Culturing Science – biology as relevant to us earthly beings

Is it possible for us to reduce our carbon emissions? (Garrett 2009, Climatic Change)

ResearchBlogging.orgYou may have heard that we’ve been having a bit of a problem called “global warming” or “climate change.”  The debate is what to do about it — can individuals, day-by-day, affect the amount of greenhouse gases in the atmosphere based on decisions involving diet, waste, and choices of consumption?  What types of alternative energy are the most efficient and effective?  How does industry need to change in order to yield or reduce carbon emissions?  Is this a problem that we can actually solve?

The journal Climatic Change published an article online on November 21 by Timothy Garrett entitled “Are there basic physical constraints on future anthropogenic emissions of carbon dioxide?”  (open access: doi:10.1007/s10584-009-9717-9).  You could easily blow this off as just another doomsday scientist — but the way he structures his argument,  stepping back from the issue and thinking about human civilization in relation to its environment in a new way, makes it stand out.

Garrett creates a new economic model, essentially reducing civilization to production and energy consumption.  The standard model used in the International Panel on Climate Chance (IPCC) Special Report on Emissions Scenarios (SRES) includes the variables p (population) and g (standard of living), which are difficult to predict, causing difficulty in creating reliable models to calculate the climatic state even 50 or 100 years from now.  Garrett argues that these variables are unnecessary, as they are simply responses to energy consumption and efficiency; that we should instead think about civilization as a huge furnace, which needs more energy as productivity increases, but is also inextricably linked to past production.  “The present and future are influenced even by the most distant past, and the past cannot be erased.”  (Waxing philosophical, are we, Garrett?)

Essentially, he boils down the human-planet system to physics.  Carbon dioxide, the output of energy consumption, exits civilization at a constant rate, but accumulates over time.  This tradeoff is represented as the variable η, which is the “rate of return” of energy to a system.  It essentially represents a feedback loop in which the greater the energy consumption and production, the greater is the potential for more consumption and production.  (Remember that carbon emissions are tied to this production and energy consumption.)  What is most important to note is that if η > 0, the system is growing, meaning energy consumption is increasing; when η < 0, it is shrinking; and when η=0, system growth is at a standstill.

It seems obvious that energy consumption would be tied to production in general.  But if energy consumption also is linked to economic growth, then we would have another way to think about how humans, energy and the environment interact.  Garrett based his calculations on the assumption that there is some constant value, λ, which links energy consumption to economic value through the equation:

a = λC,  where a = global primary energy consumption and C = global economic value

If his argument is true, λ has to be constant with time.  To show the existence of this constant, Garrett turned to data for world energy production (and thus consumption) a from the Annual Energy Review (2006) and global economic production P from United Nations data and looked at the whole 36-year timeframe for which he had data.  As you can see from his figure (below), the ratio of a/C for λ stayed constant at around 0.306 exajoules per trillion for the entire period.  (Also note the dramatic increase in η since the industrial revolution.)  (FYI: P is production rate in 1990 dollars/year.)

Garrett does admit that, since he has such a short length of data to work with, this constant could only apply to this 36-year period and not more.  However, I find his evidence sufficient to consider the model further.  As we accumulate more data on energy and economic production, it will be interesting to see if this constant λ is, in fact, constant.

This is a simple concept: that economic growth and increased energy use are linked.  However, what it implies about how to reduce energy use is harder to grasp.  This paper suggests that to bring η below zero and thus lose our forward acceleration of energy use, we have to actually shrink our economy.  For some reason, saying “shrink our consumption” seems doable, but when it is tied to the economic success of countries, developing or stable, it seems like far more of an impossible task.  In this way, Garrett’s paper points out a flaw in current discussions about climate change: we want to reduce emissions, but at the same time keep living our lives the way we do, keeping production high and the economy growing.

The next question is: what if we change our energy to non-carbon-based sources, such as wind or solar power?  For η to equal or be less than zero, we would need to make a switch to non-carbon sources at the same rate as η itself, the rate of return.  The 2005 value for η is 2.1% growth per year (see figure above; According to Garrett, “2.1% of current annual energy production corresponds to an annual addition of approximately 300 GW of new non-carbon emitting power capacity — approximately one new nuclear power plant per day.”

Garrett’s paper seems to present us with an impossible task: up the building of non-carbon-based energy sources while simultaneously downgrading our economy.  (This gets even more complicated with the news that we may be heading towards a uranium shortage, so nuclear power may not be realistic.)  It’s a hefty charge, and one that makes the future seem quite bleak.  However, this work should be taken with a grain of salt.  As much as simplification can be helpful in understanding a system, we cannot just give up.  Other factors can help mitigate our carbon emissions — if we don’t believe this then we’re wasting our time — and work should still continue to figure out those methods.

More than anything, I think that this is a really interesting way to think about humans and civilization on this planet.  When we’re talking and thinking about climate change, it’s easy to play the blame game and assign roles to different parts of the world or society, whether they be developing nations, industrialization and globalization, or rich people in mansions with enormous carbon footprints.  This paper makes the reader step back and realize that it’s not one thing — it’s the entire planet.  One country’s change isn’t going to do it.  While biking to work makes me feel good, we need everyone to bike to work in order to reduce our consumption dramatically enough to reduce emissions, and hopefully get our η in the negative.

Garrett, T. (2009). Are there basic physical constraints on future anthropogenic emissions of carbon dioxide? Climatic Change DOI: 10.1007/s10584-009-9717-9

Written by Hanner

November 30, 2009 at 1:36 pm

Posted in Journal Article

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