\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[english]{babel}



\usepackage{float}








\begin{document}

\title{21st Century Change in Global Small-Size Aerosols from Combustion
Emissions}



\author[1]{Meemong Lee}%
\author[1]{John Worden}%
\author[2]{Rebecca Bucholz}%
\author[2]{Helen Worden}%
\author[2]{Mijeong Park}%
\author[3]{Yuan Wang}%
\author[4]{Jiani Yang}%
\author[5]{Marcin Witek}%
\author[1]{Hui Su}%
\author[6]{Brendan Byrne}%
\author[6]{Kazu Miyazaki}%
\author[6]{Jonathan Jiang}%
\affil[1]{Jet Propulsion Laboratory}%
\affil[2]{National Center for Atmospheric Research, Boulder, CO}%
\affil[3]{California Institute of Technology,  Pasadena, CA}%
\affil[4]{California Institute of Technology, Pasadena, CA}%
\affil[5]{Jet propulsion Laboratory, California Institute of Technology, Pasadena, CA}%
\affil[6]{Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA}%


\vspace{-1em}



  
  \date{May 24, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
Changes in aerosol optical depth, both positive and negative, are
observed across the globe during the 21rst Century. However, attribution
of these changes to specific sources is largely uncertain as there are
multiple contributing natural and anthropogenic sources that produce
aerosols either directly or through secondary chemical reactions. Here
we show that satellite-based changes in small-mode AOD between 2002 and
2019 observed in data from MISR can primarily be explained by changes,
either directly or indirectly, in combustion emissions. We quantify
combustion emissions using MOPITT total column CO observations and the
adjoint of the GEOS-Chem global chemistry and transport model. The a
priori fire emissions are taken from the Global Fire Emission Data base
with small fires (GFED4s) but with fixed a priori for non-fire
emissions. Aerosol precursor and direct emissions are updated by
re-scaling them with the monthly ratio of the CO posterior to prior
emissions. The correlation between modeled and observed AOD improves
from a mean of 0.15 to 0.81 for the four industrial regions considered
and from 0.52 to 0.75 for the four wildfire-dominant regions considered.
Using these updated emissions in the GEOS-Chem global chemistry
transport model, our results indicate that surface PM2.5 have declined
across many regions of the globe during the 21rst century. For example,
PM2.5 over China has declined by \textasciitilde{}30\% with smaller
fractional declines in E. USA and Europe (from fossil emissions) and in
S. America (from fires). These results highlight the importance of
forest management and cleaner combustion sources in improving
air-quality.%
\end{abstract}%



\sloppy




\selectlanguage{english}
\FloatBarrier
\end{document}

