Showing posts with label humidity. Show all posts
Showing posts with label humidity. Show all posts

Sunday, August 19, 2018

Will August 2018 be the hottest month on record?

July and August are typically about 3.6ºC or 6.5ºF warmer than December and January. August is typically 1.8°C or 3.24ºF warmer than the average annual temperature. Above image shows how much higher the temperature was for selected months, compared to the annual global mean for the period 1980-2015. Will August 2018 be the hottest month on record?

Numerous temperature records have fallen across the world recently. Heat stress hazard is high under conditions of high surface air temperature and high relative humidity. When looking at heat stress hazards, it's therefore important to look at surface air temperatures over land, i.e. the temperature of the air above the land surface.

Fire hazard is high under conditions of hot and dry soil and strong wind. When looking at fire hazards, it's therefore important to look at land surface temperatures, reflecting how hot the surface of the Earth would feel to touch in a particular location. The map below shows land surface temperatures.

When calculating how much warmer it is now, a number of things must be taken into account:
  1. Baseline

    What baseline is used and how is the temperature at the baseline calculated? In the image at the top, the baseline is 1980-2015, which is a very recent period. When using a preindustrial baseline, anomalies could be more than 0.6°C higher than when using the 1951-1980 baseline that NASA normally uses.

  2. Surface temperatures or surface air temperatures?

    Above map shows land surface temperatures. As said above, this is different from surface air temperatures over land that show the temperature of the air above the land surface.

    Similarly, sea surface temperatures indicate the temperature of the water at the surface. Sea surface air temperatures, on the other hand, are slightly higher, they are measurements of the air temperature just above the surface of the water.

    NASA typically uses surface air temperatures over land, while using surface water temperatures over oceans. When instead using air temperatures globally, the temperature anomaly could be more than 0.1°C higher.
  3. Missing data

    How are missing data dealt with? To calculate the global mean on maps, NASA uses four zonal regions (90-24ºS, 24-0ºS, 0-24ºN, and 24-90ºN) and fills gaps in a region by the mean over the available data in that region. In datasets, however, missing data are typically ignored. This could make a difference of 0.2°C. Ignoring data for the Arctic alone could make a difference of 0.1°C.  
Depending on how the above three points are dealt with, the temperature in August 2018 may well be more than 3°C above the mean annual global temperature in 1750. The question is whether August 2018 will be warmer than August 2016, which was 2.3°C warmer than 1980-2015.

Anthropogenic Global Warming

Remember the Paris Agreement, when politicians pledged to take efforts to ensure that the temperature would not cross 1.5°C above preindustrial? Why did the Paris Agreement not specify a year for preindustrial? Perhaps the idea was that total anthropogenic global warming should not exceed 1.5°C. In other words, the warming that people had already caused by 1750, plus the warming people caused since 1750, plus the warming that is already baked in for the decades to come. The image below illustrates this idea and also shows that we're well above 1.5°C anthropogenic global warming.

[ click on images to enlarge ]
In the image below, temperatures have also been adjusted to better reflect a preindustrial baseline (1750), showing that temperatures were not higher than 1°C above preindustrial during the entire Holocene, until recently.

In a recent paper, James Hansen et al. conclude that temperatures also weren't more than 1°C above preindustrial during the previous interglacial, the Eemian, which implies that temperatures haven't been more than 1°C above preindustrial for the entire 200,000 years that modern people, i.e. the species homo sapiens, have existed, and that temperatures have only recently rising to levels more than 1°C above preindustrial. Quite likely, to find temperatures as high as today's, one would have to go back some 3 million years.

Fires over North America, August 2018

Fires can significantly influence temperatures in a number of ways. The images below show how fires boosted carbon dioxide, carbon monoxide and sulfur dioxide levels on August 19, 2018. Carbon dioxide and carbon monoxide both raise temperatures. On the other hand, sulfur dioxide lowers temperature by reflecting sunlight back into space.

  Top left: carbon monoxide as high as 51495 ppb 
  Top right: carbon dioxide as high as 836 ppm
  Bottom left: Smoke over North America
  Bottom right: sulfur dioxide as high as 1917.57 µg/m³
The image below illustrates to what extent smoke from fires boosted black carbon in the air over North America on August 23, 2018. Black carbon causes both cooling and warming. Black carbon shades the surface, somewhat cooling the surface of land and water, while it also absorbs heat, thus warming the air above the surface. Furthermore, black carbon causes warming by darkening the surface once it settles down. Studies have calculated that black carbon has a total net global warming effect of more than 1.1 W/m².

Dust and further aerosols

The impact of aerosols such as sulfur dioxide and dust is often overlooked. The image below shows that τ, i.e. light at 550 nm as a measurement of aerosol optical thickness due to dust aerosols, was as high as 4.0641 on June 16, 2018.

[ goats, from Wikipedia ]
Dust is one reason why temperatures didn't cross the 1°C above preindustrial mark during the peak of the recent Milankovitch cycle. A recent study calculates that the global annual mean surface temperature increases by 0.3°C for the mid-Holocene (6 ka), if the dust is completely removed.

Most dust appears to originate from the Sahara Desert, which lost its vegetation during the Holocene due to goats, according to this study, as people removed predators such as lions and tigers. As the Sahara lost its vegetation, the surface became more reflective, while dust further made that temperatures didn't rise as much as they otherwise would have.

Deforestation has caused a lot of carbon dioxide to be added during preindustrial times, and there is also the impact of black carbon aerosols, resulting from biomass and fossil fuel burning, which causes some 1.1W/m² warming today and some 0.2W/m² is coming from preindustrial activities.

In conclusion, temperatures would be a lot lower in the absence of human activities, while total anthropogenic global warming over the past few thousand years is much larger than most people think.

The situation is dire and calls for comprehensive and effective action, as described in the Climate Plan.


• NASA - The Northwest is Running Hot and Dry

• NASA GISS (Goddard Institute for Space Studies) Surface Temperature Analysis (GISTEMP)

• NASA - Just Another Day on Aerosol Earth

• Aerosols

• How much warming have humans caused?

• How much warmer is it now?

• Extinction

• Climate Plan

Friday, August 3, 2018

Peaks Matter

Heat stress

When calculating how much warmer we can expect it to get, climate models typically use linear projections based on temperature averages, such as annual global average temperatures, daily temperatures that are averages between day and night, etc. Sadly, this downplays the danger, as average temperatures are unlikely to kill people. When lives are at stake, peaks matter!

Where are temperatures rising most?

Temperatures are rising most strongly in the Arctic. Above map shows a rise of as much as 5.7°C or 10.26°F in Arctic.

Ocean heat on the move toward Arctic Ocean

The image below shows that the sea surface was 22°C or 71.6°F on August 13, 2018, at 77.958°N, 5.545°E (near Svalbard), i.e. 6.9°C or 12.4°F warmer than 47 days earlier and 16.4°C or 29.5°F warmer than it was during 1981-2011.

Local maximum temperatures can be good indicators for the maximum heat stress that can be expected in the area.

As illustrated by above image, the sea surface near Svalbard was 22°C or 71.6°F at the green circle on August 13, 2018, i.e. 16.4°C or 29.5°F warmer than 1981-2011.

This high sea surface temperature is an indicator of the temperature of the water below the surface, which in turn is an indicator of the amount of ocean heat that is entering the Arctic Ocean from the Atlantic Ocean.

Ocean heat is carried by the Gulf Stream from the North American coast toward the Arctic Ocean, as illustrated by the images below and on the right.

Warming of the Arctic Ocean comes with a number of feedbacks that accelerate this warming, such as albedo changes that take place as the Arctic snow and ice cover declines, and methane that is released from sediments containing methane in the form of hydrates and free gas.

The situation could get worse rapidly. As an example, with a decrease in cooling aerosols, which are concentrated in the Northern Hemisphere, the North Atlantic looks set to absorb more heat. A recent study calculated that the North Atlantic’s share of the uptake could increase from 6% to about 27%.

As another example, a recent study concludes: Existing models currently attribute about 20% of the permafrost carbon feedback this century to methane, with the rest due to carbon dioxide from terrestrial soils. By including thermokarst lakes, methane becomes the dominant driver, responsible for 70% to 80% of permafrost carbon-caused warming this century. Adding thermokarst methane to the models makes the feedback’s effect similar to that of land-use change, which is the second-largest source of manmade warming.

High methane levels warn about seafloor methane releases

The image on the right illustrates the danger, showing high methane levels at Barrow, Alaska, in July 2018.

When making projections of heat stress, it is important to look at all potential warming elements, including albedo changes, changes to jet streams and sea currents, higher levels of methane, high levels of water vapor, etc.

Methane is a potent greenhouse gas, causing huge warming immediately after entering the atmosphere, while this warming will be felt most strongly where the methane was released. Methane can therefore contribute strongly to local temperature peaks.

On August 6, 2018, mean global methane levels were as high as 1896 ppb. On August 8, 2018, they were as high as 1898 ppb.

Importantly, peak levels on the afternoon of August 6, 2018, were as high as 3046 ppb, as illustrated by the image on the right. The likely origin of those high levels is the Arctic Ocean, which should act as a stark warning of things to come.

Further contributors to heat stress

Next to temperature, humidity is of vital importance. A combination of high temperatures and high humidity is devastating.

A recent study shows that the risk of deadly heat waves is significantly increased because of intensive irrigation in specific regions. The study points at a relatively dry but highly fertile region, known as the North China Plain — a region whose role in that country is comparable to that of the Midwest in the U.S. That increased vulnerability to heat arises because the irrigation exposes more water to evaporation, leading to higher humidity in the air than would otherwise be present and exacerbating the physiological stresses of the temperature.

The image below shows a forecast of perceived temperatures in China on August 7, 2018.

The green circle highlights an area that is forecast to score high on the 'Misery Index' and that is centered around a location on the coast of Poyang Lake, which is connected to the Yangtze River. Temperatures there are forecast to be as high as 36.4°C or 97.4°F. At first glance, this may not look very high, but a relative humidity 68% is forecast to make it feel like 54.1°C or 129.3°F. This translates into a wet-bulb temperature of 31.03°C or 87.86°F.

The image on the right shows relative humidity. Also note the cyclones lined up on the Pacific Ocean. Cyclones can increase humidity, making conditions worse.
The high sea surface temperature anomalies that are common in the West Pacific (image right)  contribute to warmer air and stronger cyclones carrying more moisture toward Asia, as discussed in this facebook thread which also features the next image on the right, showing that cyclone Soulik is forecast to cause waves as high as 18.54 m or 60.8 ft near Japan on August 20, 2018.

If humidity kept rising, a temperature of 36.4°C at a relative humidity of 91% would result in a wet-bulb temperature of 35°C. No amount of sweating, even in the shade and in front of strong winds or a fan, can cool the body under such conditions, and it would be lethal in a matter of hours in the absence of air conditioning or cold water.

There are further factors that can contribute to make specific areas virtually uninhabitable. The urban heat effect is such a factor. El Niño is another one. Land-only temperature anomalies are higher than anomalies that are averaged for land and oceans. As temperatures keep rising, heat waves can be expected to intensify, while their duration can be extended due to jet stream blocking.

The situation is dire and calls for comprehensive and effective action as described in the Climate Plan.

Below, Paul Beckwith warns that parts of the world 'will soon be rendered uninhabitable'.

Video: Unrelenting Heat, Humidity Will Soon Make Regions UNINHABITABLE

Paul Beckwith: "How hot can it actually get? What is in store for us? When you combine the heat domes sitting over many countries with high humidity, many areas around the planet will soon reach the deadly 35°C (95°F) 100% humidity (wet bulb temperature) or equivalent situation whereby a perfectly healthy person outside, in a well ventilated area, in the shade will die from the heat in 6 hours."

Video: Most Mammals Endure Heat Waves Better Than Humans

"Most people, like the very young, the elderly, and the rest of us won’t last anywhere as long, at even lower temperatures. I discuss the latest peer-reviewed science on how parts of high-risk regions in the North China Plains, Middle East, and South Asia will soon be rendered uninhabitable by combined heat and humidity."

Video: Uninhabitable Regions with Extreme Heat and Humidity

Also watch this video, in which Guy McPherson talks about the way aerosols currently mask the full wrath of global warming.

Video: Edge of Extinction: Rate Matters

Above video is also incorporated in the video below.

Video: McPherson's Paradox

and for the bigger picture, also watch the video below.

Video: Responding to Abrupt Climate Change with Guy R. McPherson


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

• Feedbacks

• Latent Heat

• How much warming have humans caused?

• The Threat

• Extinction

• Climate Plan

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.

The situation is dire and calls for comprehensive and effective action as described in the Climate Plan.


• Climate Plan

• Wet-bulb temperature

• What is Wet Bulb temperature? By Steven Sherwood

• NOAA wet bulb calculator

• Dry Bulb, Wet Bulb and Dew Point temperatures

• Heat Index

• NOAA Heat Index calculator

• Wind chill

• NOAA Meteorological Conversions and Calculations

• An adaptability limit to climate change due to heat stress - by Steven Sherwood and Matthew Huber

• The Deadly Combination of Heat and Humidity

• Researchers find future temperatures could exceed livable limits

• Intergovernmental Panel of Climate Change (IPCC), 3rd Assessment Report, Working Group I: The Scientific Basis

• A Global Temperature Rise Of More than Ten Degrees Celsius By 2026?

• WMO examines reported record temperature of 54°C in Kuwait, Iraq°c-kuwait

• Extinction