Welschinger invariants of real del Pezzo surfaces of degree ≥ 2

We compute the purely real Welschinger invariants, both original and modified, for all real del Pezzo surfaces of degree ≥ 2. We show that under some conditions, for such a surface X and a real nef and big divisor class D Pic(X), through any generic collection of - DKX - 1 real points lying on a connected component of the real part ℝX of X one can trace a real rational curve C |D|. This is derived from the positivity of appropriate Welschinger invariants. We furthermore show that these invariants are asymptotically equivalent, in the logarithmic scale, to the corresponding genus zero Gromov-Witten invariants. Our approach consists in a conversion of Shoval-Shustin recursive formulas counting complex curves on the plane blown up at seven points and of Vakil's extension of the Abramovich-Bertram formula for Gromov-Witten invariants into formulas computing real enumerative invariants.