Arctic News: heat index

Showing posts with label heat index. Show all posts

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

https://arctic-news.blogspot.com/2024/07/high-wet-bulb-globe-temperature-danger.html

• 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.

https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.17406
Discussed at facebook at:
https://www.facebook.com/groups/arcticnews/posts/10161596967289679

• Copernicus methane forecasts

https://atmosphere.copernicus.eu/charts/packages/cams/products/methane-forecasts

• 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

Tuesday, July 26, 2016

It could be unbearably hot in many places within a few years time

On July 24, 2016, 21:00 UTC, it was 98.7°F or 37.1°C at the green circle on above image. Because humidity at the time was 72% and wind speed was 2 mph or 3 km/h, it felt like it was 140.4°F or 60.2°C.

Above image shows temperatures, i.e. 98.7°F or 37.1°C at the green circle.

Above image shows that relative humidity was 72% at the green circle.

This event occurred at a location on the border of Missouri and Arkansas, just within Missouri, as is also indicated by the red marker above Google Maps image.

As the EPA animation on the right illustrates, a relatively small rise in average temperature can result in a lot more hot and extremely hot weather.

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 'Misery Index' is the perceived air temperature as a combination of wind chill and heat index (which combines air temperature and relative humidity, in shaded areas).

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 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.

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.

The above combination of 37.1°C at 72% relative humidity at a pressure of 1013 hPa translates into a wet-bulb temperature of 32.43°C. Had humidity risen to 87% while temperature remained at 37.1°C, the wet-bulb temperature would have risen above 35°C. Alternatively, had the temperature risen to 39.9°C while humidity remained at 72%, the wet-bulb temperature would also have risen above 35°C.

This goes to show how close the world is to unbearable heat. After all, this event occurred in Missouri, i.e. at some distance from the Equator, implying that, as temperatures and humidity levels keep rising, it could be unbearably hot in many places within a few years time.

As discussed in a recent post and illustrated by the image on the right, the world could be 10°C or 18°F warmer in ten years time. Accordingly, this would lead to numbers of climate-related global deaths in line with the prognosis below.