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 haven't been below 430 parts per million (ppm) for 18 days in a row at Mauna Loa, Hawaii, as illustrated by the image below, which shows CO₂ for the last 31 days through May 15, 2025. The image also shows one recent hourly measurement exceeding 436 ppm.

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 the rate of change was also much slower, as also discussed in an earlier post.

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. 

Loss of sea ice

One feedback of high concentrations of greenhouse gases is loss of sea ice. Polar amplification of the temperature rise is hitting the Arctic hard, but 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. 

[ 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.

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. 

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

Loss of lower clouds

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.

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. On top of this, the clouds feedback itself triggers an additional surface warming of some 8°C globally.

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 also discussed at this group.

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

• 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

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.

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 also discussed at this group.

Links

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

• NASA Worldview
https://worldview.earthdata.nasa.gov

• NSIDC - National Snow and Ice Data Center - Sea Ice Today
https://nsidc.org/sea-ice-today

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

• NOAA - Weekly Average Mauna Loa CO2

https://gml.noaa.gov/ccgg/trends/weekly.html

• Climate Reanalyzer
https://climatereanalyzer.org

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

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

• Record high increase in carbon dioxide
https://arctic-news.blogspot.com/2025/04/record-high-increase-in-carbon-dioxide.html

• NOAA - ENSO: Recent Evolution, Current Status and Predictions - 5 May 2025
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

• NOAA - trends in methane

https://gml.noaa.gov/ccgg/trends_ch4

• The methane time bomb - by Andrew Glikson (2018)

https://www.sciencedirect.com/science/article/pii/S187661021830136X

• Arctic Methane Release: "Economic Time Bomb"
https://arctic-news.blogspot.com/2013/07/arctic-methane-release-economic-time-bomb.html

• Copernicus
https://climate.copernicus.eu

• Increased transparency in accounting conventions could benefit climate policy - by Gerard Wedderburn-Bisshop   

https://iopscience.iop.org/article/10.1088/1748-9326/adb7f2

discussed on facebook at: 
https://www.facebook.com/groups/arcticnews/posts/10162667311314679

• 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

Record high increase in carbon dioxide

Carbon dioxide (CO₂) concentrations grew by 3.75 parts per million (ppm) during 2024, the highest growth rate on record.

The annual global average surface concentration of CO₂ for 2024 was 422.79 ppm, according to NOAA data. The image below shows monthly global average surface concentrations of CO₂.

The above image shows the monthly global average surface concentration of CO₂ through January 2025.

The above image shows that, on April 16, 2025, concentrations of CO₂ at Mauna Loa, Hawaii, had exceeded 430 ppm for six days in a row.

On April 20, 2025, CO₂ concentrations reached 430.64 ppm at Mauna Loa, Hawaii, the highest daily average on record. 

On April 27, 2025, CO₂ was 431.13 ppm at Mauna Loa, Hawaii, the highest daily average on record. To find higher levels, one needs to go back millions of years, as illustrated by the image below from an earlier post.

Not only are concentrations of CO₂ very high, but additionally there has been an increase in total solar irradiance of ∼400 Wm⁻² since the formation of the Earth. The image below, from an earlier post, shows the combined climate forcing by changing CO₂ and solar output for the past 450 million years.

Between 14 and 15 million years ago, while concentrations of CO₂ were below 400 ppm as illustrated by the image further above (Figure 1), the temperature in central Europe was 20°C higher than today, as illustrated by the image below (adapted by Andrew Glikson from a 2020 study by Methner et al.).

[ image from earlier post, click on images to enlarge ]

In the past, large changes in concentrations of CO₂ took a long time to eventuate. The speed at which CO₂ is currently rising is unprecedented, as illustrated by the image below.

[ from earlier post ]

The image below, adapted from Climate Reanalyzer, shows the temperature anomaly in the year 2100. The image shows how much the temperature will have risen in 2100, at 2 meters above the surface and compared to the period 1890-1910, in a CMIP6 SSP585 scenario.

[ Arctic temperature anomaly in 2100 ]

The above image shows that the temperature rise over land will be much higher than over oceans, which makes the situation even more dire, given that most people live on land and could face a huge temperature rise by 2100 in a CMIP6 SSP585 scenario. 

The image on the right shows an Arctic projection of temperature anomalies in 2100 versus 1851-1900 in a CMIP6 SSP585 scenario. 

The image below shows an almost linear rise in the global temperature anomaly reaching 5.194°C in a CMIP6 SSP585 scenario in February 2100 versus 1901-2000.

CMIP6 SSP585 is the IPCC's worst-case scenario and the IPCC goes to great lengths to argue that it is merely hypothetical and that will never become real. However, there are indications that in reality, things may be even worse.

There are several points indicating that the CMIP6 SSP585 anomalies may be too conservative, as discussed before and below. One point is that different base periods are used in above images, but none of them is pre-industrial. When using a genuinely pre-industrial base, the global temperature rise will be higher. Using different bases can make a difference of more than 1°C. A higher historic rise means stronger feedbacks, e.g. that there will be more water vapor in the atmosphere. 

In a CMIP6 SSP585 scenario, temperatures are projected to keep rising beyond 2100, as illustrated by the image below, from a 2016 analysis by Brian O'Neill et al. 

In the 2016 analysis by Brian O'Neill et al., CO₂ emissions keep rising until 2100, to then fall gradually to current levels, while CO₂ concentrations in the atmosphere keep rising, to remain at levels beyond 2000 ppm and result in a temperature rise of 8°C by 2300 in a CMIP6 SSP585 scenario.

A second point indicating that anomalies could be too conservative is that a more recent study has found that crossing the clouds tipping point at 1200 ppm CO₂ could - on its own - push temperatures up by 8°C globally, in addition to the rise caused by the extra CO₂ to reach the tipping point. The image below shows a trend based on 2019-2025 annual NOAA data that points at 1200 ppm CO₂ getting crossed in 2030. 

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. Below are discussed potential rises in methane (CH₄) and nitrous oxide (N₂O). 

A third point indicating that the above anomalies could be too conservative is that emissions are increasing if not accelerating, while feedbacks are increasingly kicking in with greater ferocity and while there are additional mechanisms that are contributing to further acceleration of the temperature rise. In conclusion, a huge and accelerating temperature rise could occur soon.

Non-CO₂ warming

Less than half of the warming in the 10 years from 2010 to 2019 (unmasked, relative to 1850–1900) is caused by carbon dioxide, as illustrated by the image below, based on IPCC AR6 data. Masking (cooling) caused by specific gases and aerosols (such as sulfates) is not included in the image.

Non-CO₂ warming can be caused by many different gases and aerosols, as illustrated by the image. Warming caused by ground-level ozone, water vapor and loss of ice and lower clouds is included in the impact of the gases and aerosols mentioned on the image.

Importantly, the GWP of the non-CO₂ gases and aerosols can be very high over a short horizon, which means that rises in their concentrations can result in a huge and rapid temperature rise. Two of them, nethane and nitrous oxide, are discussed below in more detail.

Methane

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

[ from earlier post ]

Nitrous oxide

The image below shows globally averaged marine surface monthly mean nitrous oxide (N₂O) data through December 2024 (red circles), with a trend added that points at 1000 ppb getting crossed in 2031, tripling current levels.

While using different periods and types of trends can result in trends that don't show such a steep rise, the point is that such steep rises in concentrations of greenhouse gases could eventuate, based on recent data.

Large increases in N₂O emissions could occur and since N₂O is a potent greenhouse gas with a long lifetime, the impact would accumulate rapidly and the rise could follow a steep curve, the more so since N₂O emissions caused by people come mainly from applying nitrogen fertilizers and animal waste to farmland and pastures, and policy control over emissions from nitrogen fertilizers is largely absent or ineffective, while farmers are increasingly using nitrogen fertilizers in efforts to increase crop yield, especially where yields are falling due to rising temperatures and more extreme weather events. IPCC AR6 gives N₂O a global warming potential (GWP) of 273 over both 500 years and 100 years, and of 118 over 20 years, while its lifetime is 120 years.

Additionally, the impact of nitrogen fertilizers appears to have been underestimated; a 2022 study concludes that when ammonia, nitric acid and sulfuric acid are present together, they contribute strongly to the formation of cirrus clouds. Cirrus clouds exert a net positive radiative forcing of about 5 W m⁻², according to IPCC AR6, as discussed in this 2022 post.

Furthermore, nitrogen fertilizers are typically produced with natural gas, thus further driving up concentrations of methane in the atmosphere. Also, a further huge increase in both methane and N₂O emissions could result from thawing permafrost, as discussed in earlier posts. The potential for further N₂O emissions from thawing permafrost is illustrated in the screenshot below.

[ from earlier post ]

Finally, N₂O is currently the most significant ozone depleting substance (ODS) being emitted. The impact of N₂O as ODS has grown strongly over the years, relative to other ODS. Further loss of ozone in the stratosphere would cause more UV radiation to reach the surface and harm humans, animals and plants, in turn resulting in vegetation taking less CO₂ from the atmosphere and thus further driving up temperatures.

Highest temperatures on record for time of year

On April 25, 2025, the surface air temperature in the Northern Hemisphere was 16.31°C (or 61.36°F), the highest temperature on record for this day for the 6th day in a row, as illustrated by the image below. 

On April 25, 2025, the global surface air temperature was 15.37°C (or 59.67°F), the highest temperature on record for this day, higher than the 15.29°C reached on April 25, 2024, and much higher than the 15.04°C reached on April 25, 2023. The temperature for April 25, 2025, was later upgraded to 15.38°C. 

The image below shows ERA5 daily temperature anomalies from end 2022 through April 29, 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). Meanwhile, NOAA has announced that La Niña conditions have ended, meaning that temperatures are no longer suppressed and the red trend warns about a rise of more than 1°C in the course of 2026. 

Such short-term variables are smoothed out in the black linear trend which shows a steady but much slower rise of 0.5°C over about 3½ years (Jan 2023 - Sep 2026), and this rise is a much steeper rise than the 1.1°C rise over 81 years (from 1941 to 2022) of a linear trend in the image below, from an earlier image.

Arctic hit most strongly

A fourth point indicating that the above anomalies could be conservative is that, as the images below show, very high anomalies are already now showing up over the Arctic Ocean. The Arctic is hit most strongly by the temperature rise, as illustrated by the image below showing the ERA5 global temperature anomaly for February-March 2025 versus 1951-1980.

The image below shows the ERA5 global temperature anomaly for March 2025 versus 1951-1980.

The image below shows the NCEP global temperature anomaly for February-March 2025 versus 1951-1980.

Temperature anomalies for February-March 2025 over the Arctic were as much as 20°C higher than 1951-1980, as illustrated by the image on the right.

The fact that these air temperature anomalies occurred at a time of year when little or no sunlight was yet reaching the Arctic indicates the strong contribution of ocean heat to these high air temperature anomalies.

Ocean heat is pushed along the path of the Gulf Stream all the way from the Gulf of Mexico to the Arctic Ocean, by an ocean current that is formed by prevailing wind patterns that move heat from the Equator in the direction of the North Pole, while the resulting ocean current is deflected by the Coriolis Effect caused by the rotation of the Earth around its axis.

     [ Gulf Stream, click to enlarge ]

A deformed Jet Stream can at times speed up this flow, causing huge amounts of Ocean heat to get abruptly pushed into the Arctic Ocean in the path of the Gulf Stream.

The image on the right shows sea surface temperatures as high as 32°C on April 25, 2025, with markedly higher sea surface temperatures than at similar latitudes appearing in the path of the Gulf Stream, resulting from the strong flow of ocean heat from the Gulf of Mexico in the direction of the Arctic Ocean.

The result is illustrated by the image below which shows high sea surface temperature anomalies for March 2025 compared to 1980-1997, with very high anomalies (higher than 3°C) showing up in areas of the Arctic Ocean where the sea ice has disappeared. 

On the above map, a blue-colored area shows up over the North Atlantic south of Greenland, indicating relatively low temperatures. Similarly, a blue-colored area shows up over the North Atlantic on the map (image below) with ocean heat content trends, from Trenberth (2025). 

The danger is that this cooler surface water is the result not only from meltwater (from melting glaciers and sea ice), but also from stronger evaporation in the North Atlantic and stronger precipitation further down the path of the Gulf Stream toward the Arctic Ocean. Both meltwater and precipitation are forms of freshwater with low salt content compared to the high salt content of the ocean water in the North Atlantic. Formation of a cold freshwater lid at the surface of the North Atlantic can reduce heat transfer from the ocean surface to the atmosphere, resulting in more ocean heat instead moving underneath this lid toward the Arctic Ocean, as discussed at this page. 

The danger increases as temperature rise and cause more deformation of the Jet Stream, which can at times cause more heat to abruptly be moved into the Arctic Ocean, especially when combined with the occurrence of hurricanes.  

Outlook is bleak

Conditions are dire. Temperatures and concentrations of greenhouse gases are high and rising fast and Arctic sea ice is retreating. The image below, by Eliot Jacobson, shows that Earth's albedo hit yet another record low recently, as a result of less incoming solar radiation reflected back into space. This is caused by a number of things, including loss of snow and ice, loss of lower clouds, and reductions of cooling aerosols such as previously emitted by shipping.  

The image below, by Leon Simons, shows Earth's Energy Imbalance, i.e. the difference between Absorbed Solar Radiation and Outgoing Long-wave Radiation. 

Furthermore, sunspots are at a high point in this cycle and a new El Niño may emerge soon. The image below shows NOAA's outlook.

The image below shows temperatures through April 20, 2025, in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño.

     [ Arctic sea ice volume, click to enlarge ]

Feedbacks and further mechanisms

These conditions threaten to further drive up temperatures, while further acceleration of the temperature rise threatens to occur due to strengthening feedbacks and further mechanisms, including sea ice loss causing eruptions of seafloor methane and changes in ocean currents and wind patterns.

High ocean temperatures are already causing Arctic sea ice volume to be very low compared to earlier years, as illustrated by the image on the right and as discussed in this earlier post.

The combination image below compares Arctic sea ice thickness on March 13, 2025, with thickness on April 26, 2025, when open water (dark blue) shows up in a number of places inside the area covered with sea ice, which is quite striking, given that Arctic sea ice volume typically reaches its annual maximum in April.  

The temperature rise itself comes with many self-reinforcing feedbacks such as further loss of snow and ice and changes in wind patterns and ocean currents, as said, and this can cause rapid additional warming and thus extra water vapor, which also constitutes a self-reinforcing feedback, since water vapor is a potent greenhouse gas.

[ from the Extinction page ]

The image on the right illustrates how much such conditions and mechanisms could each contribute to such a huge temperature rise.

Very fast mechanisms include panic. As more people start to realize how dire the situation is and as they seek to occupy the last few habitable areas left, more people may stop showing up for work, resulting in a rapid loss of the aerosol masking effect, as industries that now co-emit cooling aerosols (such as sulfates) come to a grinding halt (see reductions in cooling aerosols).

As it becomes harder to obtain food and fuel for cooking and heating, and as the grid shuts down due to conflicts and people no longer showing up for work, many people may start collecting and burning more wood, decimating the forests that are left and resulting in more emissions that further speed up the temperature rise.

As temperatures rise, huge fires could also break out in forests, peatlands, grassland and urban areas (including backyards, landfills and buildings, in particular warehouses containing flammable materials, chemicals and fluorinated gases), further contributing to more emissions that speed up the temperature rise.

As the likeliness of further accelerating warming, the severity of its impact, and the ubiquity and the imminence with which it will strike all become more manifest—the more sobering it is to realize that a mere 3°C rise may suffice to cause human extinction.

Indeed, humans will likely go extinct with a 3°C rise and most life on Earth will disappear with a 5°C rise, as discussed in an earlier post and illustrated by the image below.

[ from earlier post ]

IPCC persists in downplaying the danger

Meanwhile, the IPCC persists in downplaying the potential for dangerous developments in efforts to hide the need for 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, as discussed in many earlier posts such as this one, this one and this one. 

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

• NOAA - Global averaged marine surface annual mean carbon dioxide data
https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_gl.txt

• NOAA - Annual Mean Global Carbon Dioxide Growth Rates 

https://gml.noaa.gov/ccgg/trends/gl_gr.html
discussed on facebook at: 
https://www.facebook.com/groups/arcticnews/posts/10162561012229679

• Climate Reanalyzer
https://climatereanalyzer.org

• The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6 - by Brian O'Neill et al. (2016)
https://gmd.copernicus.org/articles/9/3461/2016

• IPCC - warming in 2010–2019 relative to 1850–1900
https://www.ipcc.ch/report/ar6/wg1/figures/summary-for-policymakers/figure-spm-2

• NOAA - Nitrous oxide emissions grew 40 percent from 1980 to 2020, accelerating climate change

https://research.noaa.gov/nitrous-oxide-emissions-grew-40-percent-from-1980-to-2020-accelerating-climate-change

• N₂O is currently the most significant ozone-depleting substance being emitted

https://www.ccacoalition.org/news/rise-nitrous-oxide-emissions-endangers-pathway-15degc-ozone-layer-and-human-health

• Copernicus
https://climate.copernicus.eu

• NOAA - ENSO: Recent Evolution, Current Status and Predictions - 14 April 2025
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

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

• 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