Summary
Accurate measurement of fundamental parameters, such as temperature, density and composition, through the whole atmosphere and over long time scales is vitally important to identify and quantify changes in the earths climate, whether natural or anthropogenic. The NDMC group is the first to specifically focus on the global network of measurements in the mesopause region, or the boundary of the mesosphere and lower thermosphere (MLT), collectively sharing expertise on observational techniques, calibration and analysis methods and inter-comparison of measurements. Modelling studies have predicted that the middle and upper atmosphere, particularly at high latitudes, is more sensitive to change due to increases in carbon dioxide and methane and is expected to show significant cooling. To detect this, measurements are necessarily required over several decades in order to account for possible influences of the solar cycle, ozone depletion and changes in the mean flow, planetary, tidal and gravity wave activity in the underlying atmosphere. Ground based spectroscopic measurements of OH and O2 emissions provide one means of measuring temperature in the MLT region in a long-term cost-effective way. The rotational temperature technique is a well established method, relying on emission line intensity ratios and the instrumentation is robust, relatively simple and successfully automated for routine nightly operation. These criteria are essential for durable, stable, well calibrated observations over the extended time periods required. The focus of this thematic area is on the detection of climate change signals within these data sets. Strong emphasis is placed on regular and precise calibration, well documented observations and common data selection criteria and trend analysis methods. Ongoing monitoring over the global network is important to reduce uncertainty in establish trends, identify extremes or local anomalies and to determine future rates of change; in particular any recovery or response as a result of mitigation strategies employed to reduce carbon emissions.