Climate assessment within the scope of the WMO Climate System Monitoring (CSM) addresses mainly the provision of authoritative information on climate trends and anomalies which affects the climate system on global, regional and national scales. The coordination of these activities is undertaken with the effective and continuous collaboration of WMO Members and the technical support of the WMO Commission for Climatology. The international collaboration underpins WMO CSM, involving providing national reports on observed climate anomalies and related weather and extreme events with high socio-economic impacts, developing high quality global climate data sets required for assessing trends and variations in the global surface temperature and precipitations, and elaborating useful information on sea ice, sea level raise, ozone and other information describing large scale climate variability and climate change.
In all aspects of CSM, climate data sets constitute the fundamental ingredient to achieve reliable and verifiable scientific climate assessment. Therefore it is necessary to pay great attention to the quality of the data used to make sure that observed climate variations are conclusive. Good climate metadata documenting the technical and environmental conditions under which these data were recorded as well as any changes which might have affected these conditions in the past is therefore essential.
Climate change detection based on analyzing historical climate data and computing simple but highly informative climate indices enables climate scientists at national and international level to make scientific conclusions on climate change and how it affected the distribution of key climate parameters, particularly the extremes.
The WMO Commission for Climatology is working on developing WMO CSM including dataset development and dissemination, data exchange and data homogenisation, improving product and services and capacity development for developing and least developed countries. Peterson and Baddour (Climate Research, Vol. 47, 2011) described key challenges and perspectives on this topic.