Branching arrows with decision option in flowchart

%\title{Branching arrows with decision option in flowchart}
% From http://latex-community.org/forum/viewtopic.php?f=45&t=24006
\documentclass[11pt]{article}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{arrows,calc,positioning}

\tikzstyle{intt}=[draw,text centered,minimum size=6em,text width=5.25cm,text height=0.34cm]
\tikzstyle{intl}=[draw,text centered,minimum size=2em,text width=2.75cm,text height=0.34cm]
\tikzstyle{int}=[draw,minimum size=2.5em,text centered,text width=3.5cm]
\tikzstyle{intg}=[draw,minimum size=3em,text centered,text width=6.cm]
\tikzstyle{sum}=[draw,shape=circle,inner sep=2pt,text centered,node distance=3.5cm]
\tikzstyle{summ}=[drawshape=circle,inner sep=4pt,text centered,node distance=3.cm]

\begin{document}
  \begin{figure}[!htb]
    \centering
    \begin{tikzpicture}[
      >=latex',
      auto
    ]
      \node [intg] (kp)  {Sun/Radiation};
      \node [int]  (ki1) [node distance=1.5cm and -1cm,below left=of kp] {Methane/Carbon Dioxide/Burning of Fossil Fuels};
      \node [int]  (ki2) [node distance=1.5cm and -1cm,below right=of kp] {Deforestation/Melting Ice/Chemical Induced Fertilizer};
      \node [intg] (ki3) [node distance=5cm,below of=kp] {More Storms and Failing Crops};
      \node [intg] (ki4) [node distance=2cm,below of=ki3] {Extinction};

      \draw[->] (kp) -- ($(kp.south)+(0,-0.75)$) -| (ki1) node[above,pos=0.25] {} ;
      \draw[->] (kp) -- ($(kp.south)+(0,-0.75)$) -| (ki2) node[above,pos=0.25] {};
      \draw[->] (ki1) |- (ki3);
      \draw[->] (ki2) |- (ki3);
      \draw[->] (ki3) -- (ki4);
    \end{tikzpicture}
    \caption{}
    \label{}
  \end{figure}
\end{document}