  We study the global analysis for parton distributions as a function of the
QCD strong coupling strength alpha_s, and present a new series of distributions
that span the range 0.110 < alpha_s(m_Z) < 0.128. We use these distributions to
explore the correlation between alpha_s and the gluon distribution; the
viability of global analysis as a method to measure alpha_s; and the dependence
on alpha_s of predictions for W, Z, inclusive jet, and Higgs boson production
($b \bar{b} \to H$ and $gg \to H$) cross sections at the Tevatron and the LHC.
We find that the uncertainty in alpha_s is the dominant source of uncertainty
for inclusive jet production at moderately small p_T and for Higgs production
at intermediate masses in the standard model.
