Wind power is currently the most promising renewable technology and is expected to contribute significantly to achieving the “20-20-20” target set by EU - 20% reduction of greenhouse gases and 20% share of renewables by 2020. The development potential of wind power, especially offshore, is huge. The experience with large offshore wind farms so far has clearly shown that the offshore wind power is significantly more variable than the on-shore wind power, first of all because offshore wind power is more concentrated geographically than existing on-shore wind power. The focus is on time scales of interest for power system operation, thus ranging from minutes to hours. The simulations are based on the offshore wind power development plans developed in the TWENTIES project and includes details such as installed capacity and coordinates for each wind farm existing or planned to be installed in North Europe, by 2020 and 2030. For each target, a base case and a high scenario is simulated. The offshore wind power variability is quantified in terms of ramp rates.