Wind reports from moored buoys have smaller error than those from ships. Complicating the comparison of the two measurements are that NOMAD buoys report winds at a height of 5 metres (16 ft), while ships report winds from a height of 20–40 metres (66–131 ft).[24] Sea surface temperature measured in the intake port of large ships have a warm bias of around 0.6 °C (1 °F) due to the heat of the engine room.[25] This bias has led to changes in the perception of global warming since 2000.[26] Fixed buoys measure the water temperature at a depth of 3 metres (10 ft).[4]