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

Recent trends in atmospheric methane.

A guest post from Jim

Over the last year, the global increases in methane emissions have begun to raise alarms.

Here's a brief sample:

• Sarah Kaplan's report in the Washington Post, reporting 10 Sept 2024, "Emissions of methane — a powerful greenhouse gas — are rising at the fastest rate in recorded history, scientists said Tuesday, defying global pledges to limit the gas and putting the Earth on a path toward perilous temperature rise."
• The European Space Agency's post, also on 10 Sept 2024, "The Global Methane Budget 2024 paints a troubling picture of the current state of global methane emissions. The new report reveals that human activities are now responsible for at least two-thirds of global methane emissions. This marks a significant increase in human-produced methane sources over the past two decades, with emissions rising by 20%, with the fastest rise occurring over the last five years."
• NOAA's summary of 5 Apr 2024, No sign of greenhouse gases increases slowing in 2023, reports that "Atmospheric methane, less abundant than CO2 but more potent at trapping heat in the atmosphere, rose to an average of 1922.6 parts per billion (ppb). The 2023 methane increase over 2022 was 10.9 ppb, lower than the record growth rates seen in 2020 (15.2 ppb), 2021(18 ppb)  and 2022 (13.2 ppb), but still the 5th highest since renewed methane growth started in 2007. Methane levels in the atmosphere are now more than 160% higher than their pre-industrial level,"

Climate bloggers have begun to notice. For example, here's David Appell at Quark Soup: 

"I haven't followed methane much because I couldn't find a good data source, but now I have, from NASA. And even better source is the Global Carbon Project, which is updated every 7.6 days. 

After that weird lull in the mid-aughts, methane is on the rise again and is the highest it's been in 800,000 years.   

Methane's radiative forcing has increased by about 0.4 W/m^2 since 1979, while CO2's has jumped about 1.6 W/m^2 in the same interval...

It's incredible that the world, despite all the rhetoric and (token) efforts, keeps allowing this to happen. Clearly, I think, these trends will only be taken seriously once some catastrophic effects happen, and by then it will be too late. So human and we can't even help ourselves."

The Global Carbon Project's methane budget links to recent publications:

• " The primary reference ...(pre-print) Global Methane Budget 2000–2020 Here's an excerpt from the abstract: "Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Emissions and atmospheric concentrations of CH4 continue to increase, maintaining CH4 as the second most important human-influenced greenhouse gas in terms of climate forcing after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 for temperature change is related to its shorter atmospheric lifetime, stronger radiative effect, and acceleration in atmospheric growth rate over the past decade, the causes of which are still debated. "
• Additional Analyses for Methane Budget 2024:Human activities now fuel two-thirds of global methane emissions. "Methane is rising faster in relative terms than any major greenhouse gas and is now 2.6-fold higher than in pre-industrial times. Global average methane concentrations reached 1931 parts per billion (ppb) in January of 2024 (Lan et al 2024). Annual increases in methane are also accelerating for reasons that are debated..." 

With these in mind, let's look at recent trends in methane from NOAA's Global Monitoring Laboratory

Here is a graph of global methane (as ppm CO₂ equivalent) since 2000.

We can remove the monthly variations to look at the underlying trend by doing a moving twelve-month average. Most of the variations have been averaged out. Here's the result:

 

A glimpse at the raw data reveals that the annual rate of change of global atmospheric methane has been monotonically positive since 2005. These data are well-approximated by a quadratic polynomial. The error in the quadratic fit to the twelve month moving average of the observed data for atmospheric methane (in ppm CO₂ eq) ranges from -0.140411 ppm to 0.113803 ppm with an rms error 0.0665136 ppm, a percent error less than 0.21%.

This graph shows the raw methane as ppm CO₂ equivalent (in black), its twelve-month moving average (in yellow), and the moving average's best fit quadratic (in blue). 

Removal of the seasonal variation in methane does not eliminate all of the short term departures from the best fit quadratic. The remaining fluctuations appear to have a period of about seven years. It is not clear what is the underlying physical processes responsible for this variation but it appears quite regular.

Seasonal variations, in methane, removed by the moving average, account for a difference of about 0.14 ppm CO₂ eq, less than 0.4% of the annual average. Long-term variations in the moving average methane, compared to the quadratic fit, account for another difference of about 0.067 ppm CO₂ eq, less than 0.2% of the annual average. Seasonal variations account for about 80% of the total variance between the quadratic model and the observed data.

In summary, the increase in methane is well approximated by a quadratic fit to the twelve-month moving average of emissions; we project that methane emissions will rise from 33.08 ppm CO₂ eq in 2005 to about 37.37 ppm CO₂ eq in 2025, an increase of 12.9% over only two decades. 

The International Energy Agency writes,"Methane has a much shorter atmospheric lifetime than CO2 (around 12 years compared with centuries for CO2), but it is a much more potent greenhouse gas, absorbing much more energy while it exists in the atmosphere...The Intergovernmental Panel on Climate Change (IPCC) has indicated a GWP for methane between 84-87 when considering its impact over a 20-year timeframe (GWP20) and between 28-36 when considering its impact over a 100-year timeframe (GWP100). This means that one tonne of methane can considered to be equivalent to 28 to 36 tonnes of CO2 if looking at its impact over 100 years."

Methane emissions are currently increasing annually by a relative rate of about 0.95%, clearly a serious situation.

Current Composition of the Atmosphere, September, 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 previous results.

Here are the updated results; changes are more likely due to month-to-month fluctuations, not long term changes in trends:

Here are recent month to month variations from the moving average and its best fit.The crossing is now estimated to occur early March, 2030, give or take a month.

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

CO2 eq update June, 2024

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

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

Here are the previous results.

Here are the updated results; changes are more likely due to month-to-month fluctuations, not long term changes in trends:

Here are recent month to month variations from the moving average and its best fit.

The crossing is now estimated to occur mid-February, 2030, give or take a month.

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

When will CO2 ... Part V - When will the AGGI cross the 2x Pre-Industrial limit?

In our previous posts, we have examined NOAA's AGGI data for the major non-condensing greenhouse gases and their cumulative radiative forcings; we then reduced monthly variations by using a twelve month moving average. 

Now we use the moving average to extrapolate those forcings to the point where twice the pre-industrial era ceiling is crossed.

The following figure shows, over the time period 2001 to the present and extrapolated to 2030, the AGGI computed from NOAA's monthly data for mole fractions of CO₂, CH₄, and N₂O, with the quadratic fit to forcings from other species; also shown is the twelve-month moving average, and its quadratic fit. The thick red line at the top is the climate ceiling at twice the pre-industrial level of forcings. It appears that these curves cross somewhere near 2030.

The next figure shows the same data for the period since NOAA's last AGGI update, from 2020 to 2030. As above, it shows the same approximate AGGI, the twelve-month moving average, and its quadratic fit, barely distinguishable from the moving average. The thick red line at the top is the climate ceiling at twice the pre-industrial level of forcings. It is clear that these curves cross somewhere near 2030; numerical calculation shows they cross in late November 2029, give or take a month.

No, crossing the 2x pre-industrial level of forcing will not be immediate disaster, just a slow-moving mess, guaranteed to make millions if not hundreds of millions of lives miserable, getting worse as the world's climate moves from its  transient climate response to its eventual pseudo-equilibrium state.

Discussion

When looking for policy solutions, it is not unreasonable to ask what are the effects of other species on our global cumulative radiative forcings. 

We considered each major greenhouse gas aside from CO₂, removed its forcing, and looked back to see when the atmosphere contained gases with that reduced level of forcing. To estimate future conditions, we added that same time gap to the present; this is equivalent to linearizing the relation between elapsed time and the AGGI, so this is not a sophisticated approach, but it is used here for only qualitative comparisons.

The following table summarizes 

• the current total forcing from all greenhouse gases in W-m^-2, the current AGGI, the current CO₂ in equivalent in ppm, the year at which the atmosphere most recently hit that level of equivalent CO₂, and the year when the earth will cross the 2x pre-industrial threshold with that amount of CO₂, 
• the same, were only CO₂, CH₄, and N₂O present at current mole fractions, 
• the same without N₂O , 
• the same without CH₄

Had we to worry about only CO₂, CH₄, and N₂O, the atmosphere would warm like it did a decade ago, moving the date at which we would cross the 2x pre-industrial era level to 2039; by 2030, a decade's grace period will look pretty inviting, but in the long run, it is less significant.

Having to worry about only CO₂ and CH₄ would get us only less than another six years, placing us with an atmosphere like it was in Obama's first year in office and postponing the crossing to 2044.

Getting rid of methane makes a significant difference; that gets us back to 1986, when the Reagan administration was negotiating the initial The Montreal Protocol on Substances That Deplete the Ozone Layer, a time when the AGGI was less than 1, postponing the crossing to 2068. We should be so lucky. 

Policy makers should make note of this: CH₄ is a major problem, and we should be very concerned with future fugitive emissions of methane from warming tundra and the like.

Now, what about clouds?

The Earthshine data suggests that reductions in albedo are adding another 0.5-0.7 W-m^-2 to warming, a total of about 4.1 W-m^-2

(https://www.sciencedirect.com/science/article/pii/S0273117723004660)

Were this the case, then the future looks worse than grim, plunging us into a world warming by 4° C or more.

The recent launch of the EarthCARE satellite and NASA's February launch of PACE are quite timely in this regard.

A thorough understanding of the earth's clouds and aerosols is essential, if we are to make the most prudent and immediate changes in policies to deal with global warming.

Here is a press announcement of the launch: 

 Falcon 9 launches ESA’s EarthCARE mission

  https://spacenews.com/falcon-9-launches-esas-earthcare-mission/ 

 A Falcon 9 successfully launched an Earth science mission for Europe and Japan May 28 as part of the European Space Agency’s ongoing, if temporary, reliance on SpaceX for space access. The Falcon 9 lifted off from Vandenberg Space Force Base in California at 6:20 p.m. Eastern. The payload, the Earth Cloud Aerosol and Radiation Explorer (EarthCARE) spacecraft, separated from the upper stage about 10 minutes after liftoff... 

Spacecraft controllers will spend the weeks and months ahead checking out the spacecraft’s instruments and calibrating them, she said. That will allow the first release of science data from EarthCARE around the end of this year or early next year. EarthCARE is an 800-million-euro ($870 million) ESA-led mission to study clouds and aerosols in the atmosphere. The spacecraft carries four instruments, including a cloud profiling radar provided by the Japanese space agency JAXA at a cost of 8.3 billion yen ($53 million). JAXA dubbed the spacecraft Hakuryu or “White Dragon” because of the spacecraft’s appearance... 

“EarthCARE is there to study the effect of clouds and aerosols on the thermal balance of the Earth,” said Dirk Bernaerts, ESA’s EarthCARE project manager, at a pre-launch briefing May 21. “It’s very important to observe them all together at the same location at the same time. That is what is unique about this spacecraft...”

These satellite missions could not be more vital nor more timely.

Concluding thoughts

Even without the reduction in albedo, our current climate policies are not working. We are adding about 3.5 W-m^-2 to the 240 W-m^-2 we get at the surface from the sun through our atmosphere, an increase of about 1.46% in the earth's energy budget; this increase goes on day after day, and gets worse as greenhouse gas mole fractions in the atmosphere increase.

Suppose an adult - let's call him Gordo - on a 2000 kcal/day diet increases his calorie consumption by 1.46% every day, just 30 kcal a day more, a little less than that in a teaspoon of butter. What would be the consequences? 

That's an extra 29.2 kcal each and every day. At that rate,  poor Gordo will gain more than 3 pounds a year, 2 stone 3 every decade. How many decades of weight gain will it take for Gordo to realize that he has become obese? Three decades of over eating will have made Gordo gain over 90 pounds.

Just like Gordo, we need to implement drastic measures.

Postscript - the relation between the AGGI and CO₂ equivalent

We digitized the CO₂ eq and AGGI data in Figure 4, NOAA, AGGI using the online tool using Plot Digitizer. These historic data were combined with the satellite era data to create this last figure.

This figure shows, in green, the relation beween CO₂ eq in ppm (on the ordinate) and the AGGI (abscissa). Historic data are labeled with the year at which the estimate was made. Satellite era data points are also labeled. The solid blue curve is CO₂ eq = 350 ppm, which was crossed in the early Kennedy administration, in1961 - remember those days? The solid red curve is the CO₂ equivalent at twice the pre-industrial level of radiative forcings, 554.3 ppm. The black spot [OG:Remember Treasure Island?] represents current conditions.

 

One final note: The radiative forcing for CO₂ is a function of the mole fraction of both CO₂ and N₂O. To calculate CO₂ eq for a given amount of forcing, we also use the pre-industrial mole fraction of N₂O, 273.87 ppb.

For more information 

Note: All calculations were performed within Mathematica Home Edition 13.2.1.0. on a MacBook Pro with macOS Sonoma 14.5. A PDF of the original Mathematica output is available upon request to Jim Diamond, jimd at Linfield dot edu.

When will CO2 ... Part IV - The AGGI with an improved fit to monthly data

In our previous posts, we have examined NOAA's AGGI data for the major non-condensing greenhouse gases and their cumulative radiative forcings. 

In this post, we first reduce monthly variations by using a twelve month moving average, and second, use the moving average to extrapolate those forcings to the point where twice the pre-industrial era ceiling is crossed.

The following figure compares the monthly data with that of the moving average over twelve months.

Note that the time series for the twelve-month moving average is shorter than that for the original data by half an year at each end,

It is clear that the twelve-month moving average is nearly linear, and is well-approximated by a quadratic fit.

The error in the quadratic fit to the twelve-month moving average AGGI ranges from -0.0045711 to 0.00380524 with an rms error 0.00203621. 

The following figure shows the original monthly AGGI data for total radiative forcings computed from mole fractions of CO₂, CH₄, and N₂O plus the quadratic estimate for forcings from the other species in the atmosphere, its moving average over twelve months, and the quadratic fit to the twelve-month moving average AGGI. There is not much difference between the latter pair.

So the question remains: When will the AGGI reach the equivalent of 2x pre-industrial levels?

Note: All calculations were performed within Mathematica Home Edition 13.2.1.0. on a MacBook Pro with macOS Sonoma 14.5. A PDF of the original Mathematica output is available upon request to Jim Diamond, jimd at Linfield dot edu.

When will CO2 ...Part III - NOAA's monthly updates to the big 3 greenhouse gases.

NOAA's Earth System Research Laboratories (ERSL) operates the Global Monitoring Laboratory (GML):

ESRL's Global Monitoring Laboratory (GML) of the National Oceanic and Atmospheric Administration (NOAA) conducts research that addresses three major challenges; greenhouse gas and carbon cycle feedbacks, changes in clouds, aerosols, and surface radiation, and recovery of stratospheric ozone.

You can see that this source is essential for addressing the big questions about the atmosphere.

The GML includes the Carbon Cycle Greenhouse Gases (CCGG) research area, whose data products include trends in carbon dioxide, methane, nitrous oxide, and other gases.

The Carbon Cycle Greenhouse Gases (CCGG) research area operates the Global Greenhouse Gas Reference Network, measuring the atmospheric distribution and trends of the three main long-term drivers of climate change, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as carbon monoxide (CO) which is an important indicator of air pollution.

Here is the web page for recent trends.

Each tab under "Trends in CO₂, CH₄, N₂O, SF₆" contains somewhere within it a data section with links to the complete globally averaged records, including globally averaged marine surface monthly mean data (text) or (CSV) files.

These were used to examine monthly trends over the last few decades. In addition, we assumed that forcings due to ALL OTHER species, ozone, other oxides of nitrogen or sulfur, halogenated species, and the rest DID NOT DECREASE. 

The observed trend over the satellite ear in the amounts of forcings from all these species is shown in the next figure. The thick red line at the top is the AGGI corresponding to forcings as if they were due to only CO₂ with a mole fraction twice that of the pre-industrial era.   

Despite notable decreases in CFCs, there has been sufficient addition of species other than CO₂, CH₄, and N₂O so that the radiative forcing from these other species has been approximately constant over the lst decade. The full AGGI update in the next year or two will ceretainly contain precise data, but this assumption will allow us to estimate the full forcings in the atmosphere.

These data, in the years 2001 to 2022, are well approximated by a quadratic fit, as shown in the following figure.

The error in the quadratic fit to the observed data for all other contributions to AGGI ranges from -0.000423613 to 0.000691483 with an rms error 0.000340728.

We will use monthly AGGI data for amounts of warming from CO₂, CH₄, and N₂O plus this quadratic estimate for forcings from the other species in the atmosphere.

The next figure shows the results: monthly forcings from CO₂, CH₄, and N₂O plus the quadratic estimate for forcings from the other species in the atmosphere, and in a thick red line, the level of radiative forcings from twice the pre-industrial mole fraction of  CO₂, 3.74613 W-m^-2

Two features really stand out: first, there is a significant month-to-month variation in the forcings for CO₂ and CH₄, and less so for N₂O; second, the total radiative forcing is quickly approaching the level of radiative forcings from twice the pre-industrial mole fraction of  CO₂, but it is obscured by the month-to-month variations.

We can solve both problems: first reduce monthly variations by using a twelve month moving average, and second, use the moving average to extrapolate those forcings to the point where twice the pre-industrial era ceiling is crossed. 

Note: All calculations were performed within Mathematica Home Edition 13.2.1.0. on a MacBook Pro with macOS Sonoma 14.5. A PDF of the original Mathematica output is available upon request to Jim Diamond, jimd at Linfield dot edu.

When will CO2 ... Part II - NOAA's AGGI

NOAA maintains and updates an inventory of global levels of greenhouse gases, the Annual Greenhouse Gas index (AGGI).

From NOAA:Annual Greenhouse Gas Index (AGGI)

The AGGI is a measure of the direct climate-warming influence of long-lived trace gases in the atmosphere and how that influence has changed since the onset of the industrial revolution. The index was designed to enhance the connection between scientists and society by providing a normalized standard that can be easily understood and followed. The direct warming influence of long-lived greenhouse gases is well understood by scientists and has been reported by NOAA through a range of national and international assessments. Nevertheless, the language of scientists often eludes policy makers, educators, and the general public. This index is designed to help bridge that gap. The AGGI provides a way for this warming influence to be presented as a simple index.

The AGGI is more precisely a measure of the radiative forcings of greenhouse gases in the atmosphere. For simplicity, the 1990 AGGI was set to 1 (2.285 W/m²).

The NOAA Annual Greenhouse Gas Index (AGGI) tracks the increasing amount of heat being added to the atmosphere by human-related greenhouse gas (GHG) emissions. It is based on the highest quality measurements of GHGs in the atmosphere from sites around the world. Its uncertainty is very low.

In a nutshell:

• The AGGI in 2022 was 1.49, which means that we’ve turned up the warming influence from greenhouse gases by 49% since 1990.
• It took ~240 years for the AGGI to go from 0 to 1, i.e., to reach 100%, and 32 years for it to increase by another 49%.
• In terms of CO₂ equivalents, the atmosphere in 2022 contained 523 ppm, of which 417 is CO₂ alone. The rest comes from other gases.
• CO₂ is by far the largest contributor to the AGGI in terms of both amount and rate of increase.
• Note: The IPCC suggests that a constant concentration of CO₂ alone at 550 ppm would lead to an average increase in Earth’s temperature of ~3°C (5.4°F).

Here is how radiative forcings are calculated from atmospheric mole fractions, usually expressed as ppm or ppb. From NOAA: Radiative Forcing Calculations

More precisely, the usual carbon dioxide ceiling used within the Intergovernmental Panel on Climate Change (IPCC) is twice the pre-industrial amounts of greenhouse gases expressed as the equivalent amount of CO₂ in ppm.

Forcings equivalent to that due to doubling of CO₂ over pre-industrial levels total 3.74613 W-m^-2, or an index of 1.63945 relative to 1990. The following figure shows the forcings, expressed as components of the AGGI relative to 1990, of CO₂,  CH₄, N₂O,  and that due to the rest of greenhouse gases, with the climate ceiling shown in red.

The amount of long-term warming after doubling of CO₂ over pre-industrial levels is referred to as equilibrium climate sensitivy (ECS).The amount of warming in the short term is referred to as transient climate response (TCR). These terms should not be confused with each other. It may take a century or more for climate response to reach something close to equilibrium.

It should be noted that the earth is not a closed system thermodynamically. It is open, driven by the sun, so a relatively stable climate should more properly be called a stationary state or pseudo-equilibrium. We will continue to differentiate between transient climate response and the very long term pseudo-equilibrium achieved after many centuries with no other changes.

Here is a recent article from Oak Ridge National Laboratory (ORNL) about new research on estimates of ECS. Scientists combine climate models for more accurate projections

Researchers from institutions including the Department of Energy’s Oak Ridge National Laboratory have created a new methstically analyzing climate models that projects future conditions with more fidelity.

The method provides a way to adjust for models with high temperature sensitivities — a known problem in the community. By assigning different weights to models and combining them, the researchers estimate that the global temperature will increase between 2 and 5 degrees Celsius by the end of the century.

NOAA's Climate Program Office reports Increasing Certainty Of Climate Sensitivity In Models

The response of Earth’s climate to projected increases in the concentrations of energy-trapping atmospheric greenhouse gases (GHGs) is immediately evident in global temperature increases. Because the amount of future warming, or climate sensitivity, is a critical factor affecting climate projections (e.g. precipitation, extremes, sea level, sea ice, etc.) around the world, scientists need to reduce uncertainty in climate model sensitivity estimates.

These model uncertainties largely arise from how clouds, interactions with aerosols, and other processes which may amplify or diminish the impact of increasing GHGs will change in response to warmer conditions and, combined with ocean heat uptake processes and feedbacks, will contribute to climate sensitivity.

The figure is useful.

Climate sensitivity in the latest climate models, measured by examining the output of the sixth Coupled Model Intercomparison Project (CMIP6), is quite high compared to previous multi-model experiments.

Now we can see that the underlying question is this: when will total atmospheric radiative forcings reach 3.74613 W-m^-2, or an AGGI of 1.63945 relative to 1990.

Note: All calculations were performed within Mathematica Home Edition 13.2.1.0. on a MacBook Pro with macOS Sonoma 14.5. A PDF of the original Mathematica output is available upon request to Jim Diamond, jimd at Linfield dot edu.

When will CO2 ... Part I - background

Here are the leading components of the atmosphere: 

N_2, O_2, Ar, and then greenhouse gases H₂O, CO₂, and trace greenhouse gases CH₄, N₂O, O₃ and SO₂, and then smaller amounts of CFCs, HFCs, HCFCs, and the like, and then even smaller amounts of species such as SF₆. If we want to understand global warming, we really need to understand the role of these gases in our atmosphere and how they can affect climate.

Global warming has one underlying cause: man-made emissions of greenhouse gases. Yes, there are some natural processes, such as forest fires and volcanic eruptions that can influence warming, but not to the same extent as anthropogenic sources of greenhouse gases.

Don't let your crazy uncle convince you otherwise.

The greenhouse gases in the atmosphere are those that are transparent to visible light - letting sunlight through to hit the earth's surface - but which absorb infrared (IR) emissions from the earth's surface.

Most of the atmosphere is transparent to IR. Dry air is composed of 99.96% non-greenhouse gases. The leading greenhouse gas in the atmosphere is water vapor, but water vapor in the air has a temperature-dependent upper limit - its equilibrium vapor pressure; increasing water vapor above its equilibrium vapor pressure leads to precipitation of either liquid or solid water, that is, rain or snow, depending on the temperature. 

Consider these aspects of water. Suppose that you took all of the H₂ on the planet and burnt it. The only significant product of H₂ combustion is water vapor, so the vapor pressure of water would increase, and increase, and increase - until it hit the equilibrium vapor pressure, at which point it would rain or snow - a phenomenon very well known in the Pacific Northwest.

If you didn't want to burn H₂, how would you increase the amount of water vapor in the air? Easy - warm up some water. The oceans are a convenient source. Warming the globe's surface waters is a sure-fire [OG - forgive the pun] way to get more H₂O into the atmosphere.

For these reasons, H₂O(g) is regarded as a response to global warming, not a driver. One could argue that condensing water vapor into clouds will increase the albedo of the earth, reducing solar insolation at the earth's surface, and lead to global cooling. While the scientific jury is still out on this question, there is increasing evidence that warming waters lead to reduced cloud cover, not an increase. We will discuss this in the last post in this series.

The leading non-condensing greenhouse gas in the atmosphere is CO₂. It is not a minor species; it is the most significant non-condensing greenhouse gas in our atmosphere. Don't let your crazy uncle convince you otherwise.

Here's NASA:

This absorption and radiation of heat by the atmosphere—the natural greenhouse effect—is beneficial for life on Earth. If there were no greenhouse effect, the Earth’s average surface temperature would be a very chilly -18°C (0°F) instead of the comfortable 15°C (59°F) that it is today.

Some minor species!

From Wikipedia:

As of 2023, by mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

What happens when we have too much carbon dioxide?

From climate.gov:

Scientists say that doubling pre-industrial carbon dioxide levels will likely cause global average surface temperature to rise between 1.5° and 4.5° Celsius (2.7° to 8.1° Fahrenheit) compared to pre-industrial temperatures. (Current concentrations are about 1.4 times pre-industrial levels.) The full process could take hundreds of years—perhaps more than a thousand—to play out. Climate scientists call the full temperature rise from doubled carbon dioxide concentrations the equilibrium climate sensitivity.

To understand how sensitive the climate is to carbon dioxide on time frames of a century or less, scientists also study the transient climate sensitivity. They imagine that carbon dioxide will continue to increase at roughly the rate it has been, and then ask how much warming would be realized around the time when the concentration has doubled the preindustrial value. On this shorter time scale, it’s likely the planet will warm between 1° and 2.5°C (2°-4.5°F).

That is the essence of the problem: How soon will the increase in greenhouse gases make the planet too hot?

Note: All calculations were performed within Mathematica Home Edition 13.2.1.0. on a MacBook Pro with macOS Sonoma 14.5. A PDF of the original Mathematica output is available upon request to Jim Diamond, jimd at Linfield dot edu.

Changes in Earth's Albedo

 It appears that our cloud cover is becoming less reflective. Here's the abstract of a recent study of earthshine. From the abstract: 'Similarly, earthshine data show a steady decline during two decades of about 0.7 W/m2 (OG: my emphasis) which is in line with the decline of 0.5 W/m2 that would be observed from the Moon.'

Jie Wu, Enric Pallé, Huadong Guo, Yixing Ding,

Long-term trends in albedo as seen from a lunar observatory,

Advances in Space Research,

Volume 72, Issue 6,

2023,

Pages 2109-2117,

ISSN 0273-1177,

https://doi.org/10.1016/j.asr.2023.06.028.

(https://www.sciencedirect.com/science/article/pii/S0273117723004660)

Abstract: The Earth’s albedo is the fraction of short-wave solar radiation that is reflected back to space, and is key to understand the observed trends in climate change. Although there have been many observational approaches to estimate the Earth’s albedo, different methods have their own drawbacks, for example, artificial satellites have a finite life time, and are operating in a hard environment that could quickly degrade the detectors. The Moon, the only natural satellite of Earth, offers an additional platform for monitoring the Earth’s albedo. In this paper, we calculate the global TOA (top-of-atmosphere) albedo that would be observed by a theoretical observatory on the Moon, and compare it with long-term trends derived from CERES (Clouds and the Earth’s Radiant Energy System, 2000–2020) and earthshine data (1999–2017). We find that the global hourly mean albedo observed in the direction of the Moon is more variable because of the orbital movement of the Moon. However, the regional and long-term global mean albedo anomalies that would be observed by CERES and has a good general agreement by a lunar observer over 20 years the data spans. Similarly, earthshine data show a steady decline during two decades of about 0.7 W/m2 which is in line with the decline of 0.5 W/m2 that would be observed from the Moon. Besides, to compare the regional changes of albedo with CERES, the spatially-resolved decadal anomalies in the albedo are also calculated for analysis. We find that a lunar-based observatory would be capable of detecting similar changes seen from CERES. Thus, it is a a practical option to monitor the long-term trends in albedo from the point of view of capturing the variability in the TOA fluxes of the Earth’s atmosphere.

Keywords: Albedo; Lunar observatory; CERES; Earthshine

Jim sees the aurora

 Our friend Jim in New Hampshire has seen the aurora from his home near Mount Chocorua

three times in the last fifteen months. Here's one of his photos.

Jim added details:

November 13, 2023 at 02:57 UTC. 

ISO 4000, 28mm, f/1.8, 8”

Canon EOS 5D Mark III, Canon EF28mm USM lens