The Antarctic stratospheric ozone hole in 2024

by OnymousGuy

Abstract

The data says 2024 was pretty average, and "far from being fully healed", but NASA's press office says "relatively small". So which is it? "Relatively small", or "far from being fully healed"?

Background

We are approaching the end of season for this year's Antarctic stratospheric ozone hole, as the increasing springtime sunlight stimulates the Chapman cycle to produce more ozone. 

NASA's ozone watch documents the status of the Antarctic stratospheric ozone hole, with updates about every week or so, but less frequently at the end of the season. Certain parameters are tracked:

The data for the ozone hole area, the minimum ozone, and the minimum stratospheric temperature are available. Also available is a table of values showing the maximum ozone hole area and the minimum ozone values for each year...

The graphs ... show the progress of the ozone hole for 2024. The gray shading indicates the highest and lowest values measured since 1979. The red numbers are the maximum or minimum values. The stratospheric temperature and the amount of sunlight reaching the south polar region control the depth and size of the Antarctic ozone hole. The dashed line in the minimum temperature plot indicates the temperature below which Type I (NAT) PSCs can form. 

Ozone concentrations are reported in Dobson units.

The Dobson Unit (DU) is the unit of measure for total ozone. If you were to take all the ozone in a column of air stretching from the surface of the earth to space, and bring all that ozone to standard temperature (0 °Celsius) and pressure (1013.25 millibars, or one atmosphere, or “atm”), the column would be about 0.3 centimeters thick. Thus, the total ozone would be 0.3 atm-cm. To make the units easier to work with, the “Dobson Unit” is defined to be 0.001 atm-cm. Our 0.3 atm-cm would be 300 DU. 

Here are some recent images.

• ozone hole area, minimum ozone, minimum stratospheric temperature,

• annual maximum ozone hole area, annual minimum ozone.

Here is a recent false color image of the ozone hole. 

Discussion

From these figures, I would say that the 2024 ozone hole has been pretty close to its average over the satellite era. So I was a bit surprised to read this puffery from NASA:

Healing continues in the atmosphere over the Antarctic: a hole that opens annually in the ozone layer over Earth's southern pole was relatively small in 2024 compared to other years. 

During the peak of the ozone depletion season from Sept. 7 through Oct. 13, the 2024 area of the ozone hole ranked the seventh smallest since recovery began in 1992, when the Montreal Protocol, a landmark international agreement to phase out ozone-depleting chemicals, began to take effect...

The improvement is due to a combination of continuing declines in harmful chlorofluorocarbon (CFC) chemicals, along with an unexpected infusion of ozone carried by air currents from north of the Antarctic, scientists said. 

A little bit of realism creeps into the blurb from NASA, lower down in the press release.

In previous years, NASA and NOAA have reported the ozone hole ranking using a time frame dating back to 1979, when scientists began tracking Antarctic ozone levels with satellite data. Using that longer record, this year's hole ranked 20th smallest in area across the 45 years of observations.

IMO, 20th out of 45 sounds pretty average. One of the GML scientists spills the beans:

"For 2024, we can see that the ozone hole's severity is below average compared to other years in the past three decades, but the ozone layer is still far from being fully healed," said Stephen Montzka, senior scientist of the NOAA Global Monitoring Laboratory.

So which is it? "Relatively small", or "far from being fully healed"?

Ozone Depleting Substances

The ozone hole, of course, depends on the concentration of stratospheric chlorine and bromine; sources of atomic Cl and Br in the stratosphere are called ozone depleting substances. The Trump administration excised EPA information about ozone depletion and the like, so one must look to the European Union for such things.

A compound that contributes to stratospheric ozone depletion. Ozone-depleting substances (ODS) include CFCs, HCFCs, halons, methyl bromide, carbon tetrachloride, and methyl chloroform. ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere. When they break down, they release chlorine or bromine atoms, which then deplete ozone.

These species have one thing in common: they contain halogens, specifically chlorine or bromine. Each halogenated compound is associated with an ozone-depleting potential (ODP), a direct measure of its ability to destroy ozone. More from the EU:

The ozone-depleting potential (ODP) of a substance refers to the relative amount of ozone depletion caused by it. It is the ratio of the impact on ozone of the emission of a chemical substance to the impact of a similar emission by mass of CFC-11. The quantity in metric tonnes of a particular controlled substance is multiplied by its ODP to give its overall potential to deplete the ozone layer. For instance, 1 metric tonne of CFC-11 corresponds to 1 ODP tonnes (as its ODP is equal to 1), whilst for bromotrifluoromethane or halon 1301 (with an ODP = 10), 1 metric tonne corresponds to 10 ODP tonnes. The ODPs of controlled and new substances are listed in Annexes I and II of the Ozone Regulation (Regulation (EC) No 1005/2009). Some new substances have a range, rather than a single ODP value. In this online data viewer, the highest value of the ODP value range is used.

What are the current levels of atmospheric chlorine? NOAA's Global Monitoring Laboratory reports this trend.

It seems that the most that one could say, based on the data, is that mid-latitude amounts of ozone-depleting substances have dropped below half of their pre-Montreal Protocol maximum. Yes, the world is still on track to see Antarctic  mounts of ozone-depleting substances have dropped below half of their pre-protocol maxima by 2076 or so, provided that we remain vigilant in observing the protocols and their amendments. HCFCs are the issue.

And then NOAA scientists weigh in on the minimum.

NOAA scientists also release instrumented weather balloons from the South Pole Baseline Atmospheric Observatory to observe ozone concentrations directly overhead in a measurement called Dobson Units. The 2024 concentration reached its lowest value of 109 Dobson Units on October 5. The lowest value ever recorded over the South Pole was 92 Dobson Units in October 2006.

NASA and NOAA satellite observations of ozone concentrations cover the entire ozone hole, which can produce a slightly smaller value for the lowest Dobson Unit measurement.

"That is well below the 225 Dobson Units that was typical of the ozone cover above the Antarctic in 1979," said NOAA research chemist Bryan Johnson. "So, there's still a long way to go before atmospheric ozone is back to the levels before the advent of widespread CFC pollution." 

There you have, at the very end of the puff piece: "There's still a long way to go before atmospheric ozone is back to the levels before the advent of widespread CFC pollution."

Putting current radiative forcing in context

Guest post by Jim

Abstract

Current radiative forcing from all greenhouse gases, omitting aerosols from nonmetal oxides and the like, is now just under 3.5 W/m², with an Annual Greenhouse Gas Index of about 1.52. This represents approximately 1.5% of average surface insolation.  Unlike solar energy, which rises and falls with the sun, this infrared energy captured from the earth itself accumulates second by second, day and night.

How significant is this? Consider this analogy. A typical adult on a 2000 kcal/day diet ingesting daily 1.5% calories in excess will gain 31 pounds per decade, with profound consequences. Now we have been burning fossil fuels at the same high rate as our over-eater for more than two decades. How can we possibly imagine that the consequences for the planet will be less severe?

Background

My most recent re-analysis of NOAA's greenhouse gas data stated that the current Annual Greenhouse Gas Index (AGGI) stood at 1.5177, on the scale where the 1990 AGGI is set to one.

NOAA's data from 1990 reported that total forcing was 2.301 W/m², so an AGGI of 1.5177 corresponds to radiative forcing of 3.492 W/m². This is the amount of energy emitted by the earth (which glows in the infrared) and captured by greenhouse gases in the atmosphere over each square meter of the earth's surface, each second. How does this compare to the energy from the sun?

The accompanying figure is from Total Solar Irradiance CDR, at the National Centers for Environmental Information, part of NOAA. It shows Total Solar Irradiance (TSI) at the top of the atmosphere, scaled to a uniform distance from the sun.

"The Total Solar Irradiance (TSI) Climate Data Record (CDR) measures the spectrally integrated energy input to the top of the Earth's atmosphere at a base mean distance from the Sun (i.e., one Astronomical Unit)."

There are a couple of things worth noting. First, TSI over the satellite era (1979-present) is almost constant, roughly 1362 W/m², clearly negating the denialisti claims that "It's the sun!". Second, historic reconstructions of TSI over the last four centuries show that variations in TSI average about 0.5 W/m², so an increase in radiative forcing of just 1W/m² is larger than most variations in the TSI signal. An increase of 3.5 W/m² is far larger than the usual variation.

Since the earth is nearly a sphere of radius R, its surface area, approximately 4πR² , is about four times its circular cross-section, about πR². So insolation - sunlight energy falling on each unit of area - over the entire globe is about one fourth that directly under the sun, (1362/4) W/m² . This implies that the average global insolation at the top of the atmosphere is about 340.5 W/m². At the surface, this is further reduced by the albedo (reflectivity) of the earth.

The American Meteorological Society sums up the current estimates of planetary albedo:

On the average, the earth reflects 31 units of solar radiation back to the space for every 100 units received (thus, the total earth albedo is 0.31). The cloud albedo accounts for 23 units of the 31. For individual clouds, local albedo may be in excess of 0.7.

So only 69% of that 340.5 W/m², about 235 W/m², hits the earth's surface. The radiative forcing from all greenhouse gases, except the short-lived species such as ozone, SOx, or NOx, is 3.492 W/m², about 1.486% of average surface insolation. Unlike solar energy, this  infrared energy captured from the earth itself accumulates second by second, day and night.

Comparison with diet

To see what impacts this energy has on the planet, let's look at the effects of over-eating on a typical adult who maintains a healthy weight with a 2000 kcal/day diet. That same percent, 1.486%, of their daily calorie intake is 29.7 kcal/day, almost the same as the energy content of 4 g of butter, a scant teaspoon. As we all come to know sooner or later, excess calories are stored in the body as fat, roughly 3500 kcal per pound of fat. This overeating will lead to weight gain, roughly one pound every 118 days, about 3.1 pounds each year, year after year. 

A decade of this overeating leads to a gain in weight of about 31 pounds. This will make that adult at least overweight, if not obese.  The CDC states

Obesity in children and adults increases the risk for the following health conditions:

• High blood pressure and high cholesterol which are risk factors for heart disease.
• Type 2 diabetes.
• Breathing problems, such as asthma and sleep apnea.
• Joint problems such as osteoarthritis and musculoskeletal discomfort.
• Gallstones and gallbladder disease.

Two decades will make them class III obese (formerly known as morbidly obese), if not worse. The Cleveland Clinic advises

"If left untreated, class III obesity may shorten life expectancy up to 14 years. In addition to contributing to potentially serious health problems, class III obesity is associated with reduced economic and social opportunities and reduced quality of life."

As stated in the abstract, we have been burning fossil fuels at the same high rate as our over-eater for more than two decades. How can we possibly imagine that the consequences for the planet will be less severe?

Current Composition of the Atmosphere, November, 2024

Guest post by Jim

NOAA has once again released its monthly updates to CO₂, CH₄, and N₂O. See the data section for each gas. 

https://gml.noaa.gov/ccgg/

Here are the updated results. Little has changed. By 2030 the atmosphere will have such a high concentration of greenhouse gases that the effective radiative forcing will be  twice that of the pre-industrial era. 

The 2x crossing is now estimated to occur 1 April, 2030 (no joke!), give or take a month; changes in this estimate over the last year are more likely due to month-to-month fluctuations, not long term changes in trends.

Here is the combination of historic data, satellite era data, and the most recent updates from NOAA:

 

What could possibly go wrong?

 Source:https://www.dailykos.com/stories/2024/11/11/2284411/-Cartoon-Over-the-cliff