Arctic News: pathways

Showing posts with label pathways. Show all posts

Sunday, February 1, 2026

Is SSP5-8.5 the worst-case scenario?

The image below, created by Peter Carter, Climate Emergency Institute, shows WMO's averaged 2025 global temperature increase of 1.44°C on a background 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 curve (in dark red).

The image below, adapted from ClimateReanalyzer, shows that the SSP5-8.5 model points 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 versus 1901-2000 (and 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.

In the CMIP6 SSP5-8.5 model, temperatures are projected to keep rising strongly beyond 2100, as illustrated by the image below, from a 2016 paper by Brian O'Neill et al.

In the above study, CO₂ emissions keep rising in the SSP5-8.5 model until 2100, to then fall gradually to current levels (a), while CO₂ concentrations in the atmosphere keeps rising and concentrations remain at levels beyond 2000 ppm (b). This comes with radiative forcing (RF) rising to and remaining at 12 W/m⁻² (c) and average global temperature change rising to and remaining at 8°C by 2300 in the SSP5-8.5 model (d). Note that conversion of RF into temperature change depends on the value given to equilibrium climate sensitivity, which in the above study appears to be less than the 0.81°C per W/m⁻² used by IPCC AR6, while a more recent study argues that 1.2°C per W/m⁻² is more accurate, in which case the temperature change would rise to as much as 14.4°C.

Next to the size of the temperature change, the rate of change is also important. Large changes did happen before, biut they typically did occur over long periods of time. The image below illustrates that temperatures may currently be rising much faster than they ever did in history.

[ from earlier post ]

The image below uses NASA Land-only temperature anomalies versus 1880-1920, illustrating that temperature could rise much more rapidly than SSP5-8.5 suggests.

[ Image from earlier post ]

The above image uses anomalies over land-only versus an 1880-1920 base, illustrating that the 1.5°C threshold was crossed for temperatures on land since 2015. In 2015, politicians pledged at the Paris Agreement to take efforts to prevent a rise of more than 1.5°C from pre-industrial. Note again that this 1880-1920 base is not pre-industrial. Temperature anomalies can be even higher when a genuinely pre-industrial base is used.

[ see the Extinction page ]

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

The barchart on the right conceptually dates back to 2016, when analysis of contributions showed they could add up to a potentially huge rise in temperature in the near future.

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. Terrestrial vertebrates are more in danger than many other species, since they depend on numerous other species for food. Humans are terrestrial vertebrates and 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 ]

The above images add further weight to many alarming points discussed in a recent post, such as:

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. This is illustrated and supported by the rapidly rising polynomial trend added to the data in the image further above, which is based on many years of historic data and which adds further weight to the important warnings.

In conclusion, the temperature looks set to be rising higher and faster at accelerating rate, dwarfing anything seen in previous extinction events, as illustrated by the image below, from an 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.