Monday, March 24, 2025

Accelerating Temperature Rise

The Northern Hemisphere temperature was 12.86°C on March 19, 2025, a record daily high and 1.65°C higher than 1979-2000.

Very high temperature anomalies are forecast over the Arctic Ocean for November 2025. 


[ Nov 2025 temperature anomaly forecast ]
The image on the right shows the same forecast of temperature anomalies for November 2025, in this case with a Northern Hemisphere projection. Very high anomalies are visible over the Arctic Ocean, showing anomalies of 13°C, i.e. at the end of the scale, so anomalies may be even higher over some parts of the Arctic Ocean. 

What makes such high temperatures possible is a combination of mechanisms that can rapidly speed up the temperature rise. 

1. ENSO changes - a new El Niño could emerge soon.

2. Sunspots - higher than expected and reaching their peak in the current cycle in July 2025.

3. Cooling aerosols - reductions result in albedo loss.

4. Earth's Energy Imbalance - very high and rising, as illustrated by the image below by Leon Simons.

5. Greater albedo loss - as a result of sea ice loss and loss of lower clouds.
 
Arctic sea ice extent was 14.35 million km² on March 28, 2025, a record daily low for the time of year and 1.17 million km² lower than the extent in 2012 on this date. The comparison with extent in 2012 is important since Arctic sea ice extent was 3.18 million km² on September 16, 2012, an all-time low in this record dating back to 1981. 

[ Arctic-sea-ice extent, click on images to enlarge ]

A Blue Ocean Event could be declared when Arctic sea ice reaches or crosses a threshold of 1 million km² in extent. However, extent can include holes, gaps or cracks in the sea ice and melt ponds on top of the ice, all having a darker color than ice. By contrast, sea ice area is the total region covered by ice alone, making it a more critical measurement in regard to albedo than extent. Accordingly, the threshold for a Blue Ocean Event can be 1 million km² in area. 

Arctic sea ice area typically reaches its annual minimum about half September. Arctic sea ice area was only 2.24 million km² on September 12, 2012, i.e. 1.24 million km² away from a Blue Ocean Event. On March 19, 2025, Arctic sea ice area was 1.34 million km² lower than on March 19, 2012, as also discussed in an earlier post. Therefore, would there be such a difference about half September 2025, a Blue Ocean Event could be declared. 


The above image illustrates this, with the black dashed line indicating the threshold for a Blue Ocean Event and the red dotted line indicating Arctic sea ice area 1.34 million km² below what it was in 2012 for the respective date. 

Loss of albedo can occur due to retreat of sea ice, due to developments of cracks and holes in the sea ice, and due to discoloring of sea ice, which includes soot settling on the sea ice, growth of algae and ponding water on ice due to melting, as discussed in a recent study led by Philip Dreike. 

Loss of albedo can also occur due to loss of lower clouds and due to reduction in cooling aerosols (mechanism 3). Thawing of terrestrial permafrost is a further self-reinforcing feedback mechanisms that can cause more albedo loss as well as more emissions of carbon dioxide, methane and nitrous oxide, thus further accelerating the temperature rise in the Arctic. 

6. Latent heat buffer loss - as sea ice, permafrost and glaciers disappear.

Arctic sea ice decline comes both with loss of albedo and also with loss of the latent heat buffer that previously consumed a lot of heat entering the Arctic Ocean from the Atlantic Ocean and the Pacific Ocean. What makes this mechanism so important is that it constitutes a tipping point. 

   [ Arctic sea ice volume ]
Loss of Arctic sea ice volume is illustrated by the image on the right, indicating that Arctic sea ice has become much thinner over the years.

Sea ice constitutes a Buffer that previously consumed much incoming ocean heat. As temperatures rise, sea ice thins and the Buffer disappears.

The disappearance of the Buffer occurs at the same time as increasingly larger amounts of ocean heat are entering the Arctic Ocean from the North Atlantic Ocean and the Pacific Ocean. 

Consequently, the temperature of the water of the Arctic Ocean threatens to increase dramatically. 

         [ Arctic sea ice volume, click to enlarge ]
The image on the right illustrates the decline of Arctic sea ice volume over the years.

More heat in turn threatens to reach sediments at the seafloor of the Arctic Ocean and destabilize hydrates contained in the these sediments, resulting in eruptions of huge amounts of methane from hydrates as well as from methane stored in the form of free gas underneath these hydrates.  

The image below illustrates these mechanisms and their interaction and amplification, i.e. the thinning of Arctic sea ice, the increase in ocean heat and the threat of methane eruptions.
[ The Buffer is gone ]
Further mechanisms

There are many further mechanisms that jointly can rapidly speed up the temperature rise. Many of these mechanisms are self-reinforcing feedbacks that can interact and amplify each other, such as the formation of a freshwater lid at the surface of the North Atlantic, as also illustrated by the images above and below. 

[ formation of a freshwater lid at the surface of the North Atlantic ]
[ from Moistening Atmosphere ]
Global warming is causing more extreme weather events all around the world, and as temperatures keep rising, these events look set to become more extreme, i.e. hitting larger areas for longer, with higher frequency, more ubiquity and greater intensity.

[ from earlier post ]
For more on mechanisms behind a steep rise in temperature, also see this earlier post. 

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

• Climate Reanalyzer
https://climatereanalyzer.org

• Tropical Tidbits
https://www.tropicaltidbits.com

• Leon Simons - Earth's Energy Imbalance 
https://bsky.app/profile/leonsimons.bsky.social/post/3llcffaa65s2d

• Arctic and Antarctic Data Archive System (ADS) of the National Institute of Polar Research of Japan
https://ads.nipr.ac.jp

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

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

• Albedo, latent heat, insolation and more
https://arctic-news.blogspot.com/p/albedo.html

• Broadband radiometric measurements from GPS satellites reveal summertime Arctic Ocean Albedo decreases more rapidly than sea ice recedes - by Philip Dreike et al. 
https://www.nature.com/articles/s41598-023-39877-x
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