  The predictability problem in the inverse energy cascade of two-dimensional
turbulence is addressed by means of high resolution direct numerical
simulations. The analysis is done in terms of the finite size Lyapunov exponent
(FSLE) which is a measure of the growth rate at fixed error level. The
numerical results are compared with classical closure predictions and good
quantitative agreement is found. Finally, it is shown that the inertial range
predictability properties are not affected by the presence of noise induced by
the small, not resolved, scales.
