Washington, October 27 A new study by scientists has determined that it would take about 50 years of observations to detect a clear trend in upper tropospheric water vapor.

Water vapor in the upper troposphere contributes to the greenhouse effect, and scientists predict that humidity will increase in the future along with rising levels of atmospheric carbon dioxide.

However, there is currently no observing program that could detect the predicted trends.

To determine instrumental needs to measure long-term changes in upper tropospheric water vapor, R. Boers and E. van Meijgaard from Royal Netherlands Meteorological Institute, De Bilt, Netherlands, analyzed how frequently and for how long observations would need to be made to clearly detect a trend in upper tropospheric water vapor.

They used a regional climate model to simulate a perfect 150-year humidity record, and then sample from the model data to simulate realistic radiosonde water vapor observations with various observation frequencies.

The analysis shows that it would take 30 years for a clear trend to show up in the perfect record; sampling every four days, it would take at least 50 years of observations to detect this trend.

The authors suggest that these results, along with economic considerations, should be an important consideration for those planning an atmospheric water vapor monitoring program. (ANI)