Include "CO2 equivalents" and "global warming potential"

[l-emele]

Description of the issue

We already included the concepts emission, greenhouse gas emission, carbon dioxide and so on. In this context we need also CO2 equivalents and global warming potential.

Ideas of solution

If you already have ideas for the solution describe them here

Workflow checklist

• I discussed the issue with someone else than me before working on a solution
• I already read the latest version of the workflow for this repository
• The goal of this ontology is clear to me

I am aware that

• every entry in the ontology should have a definition
• classes should arise from concepts rather than from words

[han-f]

Could we start from this thought: The CO2 equivalent is an indicator which shows how strongly a certain greenhouse gas acts in comparison to carbon dioxide (CO2) ?

[l-emele]

Good start. What about metric instead of indicator? https://en.wiktionary.org/wiki/metric#Noun

I like the word metric as it is etymologically related to measurement.

[l-emele]

Actually, Wikipedia has a good definition: Carbon dioxide equivalency is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO2 that would have the same global warming potential (GWP), when measured over a specified timescale (typically 100 years).

Do we all agree that CO2 equivalent is a quantity?

[l-emele]

The IPCC defines/describes CO2 equivalents as:

The amount of carbon dioxide (CO2) emission that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of a greenhouse gas (GHG) or a mixture of GHGs. There are a number of ways to compute such equivalent emissions and choose appropriate time horizons. Most typically, the CO2-equivalent emission is obtained by multiplying the emission of a GHG by its global warming potential (GWP) for a 100-year time horizon.

(Glossary of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories)

[stap-m]

The concept of CO2 equivalent could maybe also be seen as quality: it is a specific property a greenhouse gas inherits, like its mass.

[l-emele]

Isn't the quality of the gas the global warming potential? CO2 equivalents is something that is calculated using / applying the GWP. Additionally, CO2 equivalents can be given not only for a single gas but also for a mix of gases.

In our conversion paper I have the example of 100 Mt CO2, 0.5 Mt CH4 and 0.2 Mt N2O that can be expressed as 167 Mt CO2 equivalents.

[stap-m]

Ok, then GWP would be the quality/property of the substance. CO2 equivalent is rather a mathematical concept, i.e. a factor, to make the GWP of different substances comparable?

[l-emele]

Ok, then GWP would be the quality/property of the substance.

Isn't a quantity? You can e.g. methane has a GWP of 25 (kg/kg). We already have a the (currently undefined and unused) property has_globalwarmingpotential. But we might do it differently. We could delete has_globalwarmingpotential and define instead a class global warming potential. Then we could link with the global warming potential with a has quantity value property (or something similar) to the class greenhouse gas. Then all greenhouse gases would inherit this relation.

CO2 equivalent is rather a mathematical concept, i.e. a factor, to make the GWP of different substances comparable?

Yes, exactly.

[stap-m]

I like the idea of replacing has_globalwarmingpotential and I would like to extend your proposal @l-emele:
One cannot "move" GWP from one substance to another, it is specifically dependent. But a quantity value is a generically dependent continuant. Therefore I still suggest to classify GWP as quality.
But the GWP is measured in CO2 equivalents and the corresponing quantity value would be CO2 equivalent:
A greenhouse gas has quality global warming potential which has quantity value CO2 equivalent for a certain period.
I am somehow still struggeling with understanding the usage of the quantity value class... Does this make sense from an ontological point of view ❔ @OpenEnergyPlatform/oeo-general-expert-formal-ontology

[l-emele]

Shouldn't then all quantity values be specifically dependent? We currently have the quantity values declared net capacity, nameplate capacity, power rating and storage capacity. They are in the same way dependent on objects (here power plants or energy storages) as GWPs are dependent on greenhouse gases.

In my understanding both GWP and CO2 equivalent are quantity values, but with different dimensions. GWP is a dimensionless quantity, CO2 equivalent has the dimension of mass.

[jannahastings]

But the GWP is measured in CO2 equivalents and the corresponing quantity value would be CO2 equivalent:
A greenhouse gas has quality global warming potential which has quantity value CO2 equivalent for a certain period.

On my understanding, quantity values are the outcomes of measurements or calculations and they are about some or other physical entity, which might be a quality. For global warming potential, there is clearly some sort of quality or attribute that is transformed into a quantity value in some (I assume standardised) way. But the way that 'global warming potential' is used, it is usually used together with a number right?

I found on the internet statements of two forms:

1. That (e.g.) 1kg methane has global warming potential 25kg CO2e
2. That nitrous oxide has a GWP 265–298 times that of CO2.

To me, my reading of these assertions is is that global warming potential here is a quantity value and CO2 equivalent is its unit. In (1) this is explicit, while in (2) it is implicit.

[l-emele]

I am currently trying spelling out these concepts and the methological details and differences between them in the conversion paper we are writing for the SzenarienDB project. This paper is due end of June. Maybe we wait with implementing this issue until the paper is finalised. At least from my site is now urgency for this issue, so we have time to find a solution all can agree.

[stap-m]

I think the way UO is used is something along these lines:
There are always four separate things: (1) the entity in reality (some sort of specifically dependent continuant, perhaps, or a process) (2) a number (3) a unit. The entity then has_value some (4) quantity value entity, that has_unit the unit. (And may have a specified value with a data property). The relationship between the quantity value entity (4) and the entity in the world (1) is is_about.

#434 (comment) @jannahastings commented here on the use of the UO (unit ontology). This might be helpful here, too.

[han-f]

The paper @l-emele mentioned has now been published: https://doi.org/10.5281/zenodo.3949691
GWPs are discussed in Section 4.

[sfluegel05]

We (@l-emele and me) came to the following conclusion:

• for global warming potential we can use the already existing relation has global warming potential which relates greenhouse gasses to quantity values
  We want to add the following classes:
• emission value: An emission value is a process attribute that quantifies the output of an emission process. It can be calculated using the emission factor of that emission process.
• greenhouse gas emission value: A greenhouse gas emission value is an emission value that quantifies the output of a greenhouse gas emission process.
• carbon dioxide equivalent quantity (alternative term: CO2 equivalent quantity): A carbon dioxide equivalent quantity is a greenhouse gas emission value that quantifies the combined effect of all emitted greenhouse gases by giving an equivalent amount of CO2 which would have the same effect on the climate.

@stap-m Do you agree with this?

[stap-m]

I do. Nice work.

If do not define GWP as an own class, we need to specify def of has global warming potential.
Which currently is: A relation between a portion of matter and the global warming potential it has.

We could use the proposal by @l-emele, see above, and just add it:
A relation between a portion of matter and the global warming potential it has. The global warming potential is a ratio that measures the the time-integrated radiative forcing due to a pulse emission of a given component, relative to a pulse emission of an equal mass of CO2.

[l-emele]

Hm, maybe in the end we were now too quick with the implementation.

We could use the proposal by @l-emele, see above, and just add it:
A relation between a portion of matter and the global warming potential it has. The global warming potential is a ratio that measures the the time-integrated radiative forcing due to a pulse emission of a given component, relative to a pulse emission of an equal mass of CO2.

This solution now mixes a relation and a definition of a class which I am a bit unhappy with. Further, we have this relation but it is still not applied, not even for the most obvious class greenhouse gas.

[stap-m]

@l-emele would you prefer an additional class global warming potential? We have to define it anywhere...
@jannahastings do you know a good way how to solve this?

I agree that we should add the relation to greenhouse gas and all subclasses should inherit it.

[l-emele]

@l-emele would you prefer an additional class global warming potential? We have to define it anywhere...

Yes, the addition of a class global warming potential was the purpose of this issue anyway. I still like the definition above:
Global warming potential is a ratio that measures the the time-integrated radiative forcing due to a pulse emission of a given component, relative to a pulse emission of an equal mass of CO2.
Even subclasses are possible as there are different kinds of global warming potentials differentiated by different integration time intervalls (typically 20, 100 and 500 years).

To me, 'greenhouse gas' has_global_warming_potential some 'global warming potential' makes totally sense.

Shall we re-open this issue?

[stap-m]

I agree. The definition suggests that global warming potential is a quantity value, which seems fine to me.

[stap-m]

Even subclasses are possible as there are different kinds of global warming potentials differentiated by different integration time intervalls (typically 20, 100 and 500 years).

Subclasses or individuals?

[l-emele]

I agree. The definition suggests that global warming potential is a quantity value, which seems fine to me.

Yes, right, it is a quantity value with the unit ratio, so it should be: Global warming potential is a quantity value that measures the the time-integrated radiative forcing due to a pulse emission of a given component, relative to a pulse emission of an equal mass of CO2.
It additionally should get the relation: has_unit some ratio.

Even subclasses are possible as there are different kinds of global warming potentials differentiated by different integration time intervalls (typically 20, 100 and 500 years).

Subclasses or individuals?

These would be subclasses. The individuals would be the GWPs for specific gases, but not the GWPs in general.

[l-emele]

Can I interpret your thumbs up that we have a consensus and I can implement this class?

[stap-m]

Yep, from my side.

[l-emele]

Okay, I started implementing.

While doing this, I discovered that the relation has global warming potential has the domain 'greenhouse effect disposition' and the range 'quantity value' and ('has unit' some ratio). Is does this still makes sense? The definition is: A relation between a portion of matter and the global warming potential it has. Following this definition, shouldn't be the domain be portion of matter and the relation be global warming potential.

I would argue further that the definition should be updated to A relation between a greenhouse gas and the global warming potential it has. as A greenhouse gas is a portion of matter that has the disposition to contribute to the greenhouse effect. which has the axiom 'portion of matter' and ('has disposition' some 'greenhouse effect disposition').

@sfluegel05 or @jannahastings : What do you think?

[jannahastings]

I agree.