Paleo CO2, paleo plants, and now

Science magazine, 2017 Jan 7, contained a fine short summary by Eric Hand about CO2 over the previous 500 million years. If we could talk about that without any reference to possible effects of CO2 on atmospheric energy balance, it would simplify things.

I have previously described land plants as 'suicidal' and would explain that remark.


Here is Hand's image, with my red additions, for which that author is not responsible. Added those because each time a major evolutionary change occurred in the plant kingdom, CO2 decreased. Plant got better at consuming that gas.Those reductions were followed by rebounds, but since about 220 million years ago, the net effect has been down.

If you were a daisy and time traveled back about 150 million years you'd experience about 1000 ppm CO2. Nice. 'Preindustrial' daisies scrimped along on 270 ppm. Feel their pain. Plants did this to themselves.

Any geologist will tell you this is not the complete story. CO2 is also removed from the atmosphere by silicate mineral reactions. Whenever there was more uplift, or more erosion, or more anything that let those rocks 'see' the atmosphere, CO2 would also decrease. And, as plant roots physically churn up rock bits (and chemically bother them with acids released from roots), there has been some cooperation between geology and biology in this suicidal plan.

Strictly on the basis of land plants and CO2, one might view current increases of that gas as a fine thing. On that I'd say no more.

Last point is rate of change. Two fastest CO2 increases shown above average 0.003 ppm per century. Most plants don't live very long, so they'd not notice the peril. We forgive them (not that we have any choice). A faster rate is already known to you from Antarctic ice cores (420 thousand years, etc.) of 1 ppm per century (each interglacial). During the 19th century CO2 increased 10 ppm. During the 20th century CO2 increased 100 ppm. In the 21st it will be about 200 ppm.

So, while CO2 levels we talk about now are not unusual over geological time, it appears that current rate of increase is very unusual. A long-lived tree, born into (and adapted for) 300 ppm might live to see 600. I suppose that is a very strange thing for plants. Not well researched at all.

We understand that paleo records have low temporal resolution, so they do not exclude the possibility of some centuries in the way back actually increasing 100 ppm. But there would need to have been a mechanism.

 

Biology is not a list of weird words your teachers made you memorize for exams. It is a more fascinating thing with genomes dancing to the music of physics, chemistry and geology.

It is more than I might teach. But with even this little, hoping to undo some damage of crappy schools. Help y'all hear the the music. If climate never changed (it always does) biology is still a hoot.

Gold appeals to me greatly but it is hard to avoid thinking about externalities of cyanide etc. Why Jimbo teaches us this here, I have no idea Actually I have some idea; subsurface flow of 'reduced' water. But that is too darned sciencey for this lot.