Historical climate data

What do we mean by Historical climate data?

The term historical climate data denotes surface observations above land and sea, dating back till about AD 1600 and continuing till the moment the observations lost their actual value (about five years before present). The recent observations (the past five years) are connected upon these. The observations carried out before the establishment of KNMI in 1854 are indicated as antique observations and are part of the historical observations.

The historical observations enable the construction of very long time series of climate parameters. Besides these direct climate observations we also consider observations from documentary sources. An example is the so-called 'Trekvaartseries'. For the winter period, this series gives information on the navigability (owing to ice growth) of a number of canals in the western part of the Netherlands. Such information can be used to derive winter temperatures indirectly (van den Dool et al., 1978).

Historical climate data must be distinguished form other categories of data such as paleo-observations, upper-air observations (radiosond), remote sensing images (satellite, radar) and model data (ECMWF, UKMO). De latter three categories of data are only available since World War II.

Although HISKLIM is, in principle, restricted to historical observations, it is obvious that also recent observations need our attention.  For instance the continuity of existing long climate time series towards the future needs to be considered, the homogenization of the Zwanenburg/De Bilt series and the archiving of digital and non-digital observations.
 

What is the importance of climate data?

Historical climate data and the related climate time series or databases are of major importance to the post-Kyoto process. Because of emission reductions, the FCCC (Framework Convention on Climate Change) and SBSTA (Subsidiary Body for Scientific and Technological Advice) have a greater need for clarity about anthropogenic climate change. Knowledge about natural variability of climate is therefore indispensable. For that long homogeneous time series of climate observations are needed.

Worldwide the request for long historical climate times series of good quality becomes stronger. For instance, large research programs like CLIVAR and the makers of the European Climate Assessment (ECSN) and the KNMI Climate Assessment of the Netherlands are to a great extent dependent on availability of those series. There is an increasing pressure from these research programs and other climate programs (WCRP, IPCC, GCOS) to construct well accessible databases for climate research. Furthermore, from different points of view (IPCC-TAR, GSN, EUMETNET), there is a request for time series with a higher temporal resolution (e.g. daily values instead of monthly).

The above-mentioned programs and the worldwide efforts to produce land and sea databases (COADS, CRU), are important triggers for the improvement of the accessibility of historical climate data. However, even without such triggers KNMI will make climate data accessible, simply because it belongs to her task.
 

intro-ne HISKLIM: program description | publications | datalinks

 


Theo Brandsma