The relationship between near-surface air temperature over land and the annual amplitude of the atmosphere's seasonal CO2 cycle

Craig D. Idso, Sherwood B. Idso, Robert Balling

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The seasonal growth and decay of Northern Hemispheric terrestrial vegetation creates a seasonal oscillation in the atmospheric CO2 concentration in the Northern Hemisphere. Over the past several decades, the amplitude of this seasonal cycle has risen substantially. Many potential causes of this phenomenon have been suggested; but the one that seems currently to be of most concern is global warming. This study thus seeks to determine if the rise in the near-surface air temperature of the past 35 years has been the major factor in driving the contemporaneous increase in the amplitude of the Northern Hemisphere's seasonal CO2 cycle. Annual CO2 amplitude data from ten Northern Hemispheric stations of the NOAA/CMDL continuous monitoring network were regressed against mean near-surface air temperatures over land areas located within each 5°latitude band stretching from the equator to 85°N. Temperature effects were non-existent when the CO2 amplitude and temperature data were contemporaneous, whereas they were maximal when the CO2 amplitude data lagged the temperature data by 2 years, declining slowly thereafter to become non-existent again between a lag time of 6-7 years. For the peak-impact 2-year lag situation, low-latitude temperatures were much more strongly correlated with the CO2 amplitude data than were mid- or high-latitude temperatures. The 2-year-lag results for Mauna Loa and Point Barrow indicate that Northern Hemispheric warming may have been responsible for about a fifth of the annual CO2 amplitude increase observed at Mauna Loa from 1960 to 1995 and approximately a tenth of the amplitude increase recorded at Point Barrow over this period. Consequently, the majority of the Northern Hemispheric CO2 amplitude increase appears to be due to the influence of some other factor or combination of factors, a number of which have been suggested in the literature.

Original languageEnglish (US)
Pages (from-to)31-37
Number of pages7
JournalEnvironmental and Experimental Botany
Issue number1
StatePublished - Feb 1 1999


  • CO
  • Carbon dioxide
  • Global warming
  • Mauna Loa
  • Temperature

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Agronomy and Crop Science
  • Plant Science


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