Several viable but conflicting explanations have been proposed to explain the recent ~8 p.p.b. per year increase in atmospheric methane after 2006, equivalent to net emissions increase of ~25 Tg CH
...per year. A concurrent increase in atmospheric ethane implicates a fossil source; a concurrent decrease in the heavy isotope content of methane points toward a biogenic source, while other studies propose a decrease in the chemical sink (OH). Here we show that biomass burning emissions of methane decreased by 3.7 (±1.4) Tg CH
per year from the 2001-2007 to the 2008-2014 time periods using satellite measurements of CO and CH
, nearly twice the decrease expected from prior estimates. After updating both the total and isotopic budgets for atmospheric methane with these revised biomass burning emissions (and assuming no change to the chemical sink), we find that fossil fuels contribute between 12-19 Tg CH
per year to the recent atmospheric methane increase, thus reconciling the isotopic- and ethane-based results.
The 2015 fire season and related smoke pollution in Indonesia was more severe than the major 2006 episode, making it themost severe season observed by the NASA Earth Observing System satellites that ...go back to the early 2000s, namely active fire detections from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS), MODIS aerosol optical depth, Terra Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO), Aqua Atmospheric Infrared Sounder (AIRS) CO, Aura Ozone Monitoring Instrument (OMI) aerosol index, and Aura Microwave Limb Sounder (MLS) CO. The MLS CO in the upper troposphere showed a plume of pollution stretching from East Africa to the western Pacific Ocean that persisted for 2 mo. Longer-term records of airport visibility in Sumatra and Kalimantan show that 2015 ranked after 1997 and alongside 1991 and 1994 as among the worst episodes on record. Analysis of yearly dry season rainfall from the Tropical Rainfall Measurement Mission (TRMM) and rain gauges shows that, due to the continued use of fire to clear and prepare land on degraded peat, the Indonesian fire environment continues to have nonlinear sensitivity to dry conditions during prolonged periods with less than 4 mm/d of precipitation, and this sensitivity appears to have increased over Kalimantan. Without significant reforms in land use and the adoption of early warning triggers tied to precipitation forecasts, these intense fire episodes will reoccur during future droughts, usually associated with El Niño events.
Top‐down estimates using satellite data provide important information on the sources of air pollutants. We develop a sector‐based 4D‐Var framework based on the GEOS‐Chem adjoint model to address the ...impacts of co‐emissions and chemical interactions on top‐down emission estimates. We apply OMI NO2, OMI SO2, and MOPITT CO observations to estimate NOx, SO2, and CO emissions in East Asia during 2005–2012. Posterior evaluations with surface measurements show reduced normalized mean bias (NMB) by 7% (NO2)–15% (SO2) and normalized mean square error (NMSE) by 8% (SO2)–9% (NO2) compared to a species‐based inversion. This new inversion captures the peak years of Chinese SO2 (2007) and NOx (2011) emissions and attributes their drivers to industry and energy activities. The CO peak in 2007 in China is driven by residential and industry emissions. In India, the inversion attributes NOx and SO2 trends mostly to energy and CO trend to residential emissions.
Plain Language Summary
Satellite observations are widely used to estimate air pollutant emissions and evaluate their trends. We design a new method based on Bayesian statistics to estimate emissions of major air pollutants in East Asia according to their sources (e.g., energy, industry, transportation, etc.). Results from this approach show better agreement with independent surface measurements than the previous estimates that use observations to optimize emissions by species and estimates that compile emissions using activity data and emission factors. This method provides a new perspective to analyze the trend of air pollutants by sources and is crucial for countries and regions that lack detailed and timely emission estimates for each source sector.
Key Points
A new sector‐based multispecies inversion framework is developed to estimate NOx, SO2, and CO emissions using satellite observations
The sector‐based inversion leads to smaller biases and errors in surface NO2 and SO2 simulations than a species‐based inversion
The framework provides a new perspective to analyze the trend of emissions by sectors and evaluates bottom‐up estimates
Measurements of Pollution in the Troposphere (MOPITT) satellite and ground-based carbon monoxide (CO) measurements both suggest a widespread downward trend in CO concentrations over East Asia during ...the period 2005-2016. This negative trend is inconsistent with global bottom-up inventories of CO emissions, which show a small increase or stable emissions in this region. We try to reconcile the observed CO trend with emission inventories using an atmospheric inversion of the MOPITT CO data that estimates emissions from primary sources, secondary production, and chemical sinks of CO. The atmospheric inversion indicates a ~ −2% yr−1 decrease in emissions from primary sources in East Asia from 2005-2016. The decreasing emissions are mainly caused by source reductions in China. The regional MEIC inventory for China is the only bottom up estimate consistent with the inversion-diagnosed decrease of CO emissions. According to the MEIC data, decreasing CO emissions from four main sectors (iron and steel industries, residential sources, gasoline-powered vehicles, and construction materials industries) in China explain 76% of the inversion-based trend of East Asian CO emissions. This result suggests that global inventories underestimate the recent decrease of CO emission factors in China which occurred despite increasing consumption of carbon-based fuels, and is driven by rapid technological changes with improved combustion efficiency and emission control measures.
Atmospheric carbon monoxide (CO) concentrations have been
decreasing since 2000, as observed by both satellite- and ground-based
instruments, but global bottom-up emission inventories estimate ...increasing
anthropogenic CO emissions concurrently. In this study, we use a
multi-species atmospheric Bayesian inversion approach to attribute
satellite-observed atmospheric CO variations to its sources and sinks in
order to achieve a full closure of the global CO budget during 2000–2017.
Our observation constraints include satellite retrievals of the total column
mole fraction of CO, formaldehyde (HCHO), and methane (CH4) that are
all major components of the atmospheric CO cycle. Three inversions (i.e.,
2000–2017, 2005–2017, and 2010–2017) are performed to use the observation
data to the maximum extent possible as they become available and assess the
consistency of inversion results to the assimilation of more trace gas
species. We identify a declining trend in the global CO budget since 2000
(three inversions are broadly consistent during overlapping periods), driven
by reduced anthropogenic emissions in the US and Europe (both likely from
the transport sector), and in China (likely from industry and residential
sectors), as well as by reduced biomass burning emissions globally,
especially in equatorial Africa (associated with reduced burned areas). We
show that the trends and drivers of the inversion-based CO budget are not
affected by the inter-annual variation assumed for prior CO fluxes. All
three inversions contradict the global
bottom-up inventories in the world's top two emitters: for the sign of
anthropogenic emission trends in China (e.g., here -0.8±0.5 % yr−1 since 2000, while the prior gives 1.3±0.4 % yr−1)
and for the rate of anthropogenic emission increase in South Asia (e.g.,
here 1.0±0.6 % yr−1 since 2000, smaller than 3.5±0.4 % yr−1 in the prior inventory). The posterior model CO
concentrations and trends agree well with independent ground-based
observations and correct the prior model bias. The comparison of the three
inversions with different observation constraints further suggests that the
most complete constrained inversion that assimilates CO, HCHO, and CH4
has a good representation of the global CO budget, and therefore matches best
with independent observations, while the inversion only assimilating CO
tends to underestimate both the decrease in anthropogenic CO emissions and
the increase in the CO chemical production. The global CO budget data from
all three inversions in this study can be accessed from
https://doi.org/10.6084/m9.figshare.c.4454453.v1 (Zheng et al., 2019).
The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making nearly continuous observations of atmospheric carbon monoxide (CO) since 2000. Satellite observations of ...CO are routinely used to analyze emissions from fossil fuels and biomass burning, as well as the atmospheric transport of those emissions. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the version 8 (V8) product. V8 products benefit from updated spectroscopic data for water vapor and nitrogen used to develop the operational radiative transfer model and exploit a new method for minimizing retrieval biases through parameterized radiance bias correction. In situ datasets used for algorithm development and validation include the NOAA (National Oceanic and Atmospheric Administration) and HIPPO (HIAPER Pole-to-Pole Observations) datasets used for earlier MOPITT validation work in addition to measurements from the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems – Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)), KORUS-AQ (The Korea-United States Air Quality Study), and ATom (The Atmospheric Tomography Mission) programs. Validation results illustrate clear improvements with respect to long-term bias drift and geographically variable retrieval bias. For example, whereas bias drift for the V7 thermal-infrared (TIR)-only product exceeded 0.5 % yr−1 for levels in the upper troposphere (e.g., at 300 hPa), bias drift for the V8 TIR-only product is found to be less than 0.1 % yr−1 at all levels. Also, whereas upper-tropospheric (300 hPa) retrieval bias in the V7 TIR-only product exceeded 10 % in the tropics, corresponding V8 biases are less than 5 % (in terms of absolute value) at all latitudes and do not exhibit a clear latitudinal dependence.
Rising emissions from wildfires over recent decades in the Pacific Northwest are known to counteract the reductions in human-produced aerosol pollution over North America. Since amplified Pacific ...Northwest wildfires are predicted under accelerating climate change, it is essential to understand both local and transported contributions to air pollution in North America. Here, we find corresponding increases for carbon monoxide emitted from the Pacific Northwest wildfires and observe significant impacts on both local and down-wind air pollution. Between 2002 and 2018, the Pacific Northwest atmospheric carbon monoxide abundance increased in August, while other months showed decreasing carbon monoxide, so modifying the seasonal pattern. These seasonal pattern changes extend over large regions of North America, to the Central USA and Northeast North America regions, indicating that transported wildfire pollution could potentially impact the health of millions of people.
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. Aerosols are co-emitted with CO from both fires and anthropogenic sources but with a shorter lifetime than CO. 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. 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. 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. Trends are examined by hemisphere and in regions for 2002 to 2018, with uncertainties quantified. The CO and AOD records are split into two sub-periods (2002 to 2010 and 2010 to 2018) in order to assess trend changes over the 16 years. We focus on four major population centers: Northeast China, North India, Europe, and Eastern USA, as well as fire-prone regions in both hemispheres. 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 find evidence of the atmospheric impact of air quality management policies. 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. Industrial regions with minimal emission control measures such as North India become more globally relevant as the global CO trend weakens. We also examine the CO trends in monthly percentile values to understand seasonal implications and find that local changes in biomass burning are sufficiently strong to counteract the global downward trend in atmospheric CO, particularly in late summer.
•The global decreasing trend in CO has shown a recent slowdown.•Fire emissions in NH boreal regions counteract decreasing CO in late summer.•AOD helps interpret CO trends and variability.•Trends in four industrial regions show impact from varying air quality controls.
The Measurements of Pollution in the Troposphere (MOPITT) instrument is the only satellite-borne sensor in operation that uses both thermal (TIR) and near-infrared (NIR) channels to estimate CO ...profiles. With more than 15 years (2000 to present) of validated multispectral observations, MOPITT provides the unique capability to separate CO in the lowermost troposphere (LMT, surface to 3 km (∼ 700 hPa)) from the free-tropospheric abundance. To extend this record, a new, hyper-spectral approach is presented here that will provide CO data products exceeding the capabilities of MOPITT by combining the short-wavelength infrared (SWIR, equivalent to the MOPITT NIR) channels from the TROPOspheric Monitoring Instrument (TROPOMI) to be launched aboard the European Sentinel 5 Precursor (S5p) satellite in 2016 and the TIR channels from the Cross-track Infrared Sounder (CrIS) aboard the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite. We apply the MUlti-SpEctra, MUlti-SpEcies, Multi-SEnsors (MUSES) retrieval algorithm to quantify the potential of this joint CO product. CO profiles are retrieved from a single-footprint, full-spectral-resolution CrIS transect over Africa on 27–28 August 2013 coincident with significant biomass burning. Comparisons of collocated CrIS and MOPITT CO observations for the LMT show a mean difference of 2.8 ± 24.9 ppb, which is well within the estimated measurement uncertainty of both sensors. The estimated degrees of freedom (DOF) for CO signals from synergistic CrIS–TROPOMI retrievals are approximately 0.9 in the LMT and 1.3 above the LMT, which indicates that the LMT CO can be distinguished from the free troposphere, similar to MOPITT multispectral observations (0.8 in the LMT, and 1.1 above the LMT). In addition to increased sensitivity, the combined retrievals reduce measurement uncertainty, with ∼ 15 % error reduction in the LMT. With a daily global coverage and a combined spatial footprint of 14 km, the joint CrIS–TROPOMI measurements have the potential to extend and improve upon the MOPITT multispectral CO data records for the coming decade.
Inter-annual variations in the tropical land carbon (C) balance are a
dominant component of the global atmospheric CO2 growth rate.
Currently, the lack of quantitative knowledge on processes ...controlling net
tropical ecosystem C balance on inter-annual timescales inhibits accurate understanding and projections of land–atmosphere C exchanges. In particular, uncertainty on the relative contribution of ecosystem C fluxes attributable
to concurrent forcing anomalies (concurrent effects) and those attributable
to the continuing influence of past phenomena (lagged effects) stifles
efforts to explicitly understand the integrated sensitivity of a tropical ecosystem to climatic variability. Here we present a conceptual
framework – applicable in principle to any land biosphere model – to
explicitly quantify net biospheric exchange (NBE) as the sum of anomaly-induced
concurrent changes and climatology-induced lagged changes to terrestrial
ecosystem C states (NBE = NBECON+NBELAG). We apply this framework to an
observation-constrained analysis of the 2001–2015 tropical C balance: we use
a data–model integration approach (CARbon DAta-MOdel fraMework – CARDAMOM) to merge satellite-retrieved land-surface C observations (leaf area, biomass, solar-induced fluorescence), soil C inventory data and satellite-based atmospheric
inversion estimates of CO2 and CO fluxes to produce a data-constrained
analysis of the 2001–2015 tropical C cycle. We find that the inter-annual
variability of both concurrent and lagged effects substantially contributes to the 2001–2015 NBE inter-annual variability throughout 2001–2015 across
the tropics (NBECON IAV = 80 % of total NBE IAV, r = 0.76;
NBELAG IAV = 64 % of NBE IAV, r = 0.61), and the prominence of NBELAG IAV persists across both wet and dry tropical ecosystems. The
magnitude of lagged effect variations on NBE across the tropics is largely
attributable to lagged effects on net primary productivity (NPP; NPPLAG IAV
113 % of NBELAG IAV, r = −0.93, p value < 0.05), which emerge due to the dependence of NPP on inter-annual variations in foliar C and
plant-available H2O states. We conclude that concurrent and lagged
effects need to be explicitly and jointly resolved to retrieve an accurate
understanding of the processes regulating the present-day and future trajectory of the terrestrial land C sink.
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