Is Carbon Cycling Keeping Pace with Increases in Atmospheric Carbon Dioxide?

TL;DR

This study compares global increases in atmospheric CO2 and primary production proxies over 30 years, finding that primary production increases slightly lag behind CO2 increases, but uncertainties prevent definitive conclusions.

Contribution

It provides a global analysis of the relationship between atmospheric CO2 increases and primary production proxies using Fourier analysis over 30 years.

Findings

Global primary production increase estimated at 3.75% per decade.

Atmospheric CO2 increase measured at 4.75% per decade.

Uncertainties prevent definitive conclusion on the lag between CO2 and primary production.

Abstract

Carbon dioxide (CO2) increase has been well documented, and global net primary production is of importance to a variety of ecological topics. Since CO2 increases primary production in laboratory experiments, the global effects of increasing CO2 on global primary production are of interest in both climate science and ecology. Various studies have considered increases in primary production over different regions and time scales, but the global effects of increased atmospheric CO2 and primary production remain unquantified. This study aims to compare these two variables globally to assist in determining the potential for increases in primary production to contribute to carbon sequestration, possibly slowing increases in atmospheric CO2 resulting from fossil fuel emissions. Monthly CO2 concentration data from 1985 through 2015 in distinct latitude bands (every 10 degrees) was retrieved from the NOAA Earth System Research Laboratory for a total of 18 datasets. As a proxy to quantify net primary production, the magnitude of annual CO2 cycling was computed for each dataset through Fourier analysis. Relative increases were then calculated for both CO2 increase and amplitude increase to compare the pace of carbon cycling with the pace of increases in atmospheric CO2. Globally, the increase in primary production determined by using annual CO2 cycling as a proxy was 3.75% (+/- 1.82%) per decade over the time interval studied. In contrast, the measured increase in CO2 abundance was 4.75% (+/- 0.02%) per decade. Increases in carbon cycling appear to be slightly smaller than increases in CO2 globally and in both the Northern and Southern Hemispheres, but the uncertainties in the estimate for increases in carbon cycling are too large to draw that conclusion with statistical confidence.