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Climate changes over time

Over the last few hundred years, climate changes have taken place all over the globe, including Denmark, Greenland and the Faroe Islands. Understanding these changes is of great value if we want to find out how much human activities contribute to climate changes.

To detect how much we are contributing to climate changes, we must know how much the climate changes by itself. This is the reason as to why historical weather data is of such great value.

The first direct temperature measurements go back to the 16th/17th centuries. However, reliable measurements covering the entire globe are not available before around 1860. In Denmark, temperature measurements were carried out in the Round Tower in Copenhagen from around 1750. When the DMI was established in 1872, the Institute took over climate monitoring and established a network of stations.

Climate information from earlier times is revealed in tree rings, corals and cores in lakes, marshes, oceans and ice caps. 

For climate research visit DMIs research-site:


Data of such types is by far less precise than direct measurements taken by instruments, such as thermometers. Still, instrumental measurements require a great deal of caution if used for climate change studies.

Correction of errors caused by relocation of stations, changes in instruments and observation times and not least environmental changes in the surrounding area of a measuring station, such as vegetation, buildings (urbanization), must always be included.

Measurements up through the atmosphere are obtained by balloon-borne instruments, the so-called radiosondes. In recent decades, measurements have been extended by satellite measurements.

National meteorological institutions around the world are responsible for systematic climate monitoring.

Monitoring is coordinated by the World Meteorological Organization (WMO), which has set up guidelines for measurement accuracy, measurement times and more.

WMO also coordinates the exchange of data between countries. 

Placing two rain gauges close together allows comparison and calibration of data. The manually operated rain gauge in the foreground is no longer used in Denmark. Photo John Cappelen.

By John Cappelen and Anne Mette K. Jørgensen (ret.)

For further information contact John Cappelen,

Edited by Niels Hansen, translated by Marianne Brandt,