Detection of carbon monoxide trends in the presence of interannual variability

Abstract

[1] Trends in fossil fuel emissions are a major driver of changes in atmospheric CO, but detection of trends in CO from anthropogenic sources is complicated by the presence of large interannual variability (IAV) in biomass burning. We use a multiyear model simulation of CO with year-specific biomass burning to predict the number of years needed to detect the impact of changes in Asian anthropogenic emissions on downwind regions. Our study includes two cases for changing anthropogenic emissions: a stepwise change of 15% and a linear trend of 3% yr À1 . We first examine how well the model reproduces the observed IAV of CO over the North Pacific, since this variability impacts the time needed to detect significant anthropogenic trends. The modeled IAV over the North Pacific correlates well with that seen from the Measurements of Pollution in the Troposphere (MOPITT) instrument but underestimates the magnitude of the variability. The model predicts that a 3% yr À1 trend in Asian anthropogenic emissions would lead to a statistically significant trend in CO surface concentration in the western United States within 12 years, and accounting for Siberian boreal biomass-burning emissions greatly reduces the number of years needed for trend detection. Combining the modeled trend with the observed MOPITT variability at 500 hPa, we estimate that the 3% yr À1 trend could be detectable in satellite observations over Asia in approximately a decade. Our predicted timescales for trend detection highlight the importance of long-term measurements of CO from satellites.

An examination of the long-term CO records from MOPITT and IASI: comparison of retrieval methodology

“…CO emissions inventories still present large uncertainties (Streets et al, 2013), and separating anthropogenic and biomass burning contributions is essential for attributing CO long-term trends (Strode and Pawson, 2013).…”

Transport of Asian trace gases via eddy shedding from the Asian summer monsoon anticyclone and associated impacts on ozone heating rates

“…Satellite observations show 51 increasing trends in several tropospheric Asian trace gases over the last decade, e.g. ozone at 52 ~1-3 % year -1 (Verstraeten et al, 2015), CO at 3% year -1 (Strode and Pawson, 2013), NO x at 53 ~3.8 -7.3 % year -1 (Schneider and van der A, 2012; Ghude et al, 2013). Biomass burning is 54 another major contributor to the observed growth in these trace gases (van der Werf et al, 55 2006).…”

Fire Influences on Atmospheric Composition, Air Quality and Climate

“…For 2004-2005 over North America, it was estimated that 8 % of smoke plumes reached more than 2.5 km above the boundary layer [68]; only a small number of these are lofted directly to the upper troposphere. Strode et al [28] indeed found that the influence on tropospheric CO due to biomass burning decreases with height, being smaller at 500 hPa than at the surface.…”

“…This effect, they claim, could become more severe in the future, as boreal forest regions become hotter and drier. Without examining ENSO influences, Strode et al [28] discuss how biomass burning strongly impacts the interannual variability of CO in northern mid-latitudes, which affects the ability to detect anthropogenically driven trends in CO.…”