Carbon dioxide, blood pH and no time to evolve
Posted by Dave Bath on 2008-08-09
Even if climate skeptics are correct in their denial of anthropogenic global warming, they cannot deny that atmospheric CO2 concentrations have increased dramatically since the industrial revolution, and that this increase is increasing.
Some of these skeptics argue that even increasing CO2 is not such a big problem, as much of this (50% of current CO2 released into the atmosphere) is dissolved into the ocean.
It seems that oceanographers woke up some time back that increasing CO2 is turning the oceans into not salt-water, but salty carbonic acid, and became worried about the metabolic effects on ocean life, and consequently to the food chain.
But what happens when the salty water (with some floating cells) in our own bodies becomes carbonic acid? What happens to us when our blood is more acidic than at any time since Homo Sapiens evolved?
Even if our species arose at a "high point" of 0.028%, this was at a time when CO2 was gradually falling. Depending how you crunch the numbers, there’s been either a 50% or 100% jump in CO2 over a mere 0.2% of the lifetime of our species. But we have no real idea of how this has affected our biochemistry, as no-one was doing the biochemical and physiological studies a couple of hundred years ago to give us the baseline.
Decreased pH (increased H+) concentrations are unavoidable with increased CO2, and the harmful effects are well-documented in any book on space or submarine physiology. Such texts, however, are looking at the relatively short term effects of CO2 levels approaching 1%, and don’t address the long-term and more subtle effects of the relatively rapid increase in CO2 since the Industrial Revolution (after millenia of between .020% to 0.028%, we are now around 0.039% and climbing.)
Our knowledge of CO2 overdose effects from space and diving physiology is analogous to knowing what happens to people in a room full of dense smoke, but not what happens with a lifetime of cigarette smoking, or of smoking when pregnant.
While I’m pretty sure that CO2 rises and therefore blood acidification must have some metabolic downside without a chance for evolutionary adaptation, I can’t go so far as to blame sudden jumps in CO2 to changes in non-infectious disease patterns. However, given CO2 is the major determinant of breathing rates, (and dissociation of O2 from haemoglobin), then I can’t help thinking that we should look for subtle epidemiological effects, including rising respiratory disease that is generally blamed on particulates.
Even if wars for land ravaged by rising oceans don’t happen, even without changes to distribution of pathogens, even without water shortages, in short, even without climate change, there may been an even nastier surprise awaiting unless we control carbon dioxide emissions.
- Biological Impact of Elevated Ocean CO2 Concentrations: Lessons from Animal Physiology and Earth History
Journal of Oceanography, Vol. 60, pp. 705 to 718, 2004.
- Projected climate change impact on oceanic acidification Carbon Balance Manag. 2006; 1: 2. Published online 2006 June 27. doi: 10.1186/1750-0680-1-2
- US Government CO2 historic trend data over the last few thousand years, or simply look at this graph for ice-core data at one station since 1000 CE and recent data from Mauna Loa Observatory
- Paelogeochemical data showing that the human species hasn’t had to deal with CO2 at current levels – indeed the rise of humans (not mere existence of our species), probably associated with our fitness, seems to co-incide with a sudden decrease in Carbon Dioxide (but that could be mere co-incidence).
- Yes, there is buffering of pH, but there are side effects of such buffering, and I must wonder if there is a saturation limit somewhere compatible with well-being – and whether we’ve already gone past it.