Taking into account the CO2 thermometer of Ahlbeck 
http://www.john-daly.com/co2-conc/updated.htm

and the world population CO2 relationship of Idso
http://www.co2science.org/edit/v4_edit/v4n35edit.htm 

Using US census data for world population 
http://www.census.gov/ipc/www/worldhis.html 
http://www.census.gov/ipc/www/worldpop.html 

and the TRENDS data for CO2 concentration (mauna loa and smoothed DSS) 
http://cdiac.esd.ornl.gov/ftp/trends/co2/lawdome.combined.dat 
http://cdiac.esd.ornl.gov/ftp/maunaloa-co2/maunaloa.co2 

led me to the generation of a natural CO2 concentration graph

Using a Vostok ice core CO2 response to temperature of 9.838298 ppm/degC   
http://cdiac.esd.ornl.gov/trends/temp/vostok/jouz_tem.htm 
http://cdiac.esd.ornl.gov/trends/co2/vostok.htm

Quick and dirty approach:

Vostok ice core:         
  minco2 183.9 ppm        
  maxco2 299.5 ppm       
  mintemp -8.49 degC     
  maxtemp 3.26 degC  
           
  temprange 11.75  degC       
  co2range 115.6  ppm       
           
  response 9.838298  ppm/degC       

led me to the temperature reconstruction of the past millenium.

Hans Erren

source data for the graphs:

zipped in Excel 5.0/95 format
http://members.lycos.nl/ErrenWijlens/co2/co2populationproxy50.zip

zipped in Excel 2000 format
http://members.lycos.nl/ErrenWijlens/co2/co2populationproxy.zip



this page:
http://members.lycos.nl/ErrenWijlens/co2/thermom.html

homepage:
http://members.lycos.nl/ErrenWijlens