## 12 January 2012

### Parts per million

One of the sillier arguments against climate change, especially human-affected climate change, is to claim that since CO2 is a trace gas, it can't have any significant effect.  It's now about 395 parts per million in the atmosphere.

It happens that I'm taking some medicine at the moment.  100 mg of one, and 10 mg of another.  To make the math easy, let's say I weigh 100 kg.  mg is milligram, so there are 1000 of them per gram.  1000 grams is 1 kg.

That first medication represents 1 part per million.  The second is a mere 0.1 parts per million.  The body is a complex system.  Small amounts of things can be very important.  Climate is also a complex system.

Let's continue a little in this vein.  Daily nutrition requirements, which I'll take from http://en.wikipedia.org/wiki/Reference_Daily_Intake , include:
• 1000 mg Calcium --> 10 ppm
• 1000 mg Phosphorous --> 10 ppm
• 60 mg Vitamin C --> 0.6 ppm
• 15 mg Zinc --> 0.15 ppm
• 2 mg Manganese --> 0.02 ppm
• 80 micrograms Vitamin K --> 0.008 ppm
• 6 micrograms Vitamin B-12 --> 0.0006 ppm
If you'd like to avoid scurvy, rickets, pellagra, and a host of other illnesses, you have to treat concentrations far, far lower than 400 ppm as being important.

amoeba said...

Unfortunately, I suspect those who make such mind-numbingly stupid claims about 'CO2 being a trace gas - therefore...' are more than likely immune to rational discussion.

Likewise mosquitoes are tiny compared with humans, but just try trying to sleep with one, especially in an area where mosquitoes are known to carry malaria. Malaria is of course hardly an insignificant disease, despite being the result of a blood-born infection caused by a parasite that is tiny even when compared with a mosquito.

J.Kiesewetter said...

Nice comparison, but wrong. 400 ppm CO2 is not the daily intake. So you should compare the amount of total Ca to your bodymass, and not only the amount you eat today. Or compare the amount of daily intake with your total amount of food today. (This last calculation will also result in ppm- numbers, so in the end: indeed a few ppm can have impact!)

Codeblue said...

I've found the dug-in deniers tend to say, for example, that the medicine analogy is biological so it doesn't apply (hur dur), so I've started playing the ball in their court. One way to approach the "it's too dilute" canard is with an example from the atmosphere - the ozone layer.

Ozone in the stratosphere ranges around, say, 3-9ppm. In fact, if you brought the entire ozone layer to the surface it would be only several millimeters thick. And yet, this "dilute" layer absorbs almost all of the UV-B, a good fraction of UV-A, and essentially all UV-C, the really high-frequency, deadly UV radiation.

This should give them some food for thought and at least get them to confront the talking point. If they double-down and start denying the electromagnetic properties of ozone, well, you know to start walking away and stop wasting time.

jyyh said...

if the sun shone all night how long it would take the plants to use an atmopheric ppm of CO2?

Anonymous said...

A rough calculation indicates that 1 ppmv water droplets (radius 10 microns) is enough to create a dense 'Tule' fog, like we get here in California (visibilty of several meters). Now that's something you can see!

pianoguy said...

It may also be worth noting that all the carbon-dioxide-breathing plants on the earth somehow manage to live on such low concentrations of CO2.