Reconstruction of Northern Hemisphere 1950–2010 atmospheric non-methane hydrocarbons

Abstract

Abstract. The short-chain non-methane hydrocarbons (NMHC) are mostly emitted into the atmosphere by anthropogenic processes. Recent studies have pointed out a tight linkage between the atmospheric mole fractions of the NMHC ethane and the atmospheric growth rate of methane. Consequently, atmospheric NMHC are valuable indicators for tracking changes in anthropogenic emissions, photochemical ozone production, and greenhouse gases. This study investigates the 1950–2010 Northern Hemisphere atmospheric C2–C5 NMHC ethane, propane, i-butane, n-butane, i-pentane, and n-pentane by (a) reconstructing atmospheric mole fractions of these trace gases using firn air extracted from three boreholes in 2008 and 2009 at the North Greenland Eemian Ice Drilling (NEEM) site and applying state-of-the-art models of trace gas transport in firn, and by (b) considering eight years of ambient NMHC monitoring data from five Arctic sites within the NOAA Global Monitoring Division (GMD) Cooperative Air Sampling Network. Results indicate that these NMHC increased by ~40–120% after 1950, peaked around 1980 (with the exception of ethane, which peaked approximately 10 yr earlier), and have since dramatically decreased to be now back close to 1950 levels. The earlier peak time of ethane vs. the C3–C5 NMHC suggests that different processes and emissions mitigation measures contributed to the decline in these NMHC. The 60 yr record also illustrates notable increases in the ratios of the isomeric iso-/n-butane and iso-/n-pentane ratios. Comparison of the reconstructed NMHC histories with 1950–2000 volatile organic compounds (VOC) emissions data and with other recently published ethane trend analyses from ambient air Pacific transect data showed (a) better agreement with North America and Western Europe emissions than with total Northern Hemisphere emissions data, and (b) better agreement with other Greenland firn air data NMHC history reconstructions than with the Pacific region trends. These analyses emphasize that for NMHC, having atmospheric lifetimes on the order of < 2 months, the Greenland firn air records are primarily a representation of Western Europe and North America emission histories.

Surface ozone and its precursors at Summit, Greenland: comparison between observations and model simulations

“…It should be noted that our modeling Y. Huang et al: Surface ozone and its precursors at Summit, Greenland period reflects a time when there was a reversal of the atmospheric C 2 H 6 trend, most likely reflecting emission changes during that time. Atmospheric C 2 H 6 had a decreasing trend from 1980 to 2009 (Simpson et al, 2012;Helmig et al, 2014a) but then began to increase around 2009 (Franco et al, 2015Hausmann et al, 2016;Helmig et al, 2016) in the Northern Hemisphere at a rate of increase that is approximately 4-6 times higher than its earlier rate of decline. It has been argued that the most likely cause for this trend and emission reversal is increasing emissions from oil and gas production, mostly from North America (Franco et al, 2015Hausmann et al, 2016;Helmig et al, 2016).…”

“…S1 in the Supplement). All the above changes were driven by the substantial reductions of anthropogenic C 2 H 6 emissions between emission inventories, from 3.5 (X08) to 2.5 Tg year −1 (MIX) over Asia and from 1.9 Tg year −1 (X08) to 1.4 Tg year −1 (NEI11) over the US, reflecting the decreasing trend of anthropogenic C 2 H 6 emissions during (Helmig et al, 2014a because the X08 emission inventory is based on the year 2001. Substantial changes in surface C 2 H 6 mixing ratios over the US between control simulations and NEI11_MIX reflected tempo-spatial changes in C 2 H 6 emissions from oil and gas production during the period 2001-2009.…”

Seasonal in situ observations of glyoxal and methylglyoxal over the temperate oceans of the Southern Hemisphere

“…The dominant source of glyoxal is the oxidation of parent VOCs, with isoprene globally the most important precursor (explaining 47 % of glyoxal formation) (Fu et al, 2008). Glyoxal has a global average lifetime of about 3 h (Fu et al, 2008;Myriokefalitakis et al, 2008;Stavrakou et al, 2009) and is highly water soluble and so can diffuse into aerosol or cloud water, where it is converted to SOA through the formation of low-volatility products such as organic acids and oligomers Kampf et al, 2013;Sedehi et al, 2013;Lee et al, 2011;Lim et al, 2013). α-dicarbonyl methylglyoxal (CHOCCH 3 O), a close relative of glyoxal, also forms low-volatility products in the aqueous phase (Tan et al, 2012;Sedehi et al, 2013;Lim et al, 2013), has a short global lifetime of 1.6 h and is produced by oxidation of gas phase parent compounds, predominantly isoprene (Fu et al, 2008).…”

Changes to the chemical state of the Northern Hemisphere atmosphere during the second half of the twentieth century

“…Measurements in firn air from Greenland (Aydin et al, 2011;Worton et al, 2012;Helmig et al, 2014b) suggest Northern Hemisphere C2-C5 alkane mixing ratios increased through the middle of the past century to a peak in ∼ 1980 (∼ 1970 for ethane) and then declined to roughly 1960 levels by 2000. In situ measurements from the urban areas of London (1993London ( -2008 (Dollard et al, 2007;von Schneidemesser et al, 2010) and Los Angeles (1960Angeles ( -2010 (Warneke et al, 2012) show steadily decreasing alkane mixing ratios, as do measurements at the semi-rural site of Hohenpeissenberg, Germany (von Schneidemesser et al, 2010).…”

“…The probability of RO 2 reacting with NO (leading to alkyl nitrate production) is thus governed by the ratio (Schwander et al, 1993), and the US hole, sampled using the US firn air system (Battle et al, 1996). The alkane measurements used in this work -originally reported in Helmig et al (2014b) Helmig et al (2014b) and Buizert et al (2012).…”