Showing posts with label feedback. Show all posts
Showing posts with label feedback. Show all posts

Monday, July 31, 2023

Wet Bulb Globe Temperature Tipping Point

High Wet Bulb Globe Temperatures (WBGT) are forecast to hit Louisiana, United States, over the next few days. The image below shows a forecast for August 2, 2023, 18 UTC, with WBGT as high as 35°C forecast for a location 10 miles South East of Abbeville, Louisiana, U.S.


WBGT is a measure used by weather.gov to warn about expected heat stress when in direct sunlight. It takes into account the effect of temperature, relative humidity, wind speed, and solar radiation on humans.

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.


The above image shows a Wet Bulb Globe Temperature of 35°C (95°F) forecast for August 11, 2023, 19 UTC, for a location near Baton Rouge, Louisiana, U.S. 


Heat is the leading cause of weather-related deaths in the United States, as illustrated by the above image (credit: NOAA). Heat fatalities may be conservative figures. Recent 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 recent study estimates that extreme heat accounted for 12,000 premature deaths in the contiguous U.S. from 2000 to 2010, and a recent analysis calculates that the summer 2022 heatwave killed 61,000 people in Europe alone. 

The image below shows a temperature (°F) forecast for August 1, 2023, from Climate Reanalyzer


The video below discusses this.


Misery Index

The image below show a high reading on the 'Misery Index', the perceived ('feels like') temperature that is used by nullschool.net, combining wind chill and the heat index (which in turn combines air temperature and relative humidity, in shaded areas). A Misery Index temperature of 56.1°C or 133.1°F was recorded at a location off the coast of the United Arab Emirates (green circle) on August 5, 2023.


The temperature at that location at the time was 35.2°C or 95.4°F, lower than the temperature on the land surrounding the Gulf, but the relative humidity at that spot over the water was 78%, and that combination led to this very high 'feels like' temperature. 

This constitutes a warning. The sea, rivers and lakes are traditionally seen as places to go to, to cool off. However, high temperatures combined with high humidity over water bodies can result in conditions that go beyond what humans can bear. 

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 is a biological threshold beyond which rising temperatures become lethal for humans, as discussed above. 

Secondly, as Gerardo Ceballos describes in the video below and 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. social-political 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, there is also 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.  



Conclusion

In conclusion, to combat rising temperatures, transforming society is needed urgently, along the lines of this 2022 post in combination with declaration of a climate emergency.


Links

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

• National Weather Service - Wet Bulb Globe Temperature: How and when to use it
https://www.weather.gov/news/211009-WBGT

• The emergence of heat and humidity too severe for human tolerance - by Colin Raymons et al. (2020)
https://www.science.org/doi/10.1126/sciadv.aaw1838

• Brief periods of dangerous humid heat arrive decades early
https://www.climate.gov/news-features/featured-images/brief-periods-dangerous-humid-heat-arrive-decades-early

• Evaluating the 35°C wet-bulb temperature adaptability threshold for young, healthy subjects (PSU HEAT Project) - by Daniel Vecellio et al. (2022)
https://journals.physiology.org/doi/full/10.1152/japplphysiol.00738.2021
Discussed at: https://www.facebook.com/groups/arcticnews/posts/10159973158374679

• NOAA - Weather Fatalities 2022
https://www.weather.gov/hazstat

• The Effects of Heat Exposure on Human Mortality Throughout the United States - by Drew Shindell (2021)
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GH000234

• Heat-related mortality in Europe during the summer of 2022 - by Joan Ballester et al.
https://www.nature.com/articles/s41591-023-02419-z
Discussed at: https://www.facebook.com/groups/arcticnews/posts/10160875637104679

• As Temperatures Spike, So Do Deaths from Heart Disease (2022 News release)
https://www.acc.org/About-ACC/Press-Releases/2022/03/22/20/06/As-Temperatures-Spike-So-Do-Deaths-from-Heart-Disease

• Association of Extreme Heat and Cardiovascular Mortality in the United States: A County-Level Longitudinal Analysis From 2008 to 2017 - by Sameed Khatana et al. (2022)
https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.060746

• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
https://www.nature.com/articles/s41598-018-35068-1
Discussed at: https://www.facebook.com/groups/arcticnews/posts/10156903792219679

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

• Climate Reanalyzer - Hourly Forecast Maps
https://climatereanalyzer.org/wx/fcst/?mdl_id=nam&dm_id=conus-lc&wm_id=t2

• PBS video - Too HOT and HUMID to Live: Extreme Wet Bulb Events are on the Rise 
https://www.pbs.org/video/too-hot-and-humid-to-live-extreme-wet-bulb-events-are-on-th-fazocs

• Nullschool
https://earth.nullschool.net

• How agriculture hastens species extinction | 60 Minutes (CBS News) | Gerardo Ceballos
https://www.youtube.com/watch?app=desktop&v=f21WWocqR-c

• Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines - by Gerardo Ceballos, Paul R. Ehrlich and Rodolfo Dirzo (2017)
https://www.pnas.org/content/114/30/E6089

• Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction - by Gerardo Ceballos, Paul Ehrlich, and Peter Raven (2020)
https://www.pnas.org/content/early/2020/05/27/1922686117
Discussed at: https://www.facebook.com/groups/arcticnews/posts/10158460232764679

• Rates of projected climate change dramatically exceed past rates of climatic niche evolution among vertebrate species - by Ignatio Quintero et al. (2013) 

• Pliocene and Eocene provide best analogs for near-future climates - by Kevin Burke et al. (2018)
https://www.pnas.org/doi/10.1073/pnas.1809600115
Discussed at: https://www.facebook.com/groups/arcticnews/posts/10156972951354679

• Earth is in the Midst of Abrupt, Irreversible Climate Change - by Guy McPherson (2020)
https://www.onlinescientificresearch.com/articles/earth-is-in-the-midst-of-abrupt-irreversible-climate-change.pdf

Thursday, July 6, 2023

Dire situation gets more dire every day

Conditions are dire


The world temperature was at a record high 17.23°C or 63.01°F on July 6, 2023 (black). The maximum temperature in 2022 (orange) and in 2016 (grey) was 16.92°C or 62.46°F (on July 24, 2022, and on August 13+14, 2016). The year 2016 is important, since there was a strong El Niño in 2016 and we're now again in an El Niño. 

As the image below adds, the 17.23°C temperature recorded on July 6, 2023, is a daily value, but if indicative for July 2023, the closest value for CMIP5 RCP8.5 would be 17.255°C, projected to occur in July 2035 (13 years away from now).

[ The international consortium Coupled Model Intercomparison Project (CMIP)
defines scenarios for use in climate projections. Its CMIP5 scenario (an average of
39 models of near-surface temperature and precipitation, and mean sea level pressure)
can be used in combination with Representative Concentration Pathways (RCP). ]

Why is the temperature rising so fast? 

The image below mentions a number of contributors, with charts added from an earlier post

[ click on images to enlarge ]

1. Emissions are high and greenhouse gas levels keep rising, increasing Earth's Energy Imbalance

2. We did come out of a La Niña that has for years been suppressing temperatures and we are now in an El Niño. A 2023 study led by Tao Lian predicts the current El Niño to be strong. Moving from the bottom of a La Niña to the peak of a strong El Niño could make a difference of more than half a degree Celsius, as discussed in an earlier post. Temperature anomalies can be very high during an El Niño. The image below shows that February 2016 on land was 3.28°C (5.904°F) hotter than 1880-1896, and 3.68°C (6.624°F) hotter compared to February 1880 on land. Note that 1880-1896 is not pre-industrial, the rise will be even larger when using a genuinely pre-industrial base.
The above image, from an earlier post, adds a poignant punchline: Looking at global averages over long periods is a diversion, peak temperature rise is the killer!

[ click on images to enlarge ]
3. The June 2023 number of sunspots is more than twice as high as predicted, as illustrated by the image on the right, from an earlier post and adapted from NOAA. If this trend continues, the rise in sunspots forcing from May 2020 to July 2025 may well make a difference of more than 0.25°C, a recent analysis found.

4. The January 2022 submarine volcano eruption near Tonga did add a huge amount of water vapor to the atmosphere, as discussed in an earlier post and also at facebook. Since water vapor is a potent greenhouse gas, this further contributes to speeding up the temperature rise. A 2023 study calculates that the eruption will have a warming effect of 0.12 Watts/m² over the next few years.

5. There are further things that contribute to the temperature rise, such as reductions of Sahara dust and of sulfur aerosols co-emitted with fossil fuel combustion that previously masked the temperature rise. 

The above points apply to the global temperature rise. The North Atlantic sea surface temperature is rising even stronger than the global rise, due to the following points:
  • The narrowing temperature difference between the Arctic and the Tropics is slowing down the flow of air from the Tropics to the Arctic, deforming the Jet Stream, and that can strongly prolong and amplify extreme weather events in the Northern Hemisphere, and result in stronger heating up of the North Atlantic.
  • This is also slowing down AMOC, causing more hot water to accumulate in the North Atlantic and to reach the Arctic Ocean, resulting in strong melting of sea ice from below and thus strong thinning.
  • Additionally, as temperatures rise, increased stratification further speeds up the sea surface temperature rise.
  • As the North Atlantic Ocean heats up and as cold air from the Arctic can more deeply descend over North America (due to Jet Stream deformation), the temperature difference between land and oceans widens, especially during the Northern Winter, and this can result in storms abruptly pushing strong wind along the path of the Gulf Stream, pushing ocean heat into the Arctic Ocean, with stronger evaporation occurring over the North Atlantic and with stronger precipitation (rain, snow, etc.) occurring further down the path of the Gulf Stream. This stronger evaporation cools the surface of the North Atlantic.
  • This cooling, together with cooling from increased meltwater, also results in formation of a cold freshwater lid on top of the North Atlantic, also because freshwater is less dense than saltwater.
  • This lid on top of the North Atlantic enables more hot water to flow underneath this lid into the Arctic Ocean, with the danger that more heat will reach sediments at the seafloor of the Arctic Ocean and destabilize hydrates, resulting in eruption of huge amounts of methane.
  • This sea surface cooling has until now covered up the full extent of the rise in ocean heat in the North Atlantic, but - as illustrated by the image below - the continued rise in ocean heat now is overwhelming this cooling.
The image below shows that the North Atlantic sea surface temperature was 23.3°C on June 21, 2023 (on the black line), 0.9°C higher than the 22.4°C on June 21, 2022 (on the orange line). A record high of 24.9°C was reached on September 4, 2022, even while La Niña at the time was suppressing the temperature, whereas there now is an El Niño, so the outlook is grim.

[ from earlier post ]
Feedbacks and developments that make the outlook even more threatening

Globally, methane rose to 1924.99 ppb in December 2022. The image below has a polynomial trend added that is based on April 2018 to December 2022 NOAA global methane data and is pointing at 1200 ppm CO₂e (carbon dioxide equivalent) getting crossed in 2027. The Clouds Tipping Point, at 1200 ppm CO₂e, could be crossed and this on its own could result in a further rise of 8°C. This tipping point could be crossed as early as in 2027 due to forcing caused by the rise in methane alone. When further forcing is taken into account, this could happen even earlier than in 2027.
[ from earlier post ]
[ click on images to enlarge ]
On February 22, 2023, Antarctic sea ice area was only 1,050,708 km² in size, as discussed in an earlier post. Since that time, Antarctic sea ice has been growing at a much slower pace than in previous years. On July 4, 2023, Antarctic sea ice area was 9,385,739 km² in size, and sea ice has actually been falling in size recently, as illustrated by the Nico Sun image on the right. Less sea ice means that sunlight previously reflected back into space by the sea ice is now instead getting absorbed by the Southern Ocean, in a self-reinforcing feedback loop that results in further sea ice loss, in turn further speeding up the temperature rise and making the weather ever more extreme.

[ Two out of numerous feedbacks ]
This dire situation spells bad news regarding the temperature rise to come, the more so since, on top of these dire conditions, there are feedbacks and further developments that make the outlook even more threatening. 

A huge temperature rise could be triggered abruptly, due to a multitude of feedbacks and further developments that could strongly deteriorate the situation even further, such as by causing more water vapor to get added to the atmosphere, as discussed at Moistening Atmosphere and Extreme Heat Stress.

[ see the Extinction page ]
Changes in aerosols are discussed in earlier posts such as this post and this post. The upcoming temperature rise on land on the Northern Hemisphere could be so strong that much traffic, transport and industrial activity will grind to a halt, resulting in a reduction in cooling aerosols that are now masking the full wrath of global heating. These are mainly sulfates, but burning of fossil fuel and biomass also emits iron that currently helps photosynthesis of phytoplankton in oceans, as a 2022 study points out, and less iron means less drawdown of carbon dioxide. 

Without these emissions, the temperature is projected to rise strongly, while there could be an additional temperature rise due to an increase in warming aerosols and gases as a result of more biomass and waste burning and forest fires.

The image on the right, from the extinction page, includes a potential rise of 1.9°C by 2026 as the sulfate cooling effect falls away and an additional rise of 0.6°C due to an increase in warming aerosols by 2026, as discussed in this post and earlier posts.

The image on the right indicates that the rise from pre-industrial to 2020 could be as much as 2.29°C. Earth's energy imbalance has grown since 2020, so the rise up to now may be even higher. 

Climate Tipping Points and further Events and Developments

The temperature could also be pushed up further due to reductions in the carbon sink on land. An earlier post mentions a study that found that the Amazon rainforest is no longer a sink, but has become a source, contributing to warming the planet instead; another study found that soil bacteria release CO₂ that was previously thought to remain trapped by iron; another study found that forest soil carbon does not increase with higher CO₂ levels; another study found that forests' long-term capacity to store carbon is dropping in regions with extreme annual fires; another earlier post discussed the Terrestrial Biosphere Temperature Tipping Point, coined in a study finding that at higher temperatures, respiration rates continue to rise in contrast to sharply declining rates of photosynthesis, which under business-as-usual emissions would nearly halve the land sink strength by as early as 2040.

This earlier post also discusses how CO₂ and heat taken up by oceans can be reduced. A 2021 study on oceans finds that, with increased stratification, heat from climate warming less effectively penetrates into the deep ocean, which contributes to further surface warming, while it also reduces the capability of the ocean to store carbon, exacerbating global surface warming. A 2022 study finds that ocean uptake of CO₂ from the atmosphere decreases as the Meridional Overturning Circulation slows down. An earlier analysis warns about growth of a layer of fresh water at the surface of the North Atlantic resulting in more ocean heat reaching the Arctic Ocean and the atmosphere over the Arctic, while a 2023 study finds that growth of a layer of fresh water decreases its alkalinity and thus its ability to take up CO₂, a feedback referred to as the Ocean Surface Tipping Point.

[ from Blue Ocean Event 2022? - click on images to enlarge ]
The above image depicts only one sequence of events, or one scenario out of many. Things may eventuate in different orders and occur simultaneously, i.e. instead of one domino tipping over the next one sequentially, many events may occur simultaneously and reinforce each other. Further events and developments could be added to the list, such as ocean stratification and stronger storms that can push large amounts of warm salty water into the Arctic Ocean.

While loss of Arctic sea ice and loss of Permafrost in Siberia and North America are often regarded as tipping points, Antarctic sea ice loss, and loss of the snow and ice cover on Greenland, on Antarctica and on mountaintops such as the Tibetan Plateau could also be seen as tipping points. Another five tipping points are: 

Extinction

Altogether, the rise from pre-industrial to 2026 could be more than 18.44°C, while humans are likely to go extinct with a rise of 3°C, as illustrated by the image below, from an analysis discussed in an earlier post.


This should act as a warning that near-term human extinction could occur soon. In the video below, Guy McPherson discusses how fast humans could go extinct. 


Conclusion

The dire situation is getting more dire every day, calling for a Climate Emergency Declaration and implementation of comprehensive and effective action, as described in the Climate Plan with an update at Transforming Society.


Links

• Climate Reanalyzer - World Daily 2-meter Air Temperature (90-90°N, 0-360°E)
https://climatereanalyzer.org/clim/t2_daily

• Climate Reanalyzer - CMIP5 RCP8.5 projection
https://climatereanalyzer.org/reanalysis/monthly_tseries

• NOAA - Solar cycle sunspot number progression
https://www.swpc.noaa.gov/products/solar-cycle-progression

• A Strong 2023/24 El Niño is Staged by Tropical Pacific Ocean Heat Content Buildup - by Tao Lian et al. (2023)
https://spj.science.org/doi/10.34133/olar.0011

• NSIDC - National Snow and Ice Data Center
https://www.nsidc.org

• NSIDC - Chartic interactive sea ice graph
https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph

• Cryosphere Computing - by Nico Sun
https://cryospherecomputing.com

• Nullschool
https://earth.nullschool.net

• Climate Reanalyzer - sea ice based on NSIDC index V3
https://climatereanalyzer.org/clim/seaice

• NOAA - greenhouse gases - trends CH4 (methane)
• NOAA - Solar cycle progression

• NASA gistemp Monthly Mean Global Surface Temperature - Land Only

• NOAA - Annual Northern Hemisphere Land Temperature Anomalies 

• Tonga eruption increases chance of temporary surface temperature anomaly above 1.5 °C - by Stuart Jenkins et al. (2023)
https://www.nature.com/articles/s41558-022-01568-2



• Moistening Atmosphere
• Albedo, latent heat, insolation and more

• Latent Heat

• Blue Ocean Event

• Methane keeps rising

• A huge temperature rise threatens to unfold soon

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

• Human Extinction by 2025?

• 2020: Hottest Year On Record

• The Importance of Methane in Climate Change

• The underappreciated role of anthropogenic sources in atmospheric soluble iron flux to the Southern Ocean - by Mingxu Liu et al. (2022)
https://www.nature.com/articles/s41612-022-00250-w

• How close are we to the temperature tipping point of the terrestrial biosphere? - by Katharyn Duffy et al. (2021)

• Overshoot or Omnicide? 

• Upper Ocean Temperatures Hit Record High in 2020 - by Lijing Cheng et al. (2021)

• Reduced CO₂ uptake and growing nutrient sequestration from slowing overturning circulation - by Yi Liu et al. (2022)
https://www.nature.com/articles/s41558-022-01555-7

• Cold freshwater lid on North Atlantic
• Long-Term Slowdown of Ocean Carbon Uptake by Alkalinity Dynamics - by Megumi Chikamoto et al. (2023) 
• Ocean Surface Tipping Point Could Accelerate Climate Change

• When Will We Die?

• Edge of Extinction: Extinct - HOW FAST? - video by Guy McPherson

• Edge of Extinction: Destination Destruction - video by Guy McPherson


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

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






Sunday, June 25, 2023

Extreme heat stress

Heatwaves

High Wet Bulb Globe Temperature (WBGT) is forecast to hit the Southeastern United States over the next few days. The image below shows a forecast for June 29, 2023, 18 UTC with WBGT as high as 34°C (93°F) forecast for a location near Jackson, Mississippi, U.S. 

[ click on images to enlarge ]

WBGT is a measure used by weather.gov to warn about expected heat stress when in direct sunlight. It estimates the effect of temperature, relative humidity, wind speed, and solar radiation on humans using a combination of temperatures from three thermometers:

  • A Wet bulb measures the temperature read by a thermometer covered in a wet cloth. As water evaporates from the cloth, evaporation cools the thermometer. This mirrors how the human body cools itself with sweat.
  • A black globe is used to measure solar radiation. Solar radiation heats the globe and wind blowing across it cools the globe.
  • A Dry bulb calculates the air temperature measured in the shade. It is the temperature you would see on your thermometer outside.
The images on the right earlier featured in a 2016 post

The top image, an animation from the EPA, illustrates that a relatively small rise in average temperature can have a huge impact and result in a lot more hot weather as well as in even more extreme hot weather.

[ from earlier post ]
The three images underneath, from the IPCC, show the effect on extreme temperatures when (a) the mean temperature increases, (b) the variance increases, and (c) when both the mean and variance increase for a normal distribution of temperature.

The thermodynamic wet-bulb temperature is determined by temperature, humidity and pressure (hPa), and it is the lowest temperature that can be achieved by evaporative cooling of a water-wetted ventilated surface.

As temperatures and humidity levels keep rising, there comes a point 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.

The images below show high readings on the 'Misery Index', the perceived temperature that is used by nullschool.net, combining wind chill and the heat index (which in turn combines air temperature and relative humidity, in shaded areas).

The image below shows a forecast for June 29, 2023 20 UTC, with weather conditions prolonged by circular wind patterns at 250 hPa (Jet Stream), while the Jet Stream is crossing the Equator (bottom left). Temperatures as high as 39.9°C (103.7°F) combined with a relative humidity of 35% result in perceived temperatures as high as 45°C (112.9°F) at the green circle.


As it turned out, the perceived temperature was as high as 44.9°C or 112.7°F on June 29, 2023 19 UTC, due to a 39.1°C or 102.5°F temperature and a 38% relative humidity at the surface, and with conditions prolonged by a distorted Jet Stream (at 250 hPa), with circular wind patterns and winds crossing the Equator.


The image below shows high readings on the 'Misery Index' for parts of Pakistan. On June 22, 2023, an air temperature of 45.4°C (113.7°F) and a relative humidity of 25% resulted in a perceived temperature of 51°C (123.7°F) at the area marked by the green circle. 


The above image also shows the Jet Stream (wind at 250 hPa). Distortion of the Jet Stream can lead to circular wind patterns that amplify heatwaves. As temperature rise, the temperature difference between the Equator and the Arctic narrows, distorting the Jet Stream resulting in more extreme  weather.

Perceived (feels like) air temperatures as high as 53.1°C or 127.7°F were recorded in Pakistan on July 4, 2023, 09 UTC (at green circle), with a 46.7°C or 116.1°F temperature and a 24% relative humidity recorded at the surface. Also, Jet Stream deformation shows up (at 250 hPa), with circular wind patterns and wind crossing the Equator (at the image bottom).


Meanwhile, heatwave conditions have also been affecting China, Texas and Mexico recently, with all-time high temperature records broken in each of these places. 

The press release of a 2022 Unicef report has the title 559 million children currently exposed to high heatwave frequency, rising to all 2.02 billion children globally by 2050

Fire and smoke from fires

An additional hazard is fire and the smoke from fires. The image below shows biomass-burning aerosols from fires in Canada extending over the North Atlantic on June 25, 2023, 03 UTC.


The forecast for June 29, 2023 21 UTC below shows remnants of the Canadian forest fires reaching Western Europe.


Feedbacks

As temperatures rise, fire and smoke hazards increase due to self-reinforcing feedback loops, including: 
  • [ Two out of numerous feedbacks ]
    Albedo loss and Jet Stream distortion:
    - as sea ice melts away and gets covered by meltpools and rainwater pools, soot, dust, and algae, the resulting albedo loss further pushes up temperatures
    - the narrowing temperature difference between the Arctic and the Tropics causes Jet Stream distortion, resulting in more extreme weather, incl. stronger storms that come with more lightning and can carry more oxygen to fires and spread fires faster and wider, and more intense heatwaves that can dramatically push up local temperatures, further intensifying droughts and forest fires
  • a further self-reinforcing feedback loop is that water that was previously present in the soil, is increasingly moving up into the atmosphere, as the atmosphere sucks up more water vapor (7% more water vapor for every 1°C in temperature rise ), resulting in:
    - less evapotranspiration from vegetation, in turn resulting in less clouds and rain, thus pushing up temperatures and drying out soil and vegetation even more
    - erosion and less healthy vegetation that is more vulnerable to pests and diseases such as bark beetles, resulting in an increase in dead trees providing more fuel for fires
[ from earlier post ]
The image on the right, from a news release associated with a 2022 study, shows changes in atmospheric thirst, measured in terms of reference evapotranspiration from 1980-202 (in mm).

As temperatures rise due to people's emissions, more evaporation will take place over both land and oceans, but not all water will return as precipitation, so more water vapor will stay in the air and droughts affecting the soil and vegetation will intensify.

[ from earlier post ]
Water in the soil acts as a buffer, slowing down the temperature rise, so drier soil will heat up faster and further, causing land surface temperatures to rise even more and amplifying the impact of Urban heat island and Heat dome phenomena.

The image on the right, adapted from ESA, shows land surface temperatures as high as 65°C (149°F) in India on April 26, 2022. Note that land surface temperatures can be substantially higher than air temperatures.

The Copernicus image below shows Spain on 11 July 2023, where the Land Surface Temperature (LST), i.e. the temperature of the soil, in some areas of Extremadura (Spain) exceeded 60°C or 140°F, as measured by the Sea and Land Surface Temperature Radiometer (SLSTR) instrument, a feature of the Copernicus Sentinel-3 satellites. 


How high could temperatures rise?

The image below, from NASA, shows that February 2016 was 3.24°C or 5.83°F hotter on land than 1850-1890. Note that 1850-1890 is not pre-industrial, while the 2016 peak was reached during an El Niño, which raises the question how much hotter than pre-industrial it will be at the peak of the current El Niño. 


The image below says it even more poignantly: Looking at global averages over long periods is a diversion, peak temperature rise is the killer!

The above image shows that February 2016 was 3.28°C (5.904°F) hotter than 1880-1896 on land, and 3.68°C (6.624°F) hotter compared to February 1880 on land.


World temperature was at a new record high of 17.18°C or 62.92°F on July 4, 2023 (black). Both in 2022 (orange) and in 2016 (grey), the temperature reached 16.92°C or 62.46°F (on July 24, 2022 and August 13+14, 2016). The year 2016 is important, since it was a strong El Niño year and we're now again in an El Niño.

A 2023 study led by Tao Lian predicts the current El Niño to be strong. Moving from the bottom of a La Niña to the peak of a strong El Niño could make a difference of more than half a degree Celsius, as discussed in an earlier post.

Additionally, the June 2023 number of sunspots is more than twice as high as predicted, as illustrated by the image on the right, adapted from NOAA.

Furthermore, the 2022 Tonga submarine volcano eruption did add a huge amount of water vapor to the atmosphere, as discussed in an earlier post.

Alarm bells have been ringing for many years. As an example, the image below featured in a 2015 post, showing non-linear trends including a polynomial trendline (1: blue) pointing at global temperature anomalies of over 4°C by 2060. 

Moreover, a polynomial trend for the Arctic (2: red) threatens to cause major feedbacks to kick in, triggering runaway global warming (3: white) that looks set to catch up with accelerated warming in the Arctic and result in global temperature anomalies of 16°C by 2052.
[ from a 2015 post, click on image to enlarge ]
In the 2019 video below, Roger Hallam talks with Stephen Sackur from the BBC's HardTalk series. 


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.


Conclusion

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. To combat rising temperatures, transforming society is needed, along the lines of this 2022 post in combination with declaration of a climate emergency.

Accordingly, everyone is encouraged to support and share this Climate Emergency Declaration.


Links

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

• National Weather Service - Wet Bulb Globe Temperature: How and when to use it
https://www.weather.gov/news/211009-WBGT

• Nullschool.net
https://earth.nullschool.net

• Weather tracker: China issues heatstroke alert amid historic heatwave
https://www.theguardian.com/environment/2023/jun/23/weather-tracker-china-issues-heatstroke-alert-amid-historic-heatwave

• Peaks matter
https://arctic-news.blogspot.com/2018/08/peaks-matter.html

• It could be unbearably hot in many places within a few years time
https://arctic-news.blogspot.com/2016/07/it-could-be-unbearably-hot-in-many-places-within-a-few-years-time.html

• The emergence of heat and humidity too severe for human tolerance - by Colin Raymons et al. (2020)
https://www.science.org/doi/10.1126/sciadv.aaw1838

• Brief periods of dangerous humid heat arrive decades early

• Evaluating the 35°C wet-bulb temperature adaptability threshold for young, healthy subjects (PSU HEAT Project) - by Daniel Vecellio et al. (2022) 

• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
https://www.nature.com/articles/s41598-018-35068-1

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

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

• Copernicus - Biomass-burning aerosols
https://atmosphere.copernicus.eu/charts/packages/cams/products/aerosol-forecasts

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

• Will there be Arctic sea ice left in September 2023?
https://arctic-news.blogspot.com/2023/05/will-there-be-arctic-sea-ice-left-in-september-2023.html

• Clausius–Clapeyron relation
https://en.wikipedia.org/wiki/Clausius–Clapeyron_relation

• Urban heat island
https://en.wikipedia.org/wiki/Urban_heat_island

• Heat dome
https://en.wikipedia.org/wiki/Heat_dome

• ESA - Heatwave across India
https://www.esa.int/ESA_Multimedia/Images/2022/04/Heatwave_across_India

• Evaporative Demand Increase Across Lower 48 Means Less Water Supplies, Drier Vegetation, and Higher Fire Risk
https://www.drought.gov/news/evaporative-demand-increase-across-lower-48-means-less-water-supplies

• A Multidataset Assessment of Climatic Drivers and Uncertainties of Recent Trends in Evaporative Demand across the Continental United States - by Christine Albano et al. (2022)
https://arctic-news.blogspot.com/2022/04/carbon-dioxide-crosses-422-ppm.html

• 559 million children currently exposed to high heatwave frequency, rising to all 2.02 billion children globally by 2050
https://www.unicef.org/press-releases/heatwaves-report

• Copernicus - Scorching heatwave hits Spain 
https://www.copernicus.eu/en/media/image-day-gallery/scorching-heatwave-hits-spain

• NASA - custom plots 
https://data.giss.nasa.gov/gistemp/graphs_v4/customize.html

• Climate Reanalyzer - World Daily 2-meter Air Temperature (90-90°N, 0-360°E)
https://climatereanalyzer.org/clim/t2_daily

• NOAA - Solar cycle sunspot number progression
https://www.swpc.noaa.gov/products/solar-cycle-progression

• A Strong 2023/24 El Niño is Staged by Tropical Pacific Ocean Heat Content Buildup - by Tao Lian et al. (2023)