Arctic sea ice
Arctic sea ice volume is at a record daily low. It has been at a record daily low for well over a year. The image below shows Arctic sea ice volume through December 13, 2025.
The image below shows that the November 2025 Arctic sea ice volume was the lowest on record for the month of November.
The image below, adapted from an Eliot Jacobson image, shows the annual minima of Arctic sea ice thickness through 2025.
Loss of sea ice extent means that less sunlight gets reflected back into space and instead gets absorbed by the sea surface, resulting in higher temperatures, in a self-amplifying feedback loop.
The image on the right shows Arctic snow cover and sea ice concentration on December 13, 2025.
Furthermore, loss of Arctic sea ice volume can contribute to a huge rise in temperature as a result of methane erupting from the seafloor of the Arctic Ocean. As Arctic sea ice shrinks in volume, its capacity shrinks to act as a buffer that consumes ocean heat entering the Arctic Ocean from the Atlantic Ocean. As the buffer disappears, the temperature of the water can rise strongly and abruptly, causing heat to penetrate sediments that contain huge amounts of methane in the form of hydrates and free gas underneath hydrates. Heat penetrating such sediments can destabilize such hydrates, resulting in huge eruptions of methane.
Such an event could be triggered by wild weather swings resulting from higher temperatures that come with the next El Niño that is likely to emerge and strengthen in the course of the year 2026.
Global sea ice
The image below shows that the global sea ice extent was 3.2 million km² lower than 1981-2010 on December 15, 2025, the second lowest on record for the time of year and a deviation from 1981-2010 of -3.9σ.
Antarctic sea ice
The image below shows Antarctic sea ice extent anomalies from January 1979 through December 12, 2025. Satellite data are from NSIDC, DMSP SSM/I-SSMIS and JAXA AMSR2. Anomalies are calculated using a 5-day running mean from a 1981-2010 base.
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| [ Saltier water, less sea ice. From earlier post. ] |
The above image shows that the Antarctic sea ice extent anomaly remained relatively stable for many years, but gradually increased during the period from 2007 to 2015.
This increase can be attributed to rising temperatures from 2007 resulting in stronger wind spreading the sea ice and stronger evaporation of water from the Southern Ocean coming with increased snowfall on top of the sea ice accompanied by increased meltwater, which initially lowered salinity of the sea surface, enabling sea ice to spread wide.
Eventually, in 2015, this and rising temperatures started to overwhelm the earlier impact and increasingly stronger evaporation of water from the Southern Ocean started to contribute to make the sea surface more salty, resulting in more rapid melting of the sea ice.
This is illustrated by the forecast for December 28, 2025, of the precipitable water standardized anomaly (1979-2000 baseline) on the right.
It is further illustrated by the image on the right that shows a forecast for December 29, 2025, of the precipitable water standardized anomaly (1979-2000 baseline).
Many of these feedbacks such as changes in salinity and stratification have been discussed in earlier post such as this one.
The increase in snowfall on Antarctica is also illustrated by the image below that shows the accumulated precipitation anomaly (in percentage, versus 1951-1980) for the 12-month period from December 2024 through November 2025 (ECMWF ERA5 Data, adapted from ClimateReanalyzer.org.
A study led by Alessandro Silvano (2025) shows that, over the years, the Southern Ocean surface has become more hot and salty.
This is a self-amplifying feedback, in that saltier water at the ocean surface also draws up more heat from the deep ocean, making it harder for sea ice to regrow. Increasing amounts of heat and CO₂ that were previously stored in the deep ocean by sinking circumpolar waters, threaten to instead remain at the surface and cause both atmospheric temperatures and CO₂ concentrations to rise.
The combined impact of these feedbacks can accumulate and strike rapidly. Feedbacks include the impact of sea ice decline (latent heat buffer loss + albedo loss), of the water vapor feedback, of increased stratification and salinity of the sea surface of the Southern Ocean, of heat entering the atmosphere from the ocean and of less heat getting transferred from the air to the depths of the ocean, and - as temperature rise - of triggering additional feedbacks such as loss of lower clouds and thus additionally causing more heat to be absorbed by the surface as less sunlight is getting reflected back into space.
The combined impact of these feedbacks can accumulate and strike rapidly. Feedbacks include the impact of sea ice decline (latent heat buffer loss + albedo loss), of the water vapor feedback, of increased stratification and salinity of the sea surface of the Southern Ocean, of heat entering the atmosphere from the ocean and of less heat getting transferred from the air to the depths of the ocean, and - as temperature rise - of triggering additional feedbacks such as loss of lower clouds and thus additionally causing more heat to be absorbed by the surface as less sunlight is getting reflected back into space.
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[ from earlier post ] |
Polar amplification of the temperature rise causes a relative slowing down of the speed at which heat flows from the Equator to the poles. This impacts ocean currents and wind patterns, resulting in slowing down of the Atlantic meridional overturning circulation (AMOC) and of ocean currents around Antarctica that carry heat to the deep ocean, as well as in deformation of the Jet Stream.
Sea ice cannot survive such high temperatures for long. The higher the water's salt content, the lower its melting point. Sea ice starts melting as soon as the temperature rises to -1.8°C (28.76°F), while freshwater remains frozen as long as the temperature stays below 0°C (32°F). In very salty water, sea ice will start melting at sea surface temperatures of -2°C (28.4°F). Seawater typically has a salinity of about 3.5% (35 grams of salt per liter of water).
As illustrated by the image below, the air temperature was -1.2°C or 29.8°F off the coast of Wilkes Land, Antarctica (green circle), on December 14, 2025 (03:00 UTC).
An Antarctic Blue Ocean Event (sea ice approaching a low of one million km²) threatens to occur in February 2026, with the danger that this will in turn trigger an Arctic Blue Ocean Event later in 2026.
The image on the right shows a NOAA update of Niño-3.4 region temperature anomalies and forecasts. NOAA considers La Niña conditions to occur when a one-month negative sea surface temperature anomaly of -0.5° C or less is observed in the Niño-3.4 region of the equatorial Pacific Ocean (5°N-5°S, 120°W-170°W). Also, there must be an expectation that the 3-month Oceanic Niño Index (ONI) threshold will be met, and an atmospheric response typically associated with La Niña is observed over the equatorial Pacific Ocean. These anomalies must also be forecasted to persist for 3 consecutive months.
As illustrated by the image below, the air temperature was -1.2°C or 29.8°F off the coast of Wilkes Land, Antarctica (green circle), on December 14, 2025 (03:00 UTC).
Both sea ice extent and concentration are currently low at both poles, contributing to high temperatures, since less sunlight gets reflected back into space and is instead absorbed by the surface. This spells bad news for Antarctic sea ice, which is expected to reach its minimum in February 2026.
The image on the right shows Antarctic snow cover and sea ice concentration on December 14, 2025, adapted from ClimateReanalyzer.
The combination image below shows the Antarctic sea ice concentration on December 14, 2025, by the University of Bremen (left) and by NSIDC (right). The NSIDC image also shows the median Antarctic sea ice edge 1981-2010 highlighted in orange.
The image below shows Antarctic sea ice thickness on December 15, 2025.
The next El Niño
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| [ click on images to enlarge ] |
The image below, adapted from ECMWF, shows the ENSO anomalies and forecasts for developments through November 2026 in Niño3.4 (left panel) and in Niño1+2 (right panel), indicating that the next El Niño will emerge and strengthen in the course of 2026.
Moving from the depth of a La Niña to the peak of a strong El Niño in itself can make a difference in the global temperature of more than 0.5°C, as discussed in an earlier post.
Methane
The methane danger is illustrated by the image below that shows hourly average in situ methane measurements well above 2400 ppb (parts per billion). The image is adapted from an image issued by NOAA December 13, 2025. The image shows methane recorded over the past few years at the Barrow Atmospheric Baseline Observatory (BRW), a NOAA facility located near Utqiaġvik (formerly Barrow), Alaska, at 71.32 degrees North latitude.
The methane danger is discussed in many earlier posts such as this one. Seafloor methane and methane from thawing terrestrial permafrost can add significantly and abruptly to the temperature rise.
Temperature rise
The image below shows the November 2025 temperature anomaly versus 1951-1980, based on ERA5 data.
Notes:
• Land-only? Using land-only anomalies is important, since most people do live on land in the Northern Hemisphere. When calculating the anomaly for the Northern Hemisphere on land only, the anomaly will be even higher. The two images below show a 0.5°C difference between the global anomaly and the anomaly in the Northern Hemisphere for the November 2025 anomaly.
• Land-only? Using land-only anomalies is important, since most people do live on land in the Northern Hemisphere. When calculating the anomaly for the Northern Hemisphere on land only, the anomaly will be even higher. The two images below show a 0.5°C difference between the global anomaly and the anomaly in the Northern Hemisphere for the November 2025 anomaly.
• 1880-1890 base? The 1880-1890 base is not pre-industrial, yet it is more illustrative than NASA's default 1951-1980; when using a genuinely pre-industrial base, temperature anomalies are likely to be even higher (see also the boxes on the image below).
• Red dashed line stops in 2028? The red dashed line stops in 2028 as it points at 3°C (top dotted line) crossed in 2028, which is an important threshold as humans will likely go extinct with a 3°C rise, as discussed in an earlier post.
• Red dashed line stops in 2028? The red dashed line stops in 2028 as it points at 3°C (top dotted line) crossed in 2028, which is an important threshold as humans will likely go extinct with a 3°C rise, as discussed in an earlier post.
• Lowess trend? The Lowess trend is used by NASA by default. The dashed red line is a linear extension of the Lowess trend and points at 3°C threshold crossed in 2028, but a non-linear trend and its extension may point at an even earlier year (see also this comment).
• NASA image? The background image is a screenshot of an image custom-made at data.giss.nasa.gov by Sam Carana; the blue textbox and the dashed and dotted lines are added for clarity.
• Timeline from 2022 to 2030? The timeline starts at 2022 as the image shows the 1.5°C threshold (bottom dotted line) to be crossed for all months since 2022 (black squares) and the Lowess 3-year smoothing trend (red line) indicates that the 2°C threshold (middle dotted line) was crossed in 2022. The timeline stops at 2030, as many politicians plan for emissions by people to continue to 2030 (and beyond), even though there may be no humans left by then, as the image illustrates.
• Timeline from 2022 to 2030? The timeline starts at 2022 as the image shows the 1.5°C threshold (bottom dotted line) to be crossed for all months since 2022 (black squares) and the Lowess 3-year smoothing trend (red line) indicates that the 2°C threshold (middle dotted line) was crossed in 2022. The timeline stops at 2030, as many politicians plan for emissions by people to continue to 2030 (and beyond), even though there may be no humans left by then, as the image illustrates.
• La Niña/El Niño? While the 2025 anomalies were reached in the absence of El Niño conditions elevating temperatures, the next El Niño may emerge in the course of 2026 (see above).
The November 2025 temperature anomaly was 1.32°C higher than 1951-1980. The anomaly would be significantly higher when calculated from 1850-1900 (the period typically used by the IPCC as base), and even higher when calculated from a genuinely pre-industrial base.
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| [ update of image from earlier post, click on images to enlarge ] |
The Northern Hemisphere November 2025 temperature anomaly was 1.82°C higher than 1951-1980, and 0.5°C higher than the global anomaly, as illustrated by the image below.
The above images also include boxes with a diagram and associated text from an earlier post, with more details regarding the size of the historic temperature rise and of the rise to come soon.
Clearly, the Northern Hemisphere Land Only temperature anomaly is a lot higher than the global temperature anomaly, which is important since most people live on land in the Northern Hemisphere.
Climate Emergency Declaration
UN secretary-general António Guterres recently spoke about the need for “a credible global response plan to get us on track” regarding the international goal of limiting the global temperature rise. “The science demands action, the law commands it,” Guterres said, in reference to a recent international court of justice ruling. “The economics compel it and people are calling for it.”
What could be added is that the situation is dire and unacceptably dangerous, and the precautionary principle necessitates rapid, comprehensive and effective action to reduce the damage and to improve the outlook, where needed in combination with a Climate Emergency Declaration, as described in posts such as this 2022 post and this one and as discussed in the Climate Plan group.
Links
• Danish Meteorological Institute - Arctic sea ice thickness and volume
• ClimateReanalyzer.org
• nullschool.net
• NOAA - National Centers for Environmental Prediction
also discussed on Facebook at:
https://www.facebook.com/groups/arcticnews/posts/10163589670899679
https://www.facebook.com/groups/arcticnews/posts/10163589670899679
• ECMWF
• Zach Labe - Antarctic sea ice extent and concentration
• Saltier water, less sea ice
• The danger of abrupt eruptions of seafloor methane
• NOAA - Global Monitoring Laboratory - Data Visualisation - flask and station methane measurements
https://gml.noaa.gov/dv/iadv
• NASA - GISS Surface Temperature Analysis - custom plots
• When Will We Die?
https://arctic-news.blogspot.com/2019/06/when-will-we-die.html
• Pre-industrial
https://arctic-news.blogspot.com/p/pre-industrial.html
• Transforming Society
https://arctic-news.blogspot.com/2022/10/transforming-society.html
• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html
• Climate Emergency Declaration
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html
