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Title: THE RELATIONSHIP BETWEEN NEAR-SURFACE AIR TEMPERATURE OVER LAND AND THE ANNUAL AMPLITUDE OF THE ATMOSPHERE'S SEASONAL CO2 CYCLE.

Author
item IDSO, CRAIG - ARIZONA STATE UNIV
item IDSO, SHERWOOD
item BALLING JR, ROBERT - ARIZONA STATE UNIV

Submitted to: Global Biogeochemical Cycles
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The seasonal cycle of the growth and decay of terrestrial plants in the Northern Hemisphere superimposes a seasonal cycle upon the upward trend in the carbon dioxide concentration of the atmosphere. Over the past several decades, the amplitude of this cycle has been steadily increasing, driven by the increasing productivity of Northern Hemispheric terrestrial vegetation that has historically been attributed to the aerial fertilization effect of the ongoing rise in atmospheric CO2. We investigate this phenomenon at ten Northern Hemispheric monitoring stations from 1979 to 1995 and determine its relationship to temperature variability over this period. The results of our analyses suggest that global warming has been responsible for only 10 to 20% of the increase in terrestrial productivity that has driven the increase in seasonal CO2 cycle amplitude over this time interval. Consequently, 80 to 90% of the observed increase in the amplitude of the atmosphere's seasonal CO2 cycle must be due to the direct growth-enhancing effect of the rise in the air's CO2 content, which is almost universally believed to be due to mankind's burning of fossil fuels, such as coal, gas and oil. Knowledge of this positive consequence of the world's industrial activities should be of great importance to policy makers who must decide how to deal with concerns about potential CO2-induced climate change.

Technical Abstract: 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 five-degree latitude bands stretching from the equator to 85 degrees N. Temperature effects were non-existent when the CO2 and temperature data were contemporaneous, whereas they were maximal when the CO2 data lagged the temperature data by two years, declining slowly thereafter to become non-existent again between a lag of six to seven years. For the peak- impact two-year lag situation, low-latitude temperatures were much more important than mid- or high-latitude temperatures. The two-year-lag result for Mauna Loa and Point Barrow indicates that Northern Hemispheric warming was responsible for less than a fifth of the annual CO2 amplitude increase observed at Mauna Loa from 1960 to 1995 and less than a tenth of the amplitude increase recorded at Point Barrow over this period. Be default, therefore, the majority of the amplitude amplification appears to be due to the increased terrestrial productivity provided by the aerial fertilization effect of the contemporaneous historical rise in the atmosphere's mean CO2 concentration.