Tuesday, December 13, 2011

Strangest Argument I've ever seen for Reducing Greenhouse Gas Emissions

While meandering through websites discussing global warming, I ran into one site that gives the silliest reason to stop emitting greenhouse gases...the reason is that the efficiency of our greenhouse gas emitting vehicles will decrease as the atmospheric temperature increases. (Follow this link: Global Warming-Lessons from the Second Law of Thermodynamics.) Don't try to get your head around this argument, it goes in a circle. This argument came from a physics professor.
I don't know what it is about physicists (including myself), but some of us initially seem to back some really strange and silly ideas when we move from pure physics to energy policy or energy engineering.
One of the goals of this blog is to reduce the time from "naive physicist" to "seasoned energy engineer" for those people who decide to transition careers.
I am still naive in some areas of the electricity grid, but I've learned a lot over the years with regards to how to build power plants with high rates of return on investment, even in a greenhouse gas constrained world.

So, this leads me to the article I ran across earlier today. The author, a physics professor at LaTrobe University, makes some bold statements in a new book titled "Energy: A Subtle Concept." 

1) "In tropical regions, the ambient temperature is already so high, the air already so humid, that plant-cooling and hence photosynthesis is at the limit of efficiency. Any increase in temperature and plant growth will decrease or stop."

2) "With greenhouse warming, the efficiency of every process on Earth will be compromised."  [including life]


I want to address these claims because they are completely off the mark. (It'll help if you read the review of her book in the link I posted at the beginning of this post...or again here.)



1) The author states correctly that photosynthesis requires evaporation of water. "Plant cooling"  i.e. converting liquid water into water vapor (which is required to maintain a reasonable temperature while converting sunlight, CO2 & liquid water into sugars and oxygen) is certainly required both from a first and second law basis.  But what's important is not so much the temperature, but the relative humidity. The RH determines whether the plant can evaporate water into the atmosphere. From the climate data I've seen, the relative humidity has been decreasing over the last fifty years.  (I have no clue why this is happening...I plead complete ignorance here.) People, especially physicists, should avoid alarmist phrases like "Any increase in temperature and plant growth will decrease or stop." As the RH decreases and the CO2 level increases, one would expect to see photosynthesis increase.

[On a side note, what's interesting about photosynthesis is that the deltaG of the reaction is larger than the delta H for the reaction in this direction:  6 CO2(g) + 6 H2O(l) >> C6H12O6(s) + 6 O2(g). The overall entropy of this reaction in this direction is negative...which means that a plant can never turn 100% of the energy in the UV/vis photons into chemical energy...some of the energy must go into thermal energy or into evaporating water.
On the other hand, the overall entropy of the following reaction is positive:
6 CO2(g) + 12 H2O(l) >> C6H12O6(s) + 6 O2(g) + 6 H2O(g)
This is what I meant above by "plant cooling."  This evaporation of water allows the overall reaction to have a positive generation of entropy (if for some reason heat can not be transfer to the environment.) ]
And now, in addressing statement #2, I'll break it down into two questions: a) Will a warmer environment cause the efficiency of life to decrease?, and b) Should I scrap my piston engine vehicle because global warming will cause the efficiency to decrease in the future?


2a) Life processes are not heat engines. Their efficiency of converting chemical energy into work is not dictated by the Carnot cycle. They are more like PEM fuel cells. The mitochondria in our cells use the sugar and oxygen from the plants to generate useful work, and CO2/H2O. They have proton conducting membranes that shuttle around protons while forcing electrons to complete the circuit through other proteins.
I'm not exactly sure what effect higher temperatures and higher concentrations of CO2 will have on our metabolism, but 1)  PEM fuel cells generally operate better at higher temperatures because the kinetics are the electrodes are faster, and 2) most bacteria can operate faster at higher temperatures. Global warming will not cause the efficiency of life processes to decrease because we are "fuel cells", not "heat engines." For more details check out my post titled You are a Fuel Cell.


2b) While the efficiency of life processes might increase if the temperature increases, it is true that the efficiency of our piston or turbine based power plants might decrease if the atmosphere gets warmer. The author of the book calculates a 0.5% decrease in efficiency if the bottom temperature increases by two degrees and the top temperature remains constant. (Let's ignore the fact that perhaps we could figure out how design better engines in the future.) Let's just ask the stupid question: Who cares if the efficiency of my car is 0.5% less efficiency because of global warming? This alone is not a reason for me to switch to a more expensive vehicle that might not emit greenhouse gases.
(Note that this is the silliest reason I've ever since for moving away from greenhouse gas emitting forms of energy...and I've seen a lot of them.)

So, I'm not trying to argue here that climate change won't have potential impacts. (Global warming will have impacts, both positive and negative impacts.) And there might be reasons for some communities to purchase battery or fuel cell vehicles in order to reduce local emission of NOx and particulates. What I am trying to argue is that the only reason to reduce our emissions of greenhouse gases is that if life can grow faster by building power plants that reduce emissions compared with those that do emit greenhouse gases. This depends on the overall effect of greenhouse gas emissions on life, both human and other forms of life.

Let me go through this argument step by step:
Recent global warming is clearly caused by the burning of fossil fuels at a rate faster than the CO2 can be consumed by the environment. This has the potential to increase the global average temperature over time. The question is: what will be the environmental & economic impact of the global warming?
The fourteen studies conducted as of 2009 suggest that the overall economic impact will be overall positive in the near-term and then the impact will be negative after a temperature of ~2 degC from 1990 temperatures. (see the link directly above or here again) We need more people estimating what is the economic impact of global warming. We need a lot more than 14 studies before we can even attempt to decide on what is the best plan of action regarding the emission of GHG's. (It still blows my mind that countries/states have already started implementing carbon taxes and renewable energy feed-in-tarriffs when there have only been 14 studies of the economic impact of global warming...and, on average, those studies suggest a positive economic impact of global warming for temperatures less than 2 deg C.)

Still, I understand that, while there might an overall positive economic impact in the short-term, there will be people who need to be paid so that they can adapt to a changing climate...and therefore, there might be good reasons to implement some form of greenhouse gas taxes or cap&trade structures so that we can help those who will be effected negatively by global warming.

But what I find so absurd is that there are people (such as the physicist discussed in this blog) who think that we need to stop growing and resort to global warming alarmism.
Alarmism only helps to propagate fear rather than propagate the knowledge that could be used to make the decisions we face. (The alarmism goes both way...climate alarmism as well as those people who suggest that implementing carbon dioxide cap&trade systems will destroy the economy.)

What I hope is that we can all figure out how to communicate with each other in such a way that we can continue to grow as a society, even if we have to completely cut back on emission of GHGs in the future.

We need more optimism because there are plenty of ways of turning coal and natural gas into hydrogen and sequestration-ready carbon dioxide while generating a >8%/yr real rate of return on investment.
(Though, they require the scale-up of hydrogen separation membranes. I'll write a separate post in the future about some of the ways to do this.) We can use the hydrogen to power fuel cell vehicles, to create fertilizer, or to generate electricity in gas turbines. (This would of course be in addition to the other options available that already work well in certain locations and/or times of day, such as nuclear, geothermal, hydroelectric, solar and wind.)

Our society and life in general will still grow, even on a GHG constrained planet. It would be nice if we could get all of the anti-growth environmentalists in a room with all of the pro-human-growth climate-change-skeptics, and then convince them all that the goal of life is for life to grow, and that the best way for life to grow and to expand is to build power plants that don't destroy more life than they can support. And there are plenty of power plants that can do that. And to get to that future, we just need to drown out the alarmism from both sides of the aisle. And that's the goal of this blog.

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