Let $\mathfrak{L}$ be a Leibniz algebra, $E$ a vector space and $\pi : E \to
\mathfrak{L}$ an epimorphism of vector spaces with $ \mathfrak{g} = {\rm Ker}
(\pi)$. The global extension problem asks for the classification of all Leibniz
algebra structures that can be defined on $E$ such that $\pi : E \to
\mathfrak{L}$ is a morphism of Leibniz algebras: from a geometrical viewpoint
this means to give the decomposition of the groupoid of all such structures in
its connected components and to indicate a point in each component. All such
Leibniz algebra structures on $E$ are classified by a global cohomological
object ${\mathbb G} {\mathbb H} {\mathbb L}^{2} \, (\mathfrak{L}, \,
\mathfrak{g})$ which is explicitly constructed. It is shown that ${\mathbb G}
{\mathbb H} {\mathbb L}^{2} \, (\mathfrak{L}, \, \mathfrak{g})$ is the
coproduct of all local cohomological objects $ {\mathbb H} {\mathbb L}^{2} \,
\, (\mathfrak{L}, \, (\mathfrak{g}, [-,-]_{\mathfrak{g}}))$ that are
classifying sets for all extensions of $\mathfrak{L}$ by all Leibniz algebra
structures $(\mathfrak{g}, [-,-]_{\mathfrak{g}})$ on $\mathfrak{g}$. The second
cohomology group ${\rm HL}^2 \, (\mathfrak{L}, \, \mathfrak{g})$ of Loday and
Pirashvili appears as the most elementary piece among all components of
${\mathbb G} {\mathbb H} {\mathbb L}^{2} \, (\mathfrak{L}, \, \mathfrak{g})$.
Several examples are worked out in details for co-flag Leibniz algebras over
$\mathfrak{L}$, i.e. Leibniz algebras $\mathfrak{h}$ that have a finite chain
of epimorphisms of Leibniz algebras $\mathfrak{L}_n : = \mathfrak{h}
\stackrel{\pi_{n}}{\longrightarrow} \mathfrak{L}_{n-1} \, \cdots \,
\mathfrak{L}_1 \stackrel{\pi_{1}} {\longrightarrow} \mathfrak{L}_{0} :=
\mathfrak{L}$ such that ${\rm dim} ({\rm Ker} (\pi_{i})) = 1$, for all $i = 1,
\cdots, n$.Comment: 20 pages: Continues arXiv:1307.254