.3 mm/year.
- Church & White 2011, sea-level reconstruction
Tide-gauge global mean. The splice onto TOPEX at 1993 is a join of two instruments.
- Kopp et al. 2016, PNAS, Common Era sea level
Proxy RSL + gauges. 20th century 1.4 mm/year; 0–700 CE 0.1 mm/year. Rate claim, not a height claim.
- Lambeck et al. 2014, PNAS, last glacial sea level
LGM lowstand ~−125 to −130 m. Today’s +20 cm is a rounding error on that axis.
- Dutton et al. 2015, Science, last interglacial
Eemian sea level +6 to +9 m vs now.
- EPA Climate Indicators, sea level Fig. 1
CSIRO reconstruction (inches) + NOAA satellite on one figure — the public splice.
- NOAA Laboratory for Satellite Altimetry GMSL
TOPEX/Jason/Sentinel-6, 66°S–66°N. File trend 3.17 mm/year, no GIA.
- IPCC FAR 1990, Ch. 9, sea level
2100 best estimate 66 cm (31–110 cm).
- Hoffman et al., EPA 1983 sea-level scenarios
High-end 1980s paper: up to ~2–3.5 m by 2100.
- IPCC AR6 WGI, SPM A.4.3 and Table 9.5
1971–2018: thermal expansion 50% of GMSL (47.5 mm); glaciers 22%; ice sheets 20%. Ocean 91% of extra heat.
- NASA GRACE / GRACE-FO ice sheets
2002–2025 averages: Greenland −264 Gt/year, Antarctica −135 Gt/year. 360 Gt ≈ 1 mm sea level.
- NASA Sea Level Change Portal
Satellite altimetry. 7 July 2026: 100.1 mm above 1993.
- Polar Portal, Greenland surface mass balance
Daily SMB map and 1981–2010 climatology. Seasonal, not a stopped ice sheet.
- Andersen et al. 2025, EGUsphere 2025-5015
CryoSat-2 Greenland elevation 2011–2025: interior >1,500 m near-stable; ablation zone still thinning.
- Smithsonian Global Volcanism Program
VEI and dates for Lamington, Spurr, Bezymianny, Agung, Fernandina.
- Colorado University sea-level altimetry
Satellite altimeter global mean rate.
- Hockey Stick Lab — Sheep Mountain weighting and the 1910 trajectory
MBH98 / McIntyre & McKitrick 2005. CA534 ~390×; HadCRUT5 NH 1910–1938 +1.98 °C/century.
- Mann, Bradley & Hughes 1998, Nature
Hockey-stick reconstruction. The lab above isolates the Sheep Mountain weight.
- McIntyre & McKitrick 2005, GRL
Most-weighted site >390× the least-weighted site.
- δ¹³C Ledger — mixing intercept vs the fossil fingerprint
Francey 1999, GASLAB, Rubino 2019, Koutsoyiannis 2024. Observed intercept ≈ −13.3‰, not −28‰.
- Francey et al. 1999, Tellus B
Law Dome / Cape Grim δ¹³C. Gravitational, firn, and gradient corrections.
- Koutsoyiannis 2024, Sci
Keeling-plot intercepts at four stations stay near −13‰; do not drift to −28‰.
- Stomata vs Ice — firn smoothing vs growing-season CO2
Kouwenberg Roman ~357 ppm vs Law Dome ~281 ppm. Ice averages years–decade; stomata do not.
- Kouwenberg et al. 2005, Geology
Western-hemlock stomata, Common Era CO2 including a Roman-era maximum above ice.
- van Hoof et al. 2008, PNAS
Stomatal CO2 vs ice-core smoothing on centennial scales.
Sea ice extent: Area of ocean grid cells with ice concentration of at least 15 percent. Units: million km². Climatology: 1981–2010 for both hemispheres, as published with the Sea Ice Index. Near-real-time values can be revised. December 1987 and January 1988 are missing in the monthly files (SSMR to SSM/I sensor change). Fetterer, F., K. Knowles, W. N. Meier, M. Savoie, and A. K. Windnagel. 2017, updated daily. Sea Ice Index, Version 4. Boulder, Colorado USA. National Snow and Ice Data Center. https://doi.org/10.7265/n5k072f8 doi:10.7265/n5k072f8.
Monthly temperature: NOAA National Centers for Environmental Information. Climate at a Glance: Global Time Series. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series NOAA 60°–90° land+ocean, departure from 1901–2000. GISS zonal annual is Hansen’s lab, 64°–90°, vs 1951–1980. GISTEMP Team, 2026: GISS Surface Temperature Analysis (GISTEMP), version 4. NASA Goddard Institute for Space Studies. https://data.giss.nasa.gov/gistemp/ Daily 2 m air temperature: Hersbach et al. (2020), ERA5, Copernicus Climate Change Service (C3S). Daily zonal means via Climate Reanalyzer, Climate Change Institute, University of Maine. https://climatereanalyzer.org/clim/t2_daily/ Reanalysis: observations blended by a weather model. Not a climate projection and not a station-thermometer average. Updates lag the calendar by several days.
Ordinary least-squares through complete calendar years. A slope is treated as a usable rate only when r² ≥ 0.40. Ice is not required to go to zero on a line. Hansen high-latitude red line is +0.35 °C/decade (Scenario A global, Hansen 2006) × ~2 from that model’s 2×CO2 polar/global ratio = +0.70 °C/decade, drawn from the 1988 NOAA value. Floating sea ice already displaces its own weight; its melt is not added to sea level.