Fishnut wrote: Tue Dec 16, 2025 12:57 am
6.5 × 10
18 mol is completely meaningless to me and I'd like it to mean something.
It's not exactly straightforward understanding what 7.8 × 10
13 t/Myr means either. Well, we can cancel out the million in Myr and get it to 78,000,000 t/yr or 78 Mt/yr, which is at least an easier number to look at. But we still may not really have a vision of what that means, without something to compare it to. So I thought to compare it with the rate of global human carbon emission
The present rate of human carbon emission (excluding secondary or indirect emissions like the effects of land use) is about 50 GtCO2eq/yr, or 50,000 MtCO2eq/yr. But that is tonnes of CO2 equivalent, not tonnes of carbon, which is what Chris calculated for you. So now we understand the precision of the scientist in quoting carbon burial in in mol/yr, that it avoids any ambiguity that might come from wondering whether an amount in tonnes is tonnes of carbon, or tonnes of CO2, or whatever. Since CO2 is 44g/mol, to make that number Chris calculated comparable to the usual emission numbers in tCO2eq, we need to multiply by 44/12 (or Chris could have used 44 instead of 12 in the first place). So the number becomes (2sf) 290 MtCO2eq/yr.
So now we have a context to compare this number with. So we can see that the present rate of human carbon emission (excluding indirect emissions) is about 170 times (2sf) greater than the rate of carbon burial in the Carboniferous/Permian, when it was at its highest rate. In other words, it is ridiculous expecting natural carbon burial to do very much about current human carbon emissions, except over a time-scale of numerous centuries or millennia.
I too generally get upset over reports that put things in units we can't easily grasp. For example, we'll see some report of a wildfire in N America, and they'll give its area in acres. A very large wildfire might be, say, 200,000 acres. Of course the N Americans report it like that, and the British journalists lazily don't convert it to something sensible. Or maybe they are rationally realising that they are incompetent to convert it accurately - misconversions are often seen. Very common are conversions with spurious accuracy (eg about a mile is translated to about 1.609km). But I have absolutely no vision of what 200,000 acres might look like, at least not without first converting it to something else. Maybe other people have an intuitive grasp of what large numbers of acres are, if they are used to seeing areas in such numbers. Fortunately I'm quite good at changing units, and do it in my head a lot. A number I keep in my head is 1 hectare is about 2.5 acres. Hectares are nice because they are 100m by 100m, and so there is 100 ha to the sq km. So this wildfire is 80,000 ha which is 800 sq km. And I can think about what 800 sq km is, it's an area of a bit less than 30 km by 30 km. And a Landranger OS map covers 40 km by 40 km. So I can look at a Landranger map and imagine an area that size on fire.
Of course this explains why large land areas are, in Britain, frequently given in customary units of the Wales and the Greater London. This wildfire is about 0.5 Greater Londons. Americans similarly often use state areas to compare large land areas, and again this is a unit often transmitted to us, which journalists don't convert, as if many British people might know what is a Connecticut or a South Carolina. The scale is a bit coarse at the lower size end, so I wouldn't expect to see this wildfire so described. But if they did, they might say it is about 5 DCs or 0.2 Rhode Islands. Of course, I had to look up all of these "customary" units for the conversion.