ppm

Frequently Asked Questions

Do you really have an enormous CO2 analyser attached to your server sucking in air from all over the globe?

Well... no, not really. But the Earth System Research Laboratory (part of the US National Oceanic and Atmospheric Administration) have a network of stations around the planet that sample CO2 levels. I'm pinching their data. Specifically, I'm pinching the table of monthly mean carbon dioxide globally averaged over marine surface sites, after correction for the average seasonal cycle.

They give data in real time?

Nope. It takes quite a long time for all the stations to send in their samples, for the measurements to be made, and for all the data to be collated and checked for errors. The most recent reported global average is usually a month or two old. In fact, even this is a preliminary figure - some Antarctic stations for example only send back their samples once a year. It might be eighteen months after collection that the last samples are included in the data. Having said that, the most recent reported figures do use data from a fair number of monitoring stations, and subsequent revisions are small.

So how come you're reporting the current concentration?

We have a good idea of the rate of change of carbon dioxide concentrations over time. It's reasonably stable, so the script calculates the daily rate of change averaged over the last five years - currently   parts per million per day - and uses that to estimate the current CO2 concentration.

Do you really believe it's accurate to eight decimal places?

No. Frankly, it's only reported to that precision for visual impact. The reported uncertainty in the global monthly mean concentration data is 0.13ppm. There is a pretty good chance that the first decimal place isn't too far off the truth. But if the script reported it to 1 decimal place it wouldn't be half as mesmerising.

What was that correction for a seasonal cycle that you mentioned?

Glad you asked. Every spring, when the daffodils bloom and the trees are mantled in a fresh robe of new leaves, all the new growth sucks CO2 from the atmosphere, and concentrations drop. In the autumn, as the vegetation dies back, much of the CO2 is released again.You might think that with a global average, the southern hemisphere autumn would cancel the northern hemisphere spring, and vice versa. However, there is more land in the northern hemisphere than the southern, so the upshot is that carbon dioxide levels are lower in the nothern hemisphere summer compared to the northern hemisphere winter. ESRL report the carbon dioxide concentrations both as measured, and with this seasonal cyle removed. I'm using the data that is corrected for the seasonal cycle.

Who cares what the CO2 level is?

Increasing the CO2 content of the atmosphere means that it retains more of the earth's heat. Rising CO2 levels mean that the world is getting warmer. Quite a lot warmer. Go search Google for global warming.

Why did you write it? Haven't you got anything better to do?

I was stuck on an Antarctic Research station for 6 weeks with nothing to do. I was bored. I was giving a talk on global warming. I wanted an up-to-date atmospheric CO2 concentration, and I couldn't find one. It passed a snowy afternoon. OK, I could just have forgotten it and gone out skiing instead. But I'm a geek .

Oh really? I'm a geek too as it happens. Can I have my own CO2 ticker?

Help yourself. It's dead easy to put one on your website, just follow the installation instructions.

I feel a strange urge to crush my car, put some sandals on and hug a tree.

Ha! The subliminal messsages are working!