Arctic News: feedbacks

Showing posts with label feedbacks. Show all posts

Friday, September 19, 2025

Double Blue Ocean Event 2026? (update)

Arctic sea ice looks set to continue to be at record daily volume, as it has been for more than a year. The image below shows Arctic sea ice volume through September 19, 2025.

While Arctic sea ice volume continues to be at record daily low levels, its decline since its maximum in April through to its minimum in September has been relatively slim this year, which can be the result of natural variability (including of wind patterns), of an increase of freshwater and of slowing down of AMOC.

At the same time, sea surface temperatures have kept rising, with huge amounts of ocean heat accumulating at higher latitudes north recently, as illustrated by the image below that shows sea surface temperature anomalies at 30°N-90°N.

[ image from earlier post, click to enlarge ]

High (and rising) greenhouse gas concentrations combined with a decrease in aerosol masking are causing Earth's energy imbalance to keep rising, which comes with feedbacks including more water vapor in the atmosphere, a decrease in lower clouds and decline of the snow and ice cover. The decline of sea ice is illustrated by the image below that shows the global sea ice area anomaly through September 18, 2025.

Ominously, the Antarctic sea ice area anomaly has been very low this year. The image below shows the 2025 anomaly (in black) from April through September 18, 2025, a period during which very little sunlight has reached the Southern Hemisphere. Furthermore, the low anomaly has been reached in the absence of an El Niño.

This spells bad news for Antarctic sea ice, which almost crossed the threshold for a Blue Ocean Event on February 22, 2023, as illustrated by the image below.

[ image from earlier post, click to enlarge ]

In conclusion, a Blue Ocean Event could occur in the Southern Hemisphere in early 2026. This could be followed by a Blue Ocean Event in the Northern Hemisphere later in 2026, in particular if a new El Niño will emerge in the course of 2026 and further feedbacks are triggered, such as seafloor methane eruptions.

The danger is also illustrated by the image below, adapted from an image issued by NOAA September 19, 2025, showing hourly methane averages recorded at the Barrow Atmospheric Baseline Observatory (BRW), a NOAA facility located near Utqiaġvik (formerly Barrow), Alaska, at 71.32 degrees North.

Climate Emergency Declaration

The situation is dire and the precautionary principle calls for rapid, comprehensive and effective action to reduce the damage and to improve the situation, as described in this 2022 post, where needed in combination with a Climate Emergency Declaration, as discussed at this group. </ div>

Links

• Kevin Pluck - Sea ice visuals
https://seaice.visuals.earth

• Danish Meteorological Institute - Arctic sea ice thickness and volume
https://ocean.dmi.dk/arctic/icethickness/thk.uk.php

• NOAA - Global Monitoring Laboratory - Data Visualisation - flask and station methane measurements
https://gml.noaa.gov/dv/iadv

• Double Blue Ocean Event 2026?

https://arctic-news.blogspot.com/2025/09/double-blue-ocean-event-2026.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

Wednesday, September 3, 2025

Arctic sea ice September 2025

The image below shows Arctic sea ice concentration on September 9, 2025.

Over the years, the global monthly sea ice concentration has fallen significantly (compared to 1951-1980). The image below shows the global monthly sea ice concentration anomaly through August 2025.

Albedo loss due to very low global sea ice area

The global sea ice area was 2.50 million km² below the 1981-2010 mean on September 10, 2025, a deviation from 1981-2010 of -4.32σ.

The above image shows the situation through September 9, 2025. It is significant that the global sea ice area anomaly has been strongly negative this year, even despite the absence of an El Niño.

Sea ice decline can occur by reduction in the area covered by the sea ice, resulting in albedo loss. Sea ice decline can also occur as the sea ice darkens, which can occur due to melting, cracking and thinning of the ice, due to rain and meltwater forming pools on top of the ice, due to growth of algae and due to settling down of aerosols on the sea ice, all of which will also result in albedo loss.

Loss of sea ice area results in albedo loss, which means that less sunlight gets reflected back into space and more heat instead gets absorbed by the ocean.

[ image from earlier post ]

Arctic sea ice thickness and volume

Sea ice decline also occurs as a result of thinning of the sea ice. The image on the right shows Arctic sea ice thickness on September 11, 2025.

Sea ice thickness can be hard to measure, due to rain and meltwater forming pools on top of the ice, while clouds can also obscure satellite imaging.

On the image below, adapted from dmi.dk, markers are added for September (red) and April (blue) corresponding with the year's minimum- and maximum volume, showing the downward path over the years for both the annual sea ice volume minimum and maximum. Magenta bars are added in years when the melting volume from April to September was large, while green bars are added in years when it was small.

Arctic sea ice volume in April 2025 was about 19,000 km³, which raised fears that virtually all Arctic sea ice could disappear in September 2025, resulting in a Blue Ocean Event.

Meanwhile, sea ice volume has fallen to about 4,000 km³ on September 12, 2025, as illustrated by the image below. Arctic sea ice volume was at a record low for the day on September 15, 2025, as it has been for more than a year.

Why a Blue Ocean Event is so dangerous

PIOMAS estimates that 16,400 km³ of ice is lost every year (1979-2010 average) from April to September, consuming an amount of energy of 5 x 10²¹ Joules (the image on the right shows calculations, click on this link or on the image to enlarge).

Once the latent heat buffer is lost, further heat must go elsewhere. During the phase change from ice to water, the temperature doesn't rise, i.e. all the energy goes into the process of changing ice into water. Once all ice has melted, further heat will raise the temperature of the water. The amount of energy that is consumed in the process of melting the ice is as much as it takes to heat an equivalent mass of water from zero°C to 80°C.

Decline of the snow and ice cover comes with numerous feedbacks, the loss of the latent heat buffer (feedback #14 on the feedbacks page) is only one of them. Further feedbacks include the loss of albedo (feedback #1), increases in emissions (feedback #2), loss of emissivity (feedback #23), while there are also changes to the Jet Stream (feedback #14) and changes to clouds and water vapor (feedback #20), and there are mechanisms and circumstances aggravating the danger, such as the slowdown of AMOC and further changes to ocean currents.

Eruption of methane from the seafloor of the Arctic Ocean (feedback #16) is one of the most dangerous feedbacks. As the seafloor of the Arctic Ocean heats up, heat can penetrate sediments and cause destabilization of hydrates, resulting in eruption of methane. As the seas in the Arctic Ocean can be very shallow, the methane can erupt with force in the form of plumes, with little opportunity for the methane to get decomposed in the water. Furthermore, there is very little hydroxyl in the air over the Arctic, which extends the lifetime of methane over the Arctic.

[ The Buffer is gone, from Accelerating Temperature Rise ]

Sea ice constitutes a buffer that previously consumed much incoming ocean heat (left); as sea ice thins, the buffer disappears while more heat also enters the Arctic Ocean (right). Further heat entering the Arctic Ocean from the Atlantic Ocean and the Pacific Ocean threatens to destabilize sediments that contain methane, causing eruption of huge amounts of methane.

The image below, adapted from an image issued by NOAA on September 16, 2025, shows hourly methane averages recorded at the Barrow Atmospheric Baseline Observatory (BRW), a NOAA facility located near Utqiaġvik (formerly Barrow), Alaska, at 71.32 degrees North.

The image below, adapted from Copernicus, shows a methane forecast for September 6, 2025 12:00, run that day at 00 UTC. High methane levels are visible on the West Coast of Canada, also discussed on facebook.

The image below shows that the NOAA 21 satellite recorded methane levels as high as 2559 parts per billion (ppb) at 399.1 mb on September 6, 2025 AM.

High temperatures and ocean heat

In August 2025, high temperature anomalies (compared to 1951-1980) were recorded at both poles, as illustrated by the image below.

The image below shows the NASA August 2025 temperature anomaly (versus 1951_1980).

Ominously, the global temperature anomaly has gone up again recently, despite the current absence of an El Niño. The anomaly for August 2025 was 1.51°C above 1903-1912 (not pre-industrial), as illustrated by the image below.

The image below shows temperature anomalies from 1951-1980 (NCEP/NCAR data).

The image below shows sea surface temperature anomalies through August 2025 (ERA5 Data).

The image below shows NASA land-only anomalies from 1880-1920 (not pre-industrial) through August 2025, when the anomaly was 1.82°C. The red line is a 3-year Lowess Smoothing trend. If this trend continued unchanged (dashed red), the anomaly could cross 3°C in 2029, causing mass extinction.

Note that when using a genuinely pre-industrial base, anomalies can be much higher than depicted in the above images. A 3°C anomaly constitutes an important threshold, since humans will likely go extinct with such a rise. As illustrated by the image below, the rise may already be more well over 2°C, while we may face a potentially huge temperature rise over the next few years.

[ from the post When will humans go extinct? ]

[ from: When Will We Die? ]

Recent research led by David Fastivich finds that, historically, vegetation responded at timescales from hundreds to tens of thousands of years, but not at timescales shorter than about 150 years. It takes centuries for tree populations to adapt - far too slow to keep pace with today’s rapidly warming world.

Note that healthy vegetation relies not only on temperature, but also on the presence of good soil, microbes, rain, soil nutrients, pollinators, habitat, groundwater and an absence of toxic waste, pests and diseases.

A 2018 study by Strona & Bradshaw indicates that most life on Earth will disappear with a 5°C rise (see box on the right). Humans, who depend on a lot of other species, will likely go extinct with a 3°C, as discussed in the earlier post When Will We Die?

The image below shows Arctic air temperature through September 5, 2025, with the inset highlighting the Arctic and the global temperature anomaly that day. The temperature in the Arctic reached a daily record high of 2.4°C on September 5, 2025, an anomaly of +2.46°C compared to 1979-2000.

The image below shows sea surface temperatures in the Gulf through September 7, 2025, when the sea surface reached a record daily high temperature of an average of 30.84°C, an anomaly of +1.53°C compared to 1982-2010, with the inset highlighting the Gulf and the global sea surface temperature anomaly that day.

The image below shows high Ocean Heat Content in the Gulf through September 7, 2025.

Equivalent Ocean Heat Content on September 8, 2025, is illustrated in the image below.

The temperature of the ocean is very high in many areas, as illustrated by the image below. The image below shows sea surface temperatures around North America as high as 33°C on September 1, 2025.

In conclusion, a lot of ocean heat is still on its way toward the Arctic Ocean along the path of the Gulf Stream.

The Jet Stream is getting increasingly distorted, which threatens to - at times - speed up the flow of large amounts of heat into the Arctic Ocean. The image below shows the situation on September 10, 2025.

The image on the left shows the Jet Stream following the path of the Gulf Stream over the North Atlantic, with one branch going south and moving backward, while another branch is moving North over the Arctic Ocean, with both branches displaying circular patterns.

The image on the right shows the Jet Stream reaching speeds over the Arctic Ocean as high as 253 km/h with wind power density as high as 67.9 kW/m² (at the green circle).

Land Evaporation Tipping Point

Higher temperatures come with stronger feedbacks, such as stronger evaporation resulting in both a lot more water vapor and a lot more heat getting transferred from the surface to the atmosphere. Much of this will return to the surface with precipitation such as rain and snow, but 7% more water vapor will end up in the atmosphere for every degree Celsius rise in temperature. Moreover, water vapor is a potent greenhouse gas that will increase temperatures and it is a self-amplifying feedback that can strongly contribute to further acceleration of the temperature rise.

Precipitable water can be expressed in kg/m² or in millimeters (mm), with the latter representing the depth of the water if all the atmospheric vapor were condensed into liquid form and spread across the surface, while kilograms per square meter (kg/m²) represents the mass of that water per unit area (1 kg/m² = 1 mm). As illustrated by the image below, the monthly precipitable water anomaly (in kg/m², versus 1951-1980) has increased over time, in line with rising temperatures.

At the same time, the monthly total precipitation anomaly (versus 1951-1980) has decreased over time, as illustrated by the image below.

This decrease in precipitation indicates that over time, less and less evaporation is taking place over land, in turn indicating that the Land Evaporation Tipping Point is getting crossed in areas where water is no longer available locally for further evapotranspiration, i.e. from all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration, including transpiration from vegetation, evaporation from the soil surface, from the capillary fringe of the groundwater table, and from water bodies on land, as also discussed at this page and at this article on the Water Vapor-Pressure Deficit (VPD).

Once this tipping point gets crossed, the land and atmosphere will heat up strongly. Additionally, more water vapor in the atmosphere accelerates the temperature rise, since water vapor is a potent greenhouse gas and this also contributes to speeding up the temperature rise of the atmosphere (as also discussed on facebook here, here and here).

The image below, adapted from Copernicus, shows the global fall in relative humidity over land over time.

[ image from Moistening Atmosphere ]

Climate Emergency Declaration

The temperature rise is accelerating and the rise could accelerate even more due to decreases in buffers (as described in earlier posts such as this one), due to strengthening feedbacks, especially during an El Niño, and due to further reduction of the aerosol masking effect, which are all developments that could rapidly speed up existing feedbacks and trigger new feedbacks.

The situation is dire and the precautionary principle calls for rapid, comprehensive and effective action to reduce the damage and to improve the situation, as described in this 2022 post, where needed in combination with a Climate Emergency Declaration, as discussed at this group.

Links

• University of Bremen - sea ice concentration and thickness

https://seaice.uni-bremen.de/start

• Danish Meteorological Institute - Arctic sea ice thickness and volume
https://ocean.dmi.dk/arctic/icethickness/thk.uk.php

• PIOMAS - Arctic Sea Ice Volume Reanalysis

https://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly

• Climate Reanalyzer

https://climatereanalyzer.org

• Kevin Pluck - Sea ice visuals
https://seaice.visuals.earth

• NOAA - sea surface temperatures
https://www.ospo.noaa.gov/products/ocean/sst/contour/index.html

Also discussed on facebook at:
https://www.facebook.com/photo/?fbid=10172670654340161&set=p.10172670654340161

• University of Miami - Rosenstiel School - North Atlantic OHC
https://isotherm.rsmas.miami.edu/heat/weba/atlantic.php

• Brian McNoldy - Ocean Heat Content
https://bmcnoldy.earth.miami.edu/tropics/ohc
discussed on Facebook at:
https://www.facebook.com/groups/arcticnews/posts/10163172734849679

• NOAA - Climate Prediction Center - ENSO: Recent Evolution, Current Status and Predictions
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

• NOAA - Global Monitoring Laboratory - Data Visualisation - flask and station methane measurements

https://gml.noaa.gov/dv/iadv

• When Will We Die?
https://arctic-news.blogspot.com/2019/06/when-will-we-die.html

• Copernicus

https://atmosphere.copernicus.eu

also discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10163179340334679

• ECMWF - El Niño forecast
https://charts.ecmwf.int/products/seasonal_system5_nino_annual_plumes

• nullschool.net

https://earth.nullschool.net

• When will humans go extinct?
https://arctic-news.blogspot.com/2022/02/when-will-humans-go-extinct.html

• Coupled, decoupled, and abrupt responses of vegetation to climate across timescales - by David Fastovich et al. (2025)
https://www.science.org/doi/10.1126/science.adr6700
discussed on Facebook at:
https://www.facebook.com/groups/arcticnews/posts/10162972980774679

• Arctic Blue Ocean Event 2025?
https://arctic-news.blogspot.com/2025/03/arctic-blue-ocean-event-2025.html

• Arctic Blue Ocean Event 2025? (update June 2025)

https://arctic-news.blogspot.com/2025/06/arctic-blue-ocean-event-2025-update-June-2025.html

• Arctic Blue Ocean Event? (update July 2025)
https://arctic-news.blogspot.com/2025/07/arctic-blue-ocean-event-update-july-2025.html

• Blue Ocean Event

https://arctic-news.blogspot.com/p/blue-ocean-event.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

Wednesday, July 2, 2025

Saltier water, less sea ice

The Southern Meriodinal Ocean Circulation (SMOC) used to be driven by a cold freshwater layer resulting from melting Antarctic sea ice, enabling circumpolar waters to cool off and freshen, making them more dense and sink to the bottom.

[ Antarctic waters sinking to the bottom, click on images to enlarge ]

This is illustrated by the above image, from a study led by Violaine Pellichero (2018), showing water-mass transformation within the Southern Ocean mixed-layer under sea-ice. Schematic cross-section illustrating the main water-masses in the Southern Ocean (Antarctic Intermediate and Mode Waters in red, Circumpolar Deep Waters in gray, and Dense Shelf Waters and Antarctic Bottom Waters in blue) and their interaction with ice and the surface. The water-masses are denoted by their neutral density values and the arrows corresponding to each water-masses indicate subduction (downward) or upwelling (upwards). The violet arrows illustrate the effect of northward sea-ice extent and freshwater transport. The green line is the mixed-layer.

A study led by Alessandro Silvano (2025) finds that, over the years, surface waters have become more salty.

By combining satellite observations with data from underwater robots, researchers built a 15-year picture of changes in ocean salinity, temperature and sea ice, as illustrated by the above image. Around 2015, surface salinity in the Southern Ocean began rising sharply – just as sea ice extent started to crash.

When surface waters become saltier, they sink more readily, stirring the ocean’s layers and allowing heat from the deep to rise. This upward heat flux can melt sea ice from below, even during winter, making it harder for ice to reform. This vertical circulation also draws up more salt from deeper layers, reinforcing the cycle.

In addition to heat rising up from the deep, there is the danger that increasing amounts of both heat and carbon dioxide (CO₂), previously stored in the deep ocean by sinking circumpolar waters, will instead remain at the surface and cause both atmospheric temperatures and CO₂ concentrations to rise.

In the video below, Paul Beckwith discusses the recent study.

The video below by @JustHaveaThink also discusses the recent study.

Saltier water, less sea ice

[ Saltier water, less sea ice ]

The higher the water's salt content, the lower its melting point. Seawater typically has a salinity of about 3.5% (35 grams of salt per liter of water). Sea ice starts melting when the temperature rises to about -2°C (28.4°F). By contrast, freshwater remains frozen as long as the temperature remains below 0°C (32°F).

What is causing the Southern Ocean surface to become more salty? Higher temperatures come with feedbacks, such as stronger evaporation resulting in both a lot more water vapor and a lot more heat getting transferred from the surface to the atmosphere.

Much of the water vapor will return to the surface in the form of precipitation such as rain and snow, but part of this precipitation will fall over Antarctica. Increased snowfall over Antarctica can be attributed to rising air temperatures and stronger evaporation, changes in atmospheric circulation and the effects of ozone depletion.

Furthermore, 7% more water vapor will remain in the atmosphere for every degree Celsius rise in temperature. Since water vapor is a potent greenhouse gas, this will further increase temperatures, making it a self-amplifying feedback that can significantly contribute to further acceleration of the temperature rise.

Accumulating feedbacks

Warmer oceans result in stronger stratification (feedback #29), further contributing to make it harder for heat to reach the deeper parts of oceans. As a result, a larger proportion of the heat that was previously entering oceans will instead remain in the atmosphere or accumulate at the ocean surface, and slowing down of the Atlantic Meriodinal Overturning Circulation (AMOC) further contributes to this.

[ from earlier post ]

More evaporation typically makes the sea surface more salty, while more precipitation, melting of sea ice and run-off from rivers and glaciers typically make the ocean surface fresher. As the recent study shows, the Southern Ocean surface is becoming more salty, which contributes to higher sea surface temperatures and in more melting of the sea ice. It's a self-amplifying feedback, in that saltier water at the ocean surface 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.

Less sea ice also comes with loss of albedo (water is less reflective than ice, feedback #1), loss of the latent heat buffer (as sea ice disappears, heat can no longer be consumed by the process of melting, and the heat will instead go into increasing the temperature, feedback #14) and loss of emissivity (water is less efficient than ice in emitting in the far-infrared region of the spectrum, feedback #23), while warmer water result in more water vapor and less low-level clouds that reflect sunlight back into space (feedback #25).

The image below, from an earlier post, illustrates that higher temperatures come with feedbacks and the impact of one feedback can amplify the impact of other feedbacks.

[ image from: 10°C or 18°F warmer by 2021? ]

The above image depicts some of the dangers of feedbacks for the Arctic. Many feedbacks also apply to the Antarctic, but the bottom part of the image on the right may be particularly applicable to the Southern Hemisphere, which has more ocean surface and Antarctica constitutes a huge land mass on and around the South Pole.

Covering more than 70% of Earth’s surface, our global ocean has absorbed about 90% of the warming that has occurred in recent decades due to increasing greenhouse gases, and the top few meters of the ocean store as much heat as Earth's entire atmosphere, as described by a NASA post.

Even a small change could therefore result in a huge rise in the global air temperature.

Climate Emergency Declaration

The situation is dire and the precautionary principle calls for rapid, comprehensive and effective action to reduce the damage and to improve the situation, as described in this 2022 post, where needed in combination with a Climate Emergency Declaration, as discussed at this group.

Links

• The southern ocean meridional overturning in the sea-ice sector is driven by freshwater fluxes - by Violaine Pellichero (2018)

https://www.nature.com/articles/s41467-018-04101-2

• Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites - by Alessandro Silvano et al. (2025)
https://www.pnas.org/doi/full/10.1073/pnas.2500440122
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10162876582119679

• Abrupt Antarctic Ocean Regime Shift: Reversed SMOC - Southern Meridional Overturning Circulation - video by Paul Beckwith

https://www.youtube.com/watch?v=12Ch-NIYxvQ

• Feedbacks
https://arctic-news.blogspot.com/p/feedbacks.html

• Water Vapor Feedback
https://arctic-news.blogspot.com/2024/09/water-vapor-feedback.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

Thursday, May 22, 2025

Paris Agreement thresholds crossed (update May 2025)

High temperatures persist

In the image below, created with NASA data, the decade from 1904 through 1913 is used as a custom base, illustrating that the temperature anomaly has been more than 1.5°C above this base for each of the past consecutive 22 months (July 2023 through April 2025), and even longer when compared to a pre-industrial base. The red line shows a trend (two-year Lowess Smoothing) that is pointing at 2°C above this base (1904-1913) getting crossed in the course of 2026.

[ trend points at 2°C above 1904-1913 getting crossed in 2026 ]

The temperature rise on land looks even more threatening, as illustrated by the image below.

The above image shows land only monthly temperature anomalies from 1880-1920, with the red line (2-year Lowess Smoothing trend) showing an acceleration in April 2022. If extended, the red line points at crossing 3°C in the course of 2026. Humans are likely to go extinct with a 3°C rise, as discussed in earlier posts such as this one.

An earlier analysis mentions that, when using 1750 as a base, this could add 0.3°C to the historic rise. The analysis adds that when using an even earlier base, even more could be added to the historic temperature rise.

Those who seek to delay or sabotage climate action typically call for use of a late base, in efforts to minimize the historic temperature rise. Using an earlier base can mean that temperatures are already higher than the thresholds that politicians at the adoption of the Paris Agreement pledged wouldn't be crossed, and it can also imply that the temperature rise is accelerating faster and further, due to stronger feedbacks such as more water vapor in the atmosphere and disappearance of lower clouds, all of which would constitute a stronger call for climate action.

The image below illustrates that air temperatures in the Northern Hemisphere have been very high over the past few months, at times reaching record high temperatures for the time of year, e.g. the temperature in the Northern Hemisphere was 10.08°C on May 14, 2025, the highest temperature on record for that day.

[ from earlier post, click on images to enlarge ]

These record high temperatures are the more significant as they were reached under ENSO-neutral conditions. On May 24, 2025, the sea surface temperature was 27.51°C, 0.35°C below 1991-2020, in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño, as illustrated by the image below. The Niño 3.4 anomaly is now lower than it has been for each day in March 2025, when La Niña conditions dominated.

The ENSO outlook below is dated May 8, 2025. It shows that ENSO-neutral conditions are likely to persist for the remainder of 2025, edging on La Niña conditions.

The ENSO outlook is dated May 18, 2025.

As said, to see such high temperatures under ENSO-neutral conditions is significant, it indicates that feedbacks are stronger than many models have anticipated, which implies that feedbacks will continue to grow stronger, given the rapid temperature rise over the past few years (black trend). A new El Niño may develop soon, potentially in April 2026, as the red trend in the image below warns about. The result could be a huge rise in temperature over the course of 2026 (red trend).

As said, different bases can be used, e.g. in the above images anomalies are calculated versus bases such as 1904-1913, 1880-1920, 1991-2020 and 1901-2000. None of them is pre-industrial. So, what would the temperature anomaly look like when a genuinely pre-industrial base was used?

The image below, from an earlier post, uses NASA monthly data through March 2023. Data are first adjusted from NASA's default 1951-1980 base to an earlier 30-year base, i.e. a 1886-1915 base, and then further adjusted by 0.99°C to reflect ocean air temperatures, higher polar anomalies and a pre-industral base.

The image below is an update, the same adjustments are made to data through April 2025.

How the 0.99°C adjustment in the above images is calculated is shown in the bright yellow inset of the image below.

[ from April 2024 post, click on images to enlarge ]

The images show that, when adjusting the data and using a genuinely pre-industrial base, the temperature rise may have already crossed both the 1.5°C and the 2°C thresholds that politicians at the 2015 Paris Agreement pledged shouldn't and wouldn't be crossed.

IPCC keeps downplaying the danger

The IPCC keeps downplaying the danger in many ways. One way the IPCC does this is by selecting a base that minimizes the temperature rise and then to keep making the claim that we're still well below the 1.5°C threshold. The above image, from an April 2024 post, shows that the February 2024 temperature was 1.76°C above 1885-1915, and potentially 2.75°C above pre-industrial (bright yellow inset right). The red line (a six-months Lowess smoothing trend) highlights the steep rise that had already taken place by then. Minimizing the temperature rise will also minimize feedbacks that come with the temperature rise, such as a rise in water vapor and loss of lower clouds, which are self-amplifying feedbacks that further accelerate the temperature rise. In other words, by minimizing the historic temperature rise, the IPCC also seeks to minimize the rise to come.

[ from a 2014 post, click on images to enlarge ]

An additional way used by the IPCC to downplay the danger is to suggest there was a "carbon budget", as if there was an amount of carbon to be divided among polluters that could continue to be consumed for decades to come.

The image on the right, from a 2014 post, points at the fallacy and deceit that comes with a carbon budget, carbon credits, offsets and net-zero emission targets that would, according to the IPCC, accomplish and maintain a "balance" between sources and sinks.

Instead, comprehensive and effective action is needed on multiple lines of action, simultaneously yet separately.

Indeed, action is needed to reduce concentrations of carbon both in oceans and in the atmosphere, while on land, the soil carbon content needs to increase, which can best be achieved by methods such as pyrolysis of biowaste and adding the resulting biochar to the soil, to reduce emissions, reduce fire hazards, sequester carbon, support the presence of moisture & nutrients in the soil and thus support the health & growth of vegetation, as discussed at the Climate Plan group and the biochar group.

The IPCC has failed on at least three points:
1. failed to warn about the historic temperature rise and associated larger feedbacks

2. failed to warn about mechanisms that could cause further acceleration of temperature rise soon

3. failed to point at the best ways to combat climate change.

Higher temperatures come with feedbacks, as illustrated by the image below, from an earlier post.

[ the temperature in the atmosphere can keep rising, even in the absence of further emissions ]

The above image illustrates how feedbacks and crossing of tipping points can cause the temperature of the atmosphere to keep rising, even in the absence of further emissions, due to shrinking heat sinks (e.g. sea ice thickness loss and oceans taking up less heat).

The IPCC failed to warn about Antarctic sea ice decline, and - importantly - the amplifying impact of Antarctic sea ice decline on the global temperature rise. This was addressed in an earlier post as follows:
Sea ice loss results in less sunlight getting reflected back into space and instead getting absorbed by the ocean and the impact of Antarctic sea ice loss is even stronger than Arctic sea ice loss, as Antarctic sea ice is located closer to the Equator, as pointed out by Paul Beckwith in a video in an earlier post. A warmer Southern Ocean also comes with fewer bright clouds, further reducing albedo, as discussed here and here. For decades, there still were many lower clouds over the Southern Ocean, reflecting much sunlight back into space, but these lower clouds have been decreasing over time, further speeding up the amount of sunlight getting absorbed by the water of the Southern Ocean, and this 'pattern effect' could make a huge difference globally, as this study points out. Emissivity is a further factor; open oceans are less efficient than sea ice when it comes to emitting in the far-infrared region of the spectrum (feedback #23 on the feedbacks page).

A 2024 study led by Norman Loeb finds that large decreases in stratocumulus and middle clouds over the sub-tropics and decreases in low and middle clouds at mid-latitudes are the primary reasons for increasing absorbed solar radiation trends in the northern hemisphere.

Slowing down of the Atlantic meridional overturning circulation (AMOC) can cause more heat to accumulate at the ocean surface. Higher sea surface temperatures also come with greater stratification (image below, from earlier post).

Stratification and further changes in oceans and in wind patterns can cause a freshwater lid to form on top of the ocean surface, enabling more hot & salty water to flow underneath this lid (feedback #28), contributing to calving of glaciers and destabilization of sediments at the seafloor.

Increases in water vapor in the atmosphere, loss of sea ice and loss of lower clouds are three self-amplifying feedbacks, i.e. as temperatures rise, such feedbacks will push temperature up even further and due to their self-amplification, the temperature rise will accelerate.

Sea ice loss

One feedback of high temperatures and high concentrations of greenhouse gases is loss of sea ice. Polar amplification of the temperature rise is hitting the Arctic hard, and is also causing dramatic loss of Antarctic sea ice. Global sea ice area has been very low for the past few years, as illustrated by the image below. This has caused a lot of sunlight that was previously reflected back into space, to instead get absorbed by the sea surface. On May 24, 2025, global sea ice area was 17.75 million km², lowest on record for the day.

The image below, adapted from the Danish Metereological Institute, shows that Arctic sea ice volume on May 29, 2025, was at a record low for the time of year, as it has been for more than a year.

Sea ice is disappearing over large parts of the Arctic Ocean. The image below, adapted from the University of Bremen, shows sea ice concentration on May 29, 2025.

The screenshot below, from an earlier post, further illustrates the dangers that come with sea ice loss. Eruptions of methane from the seafloor of the Arctic Ocean is one of the most terrifying dangers.

As the image below illustrates, some of the thickest sea ice disappears from the Arctic Ocean as it gets broken up by sea currents and the pieces get moved out along the edges of Greenland. The image shows how, on May 27, 2025, the sea ice gets broken up just north of Greenland, due to ocean currents that will also move the pieces to the south, alongside the edges of Greenland, toward the North Atlantic.