Monotonicity and discretization error estimates for convection-diffusion problems

Monotone operators provide a basis for pointwise bounds of the solution and discretization errors. We apply this technique for convection-diffusion problems, including an anisotropic diffusion term and show that the discretization error has a higher order of accuracy near Dirichlet boundaries or, alternatively, the second order of the global error remains even if we use a lower order of approximation near the Dirichlet boundary.