Tuesday, January 30, 2018

What are the effects of carbon dioxide in the atmosphere?

Apart from the obvious, or course.  Once, when our planet was young, the atmosphere was very high in carbon dioxide.  Then photosynthesis evolved and the cyanobacteria that spread across the oceans turned most of that carbon dioxide into oxygen about two and a half billion years ago.  Modern complex life, like ourselves, loves oxygen but for the creatures at the time this was a huge problem since oxygen was toxic to them and most of them died.  Plus the interruption of the greenhouse effect combined with the dimmer sun we had back then to turn Earth into a giant snowball for a bit.

But here we are billions of years later and carbon dioxide levels are increasing.  We should be worried about increasing temperatures but are there other reasons to worry?  For a very long time, compared to humanity, Earth's carbon dioxide levels were around 280 parts per million.  That's been going up recently and is now at 407 parts per million, a 45% increase.

If you are a photosynthesizing plant you might have complex feelings about this but if you're a mammal who really just wants to expel carbon dioxide from your lungs then there really isn't any upside.  We know that sufficiently high carbon dioxide concentrations will kill us but that takes  an atmosphere that's well above 10% carbon dioxide, 10,000 parts per million, very far from any levels we could plausibly reach by burning too much coal.  But some researchers have investigated the effect on people's cognitive abilities from going from 600 ppm to 1000 ppm and found easily measurable declines.  Now, poorly ventilated indoor spaces might easily get up to 2000 ppm so that's something to think about when designing office spaces.  But if a 400 ppm difference can result in obvious differences for people proofreading papers when briefly exposed can we be sure that there isn't some difference in human physiology that would stem from a 100 ppm difference across an entire childhood?  How about a 200 or 300 ppm difference?

This probably won't be a huge difference but it's not something that's been researched and not something you really could ethically research in humans.  But it is something that I think is underplayed in in our rhetoric about climate change.

Wednesday, January 24, 2018

Genetic engineering and chlorophyll

One of the interesting discussions in The Wizard and the Prophet was what the wizards are trying to get up to next in terms of trying to increase food production.  One idea goes to the fundamentals of photosynthesis.

The most important protein in photosynthesis is affectionately known as RuBisCO and makes up about half the protein in a leaf.  Photosynthesis seems to be pretty hard and so RuBisCO doesn't work as well as most other catalyst proteins.  It's supposed to grab the carbon in carbon dioxide from the air but frequently grabs plain oxygen instead.  I suppose it worked a lot better before the Great Oxygen Catastrophe.  Some plants have versions that are a bit more selective but they work more slowly.  Some are faster but they mess up which to grab more frequently.  Biologists hoped they could improve RuBisCO but it seems that evolution did about as good a job as could be done.

There are some plants, though, that do have method of photosynthesis that's often better than the run of the mill one.  They spend a little energy to concentrate carbon dioxide in cells where the RuBisCO is and so when RuBisCO grabs a random air molecule its more likely to be CO2 instead of O2, speeding up photosynthesis.  The extra energy means this isn't always a benefit, but it usually is.

Many plant species have developed this C4 carbon fixation process, as it's known, in nature.  Notably corn does it this way.  But researchers are hoping that you could develop a strain of rice that works that way too.  That is very ambitious.  Changing a single protein like RuBisCO is easy but this would involve growing whole new structures in the leaves to channel the CO2 and that doesn't involve just new proteins but new development paths.

That's very nifty but when I was reading the chapter my mind was going somewhere else.  The Great Oxygen Catastrophe was very good to use oxygen breathing creatures but it really sucked for plants.  Wouldn't the kind thing, for plants, be to let them live in a high CO2, low O2 environment?  And you could give the plants a high speed, low specificity version of RuBisCO that would work really well in that environment.

I'm mostly thinking of this in terms of growing plants in outer space but it could be applied in greenhouses too.  Enclosed environments also reduce the need for pesticides and herbicides though obviously the enclosures are expensive and have their own environmental impact.  And certainly there would be an energy cost in getting the oxygen the plants produce out of these buildings.

Oxygen free environments are dangerous.  But ones filled with CO2 less so.  Normally when you aren't getting any oxygen you feel perfectly fine as you get stupider and more lethargic until you die.  Here's a video from Smarter Every Day showing someone in a low pressure environment similar to a depressurized airplane and how he acts until given a breath mask.  When you hold your breath and feel like you're running out of air that sensation is caused by the buildup of CO2 rather than the lack of O2.  These always went together in our ancestral environment so there was no need for us to distinguish.  So at least in these greenhouses people with mask trouble could at least notice something wrong and leave.

I'm sure that some of you are thinking, "wait, how does this relate to all the CO2 we're pumping into the atmosphere?"   Well, plants will like the extra CO2 but the extra heat will make RuBisCO even less selective so for moderate warming it depends on the plant in question and for high global warming its generally bad.  Plus there are all those other very hard to predict changes in rainfall, etc, which would almost certainly be painful.  So lets not forget to work on better renewable energy too.

Tuesday, January 23, 2018

Book review: The Wizard and the Prophet

I just recently finished The Wizard and the Prophet by Charles C. Mann.  He'd previously written a book about the Columbian exchange I'd really liked, 1493, so I was ready to like this book too.

It concerns the dueling ideals of two men regarding man's relationship with the environment.  The prophet of the title, William Vogt, believed that the world has a finite carrying capacity that humans had to respect and that we had to limit ourselves to what the Earth could sustain.  The wizard, Norman Borlaug, worked tirelessly to increase the yields of the crops that man depends on and allowed large new generations of people to grow up without the famine that had plagued their parents.

Going through the book Mann seems to do an admirable job of looking at the lives of each; their successes and failures and the events that led them to be the people they were.  And the books makes a valiant effort to portray both fairly though, as you might expect, I end up sympathizing with the wizards more than the prophets.

I do worry, though, that it's the third position Mann introduces that is the correct one.  Vogt believes that mankind must constrain its reproduction and stop consuming as much.  Borlaug believes that mankind must learn to better use the environment to support ever more people.  Lynn Margulis believes that it would be unprecedented for mankind to do either of these so we should expect overpopulation and dieoff in the future.

My first reaction was "Wait, is this the same same Lynn Margulis who..." and yes it was.  She had argued that symbiosis rather than competition was the primary force in the evolution of our cells.  It was entirely true that mitochondria and chloroplasts were once independent bacteria who came to live inside eukaryotic cells.  It was untrue that the flagellum or the other orgenelles of the cell had also originated as symbiotes. 

We are lucky that affluence has reduced our desire to have many children.  Yet, there are those who desire many children even in affluence and there's no reason to think that this desire isn't at least partially heritable.  We may stem this, for a time, with violence but the will to violence fades .  We may race ahead of necessity in terms of our civilization's ability to provide sustenance.  Yet, the sun only puts out so much energy.  There are limits to the computation cycles that can be extracted from a unit of energy.  And expanding at the speed of light resources grow as the cube of time but demand grows exponentially and an exponent must always beet a polynomial in the end.

I'm closer to an average than a sum utilitarian so I can swallow this repugnant conclusion, even if I don't want to.

The very long run for SARS Covid 2

Many of the worst pandemics that afflict us are from pathogens that don't normally prey on humans.  Probably the most famous pandemic in...