CO2: Emissions & Changes in Atmospheric Levels

In previous posts, I have shown the 1750-2008 global CO2 emission trends and the atmospheric CO2 concentrations at Mauna Loa, Hawaii. In this post, I compare annual CO2 emissions with annual changes in atmospheric CO2.  The resulting chart shows the portion of CO2 emissions that remains in the atmosphere and the portion that is soaked up by the land & ocean.  Links to the R script and source data files are provided.

Introduction

This is the 2nd in my CO2 series of posts (1st post here).  In this post I compare annual fossil fuel CO2 emissions  with annual atmospheric CO2  concentration changes to see how much of the CO2 emissions remain in the atmosphere. My goal is to reproduce part of the analyses carried out by Jim Hansen and Sarmiento and many others. Here’s a copy of Hansen’s chart.

CO2 Concentration – Mass Calculations

I found reproducing Hansen’s chart  to be a relatively simple task once I familiarized myself with a few large scale units of measure that are used in global  carbon budget analysis:

• Metric tonne  (mt) = 1000 kg; 10^6 grams
• Gigatone (Gt) = 10^ 9 mt; 10^15 grams; Pg
• Petagram (Pg) = 10^15 grams;  Gt

Another point to note is that some data is expressed in mass of C while other data is reported in CO2.  It’s easy to convert between C and CO2

• C = 0.273 * CO2
• CO2 = 3.66 * C

Finally, here are the conversion factors to convert atmospheric CO2 concentration to mass of CO2 and C: (see CDIAC link for full set of conversion factors)

• 1 ppmv of atmospheric CO2 = 7.82 Gt CO2; 2.13 Gt C

I put together a simple Excel calculator to convert CO2 concentrations to mass. You can download it from Google Docs here. Google spreadsheet does not currently let you protect cells, so please don’t use on-line, rather download it if you want to try it out yourself. Simply go to File > Export and select Excel. You can ignore the Excel format warning when you load the workbook.

CO2 Emissions and Atmospheric CO2 Chart

Here’s my version of Hansen’s chart.

I’ve made a few changes to Hansen’s chart:

• I plot data from 1960 to 2006, versus Hansen’s 1950 to 2000
• I added summaries for 1960 – 2006
• I use PgC units rather than equivalent GtC units
• I adjusted color scheme
• I did not include the 7 year moving average

CO2 Emissions & Atmospheric Concentrations

The portion of CO2 emissions from fossil fuel that remains airborne varies from 13 to 100% on a year to year basis, the 1960-2006 average was 56.9%. This means that 43.1% of the 1960-2006 fossil fuel CO2 emissions was soaked up by the land and ocean.

With a 57% airborne retention, an annual emission of 8 GtC  per year would increase atmospheric CO2 by  2.14  ppmv/yr ([8GtC/2.13Gt/C /ppmv CO2]*0.57 =2.14 ppmv).

In future posts I will examine the impact of CO2 on ocean pH  and the cause-effect relationship between CO2 and temperature.

R Script and Data File

Here are Google document links to the R script and CSV file for those readers who would like to prepare your own charts.

• R script
• Data
  • Web page
  • CSV file

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