Showing posts with label water vapor. Show all posts
Showing posts with label water vapor. Show all posts

Wednesday, July 2, 2025

Saltier water, less sea ice

The Southern Meriodinal Ocean Circulation (SMOC) used to be driven by a cold freshwater layer resulting from melting Antarctic sea ice, enabling circumpolar waters to cool off and freshen, making them more dense and sink to the bottom. 
[ Antarctic waters sinking to the bottom, click on images to enlarge ]
This is illustrated by the above image, from a study led by Violaine Pellichero (2018), showing water-mass transformation within the Southern Ocean mixed-layer under sea-ice. Schematic cross-section illustrating the main water-masses in the Southern Ocean (Antarctic Intermediate and Mode Waters in red, Circumpolar Deep Waters in gray, and Dense Shelf Waters and Antarctic Bottom Waters in blue) and their interaction with ice and the surface. The water-masses are denoted by their neutral density values and the arrows corresponding to each water-masses indicate subduction (downward) or upwelling (upwards). The violet arrows illustrate the effect of northward sea-ice extent and freshwater transport. The green line is the mixed-layer.

A study led by Alessandro Silvano (2025) finds that, over the years, surface waters have become more salty.
By combining satellite observations with data from underwater robots, researchers built a 15-year picture of changes in ocean salinity, temperature and sea ice, as illustrated by the above image. Around 2015, surface salinity in the Southern Ocean began rising sharply – just as sea ice extent started to crash. 
When surface waters become saltier, they sink more readily, stirring the ocean’s layers and allowing heat from the deep to rise. This upward heat flux can melt sea ice from below, even during winter, making it harder for ice to reform. This vertical circulation also draws up more salt from deeper layers, reinforcing the cycle.

In addition to heat rising up from the deep, there is the danger that increasing amounts of both heat and carbon dioxide (CO₂), previously stored in the deep ocean by sinking circumpolar waters, will instead remain at the surface and cause both atmospheric temperatures and CO₂ concentrations to rise.

In the video below, Paul Beckwith discusses the recent study. 


The video below by @JustHaveaThink also discusses the recent study. 


Saltier water, less sea ice

   [ Saltier water, less sea ice ]
The higher the water's salt content, the lower its melting point. Seawater typically has a salinity of about 3.5% (35 grams of salt per liter of water). Sea ice starts melting when the temperature rises to about -2°C (28.4°F). By contrast, freshwater remains frozen as long as the temperature remains below 0°C (32°F).

What is causing the Southern Ocean surface to become more salty? Higher temperatures come with feedbacks, such as stronger evaporation resulting in both a lot more water vapor and a lot more heat getting transferred from the surface to the atmosphere. 

Much of the water vapor will return to the surface in the form of precipitation such as rain and snow, but part of this precipitation will fall over Antarctica. Increased snowfall over Antarctica can be attributed to rising air temperatures and stronger evaporation, changes in atmospheric circulation and the effects of ozone depletion. 

Furthermore, 7% more water vapor will remain in the atmosphere for every degree Celsius rise in temperature. Since water vapor is a potent greenhouse gas, this will further increase temperatures, making it a self-amplifying feedback that can significantly contribute to further acceleration of the temperature rise. 

Accumulating feedbacks

Warmer oceans result in stronger stratification (feedback #29), further contributing to make it harder for heat to reach the deeper parts of oceans. As a result, a larger proportion of the heat that was previously entering oceans will instead remain in the atmosphere or accumulate at the ocean surface, and slowing down of the Atlantic Meriodinal Overturning Circulation (AMOC) further contributes to this. 
[ from earlier post ]
More evaporation typically makes the sea surface more salty, while more precipitation, melting of sea ice and run-off from rivers and glaciers typically make the ocean surface fresher. As the recent study shows, the Southern Ocean surface is becoming more salty, which contributes to higher sea surface temperatures and in more melting of the sea ice. It's a self-amplifying feedback, in that saltier water at the ocean surface draws up more heat from the deep ocean, making it harder for sea ice to regrow. Increasing amounts of heat and CO₂ that were previously stored in the deep ocean by sinking circumpolar waters, threaten to instead remain at the surface and cause both atmospheric temperatures and CO₂ concentrations to rise. 

Less sea ice also comes with loss of albedo (water is less reflective than ice, feedback #1), loss of the latent heat buffer (as sea ice disappears, heat can no longer be consumed by the process of melting, and the heat will instead go into increasing the temperature, feedback #14) and loss of emissivity (water is less efficient than ice in emitting in the far-infrared region of the spectrum, feedback #23), while warmer water result in more water vapor and less low-level clouds that reflect sunlight back into space (feedback #25). 

The image below, from an earlier post, illustrates that higher temperatures come with feedbacks and the impact of one feedback can amplify the impact of other feedbacks.


The above image depicts some of the dangers of feedbacks for the Arctic. Many feedbacks also apply to the Antarctic, but the bottom part of the image on the right may be particularly applicable to the Southern Hemisphere, which has more ocean surface and Antarctica constitutes a huge land mass on and around the South Pole. 

Covering more than 70% of Earth’s surface, our global ocean has absorbed about 90% of the warming that has occurred in recent decades due to increasing greenhouse gases, and the top few meters of the ocean store as much heat as Earth's entire atmosphere, as described by a NASA post. 

Even a small change could therefore result in a huge rise in the global air temperature.

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

• The southern ocean meridional overturning in the sea-ice sector is driven by freshwater fluxes - by Violaine Pellichero (2018) 

• Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites - by Alessandro Silvano et al. (2025)
https://www.pnas.org/doi/full/10.1073/pnas.2500440122
discussed on facebook at: 
https://www.facebook.com/groups/arcticnews/posts/10162876582119679

• Abrupt Antarctic Ocean Regime Shift: Reversed SMOC - Southern Meridional Overturning Circulation - video by Paul Beckwith 
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Wednesday, September 4, 2024

Water Vapor Feedback



Earth's Energy Imbalance is now about four times as high as it was a decade ago, as illustrated by the above image, by Eliot Jacobson. As a result, feedbacks are starting to kick in with greater ferocity.

Water vapor feedback

One such feedback is the water vapor feedback. The temperature rise results in more evaporation, i.e. more water vapor and heat will enter the atmosphere, much of which will return to the surface in the form of precipitation, but some will remain in the atmosphere, as there will be 7% more water vapor for every 1°C warming. As illustrated by the image below, created with NOAA data, surface precipitable water was 27.181 kg/m² in August 2024, a record high for this month.

[ surface precipitable water through August 2024 ]

How much more water vapor currently is in the atmosphere compared to pre-industrial depends on how much the temperature has risen since pre-industrial. The February 2024 temperature was 1.76°C above 1885-1915, which could be as much as 2.75°C above the pre-industrial temperature. A 2.75°C rise corresponds with almost ⅕ more water vapor in the atmosphere.

More ocean heat and water vapor moving to Arctic

The temperature rise also comes with stronger wind. An earlier post points at a study that found increased kinetic energy in about 76% of the upper 2,000 meters of global oceans, as a result of intensification of surface winds since the 1990s.

Stronger wind speeds up ocean currents, enabling more ocean heat to move to the Arctic, while stronger wind also enables more water vapor to move to the Arctic and more rain to fall closer to the Arctic, along the path of prevailing ocean currents and wind patterns. As a result, both heat and water vapor will increase in the Arctic. 

This will in turn further increase the temperature rise in the Arctic, since water vapor is a potent greenhouse gas, while more water vapor also results in less hydroxyl, thus extending methane's lifetime.

The resulting temperature rise in the Arctic also reduces the snow and ice cover, further amplifying the temperature rise in the Arctic, while the temperature rise and the presence of more open water will also enable more evaporation, resulting in more water vapor in the atmosphere over the Arctic. 

High levels of methane are already present over the Arctic and the water vapor feedback makes things worse. Additionally, more ocean heat entering the Arctic Ocean threatens to further destabilize sediments at the seafloor that contain methane hydrates and cause even more methane to erupt, resulting in huge amounts of methane entering the atmosphere over the Arctic, from the hydrates and also from free gas underneath the hydrates.

[ click on images to enlarge ]
More water vapor and rainfall combined with higher temperatures will also cause more methane releases from lakes, wetlands and permafrost on land in the northern parts of Canada, Europe and Siberia. 

The image on the right shows a forecast by Climate Reanalyzer of high temperature anomalies in the northern parts of Europe on September 7, 2024. 

The image below shows high methane levels forecast by Copernicus at surface level in northern Europe on September 7, 2024, 03 UTC (run 00 UTC). 


As the image below shows, methane concentrations as high as 2400 parts per billion (ppb) were recently recorded at the NOAA observatory in Utqiagvik (Barrow), Alaska.


As Earth's Energy Imbalance keeps rising, an increasing amount of heat accumulates in oceans. The image below, adapted from NOAA, illustrates the huge amount of heat present in the ocean around North America, with sea surface temperatures as high as 33.6°C (92.48°F) recorded on September 6, 2024. The image also shows the Gulf Stream (middle right), the Atlantic ocean current that carries heat from the Gulf of Mexico to the Arctic Ocean. 


The image below, by Brian McNoldy shows that ocean heat content in the Gulf of Mexico was at record high on September 4, 2024.


The temperature rise is hitting the Arctic hard, as illustrated by the image below, created with NASA content.


The temperature rise in the air is most profound at both poles, a phenomenon known as polar amplification, as illustrated by the temperature anomaly map for August 2024 below. 


[ from earlier post ]
Oceans are still absorbing an estimated 91% of the excess heat energy trapped in the Earth's climate system due to human-caused global warming. If just a small part of that heat instead remains in the atmosphere, this could constitute a huge rise in temperature. Heat already stored in the deeper layers of the ocean will eventually be released, committing Earth to at least some additional surface warming in the future.

Polar amplification of the temperature rise causes a relative slowing down of the speed at which heat flows from the Equator to the poles. This impacts ocean currents and wind patterns, resulting in slowing down of the Atlantic meridional overturning circulation (AMOC) and of ocean currents around Antarctica that carry heat to the deep ocean, as well as in deformation of the Jet Stream. 

A recent study warns about intensification of global warming due to the slowdown of the overturning circulation. The overturning circulation carries carbon dioxide and heat to the deep ocean, where it is stored and hidden from the atmosphere. As the ocean storage capacity is reduced, more carbon dioxide and heat are left in the atmosphere. This feedback accelerates global warming.
[ from earlier post ]
Warmer oceans also result in stronger stratification, which further contributes to make it harder for heat to reach the deeper parts of oceans. As a result, a larger proportion of heat that was previously entering oceans will instead remain in the atmosphere or accumulate at the ocean surface, and slowing down of the overturning circulation further contributes to this, as discussed above. 

At the same time, overall global wind strength increases as temperatures rise, and as the Jet Stream gets more deformed, this can at times strongly boost the flow of wind and water along prevailing ocean currents, wind patterns and storm tracks that carry heat toward the Poles. Furthermore, polar amplification of the temperature rise results in a relatively stronger rise in water vapor in the air over Antarctica and the Arctic. 


At times, part of this accumulated energy can, in the form of ocean heat and precipitable water, be abruptly transported to the Arctic, along the path of prevailing ocean currents and wind patterns boosted by stronger wind and storms. This is illustrated by the above image that shows unusually high amounts of precipitable water recorded near the North Pole on September 1, 2024, at 04 UTC (20 kg/m² at the green circle). This can be further facilitated by the formation of a freshwater lid at the surface of the North Atlantic that enables more ocean heat to travel underneath this lid to the Arctic Ocean. 


Temperatures remain high

Temperatures remain high, even while a transition to La Niña is expected by Sep-Nov 2024, persisting through Jan-Mar 2025, as illustrated by the image below, adapted from NOAA.


The image below, from an earlier post and adapted from NOAA, illustrates that El Niño conditions were present from June 2023 through April 2024, and that ENSO-neutral started in May 2024. While El Niños typically occur every 3 to 5 years, as NOAA explains, El Niños can occur as frequently as every two years, as happened in 2002, 2004 and 2006, and as illustrated by the image below. The danger is that we could move into a new El Niño in 2025, while temperatures remain high due to feedbacks and while sunspots move toward a peak in this cycle, expected to occur in July 2025.


The image below illustrates that, for 14 consecutive months, the temperature anomaly has exceeded 1.2°C above 1951-1980 or (more aptly) 2°C above pre-industrial, and is rising again, even while El Niño ended April 2024.


Similarly, the image below illustrates that, for more than 14 consecutive months, the temperature anomaly has been high, i.e. about 0.8°C (± 0.3°C) above the 1991-2020 average and much more when compared to a pre-industrial base, with little or no sign of a return to earlier temperatures. On September 2, 2024, the temperature was 0.8°C above 1991-2020, the highest anomaly on record for that day of the year.

[ click on images to enlarge ]

The image below, created with NASA data while using a 1903-1924 custom base, illustrates that the monthly temperature anomaly through August 2024 has been more than 1.5°C above this base for each of the past consecutive 14 months, and even more when compared to a pre-industrial base. The red line shows the trend (2-year Lowess Smoothing) associated with the rapid recent rise.


A huge temperature rise could unfold by 2026, as the joint result of changes in the atmosphere, changes in surface and cloud albedo, changes in wind patterns & ocean currents, and further developments, e.g. in a cataclysmic alignment, a strong El Niño could develop in 2025 which, in combination with higher than expected sunspots, could make a difference of 0.75°C. Sunspots are expected to reach a peak in the current cycle in July 2025. 

Sea ice disappearing fast

Sea ice is disappearing over large parts of the Arctic Ocean, including near the North Pole. 


The above compilation image shows, on the left, that Arctic sea ice volume was at a record low for the time of year on September 5, 2024, as it has been for most of the year. On the right, an image by the University of Bremen showing sea ice concentration on September 5, 2024.


In the above compilation image, the NASA Worldview image on the left shows Arctic sea ice on September 10, 2024.

The Danish Meteorological Institute (DMI) image at the top right is from an earlier date, not yet showing the 2024 minimum, yet it does show that the minimum volume in earlier years was not as far below 5000 km³ as it was in 2024. The 2024 minimum is depicted on the DMI image on the bottom right, showing that Arctic sea ice volume was well below 5000 km³ on September 10, 2024.


In the above image the two DMI images overlap, highlighting that Arctic sea ice volume did reach a record low in 2024. 


Global sea ice extent was 21.04 million km² on September 4, 2024, a record low for the time of year, as feedbacks start kicking in with greater ferocity, including less albedo, latent heat buffer and emissivity, more water vapor, less lower clouds, Jet Stream changes, more emissions, lightning and forest fires, stronger rainfall and heatwaves causing more run-off of heat, and stronger storms that can push ocean heat toward the poles, all contributing to accelerate sea ice loss and the temperature rise, as discussed in earlier posts such as this one. 

[ for more background, also view the Extinction page ]
A huge temperature rise could occur soon

As a result, several tipping points threaten to be crossed in the Arctic soon, as described in an earlier post, including the latent heat tipping point and a Blue Ocean Event (starting when Arctic sea ice extent will fall below 1 million km²), which would further speed up the temperature rise in the Arctic.

As temperatures keep rising in the Arctic, changes to the Jet Stream look set to intensify, resulting in loss of terrestrial albedo in the Arctic that could equal the albedo loss resulting from sea ice decline.

Further feedbacks include permafrost degradation, both terrestrial and on the seafloor of the Arctic Ocean, which looks set to cause huge releases of greenhouse gases (particularly CO₂, CH₄ and N₂O).

This would in turn also cause more water vapor to enter the atmosphere, further speeding up the temperature rise, especially in the Arctic, where vast amounts of methane are contained in sediments at the seafloor and where there is very little hydroxyl in the air to break down the methane.

Temperatures look set to rise further in the Arctic, due to falling away of sulfate aerosols, as illustrated by the IPCC image below that shows how much temperatures are currently suppressed in the Arctic due to aerosols and thus also shows how much temperatures in the Arctic look set to rise as the aerosol masking effect falls away.


Furthermore, the combined impact of aerosols and nitrogen fertilizers has been underestimated; a recent study concludes that when ammonia, nitric acid and sulfuric acid are present together, they contribute strongly to the formation of cirrus clouds.

At the same time, there could be a temperature rise due to releases of other aerosols that have a net warming impact, such as black and brown carbon, which can increase dramatically as more wood burning, forest fires and urban fires take place, which again would hit the Arctic hard by darkening the surface as they settle on the snow and ice cover, thus speeding up its decline.

The image below, with forecasts for September 9, 2024 03 UTC (run 00 UTC) adapted from Copernicus, illustrates gases and aerosols released due to forest fires burning in the Amazon.


The joint impact could cause the clouds tipping point to get crossed, adding an abrupt further 8°C to the rise, and altogether, a global temperature rise could unfold of more than 18°C above pre-industrial, as illustrated by the image further above on the right, and as also discussed at Extinction. This could in turn cause the water vapor tipping point to get crossed, which means that from then on the increase in water vapor alone would suffice to keep increasing the temperature, in a runaway greenhouse process in which evaporation could cause a global surface temperature rise of several hundred degrees Celsius and make our planet as inhospitable as Venus, as this study concludes and as discussed at this post.

[ click on images to enlarge ]
A 2020 study led by Jorgen Randers concludes that the world is already past a point-of-no-return for global warming, as self-sustained thawing of the permafrost will continue for hundreds of years, even if global society did stop all emissions of man-made greenhouse gases immediately, due to a combination of declining surface albedo (driven by decline of the Arctic snow and ice cover), increasing amounts of water vapor in the atmosphere (driven by higher temperatures), and changes in concentrations of further greenhouse gases in the atmosphere (driven by changes in sinks and sources of carbon dioxide and methane such as thawing permafrost), as illustrated by the image on the right, from an 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

• Earth Energy Imbalance - by Eliot Jacobson

• NOAA - Physical Sciences Laboratory
https://psl.noaa.gov

• NOAA - Global Monitoring Laboratory - Carbon Cycle Gases
https://gml.noaa.gov/dv/iadv/graph.php?code=BRW&program=ccgg&type=ts

• Cataclysmic Alignment threatens Climate Catastrophe
• Sunspots
https://arctic-news.blogspot.com/p/sunspots.html

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

• Ocean Heat Content - by Brian McNoldy
https://bmcnoldy.earth.miami.edu/tropics/ohc

• Recent reduced abyssal overturning and ventilation in the Australian Antarctic Basin - by Kathryn Gunn et al. 
https://www.nature.com/articles/s41558-023-01667-8
Discussed on facebook at: 

• Copernicus - Atmosphere

• NASA - Gistemp

• NASA - Worldview

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

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

• Arctic Data archive System - National Institute of Polar Research - Japan
https://ads.nipr.ac.jp/vishop

• Will temperatures keep rising fast?
https://arctic-news.blogspot.com/2023/12/will-temperatures-keep-rising-fast.html

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

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

• The Clouds Feedback and the Clouds Tipping Point
https://arctic-news.blogspot.com/p/clouds-feedback.html

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

• Resetting tropospheric OH and CH4 lifetime with ultraviolet H2O absorption - by Michael Prather et al. 
https://www.science.org/doi/abs/10.1126/science.adn0415
Discussed on facebook at: 
https://www.facebook.com/groups/arcticnews/posts/10161571351924679

• 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


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Friday, August 2, 2024

High feels like temperature forecast

Temperatures are forecast to reach 46.5°C or 115.8°F in Saudi Arabia (green circle left) and to reach 36.1°C or 96.9°F in China (green circle right) on August 4, 2024 06 UTC.

As illustrated by the image below, 'feels like' temperatures are forecast to reach 42.1°C or 107.9°F in Saudi Arabia (green circle left) and 53.6°C or 128.4°F at that location in China (green circle right), i.e. at Gaoyou, Yangzhou, Jiangsu, China, 325 km North of Shanghai, China, on August 4, 2024 06 UTC.


What makes the difference is that the 'feels like' temperature is the perceived air temperature as a combination of the heat index and wind chill. The heat index combines air temperature and relative humidity, in shaded areas. Relative humidity is forecast to be 7% in Saudi Arabia at the green circle left and 69% in China at the green circle right on August 4, 2024 06 UTC, as illustrated by the image below. 


The image below shows an even higher 'feels like' temperature of 55°C (130.9°F) that was recorded at a location 368 km north of Shanghai, China, on August 4, 2024, 09 UTC, caused by a combination of a temperature of 35.5°C (95.8°F) and a relative humidity of 75%, also resulting in a wet bulb temperature of 31.4°C (88.4°F). The image was made with a screenshot of current conditions (nowcast) at the time, but later readings show lower values (see image further below).


In hindsight, the highest 'feels like' temperature turned out to be 53.6°C (128.6°F), recorded at a location 361 km north of Shanghai, China, on August 4, 2024, 09 UTC, caused by a combination of a temperature of 35.6°C (96.2°F) and a relative humidity of 72%, also resulting in a wet bulb temperature of 31°C (87.7°F), as illustrated by the image below. 


The above image also shows wind at surface level, with a large circular wind pattern showing up south of Japan, which may have influenced conditions.  

An earlier post showed that a 'feels like' temperature of 54°C (129.1°F) hit an area west of Wuhan, China, on July 23, 2024.

High Wet Bulb Globe Temperature in California

Wet Bulb Globe Temperature takes into account the effect of temperature, relative humidity, wind speed, and solar radiation. Wet Bulb Globe Temperature is used by weather.gov to warn about extreme heat stress when in direct sunlight, as is forecast to occur in California in the grey areas on August 6, 2024 at 21 UTC. 

[ click on images to enlarge ]
The above image shows that a very high wet bulb global temperature is forecast for August 6, 2024, 21 UTC, at a location 7 miles west of Imperial, California, with the following details (inset):
- Temperature : 113°F or 45°C
- Apparent Temperature : 123°F or 51°C
- Wet Bulb Globe Temperature : 97°F or 36°C
- Dew Point : 69°F or 21°C
- Relative Humidity : 25%

Heat stress fatalities

Heat stress is the leading cause of weather-related deaths in the United States, as illustrated by the image below (credit: NOAA, text below from earlier post).


As the above image notes, the values for heat fatalities may be conservative. Research finds that where heat is being listed as an official cause of death, this likely underestimates the full toll of these events. Extreme heat can trigger heart attacks and strokes. In addition, some heart disease risk factors, such as diabetes—as well as heart medications, such as diuretics and beta blockers—can affect a person’s ability to regulate their body temperature and make it difficult to handle extreme heat. The study finds that extreme heat accounted for about 600-700 additional deaths from cardiovascular disease annually. A study estimates that extreme heat accounted for 12,000 premature deaths in the contiguous U.S. from 2000 to 2010, and an analysis calculates that the summer 2022 heatwave killed 61,000 people in Europe alone.

Temperature thresholds

As temperatures and humidity levels keep rising, a tipping point can be reached where the wind factor no longer matters, in the sense that wind can no longer provide cooling. The human body can cool itself by sweating, which has a physiological limit that was long described as a 35°C wet-bulb temperature. Once the wet-bulb temperature reaches 35°C, one can no longer lose heat by perspiration, even in strong wind, but instead one will start gaining heat from the air beyond a wet-bulb temperature of 35°C.

Accordingly, a 35°C wet-bulb temperature (equal to 95°F at 100% humidity or 115°F at 50% humidity) was long seen as the theoretical limit, the maximum a human could endure.

A 2020 study (by Raymond et al.) warns that this limit could be regularly exceeded with a temperature rise of less than 2.5°C (compared to pre-industrial). A 2018 study (by Strona & Bradshaw) indicates that most life on Earth will disappear with a 5°C rise. Humans, who depend for their survival on many other species, will likely go extinct with a 3°C rise, as illustrated by the image below, from an earlier post.


A 2022 study (by Vecellio et al.) finds that the actual limit is lower — about 31°C wet-bulb or 87°F at 100% humidity — even for young, healthy subjects. The temperature for older populations, who are more vulnerable to heat, is likely even lower. In practice the limit will typically be lower and depending on circumstances could be as low as a wet-bulb temperature of 25°C.

As temperatures rise, high 'feels like' temperatures and high wet bulb globe temperatures can be expected to occur more and more. 

Wildlife, pets, livestock and vegetation also suffer at higher temperatures. A recent study finds thresholds where vegetation productivity experiences rapid suppression, with threshold crossings occurring first of all in tropical regions. The study adds that restricting global warming to just 1.5°C can increase safe areas for vegetation growth by 13% compared to allowing warming to reach 2°C above preindustrial levels. Crop failure, loss of vegetation (and benefits such as shade) and water shortages add to the predicament of high (and rising) temperatures.

Water vapor feedback

[ from Moistening Atmosphere ]
The water vapor feedback is one of numerous self-amplifying feedbacks that accelerate the temperature rise. Just the temperature rise itself will cause more water vapor to be present in the atmosphere. Rising temperatures will result in more water vapor in the atmosphere at a rate of 7% more water vapor for every 1°C warming, and this will further amplify the temperature rise, since water vapor is a potent greenhouse gas, as discussed at the extinction page.

The February 2024 temperature was 1.76°C above 1885-1915, which could be as much as 2.75°C above the pre-industrial temperature. A 2.75°C rise corresponds with almost ⅕ more water vapor in the atmosphere.

As illustrated by the image below, created with NOAA data, surface precipitable water reached a record high of 27.395 kg/m² in July 2024. 


Climate change danger assessment

The image below, earlier discussed here, expands risk assessment beyond its typical definition as the product of the severity of impact and probability of occurrence, by adding a third dimension: timescale, in particular imminence.

Imminence alone could make that the danger constituted by rising temperatures needs to be acted upon immediately, comprehensively and effectively. While questions may remain regarding probability, severity and timescale of the dangers associated with climate change, the precautionary principle should prevail and this should prompt for action, i.e. comprehensive and effective action to reduce damage and improve the situation is imperative and must be taken as soon as possible.

Rapidly rising temperatures constitute tipping points in several ways

Firstly, there are thresholds beyond which rising temperatures become lethal for humans, as discussed above.

Secondly, some species are more vulnerable than other species. As Gerardo Ceballos describes in a 2017 analysis, there is a biological tipping point that threatens annihilation of species via the ongoing sixth mass extinction. Researchers such as Gerardo Ceballos (2020), Kevin Burke (2018) and Ignation Quintero (2013) have for years warned that mammals and vertebrates cannot keep up with the rapid rise in temperature. Humans are classified as vertebrate mammals, indicating that we will not avoid the fate of extinction, Guy McPherson (2020) adds.

Thirdly, there are further tipping points, e.g. sociopolitical ones. On the one hand, it would be good if people became more aware, as this could prompt more people into supporting the necessary action. On the other hand, as temperatures keep rising and politicians keep downplaying the dangers, there is a danger that panic will break out, dictators will grab power and civilization as we know it will collapse abruptly, as warned about earlier, e.g. in 2007.

High methane levels over Arctic Ocean

Humans will likely go extinct with a 3°C rise and one of the most-dreaded feedbacks that could contribute to such a rise is methane. Ominously, high methane levels are forecast over the Arctic Ocean for August 11, 2024, as illustrated by the image below, adapted from Copernicus. 


The above image shows a forecast for August 11, 2024, 00 UTC, at 850 hPa. High methane levels are present over the Arctic Ocean on the forecast. Note that the scale goes up to 24,840 parts per billion (ppb) for the dark red color. 

Ominously, high methane levels were also recorded recently at Barrow, Alaska. 


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

• Nullschool
https://earth.nullschool.net

• Wet Bulb Globe Temperature
https://digital.mdl.nws.noaa.gov

• High Wet Bulb Globe Temperature Danger

• Wet Bulb Globe Temperature Tipping Point
https://arctic-news.blogspot.com/2023/07/wet-bulb-globe-temperature-tipping-point.html

• Extreme heat stress
https://arctic-news.blogspot.com/2023/06/extreme-heat-stress.html

• Increased crossing of thermal stress thresholds of vegetation under global warming - by Xiangyi Li et al. 
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