We present a simple statistical approach for estimating the greenhouse gas
emissions of large cities using accurate long-term data of
column-averaged greenhouse gas abundances collected by a nearby FTIR
(Fourier transform infrared) spectrometer. This approach is then used to
estimate carbon dioxide emissions from Tokyo.
FTIR measurements by the Total Carbon Column Observing Network
(TCCON) derive gas abundances by quantitative spectral
analysis of molecular absorption bands observed in near-infrared
solar absorption spectra. Consequently these measurements only
include daytime data.
The emissions of Tokyo are derived by binning measurements according to wind
direction and subtracting measurements of wind fields from outside the
Tokyo area from measurements of wind fields from inside the Tokyo area.
We estimate the average yearly carbon dioxide emissions from the area of
Tokyo to be 70±21±6MtCyr-1 between 2011 and
2016, calculated using only measurements from the TCCON site in
Tsukuba (north-east of Tokyo) and wind-speed data from nearby
radiosondes at Tateno. The uncertainties are estimated from the
distribution of values and uncertainties of parameters (±21)
and from the differences between fitting residuals with polynomials or
with sines and cosines (±6).
Our estimates are a factor of 1.7 higher than estimates using the
Open-Data Inventory for Anthropogenic Carbon dioxide emission
inventory (ODIAC), but when results are scaled by the
expected daily cycle of emissions, measurements simulated from
ODIAC data are within the uncertainty of our results.
The goal of this study is not to calculate the best possible
estimate of CO2 emissions but to describe a simple method which
can be replicated easily and uses only observation data.
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