El Niño-Southern Oscillation (ENSO) is a climate pattern that fluctuates from El Niño to La Niña conditions and back. El Niño raises temperatures, whereas La Niña suppresses temperatures. This year, there have been neutral to La Niña conditions, as illustrated by the image below, which also shows that over the past few months, there has been a zigzag pattern of rises and falls around the mean sea surface temperature in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño.
[ click on images to enlarge ]
On September 13, 2025, the temperature reached an anomaly in this area of -0.54°C versus 1991-2020, indicating that La Niña conditions are likely to dominate late 2025/early 2026. The inset on the above image shows the Niño 3.4 area and sea surface temperature anomalies versus 1991-2020 on that day.
The image on the right, adapted from NOAA, shows the ENSO outlook (CFSv2 ensemble mean, black dashed line) favoring La Niña late 2025/early 2026.
The image on the right, adapted from ECMWF, shows an ENSO forecast for developments in Niño3.4 through August 2026, indicating that the next El Niño may emerge early 2026 and grow in strength in the course of 2026.
Rising temperature in absence of El Niño
Critical is the temperature on land, which is after all where people live. The image below shows that in 2025, monthly temperature anomalies (from 1880-1920) on land have fallen from a high of +2.93°C in January 2025 to +1.45°C in July 2025, in line with the temperature suppression that comes with a move into La Niña.
The anomaly was +2.93°C in January 2025, very close to +3°C. Note that when using a genuinely pre-industrial base, anomalies can be much higher than depicted in the above image. While anomalies have come down somewhat, the anomaly rose again to +1.82°C in August 2025, which could indicate that acceleration of the temperature rise is overwhelming the temperature suppression that comes with a move into La Niña.
The sea surface temperature anomaly keeps rising, in particular from the latitudes of 30° and higher north, as illustrated by the image below.
Adding to fears that the temperature rise is accelerating despite the absence of El Niño is the most recent rise of the global temperature anomaly. As illustrated by the image below, the global temperature anomaly versus 1991-2020 has risen strongly recently, from +0.21°C on July 4, 2025, to +0.83°C on September 20, 2025.
A +3°C temperature rise constitutes an important threshold, since humans will likely go extinct with such a rise, as illustrated by the image below.
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 rise, as discussed in the earlier post When Will We Die?
The map below shows the size of the population rather than the size of the territory, decreasing the size of Canada, Mongolia, Australia, and Russia, and highlighting how many people are vulnerable to heat stress.
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.
[ Arctic sea ice thickness, click on images to enlarge ]
The above combination image shows Arctic sea ice thickness on March 13, 2025 (left), April 28, 2025 (center) and May 13, 2025 (right). The image on the right shows more open water off the coast of Siberia.
[ Arctic sea ice concentration ]
The above image is a screenshot of part of a NASA Worldview satellite image for May 1, 2025. The image similarly shows open water off the coast of Siberia. The red dots indicate fires.
The image on the right, adapted from NSIDC, shows Arctic sea ice concentration on May 13, 2025.
Arctic sea ice is under threat as numerous conditions are becoming increasingly dire, as discussed in earlier posts such as this one.
For some of these conditions, further updates are added below (carbon dioxide, temperature, variables and Arctic sea ice).
Carbon dioxide
A daily carbon dioxide (CO₂) concentration of 431.25 parts per million (ppm) was recorded on May 10, 2025, at Mauna Loa, Hawaii, the highest daily average on record.
CO₂ concentrations haven't been below 430 ppm for 14 days in a row at Mauna Loa, Hawaii, as illustrated by the above image, which shows CO₂ for the last 31 days through May 10, 2025. The image below gives another view of daily concentrations.
One has to go back millions of years in time to find CO₂ concentrations this high, while the impact of high CO₂ concentrations back in history was lower due to lower solar output and the rate of change was also much slower, as also discussed in an earlier post.
The image below illustrates that the weekly mean CO₂ concentration at Mauna Loa, Hawaii, was 430.60 ppm in the week beginning on April 27, 2025, i.e. 4.02 ppm higher than the weekly value from one year ago (green inset).
Weekly CO₂ for the week starting May 4, 2025, was 430.86 ppm at Mauna Loa, Hawaii, compared to 426.92 ppm one year ago, a difference of 3.94 ppm, as illustrated by the image below.
The annual global average surface concentration of carbon dioxide (CO₂) for 2024 was 422.79 parts per million (ppm). CO₂ concentrations grew by 3.75 ppm during 2024, the highest growth rate on record, as discussed in an earlier post.
Temperature
The global surface air temperature was 15.72°C on 9 May 2025, the highest temperature on record for this day, as illustrated by the image below.
The global surface air temperature was 15.75°C on 10 May 2025, again the highest temperature on record for this day. The image below shows ERA5 daily temperature anomalies from end 2022 through May 10, 2025, with two trends added, a black linear trend and a red cubic (non-linear) trend that reflects stronger feedbacks and that follows ENSO (El Niño/La Niña) conditions more closely. This red trend warns about further acceleration of the temperature rise.
The shading added in the above image reflects the presence of El Niño conditions that push up temperatures (pink shading), La Niña conditions that suppress temperatures (blue shading), or neutral conditions (gray shading). The trends warn about feedbacks and further mechanisms pushing up temperatures over the next few years.
The above image shows two bases to compare the anomalies with, 1991-2000 (left axis) and 1901-1930 (right axis). Neither of these two bases is pre-industrial, anomalies will be higher when using a genuinely pre-industrial base.
The image below shows NASA monthly data through April 2025 compared to a custom 1903-1924. This 1903-1924 base is not pre-industrial either, anomalies will be higher when using a genuinely pre-industrial base. The monthly temperature anomaly has now been more than 1.5°C higher than this 1903-1924 base for 22 consecutive months (July 2023 through April 2025, marked with red text). Anomalies are rising rapidly, the red line (2-year Lowess Smoothing trend) points at 2°C higher than 1903-1924 getting crossed in the course of 2027.
[ more than 1.5°C above base for 22 consecutive months, trend points at 2°C above 1903-1924 crossed in 2027 ]
The picture can change when using a different base that anomalies are compared with. To illustrate this, the image below uses the decade from 1904 through 1913 as a custom base, resulting in higher anomalies and a trend 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 ]
An earlier analysis of pre-industrial suggests that using 1750 as a base could add as much as 0.3°C to the historic rise, while using a 3480 BC base could add as much as 0.79°C to the historic rise.
Those who seek to sabotage climate action typically call for use of a base that minimizes the historic temperature rise. A higher historic rise can imply 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 more due to stronger feedbacks such as more water vapor in the atmosphere and disappearance of lower clouds, so that would constitute a stronger call for climate action.
The Arctic is hit hardest by the temperature rise, as illustrated by the image below, which shows temperature anomalies compared to 1951-1981 for the period from November 2024 through April 2025.
The image below illustrates that the global temperature was at a record high for the time of year for five days in a row, i.e. from April 24, 2025, through April 28, 2025.
Variables
Some variables have a short-term impact on the temperature rise, including volcanoes, sudden stratospheric warming, sunspots and El Niño/La Niña variations. There have been no volcano eruptions and no sudden stratospheric warming events recently that could have provided significant cooling. Sunspots are at a high point in this cycle, which pushes up temperatures. Regarding ENSO (El Niño-Southern Oscillation), current conditions are ENSO-neutral, highlighting the significance of the high current temperatures, while a new El Niño may emerge soon. The image below shows NOAA's ENSO outlook dated May 11, 2025.
The image below shows temperatures through May 9, 2025, in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño.
[ temperature in Niño 3.4 area ]
Mechanisms such as self-amplifying feedbacks and crossing of tipping points, and further developments such as loss of the aerosol masking effect, can jointly contribute to further accelerate the temperature rise, resulting in a rise from pre-industrial of more than 10°C, while in the process also causing the clouds tipping point to get crossed and that can push the temperature rise up by a further 8°C, as discussed in earlier posts such as this one.
Arctic sea ice volume and area
Loss in sea ice can dramatically push up temperatures, as discussed in earlier posts such as this one. High ocean temperatures are causing Arctic sea ice volume to be very low compared to earlier years. The image below shows Arctic sea ice volume over the years in red for April, the month when Arctic sea ice typically reaches its maximum volume for the respective year.
The image below shows Arctic sea ice volume from 2000, with markers indicating volume in September (red) and in April (blue), corresponding to the year's minimum- and maximum volume.
The image below shows Arctic sea ice volume through May 14, 2025.
The image below illustrates that Arctic sea ice disappears not only as it melts away from below, due to heating up of the water of the Arctic Ocean. Arctic sea ice can also disappear as it gets broken up by ocean currents and moves out of the Arctic Ocean. The image shows how, on May 6, 2025, the sea ice gets broken up just north of the northern tip of Greenland, due to ocean currents that will also move the pieces to the south, alongside the edges of Greenland, toward the North Atlantic.
[ click on images to enlarge ]
On May 13, 2025, Arctic sea ice area was second lowest on record for that day, as illustrated by the image below.
The comparison with the year 2012 is important, since Arctic sea ice area reached its lowest minimum in 2012. Arctic sea ice area was only 2.24 million km² on September 12, 2012, i.e. 1.24 million km² above a Blue Ocean Event. While on May 13, 2025, Arctic sea ice area was only 0.8 million km² lower than on May 8, 2012, the difference between anomalies typically gets narrower in May. Therefore, if the difference between 2025 and 2012 will widen again, a Blue Ocean Event may occur in September 2025, as discussed in an earlier post.
Methane
Loss of Arctic sea ice can also trigger a very dangerous feedback: eruptions of methane from the seafloor of the Arctic Ocean. Methane in the atmosphere is already very high and large additional methane releases threaten to cause hydroxyl depletion, in turn extending the lifetime of all methane currently in the atmosphere.
Data for the annual increase in methane have been updated by NOAA. in 2024, there was a higher increase than in 2023, the 2024 increase was almost 10 parts per billion (ppb).
The image below shows the annual methane increase data (red circles), with two trends added. A quadratic trend (blue) is based on all available data (1894 through 2024), while a quintic trend (pink) is based on 2017 through 2024 data. The pink trend warns about a huge increase in methane, which could eventuate due to eruptions of seafloor methane.
In the video below, methane emissions are discussed by Peter Wadhams, Paul Beckwith, Peter Carter and Herb Simmens
Methane concentrations in the atmosphere have been around 1960 parts per billion (ppb) recently at Mauna Loa, Hawaii, as illustrated by the image below.
Methane is more potent as a greenhouse gas than carbon dioxide. Methane also has indirect effects, such as ground-level ozone and stratospheric water vapor, while methane partly turns into carbon dioxide. Importantly, the warming potential of a pulse of methane will decrease over time, given methane's relatively short lifetime.
Accordingly, there are different ways to calculate methane's carbon dioxide equivalent (CO₂e). Also important is whether a specific concentration of methane is used (in ppb) or the weight is used of a pulse of methane. In each of these cases, different multipliers can be used to calculate methane's CO₂e.
When using a multiplier of 200, a methane concentration of 1960 ppb would translate into 392 ppm of CO₂e. As mentioned above, a daily CO₂ concentration of 431.25 ppm was recorded at Mauna Loa, Hawaii, on May 10, 2025. So, when adding up these two, the joint CO₂e would be 823.25 ppm CO₂e, i.e. just 376.75 ppm short of the clouds tipping point (at 1200 ppm). This joint total doesn't yet include contributions of nitrous oxide and other drivers, so the situation is even more dire. Moreover, concentrations of greenhouse gases are increasing and they may increase even more dramatically soon.
So, what multiplier is best used when calculating methane's CO₂e? The IPCC already uses a slightly higher GWP for methane emissions from fossil fuel fugitive emission sources than for other methane emissions. So, the idea of using different multipliers in different scenarios is not new.
One multiplier could be used that does include cooling aerosols and another one that doesn't. Most carbon dioxide results from burning coal and oil, which comes not only with high CO₂ emissions, but also with co-emissions of cooling aerosols. On the other hand, there are little or no cooling aerosols co-emitted with methane emissions. Therefore, inclusion of cooling aerosols could result in a higher multiplier to be used when translating concentrations of methane into CO₂e, compared to carbon dioxide.
[ warming contributions, from earlier post, click on images to enlarge ]
[ warming responsibility by sector ]
To illustrate this point, the above image shows contributions to warming from 2010 to 2019, using IPCC AR6 data. If masking (cooling) would be included in the image by subtracting cooling by sulfates from CO₂, then the contribution of CO₂ would be proportionally lower, while the contribution of methane would be proportionally higher than what the image shows.
The image on the right is from a recent analysis by Gerard Wedderburn-Bisshop.
Given the dire outlook and given methane's higher potency as a greenhouse gas, it makes most sense to seek urgent and dramatic reductions in methane and such action should not be allowed to be sabotaged by those who propose a low multiplier when calculating methane's CO₂e.
IPCC
Meanwhile, the IPCC remains silent. No updates or special reports on topics such as acceleration of the temperature rise. Instead, the IPCC keeps persisting in downplaying the potential for such dangerous developments (in terms of the severity, probability, ubiquity and imminence of their impact), in efforts to hide the most effective climate action. The IPCC keeps pointing at less effective policies such as support for BECCS and biofuel, while continuing to make it look as if there was a carbon budget to divide among polluters, as if polluters could continue to pollute for decades to come.
There are at least five mechanisms that cause the water of the Arctic Ocean to heat up, as described below.
1. Direct Heat. Heat from sunlight directly reaches the surface, i.e. the sea ice or the water of the Arctic Ocean.
The August 8, 2023, image on the right, from Climate Reanalyzer, shows a 1-3 days forecast of maximum surface temperatures (2m). Heatwaves over land can extend over the Arctic Ocean.
High levels of emissions and greenhouse gases over the Arctic increase the amount of heat that is reaching the water of the Arctic Ocean and the sea ice.
The NASA satellite image below shows smoke from forest fires in Canada moving over the Beaufort Sea and over the sea ice on August 6, 2023.
[ click on images to enlarge ]
A recent study highlights that forest fires can strongly contribute to the temperature rise. Smoke, soot and further aerosols settling on the sea ice also darken the surface, resulting in more sunlight getting absorbed (feedback #9 on the feedbacks page).
The image on the right, from a Copernicus news release dated August 3, 2023, shows the dramatic growth in emissions from fires in Canada up to end July 2023.
The news release quotes Copernicus Atmosphere Monitoring Service senior scientist, Mark Parrington, who comments: "As fire emissions from boreal regions typically peak at the end of July and early August, the total is still likely to continue rising for some more weeks."
The Climate Reanalyzer image below shows that the temperature in the Arctic was at a record high for the time of year of 5.64°C or 42.15°F on August 9, 2023. Earlier, a record temperature of 5.81°C or 42.46°F was reached (on July 27, 2023).
Arctic sea ice typically reaches its minimum extent half September, when temperatures in the Arctic fall below 0°C and water at the surface of the Arctic Ocean starts refreezing.
2. Heat from Rivers. Hot water from rivers ending in the Arctic Ocean is another way the water is heating up and this is melting the sea ice from the side.
The August 10, 2023, image below, from nullschool.net, illustrates the added impact of heat that is carried by rivers into the Arctic Ocean, with sea surface temperatures as high as 20.4°C or 68.7°F recorded at a location where the Mackenzie River flows into the Arctic Ocean (at the green circle, where the green arrow is pointing at).
On August 6, 2023, the sea surface was 14.5°C or 26.2°F hotter than in 1981-2011, at a nearby location where the Mackenzie River is flowing into the Arctic Ocean, as illustrated by the image below.
The image on the right shows that on August 10, 2023, the sea surface temperature was 17.6°C or 63.7°F at a location where the Lena River in Siberia enters the Arctic Ocean, i.e. 14.2°C or 25.5°F hotter than it was in 1981-2011 (at green circle).
The Lena River flows into the Laptev Sea which is mostly less than 50 meters deep, making it relatively easy for surface heat to reach the seafloor.
The NOAA image underneath on the right shows sea surface temperatures in the Bering Strait as high as 19.2°C or 66.56°F on August 8, 2023.
The image illustrates that the water can heat up strongly where hot water from rivers and run-off from rainwater enters the Bering Strait.
3. Ocean Heat. Yet another mechanism is heat that is entering the Arctic Ocean from other oceans, i.e. from the North Atlantic Ocean and the Pacific Ocean. Sea ice underneath the sea surface is melting from below due to ocean heat.
An earlier post discusses why we are currently facing record high sea surface temperatures in the North Atlantic.
The image below shows how the Gulf Stream is pushing ocean heat toward the Arctic Ocean, while sea surface temperatures show up as high as 33.1°C or 91.58°F on August 9, 2023.
The Gulf Stream is an ocean current that extends into the Arctic Ocean, as pictured below and discussed at this page. This ocean current is driven by the Coriolis force and by prevailing wind patterns.
This ocean current contributes to the stronger and accelerating rise in temperature in the Arctic (compared to the rest of the world), which in turn causes deformation of the Jet Stream that can at times cause strong winds that speed up this ocean current, as discussed in earlier post such as this 2017 one.
4. Sea ice moving out. The Arctic Ocean is also heating up as sea ice is getting pushed into the Atlantic Ocean. Even the thickest sea ice can break up into pieces and move along with the flow of meltwater from glaciers, ocean currents and/or strong wind.
[ Click on images to enlarge ]
The animation below, created with NASA Worldview satellite images, shows the northern tip of Greenland at the top left of each frame. The green square on the image on the right indicates the area of the animation. It's around Prinsesse Thyra Island in Northeast Greenland National Park.
This is where typically the thickest sea ice is located. The animation shows the sea ice breaking up and moving out of the Arctic Ocean. What is left of the pieces will eventually melt in the Atlantic Ocean. Pieces of sea ice that are pushed out of the Arctic Ocean reduce the latent heat buffer, as they can no longer consume heat in the Arctic Ocean through melting.
5. Sea ice sealing off the Arctic Ocean from the atmosphere
The sea ice used to reach its lowest extent approximately half September. With the change in seasons, air temperatures decrease and sea ice starts increasing in extent at the sea surface. The image below illustrates how, as the Arctic Ocean starts freezing over, less heat will from then on be able to escape to the atmosphere. Sealed off from the atmosphere by sea ice, greater mixing of heat in the water will occur down to the seafloor of the Arctic Ocean, as discussed in FAQ#21.
In October, sea ice has stopped melting and is increasing in extent at the surface of the Arctic Ocean. Also, as land around the Arctic Ocean freezes over, less fresh water will flow from rivers into the Arctic Ocean, while hot, salty water will continue to flow into the Arctic Ocean. As a result, the salt content of the Arctic Ocean increases, all the way down to the seafloor of the Arctic Ocean, increasing the danger that ice in cracks and passages in sediments at the seafloor will melt, allowing methane contained in the sediment to escape and enter the atmosphere.
Warmer water reaching these sediments can penetrate them by traveling down cracks and fractures in the sediments, and reach the hydrates. The image on the right, from a study by Hovland et al., shows that hydrates can exist at the end of conduits in the sediment. Such conduits were formed when some of the methane did escape from such hydrates in the past. Heat can travel down such conduits relatively fast and reach methane hydrates that keep methane in cages of ice. As heat reaches the ice cages, a temperature rise less than 1°C can suffice to destabilize such cages, resulting in a huge abrupt eruption, as the methane expands more than 160 times in volume.
[ The Buffer has gone, feedback #14 on the Feedbacks page ]
Further increasing the danger, this return of the sea ice results in less moisture evaporationg from the water, which together with the change of seasons results in lower hydroxyl levels at the higher latitudes of the Northern Hemisphere, in turn resulting in less methane getting broken down in the atmosphere over the Arctic.
Feedbacks and further developments
More generally, the rapid temperature rise threatens to cause numerous feedbacks to accelerate and further developments to occur such as crossing of tipping points, with the danger that the temperature will keep rising.
In the video below, Peter Carter, Paul Beckwith and Dale Walkonen discuss the situation.
One such feedbacks is the formation and growth of a cold freshwater lid at the surface of the North Atlantic that enables large amounts of salty and relatively hot water to flow underneath this lid and underneath the remaining sea ice, to enter the Arctic Ocean, as discussed earlier here, as well as here and at the feedbacks page.
This further increases the danger of destabilization of methane hydrates contained in sediments at the seafloor of the Arctic Ocean.
Ominously, some very high methane levels were recorded recently at Barrow, Alaska, as illustrated by the NOAA image below.
Conclusion
The situation is dire and the outlook is getting more grim every day, calling for a Climate Emergency Declaration and implementation of comprehensive and effective action, as described in the Climate Plan and as most recently discussed at Transforming Society.
