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The large decline in CO found over Northeast China is initially associated with an improvement in combustion efficiency, with subsequent additional air quality improvements from 2010 onwards. We find evidence of the atmospheric impact of air quality management policies. In general, CO declines faster in the first half of the record compared to the second half, while AOD trends show more variability across regions. We focus on four major population centers: Northeast China, North India, Europe, and Eastern USA, as well as fire-prone regions in both hemispheres. The CO and AOD records are split into two sub-periods (2002 to 20 to 2018) in order to assess trend changes over the 16 years. Trends are examined by hemisphere and in regions for 2002 to 2018, with uncertainties quantified. Other satellite instruments measuring CO in the thermal infrared, AIRS, TES, IASI, and CrIS, show consistent hemispheric CO variability and corroborate results from the trend analysis performed with MOPITT CO. We use the long-term records of CO from the Measurements of Pollution in the Troposphere (MOPITT) and AOD from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument.
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#VCDS 12.12 VS 18.4 DRIVERS#
A combined trend analysis of CO and aerosol optical depth (AOD) measurements from space helps to diagnose the drivers of regional differences in the CO trend. Aerosols are co-emitted with CO from both fires and anthropogenic sources but with a shorter lifetime than CO. Following past studies to quantify decadal trends in global carbon monoxide (CO) using satellite observations, we update estimates and find a CO trend in column amounts of about −0.50 % per year between 2002 to 2018, which is a deceleration compared to analyses performed on shorter records that found −1 % per year.