Is SSP5-8.5 the worst-case scenario?

SSP5-8.5

SSP5-8.5 is one of a number of Shared Socioeconomic Pathways (SSP). It is a scenario in which radiative forcing would be 8.5 W/m⁻² in 2100. The image on the right shows the IPCC projection of the temperature rise in 2081–2100 relative to 1850–1900 corresponding with a SPP5-8.5 scenario (from IPCC AR6 WG11 SPM).

The image below, created by Peter Carter, Climate Emergency Institute, shows the WMO's averaged 2025 global temperature increase of 1.44°C on top of IPCC AR6 WG1 Figure 4.02 (a), illustrating that the WMO rise of 1.44°C for 2025 is spot on the SSP5-8.5 projection (in dark red).

SSP5-8.5 is often said to be a "worst-case" scenario, but as illustrated by the image below, current temperatures are on track or even exceeding SSP5-8.5 projections, given that the rise in 2024 was 1.55°C and 2025 resembled a La Niña year. So, has the IPCC been downplaying the danger? It sure makes one wonder whether SSP5-8.5 is the worst-case scenario. Indeed, Business As Usual (BAU) may turn out to be even worse, so let's have a closer look at what the outlook for some of the worst-case scenarios could be. 

A further image by Peter Carter is added below. 

How much could temperatures rise?

The image below, adapted from ClimateReanalyzer, shows the Coupled Model Intercomparison Project Phase 6 (CMIP6) for the SSP5-8.5 scenario pointing at a temperature rise of 1.661°C in February 2025, of 4.388°C in February 2083 and of 5.163°C in February 2100, when using a 1901-2000 base (temperatures will be higher when a genuinely pre-industrial base is used).



The map below shows the CMIP6 SSP5-8.5 rise versus 1881-1920 in February 2100. The map shows that the temperature rise in areas on land (where most people live) could be as much as 8°C higher in Feb 2100 in the SSP585 model.

The map warns that temperatures over large parts of the Arctic may be as much as 20°C higher than 1881-1920 in February 2100. This would suggest that by 2100 the snow and ice cover in the Arctic will have declined dramatically and that huge amounts of greenhouse gases will likely have been released from the seafloor of the Arctic Ocean and from thawing terrestrial permafrost, with huge albedo changes as well as loss of the latent heat buffer, further accelerating the temperature rise over the years. There are further contributors to a rapid and potentially huge temperature rise, so the SSP5-8.5 model may severely underestimate the temperature rise. Indeed, the SSP5-8.5 model may not be the worst-case scenario.

CMIP6 SSP5-8.5 can be used to project temperature rises beyond 2100, as illustrated by the image below, from an earlier post and from a 2016 paper by Brian O'Neill et al.

[ from earlier post, click on images to enlarge ]

In the above analysis, CO₂ emissions keep rising in CMIP6 SSP5-8.5 to about 35 GtC in 2100, to fall gradually after 2100 (a), while atmospheric CO₂ concentrations keep rising and remain at levels higher than 2000 ppm beyond 2250 (b), while radiative forcing (RF) rises to and remains at 12.5 W/m⁻² (c) and global mean temperature change rises to 8°C in 2300 (d).

Equilibrium climate sensitivity (ECS) can be used to convert RF into °C temperature change. ECS in IPCC AR6 is 3, i.e. lower than in CMIP models. A study led by James Hansen concludes the IPCC ECS is too low and suggests to use 1.2°C per W/m⁻², which in a 8.5 W/m⁻² scenario would correspond with a 10.2°C temperature anomaly in 2100. Hansen et al. add that equilibrium global warming for today’s GHG amount is 10°C, which is reduced to 8°C by today’s human-made aerosols.

A 2020 analysis by Jorgen Randers et al. (image above on the right) points out that, even if all greenhouse gas emissions by people could stop immediately and even if the temperature anomaly could fall to 0.5°C above pre-industrial, greenhouse gas levels would start rising again after 2150 and keep rising for centuries to come.

The image on the right uses content from a study by Christina Schädel et al, which concludes that permafrost fires and thaw will release 63 Gt C for each degree Celsius rise in temperature from a 389-691 Gt pool of permafrost carbon.

That 63 Gt C would translate into 231 Gt CO₂ if only CO₂ gets released. By comparison, the total annual human emissions are now about 55 Gt CO₂e and NOAA calculates that the atmosphere has changed from 1750 to 2024 by 539 CO₂e due to people's greenhouse gas emissions.

Importantly, some of the carbon will be released in the form of methane and CO₂e is much higher for releases in the form of methane than for carbon dioxide, especially when a high multiplier is used to calculate methane's CO₂e. Even worse, releases from submarine permafrost would come mostly in the form of methane.

The danger is even more menacing when looking at how fast temperatures are rising in the Arctic and when including more feedbacks, i.e. not only the impact of permafrost fires and permafrost thaw, but also the impact of destabilizing sediments at the seafloor of the Arctic Ocean resulting in eruptions of huge amounts of methane, on top of the impact of albedo loss and loss of the latent heat buffer of declining sea ice and permafrost.

How fast could temperatures rise?

Next to the size of the temperature change, the rate of change is also important. Large changes did take place in prehistoric times, but they typically did take a long time to evolve. The current temperature rise looks set to be huge and also looks set to be rising at accelerating speed, dwarfing anything seen in previous extinction events. The image below, from an earlier post, shows extinction rates and temperature changes for the five major extinction events (grey vertical lines).

The image and quote below also featured in an earlier post by Andrew Glikson. 

“The paleoclimate record shouts to us that, far from being self-stabilizing, the Earth's climate
system is an ornery beast which overreacts even to small nudges” (Wally Broecker)

[ from an earlier post ]

The image below further illustrates that temperatures may currently be rising much faster than they ever did in history.

[ from earlier post ]

Contributors to a potentially huge temperature rise

[ see the Extinction page ]

The bar-chart on the right conceptually dates back to 2016, when analysis of contributions concluded they could add up to a potentially huge rise in temperature in the near future. The bar-chart includes an 8°C rise when CO₂e levels cross 1200 ppm (CO₂ emissions peak at 130Gt before 2100 and concentrations stay above 2000 ppm from 2350 in the O'Neil analysis, while methane and N₂O emissions keep rising beyond 2100 in RCP8.5).

The image below uses NASA Land-only temperature anomalies versus 1880-1920, illustrating that temperature could rise more rapidly than SSP5-8.5 suggests. The image illustrates that the 1.5°C threshold was crossed for temperatures on land since 2015, when politicians pledged (at the Paris Agreement) to take efforts to prevent a rise of more than 1.5°C from pre-industrial from occurring. 

Note that this 1880-1920 base is not pre-industrial; temperature anomalies can be higher when using a genuinely pre-industrial base. 

The image below has a polynomial trend added that points at 3°C getting crossed on land in early 2027. 

As discussed, crossing 3°C on land is important, since most people live on land and there are indications that such a rise will cause many species (including humans) to go extinct.

Meanwhile, the 3-year running average for the mean rate of atmospheric CO₂ growth through January 2026 broke 8.00 ppm per 3 years, reaching a new record high growth rate of 8.06 ppm per 3 years, as illustrated by the Eliot Jacobson image below. 

Below are 14 contributors to a potentially huge temperature rise:

1. High and rising greenhouse gas concentrations

2. Earth Energy Imbalance rapid and accelerating rise
3. Rapid and accelerating decline in Earth Albedo
- Sea ice decline
- Snow and ice cover on land decline
- The aerosol masking effect getting reduced
- Lower clouds reflectivity decline
4. Further feedback kicking in with accelerating ferocity
- Water vapor feedback
- Ocean stratification, acidification and hypoxia (dead zones)
- Polar amplification of the temperature rise

- Jet Stream distortion and more extreme weather events
- Sea currents such as AMOC and SMOC slowing down
- Decline in the capacity of oceans and land to take up CO₂ and heat
5. Thinning of sea ice resulting in loss of the ability to consume incoming ocean heat
6. More fuel getting burned worldwide
7. Worldwide rise in agricultural emissions
8. Depletion of soil moisture and water from lakes, rivers and aquifers
9. Deforestation, loss of soil carbon and associated emissions

- Forest fires increase

- Trees becoming more vulnerable to droughts, fires, pests and diseases

- More trees cut and burned to create pasture, for construction and energy use

- Increase in ozone due to storms and lightning
10. Loss of wildlife and biodiversity
11. Pollution of water and soil 

- Oil spills on sea, infrastructure collapse on land 

- Pesticides, agricultural chemicals, etc. 

- Plastic and PFAS contamination

- Flooding and fires in urban areas (waste, toxic substances from warehouses, etc.)

- Pollution from military activities
12. Politicians hardly take environmental and climate action
13. Many media focus on selling consumables instead of on climate action
14. Meanwhile, a new El Niño may emerge in the course of 2026

While each of these points is alarming in itself, they can also amplify each other and together they can cause a dramatic and rapid temperature rise, as discussed in a recent post and as illustrated and supported by the rapidly rising polynomial trend in the image below, which is based on many years of historic data and which adds further weight to important warnings.

[ Image from earlier post, also discussed on facebook  ]

When could humans go extinct?

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

A 2018 study (by Strona & Bradshaw) indicates that most life on Earth will disappear with a 5°C rise. What does this mean for humans?

Terrestrial vertebrates are more in danger than many other species, since they depend on numerous other species for food. Humans are terrestrial vertebrates and humans are also large warm-blooded mammals with high metabolic rates, thus requiring more habitat. It also takes a long time for humans to reach maturity. Additionally, humans have become addicted to processed food, fossil fuels, plastic, etc. Furthermore, humans require large amounts of fresh water, including for sweating when temperatures rise. A 3°C rise may therefore suffice to cause humans to disappear, as illustrated by the image below.

[ from earlier post ]

Climate Emergency Declaration

The situation is dire and unacceptably dangerous, and the precautionary principle necessitates rapid, comprehensive and effective action to reduce the damage and to improve the outlook, where needed in combination with a Climate Emergency Declaration, as described in posts such as in this 2022 post and this 2025 post, and as discussed in the Climate Plan group.

Links

• Climate Emergency Institute
https://www.climateemergencyinstitute.com
image discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10163795386309679

https://www.facebook.com/groups/arcticnews/posts/10163807449809679

• WMO confirms 2025 was one of warmest years on record
https://wmo.int/news/media-centre/wmo-confirms-2025-was-one-of-warmest-years-record

• WMO confirms 2024 as warmest year on record at about 1.55°C above pre-industrial level
https://wmo.int/news/media-centre/wmo-confirms-2024-warmest-year-record-about-155degc-above-pre-industrial-level

• IPCC AR6 WG1 Figure 4.2 (a)
https://www.ipcc.ch/report/ar6/wg1/figures/chapter-4/figure-4-2

• Understanding Shared Socio-economic Pathways (SSPs) 

https://climatedata.ca/resource/understanding-shared-socio-economic-pathways-ssps

• CMIP6 and Shared Socio-economic Pathways overview 

https://climate-scenarios.canada.ca/?page=cmip6-overview-notes

• 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

• Is CMIP6 SSP585 the worst-case scenario? (2024 post)

https://arctic-news.blogspot.com/2024/05/is-cmip6-ssp585-the-worst-case-scenario.html

• Greenhouse gas rising

https://arctic-news.blogspot.com/2026/01/greenhouse-gas-rising.html

• Permafrost and wildfire carbon emissions indicate need for additional action to keep Paris Agreement temperature goals within reach - by Christina Schädel et al. 

https://www.nature.com/articles/s43247-026-03189-5

discussed on Facebook at: 
https://www.facebook.com/groups/arcticnews/posts/10163804667894679

• The climate change runaway chain reaction-like process - by Andrew Glikson 
Amplifying feedbacks leading to accelerated planetary temperatures 

https://arctic-news.blogspot.com/2021/06/the-climate-change-runaway-chain-reaction-like-process.html

also discussed on facebook at: 
https://www.facebook.com/SamCarana/posts/10165533175460161

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

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

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

• The threat of seafloor methane eruptions
https://arctic-news.blogspot.com/2025/11/the-threat-of-seafloor-methane-eruptions.html

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

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

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

• Endangerment Finding in danger?
https://arctic-news.blogspot.com/2025/04/endangerment-finding-in-danger.html

• Transforming Society
https://arctic-news.blogspot.com/2022/10/transforming-society.html

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• Climate Emergency Declaration
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html

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 temperature rise caused by the extra CO₂ to reach the tipping point. The image below shows a trend based on 2019 through 2024 annual NOAA data that points at 1200 ppm CO₂ getting crossed in 2030. 

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. 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