Apologies for getting into a more academic mode today, but I feel
that this issue is one that needs a good deal of research to fully address it,
especially considering the recent changes that the Obama Administration made to
the U.S.'s "official" social cost of carbon.
Carbon dioxide (CO2) is a greenhouse gas (GHG) that is emitted as
a side effect of burning various fossil fuels. It is the primary cause of
global climate change, and yet its impacts on mankind differ because of the
different locations humans inhabit, and the discrepancies in wealth and
socioeconomic status that various countries possess. These conditions make
estimating the social cost of carbon quite difficult, but an accurate
assessment of carbon’s costs to mankind is essential to raise awareness of and
spur action on climate change.
The social cost of carbon (SCC) is defined, broadly speaking, as
the damage each ton of carbon emitted into the atmosphere causes to mankind.
The SCC is what agencies such as the Environmental Protection Agency (EPA) and
Department of Energy (DOE) use when crafting regulations: as the SCC rises, the
regulations promulgated by these agencies become stricter, and vice versa. This
makes estimating the SCC of vital importance to the preservation of the
environment and the economy. If the SCC is underestimated, countries will not
take sufficient steps to reduce their emissions, and further damage to the
environment, and eventually countries’ economies, will result. However, if the
SCC is overestimated, the regulations put into place will be onerous and a drag
on current and future economic growth. Therefore, getting the price of the SCC
right is essential for harmonizing the relationship between economic growth and
the environment.
Because of its importance to both environmental and economic
conditions, several governments, academics, and advocacy organizations have
studied the social costs of carbon and come up with what they believe to be
accurate estimates for that number. In 2010, the United States had a SCC of $22/ton, assuming a discount rate of
3%. However, in May 2013,
the Obama Administration updated the SCC to a price of approximately $35/ton,
citing changes in sea level rise projections, as well as agricultural impacts,
among other things. Other studies looking at the social costs of carbon have an
average of $43/ton, but also reveal a large spread in the data, with a standard deviation of
$83/ton. This spread occurs in reality as well: while Norway plans to double its carbon tax (which is a reflection of the SCC) to $70/ton
this year, the EU’s cap-and-trade system currently only prices carbon at $6.50/ton.
Difficulties When
Accurately Pricing the SCC
Uncertainty of future climate impacts causes
spreads in CCS price estimates.
The aforementioned large spread in SCC prices primarily reflects
the uncertainty in what impacts climate change will have on the globe, and for
specific countries and regions. One of the hardest things for climate change
scientists to predict is the specific impacts increasing CO2 levels will have
on the environment. While scientists can make generalizations about what
impacts are more likely to occur in a GHG-intensive world, translating those
impacts into specific monetary figures is a daunting task. For example,
agriculture in many regions around the Mediterranean Sea may suffer in a warmer
world because of shifts in precipitation patterns and timing, but farmers at
higher latitudes may enjoy longer growing seasons, increasing their
productivity. This uncertainty means that, consequently, SCC prices vary
greatly.
SCC calculations do not take all variables into
account.
While many SCC studies do their best to include as many variables
in their calculations as is feasible, certain environmental aspects are left
out of the equation because of their incalculable nature. For example,
biodiversity is a valuable part of our environment; understanding the makeup
and interaction of different species has resulted in many notable medical
advances such as the development of gene mapping and cell division,
among other things. However, biodiversity by itself carries no explicit monetary value in
equations. As a result, it is not included in SCC equations. This means
that the SCC price may end up being undervalued. Many other
environmental assets are also not included in SCC equations for the same
reasons, so the full costs to the environment are not captured by current SCC
prices.
Model biases and incompleteness may skew
results.
One more factor that leads to inconsistent SCC prices is the use
of the models themselves. Three main models are used to calculate SCC prices: the FUND, PAGE,and DICE models. These
models are almost always used to calculate the SCC, while other models that are available are discarded in
the process. The data sets used by these models are developed by the same authors, and are not
usually questioned. Additionally, the models do not account for
variation in local effects, choosing instead to make uniform assumptions, and
also ignore potential high-impact climate effects, like
the melting of the Greenland ice cap. These conditions limit the potential
for really understanding the full scope of carbon impacts, as well as SCC price
ranges. Some of these changes may result in an order-of-magnitude difference in
a carbon cost, which means ignoring them could have serious ramifications for
both the environment and the economy in the future.
Recommendations
Provide an open comment period when SCC models
are updated.
One of the major issues with models exploring SCC prices is that
the models themselves are subject to the inherent biases of the researchers
developing and modifying them. Including an open comment period when the models
are updated can ensure that outside concerns about model assumptions or
specific operating parameters are taken into account. This will help to make
sure that different ideas about SCC factors are heard and understood by the
researchers updating the models, and help the models more accurately identify
the correct SCC price.
Use a declining discount rate for projections of
SCC prices over 25 years into the future.
One of the main issues with SCC price projections is that discount
rates (which are used to help determine whether it is preferable to fund a
project with public money, or to let the private sector handle it) can
substantially reduce the damage estimates from climate change in the future.
Including a declining discount rate can help to offset the impacts of
discounting across generational timespans. While France and the United Kingdom already use a declining discount rate, the
U.S. Office of Management and Budget instead recommends using a flat discount
rate. Having a flat rate means that even discount rates of 3% create
damages in the future that are quite minimal compared to climate change projections. Reducing
the discount rate to 1% over time will account for future damages due to
climate change more accurately and paint a more realistic picture of climate
change’s intergenerational impacts. Because one generation is approximately 25 years,
declining the discount rate to 1% after that time in the future can help to
measure intergenerational impacts of carbon with more clarity.
Include climate change
“tipping points” in model calculations.
One of the major concerns of climate change scientists today is
the possibility of a climate “tipping point,” where changing temperatures cause rapid and unexpected shifts in the climate that
could be catastrophic for the global economy. These events have a
relatively small chance of happening, but their costs are extremely high, so
much so that including them in SCC models will change the output prices. Including
these events will help models to capture the full scope of potential effects
from future climate change and produce a more accurate cost of carbon in the
process.
While the social cost of carbon is difficult to estimate and
project because of the complexity of climate change, it is nonetheless a very
necessary and important part of climate economics. Getting the price of carbon
right will help policymakers to assess and develop policies to mitigate climate
change’s effects while providing for economic growth. Because many of the
problems with calculating the SCC lie with the models used to calculate the
value, modifying those models to more fully include the effects of climate
change will be instrumental in getting the “correct” SCC price. Changing the
discount rate will also better account for the intergenerational effects.
Hopefully, if the SCC price is closer to the “actual” price observed in
reality, it will provide policymakers with better information so that they will
be able to make the necessary changes to mitigate climate change and adapt the
global economy to its effects.


