Arctic News: May 2025

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.

[ click on images to enlarge ]

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

• NASA - datasets and images
https://data.giss.nasa.gov

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

• Copernicus - Climate Pulse
https://pulse.climate.copernicus.eu

• Climate Reanalyzer
https://climatereanalyzer.org

• 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 - Climate Prediction Center - El Niño/Southern Oscillation (ENSO) Diagnostic Discussion

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml

• Pre-industrial
https://arctic-news.blogspot.com/p/pre-industrial.html

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

• NOAA - Office of Satellite And Product Operations - Sea Surface Temperatures
https://www.ospo.noaa.gov/products/ocean/sst/contour/index.html

• Nullschool.net
https://earth.nullschool.net

• Jet Stream
https://arctic-news.blogspot.com/p/jet-stream.html

• Cold freshwater lid on North Atlantic
https://arctic-news.blogspot.com/p/cold-freshwater-lid-on-north-atlantic.html

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

• University of Bremen
https://seaice.uni-bremen.de/start

• NASA - Worldview satellite images
https://worldview.earthdata.nasa.gov

• 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

Saturday, May 17, 2025

Heads in the clouds while Earth is burning

Changes in clouds

The high impact that changes in clouds have on the global temperature is becoming more and more clear as more scientific studies appear. Nonetheless, many people keep their heads in the clouds and act as if nothing is changing.

[ James Hasen et al. Earth’s albedo (reflectivity, in percent), seasonality removed ]

[ James Hansen: Inferred contributions
to reduced Earth albedo ]

There are many reasons for this apathy. Loss of albedo due to loss of lower clouds, loss of sea ice and loss of the aerosol masking effect are all concepts that can be hard to grasp. As an example, the aerosol masking effect is getting progressively reduced, e.g. due to tightening shipping emissions regulations. The image above and on the right are by Hansen et al.

For the average person, many effects of the temperature rise are also hard to notice, such as stronger ocean stratification and stronger wind.

Feedbacks can be complex, e.g. decline of Arctic snow and ice comes with albedo loss as well as loss of the latent heat buffer, while Arctic amplification of the temperature rise can lead to changes in ocean currents and deformation of the Jet Stream. Compound impacts threaten to occur, such as formation of a lid at the surface of the North Atlantic Ocean enabling more heat to move to the Arctic Ocean, in turn causing huge amounts of methane to erupt from the seafloor, thus further contributing to the danger that the 1,200 ppm CO₂e cloud tipping point will get crossed that causes an extra 8°C rise, which this 2019 post warned about.

It is hard to reduce greenhouse gas emissions and to remove greenhouse gases from the atmosphere, while there also is a lag between carbon dioxide (CO₂) emissions and their maximum impact and a “lag time” between climate action and an actual decrease in CO₂ levels, due to transient growth as a result of delayed feedback. “It’s like trying to slow down an enormous train – you can’t stop it all at once, there will be a delay between applying the brakes and the train coming to a halt. And in talking about CO₂ levels, this could have catastrophic consequences,” explains Mahommad Farazmand, warning that even if CO₂ emissions decreased, transient growth would still push the climate into a tipping point, resulting in a temperature increase of 6°C.

One of the biggest causes why climate action is delayed, if not sabotaged, is the way climate change is or rather isn't reported in the media. In the video below, Paul Beckwith discusses the analysis by Hansen et al.

Further below, this post looks at two conditions that enable loss of lower clouds, i.e. high concentrations of greenhouse gases that result in higher temperatures and loss of sea ice.

High concentrations of greenhouse gases

Daily CO₂ concentrations have been below 430 parts per million (ppm) only once over the past 31 days at Mauna Loa, Hawaii, as illustrated by the image below, which shows CO₂ through May 20, 2025. The image also shows one recent hourly measurement approaching 440 ppm (arrow).

A daily CO₂ concentration of 431.25 ppm was recorded on May 10, 2025, at Mauna Loa, Hawaii, the highest daily average on record. 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 while the rate of change was also much slower, as also discussed in an earlier post.

The image below shows monthly CO₂ concentrations at Mauna Loa, Hawaii.

High concentrations of greenhouse gases lead to high temperatures and the temperature rise itself comes with many feedbacks including more water vapor in the atmosphere, loss of sea ice and loss of lower clouds.

In the image below, a value of 430 ppm CO₂ has been manually added as a potential value for 2025 (blue circle), but this value is not included in the calculation of the trend, which is based only on 2019 through 2024 data (red circles). The trend points at the clouds tipping point at 1200 ppm CO₂ getting crossed in 2030. Crossing this tipping point could - on its own - push temperatures up by 8°C globally, in addition to the temperature rise caused by the extra CO₂ to reach the tipping point.

Moreover, the clouds tipping point is actually at 1200 ppm CO₂e (carbon dioxide equivalent), so when taking into account the impact of growth of other greenhouse gases and further mechanisms, the tipping point could be crossed much earlier than in 2030. The clouds tipping point is also discussed in the section at the end of this post.

Temperature

The image below illustrates that air temperatures in the Northern Hemisphere have been very high for 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.

These record high temperatures are the more significant as they were reached under ENSO-neutral conditions, as illustrated by the image below. On May 20, 2025, the sea surface temperature was 27.65°C, 0.19°C below 1991-2020, in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño.

Loss of sea ice

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 20, 2025, global sea ice area was 17.6 million km², lowest on record for the day.

Over the past few days, Arctic sea ice area has been second lowest for the time of year, Arctic sea ice area was only lower around this time of year in 2016, a strong El Niño year, as illustrated by the image below.

The above image also shows that Arctic sea ice area around this time of year was much lower than it was in 2012, the year when Arctic sea ice would reach a record low later that year (2.24 million km² on September 12, 2012).

[ click on images to enlarge ]

The image on the right is adapted from NASA and shows anomalies versus 1951-1980 of up to almost 4°C. The image also shows that the Arctic is heating up much faster than the rest of the world, a phenomenon also known as accelerated Arctic temperature rise.

The next image on the right illustrates how two of these feedbacks contribute to the accelerated Arctic temperature rise:

[ Two out of numerous feedbacks ]

Feedback #1: albedo loss as sea ice melts away and as it gets covered by soot, dust, algae, meltpools and rainwater pools;

Feedback #19: distortion of the Jet Stream as the temperature difference narrows between the Arctic and the Tropics, in turn causing further feedbacks to kick in stronger, such as hot air moving into the Arctic and cold air moving out, and more extreme weather events bringing heavier rain and more intense heatwaves, droughts and forest fires that cause black carbon to settle on the sea ice.

Arctic sea ice volume has been at a record low for more than a year, as illustrated by the image below.

Loss of sea ice and loss of lower clouds are self-amplifying feedbacks, i.e. as temperatures rise, there is loss that accelerates the temperature rise, which in turn causes even more loss, etc. Due to this self-amplification, the temperature rise can accelerate. For more, also have a look at the Feedback section of this 2024 post, the Feedbacks page, and the section below.

Loss of lower clouds

For years studies have pointed at the danger that, as temperatures rise, the rise itself can cause a reduction in lower clouds. Since lower clouds reflect a lot of sunlight back into space, their decrease is in turn pushing up and accelerating the temperature rise.

Earlier studies include this 2015 study, this 2017 study and this 2022 study. The image below is from a 2021 study led by Goode that warns that warming oceans cause fewer bright clouds to reflect sunlight back into space, resulting in the Earth's surface absorbing more energy instead.

The image below shows the Pattern Effect, illustrating the danger that oceans are becoming less able to take up heat, thus leaving more heat in the atmosphere, which will in turn result in loss of lower clouds.

The white band around -60° (South) indicates that the Southern Ocean has not yet caught up with global warming, featuring low-level clouds that reflect a lot of sunlight back into space. Over time, these low clouds will decrease, resulting in more sunlight getting absorbed by the Earth's surface and causing additional global warming. A 2021 study led by Zhou finds that, after this 'pattern effect' is accounted for, committed global warming at present-day forcing rises by 0.7°C.

The combination image below is from a 2022 study led by Barkhordarian. Forcing by elevated well-mixed GHG levels has virtually certainly caused the multiyear persistent 2019–2021 marine heatwave. The warming pool is marked by concurrent and pronounced increase in annual mean, and variance of SSTs (Figure below left) and decrease in cold-season low-cloud’s cooling effect. EUMETSAT satellite data shows a 5% decade⁻¹ decreasing trend in cold-season cloud cover during 1995–2018 (Figure below right). Low-cloud cover reduction is the major contribution to the observed decline in total cloud fraction, resulting in decreases of winter-time low-cloud’s cooling effect.

What makes loss of lower clouds so dangerous is that it can continue, even if emissions remain constant. So, where loss of sea ice continues while emissions remain constant, the temperature can keep rising, and as the temperature rise results in further loss of lower clouds, this will accelerating the temperature rise.

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

The above image also illustrates how the temperature of the atmosphere can keep rising, even in the absence of further emissions, due to shrinking of heat sinks, such as loss of sea ice thickness or oceans taking up less heat, or as certain thresholds or tipping points get crossed.

Clouds Tipping Point

The clouds tipping point refers to abrupt disappearance of lower clouds, more specifically the stratocumulus decks. Stratus cloud decks cover about 20% of subtropical oceans and are prevalent in the eastern portions of those oceans—for example, off the coasts of California or Peru. The clouds cool and shade Earth as they reflect the sunlight that hits them back into space. Tapio Schneider et al. (2019) calculate that these clouds begin to break up when carbon dioxide equivalent (CO₂e) levels rise above the tipping point of 1,200 ppm.

Disappearance of these clouds will make the temperatures go up strongly and rather abruptly. By the time CO₂e levels will have risen to this clouds tipping point of 1,200 ppm CO₂e, temperatures will already have gone up a lot in line with the warming from rising CO₂e levels and feedbacks. On top of this, the clouds feedback itself triggers an additional surface warming of some 8°C globally, which is a tipping point and once crossed, it's very hard to revert, i.e. CO₂e would have to fall by a huge amount for lower clouds to reappear.

Links

• Global warming in the pipeline - by James Hansen et al. (2023)

https://academic.oup.com/oocc/article/3/1/kgad008/7335889

• Large Cloud Feedback Confirms High Climate Sensitivity - by James Hansen et al. (2025)

https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf

• Maximum warming occurs about one decade after a carbon dioxide emission - by Katharine Ricke et al. (2014)
https://iopscience.iop.org/article/10.1088/1748-9326/9/12/124002

• News release: Time Lag Between Intervention and Actual CO2 Decrease Could Still Lead to Climate Tipping Point (2021)
https://news.ncsu.edu/2021/12/time-lag-could-still-lead-to-climate-tipping-point
• Study: Investigating climate tipping points under various emission reduction and carbon capture scenarios with a stochastic climate model - by Alexander Mendez et al. (2021)
https://royalsocietypublishing.org/doi/10.1098/rspa.2021.0697
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10159745007124679

• NOAA - Daily Average Mauna Loa CO2
https://gml.noaa.gov/ccgg/trends/monthly.html

• NOAA - Mauna Loa - Carbon Cycle Gases

https://gml.noaa.gov/dv/iadv/graph.php?code=MLO&program=ccgg&type=ts

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

• Observational Assessment of Changes in Earth’s Energy Imbalance Since 2000 - by Norman Loeb et al. (2024)
https://link.springer.com/article/10.1007/s10712-024-09838-8

discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10161449934634679

• Positive tropical marine low-cloud cover feedback inferred from cloud-controlling factors - by Xin Qu et al. (2015)
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2015GL065627

• Interpretation of Factors Controlling Low Cloud Cover and Low Cloud Feedback Using a Unified Predictive Index - by Hideaki Kawai et al. (2017)
https://journals.ametsoc.org/view/journals/clim/30/22/jcli-d-16-0825.1.xml

• Estimated cloud-top entrainment index explains positive low-cloud-cover feedback - by Tsuyoshi Koshiro et al. (2022)
https://www.pnas.org/doi/10.1073/pnas.2200635119

• News release: Earth is dimming due to climate change
Warming oceans cause fewer bright clouds to reflect sunlight into space, admitting even more energy into earth's climate system
https://news.agu.org/press-release/earth-is-dimming-due-to-climate-change
• Study: Earth's Albedo 1998–2017 as Measured From Earthshine - by Philip Goode et al. (2021)
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL094888
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10159604016414679

• NASA - zonal means
https://data.giss.nasa.gov/gistemp/zonal_means

• News release: Paying for emissions we’ve already released
https://www.llnl.gov/news/paying-emissions-weve-already-released
• Study: Greater committed warming after accounting for the pattern effect - by Chen Zhou et al. (2021)
https://www.nature.com/articles/s41558-020-00955-x
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10159009753799679
and at:
https://www.facebook.com/SamCarana/posts/10164808484750161
and in the post at:
https://arctic-news.blogspot.com/2021/01/2020-hottest-year-on-record.html

• News release: Systematic warming pool discovered in the Pacific due to human activities
https://www.cliccs.uni-hamburg.de/about-cliccs/news/2022-news/2022-06-21-pm-marine-heat-waves.html
• Study: Recent marine heatwaves in the North Pacific warming pool can be attributed to rising atmospheric levels of greenhouse gases - by Armineh Barkhordarian et al. (2022)
https://www.nature.com/articles/s43247-022-00461-2
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10160085259739679

and in the post at:
https://arctic-news.blogspot.com/2023/05/will-there-be-arctic-sea-ice-left-in-september-2023.html

Possible climate transitions from breakup of stratocumulus decks under greenhouse warming - by Tapio Schneider et al. (2019)
https://www.nature.com/articles/s41561-019-0310-1

• 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

Saturday, May 3, 2025

Arctic sea ice May 2025

[ 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.

Below are warnings from earlier posts.

[ from earlier post, also note the recent discussion on monthly methane ]

[ from earlier post ]

Also noteworthy is this analysis by Andrew Glikson and work by Peter Wadhams et al.

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.