Interannual growth rate variations of atmospheric CO₂ and its δ¹³C, H₂, CH₄, and CO between 1992 and 1999 linked to biomass burning

Abstract

[1] High-precision, multispecies measurements of flask air samples since 1992 from CSIRO's global sampling network reveal strong correlation among interannual growth rate variations of CO 2 and its d 13 C, H 2 , CH 4 , and CO. We show that a major fraction of the variability is consistent with two emission pulses coinciding with large biomass burning events in 1994/1995 and 1997/1998 in tropical and boreal regions, and observations of unusually high levels of combustion products in the overlying troposphere at these times. Implied pulse strengths and multispecies emission ratios are not consistent with any other single process, but do not exclude possible contributions from covarying processes that are linked through climatic forcing. Comparison of CO 2 with its d 13 C indicates that most of the CO 2 variation is from terrestrial exchange, but does not distinguish forcing by biomass burning from imbalance in photosynthesis/respiration of terrestrial ecosystems. Partitioning of terrestrial CO 2 fluxes is constrained by H 2 , CH 4 , and CO, all of which are products of biomass burning but which have no direct link to net respiration of CO 2 . While CO is a strong indicator of biomass burning, its short lifetime prevents it from usefully constraining the magnitude of CO 2 emissions. If the H 2 and CH 4 variations were dominated by biomass burning, they would imply associated carbon emissions in excess of mean annual levels of other years, of 0.6-3.5 and 0. 8-3.7 Pg C for 19948-3.7 Pg C for /19958-3.7 Pg C for and 19978-3.7 Pg C for /1998. The large range in emission estimates mainly reflects uncertainty in H 2 /CO 2 and CH 4 /CO 2 emission ratios of fires in these years.

Multiple constraints on regional CO2 flux variations over land and oceans

“…Biomass burning is anticorrelated with precipitation, reinforcing the land NPP driven response to ENSO. Modeled global IAV in natural biomass burning agrees with Langenfelds et al [2002] and Duncan et al [2003] in predicting maxima and minima emissions in years 1994/1995 and 1995/1996, respectively. Extremely high emissions in 1997/1998, largely associated with fires in southeast Asia [van der Werf et al, 2003], are not captured by LPJ.…”

Continuous measurements of greenhouse gases and atmospheric oxygen at the Namib Desert Atmospheric Observatory

“…From this the Allan variance was computed. The Allan variance, a method for computing the frequency stability of clocks, can also be used to analyze the noise of a sensor (Siraya, 2001;Land et al, 2007). Allan variance is given as…”

“…where τ is the sampling interval, N is the number of measurements of some quantity T i , and n is the number of adjacent values of T i in τ (Land et al, 2007). Akin to the standard deviation, the Allan deviation is the square root of the variance,…”

“…Growth rates of methane vary with location and latitude (Langenfelds et al, 2002;Dlugokencky et al, 1994), so these higher growth rates could be a result of a larger source of CH 4 from the Southern Hemisphere for this year. Atmospheric growth rates of N 2 O were only obtained for the two sites with sufficiently overlapping time series at the time of writing, NMB and NDAO.…”

Evolution and variation of atmospheric carbon dioxide concentration over terrestrial ecosystems as derived from eddy covariance measurements

“…The Northern Hemisphere dominates the annual cycle of CO 2 concentration because it has much greater land area and plant biomass than the Southern Hemisphere (Yu et al, 2014). CO 2 emissions from forest fires in the tropical and boreal region have also been found to contribute the interannual variablity in the CO 2 growth rate (Langenfelds et al, 2002;Patra et al, 2005;Zhang et al, 2007). It is also interesting to note that Gray et al (2014) and Zeng et al (2014) have shown that the intensification of agriculture may have been a key contributor to the increase in atmospheric CO 2 seasonal amplitude.…”