Climate monitoring is the process of observing and understanding the atmosphere, oceans and other components of the Earth System.
At its simplest, monitoring consists in measuring and recording things like temperature and rainfall. Records of temperature and rainfall together with measurements of humidity, deep ocean temperature, sea level, pressure, wind speed and many, many others help to build a complete picture of the global climate.
Where long term records exist we can use these to describe how current conditions fit into the long-term context of a variable and changing climate. In some cases it is also possible to explain what we see in terms of the diverse drivers - natural and human - of the climate system.
Care must be taken in putting together climate monitoring data sets. Even subtle changes in the way that measurements are made can show up in records as an apparent change in the climate itself. A great deal of work is done to understand how best to build consistent long-term records from historical observations and how to join these with modern observations from satellites.
Another difficulty is that for some parts of the world we have only short records, or, in some cases, no records at all. Using information about how temperature or other factors at nearby locations are related, it is sometimes possible to estimate what happened in an area where there are few or no observations. However, because these are estimates, it is also important to understand and quantify how accurate our estimates might be.
Because of the care taken in their production, data sets of observations produced for climate monitoring are used by scientists across the world in studies of climate change and variability, of causes and effects.
The weather and climate affect the way that we live and the decisions that we make. If you take a holiday in a foreign country, it is common to ask what clothes you should pack based on the weather that is usual for that region. In other situations, for example, designing a building or planning a sewage system, it might be important to know what are the highest and lowest temperatures recorded near the site, or how much rain can fall in any given period.
The importance to society of the climate and weather means that there is great value in having access to reliable long term records. The same records can also be used to build and test the systems used to make long-term climate predictions.
The Met Office Hadley Centre monitors a wide range of climate variables and indices, such as air temperature over the land and oceans, sea-surface temperatures, ocean temperatures at different depths beneath the surface, humidity, surface pressure, sea ice and temperatures throughout the atmosphere. The Met Office also uses data sets generated in other institutions to build a comprehensive view of global climate.
Because of the difficulties of dealing with changes in instrumentation and areas with sparse data, Met Office scientists compare their results with those from other centres. Comparisons between data sets help to hone our understanding of the accuracy and reliability of our data sets in a process of continual refinement.
The Met Office participates in a wide variety of international monitoring activities such as the production of comprehensive reports such as the WMO annual statement on the global climate, the Bulletin of the American Meteorological Society annual State of the Climate report and the IPCC reports. The Met Office also participates in international activities to identify and digitise historical observations of weather from archives around the world.
Further information and other data are available from www.metoffice.gov.uk/hadobs
Last updated: 26 September 2013