Average temperatures in the world and in the Netherlands, 1900-2002
The average temperature in De Bilt was approximately 1 °C higher in the last 20 years than at the start of the 20th century. The global increase was approximately 0.6 °C.
Temperature in the Netherlands on the increase
The average temperature in De Bilt was approximately 1 °C higher in the last 20 years than in the period 1901-1920. The top ten of warm years since 1901 consists exclusively of years after 1989 (KNMI, 2003). At 10.8 °C, 2002 was also a warm year; it was 1.4 °C above the average for the period 1961-1990. In the last fifteen years, warmer-than-normal temperatures have been measured mainly in the winters and springs. The summer of 2003 was the hottest summer but one since 1901; only 1947 was hotter.
The graph shows the deviation from the annual average temperature as compared to the average temperature in the period 1961-1990 (the zero line).
Global temperature also on the increase
The increase in temperatures in the Netherlands matches the European and global pattern. The observed global rise in the earth's temperature during the twentieth century was 0.6 ± 0.2 °C (IPCC, 2001).
Link to climate change
The main reason for the increase in the average temperature on earth in the last 50 years is probably the result of the enhanced greenhouse effect caused by man. This enhanced greenhouse effect is a result of the emission of greenhouse gases to the atmosphere. Furthermore, there are natural processes that affect the average annual temperature on earth. These are, for example, variations in the strength of solar radiation, volcanic eruptions, El Nino, and chaotic fluctuations in the climate.
The increase in the temperature in the Netherlands is probably caused mainly by the enhanced greenhouse effect. Some of the increase is also ascribed to the increase in weather patterns involving south-westerly winds (KNMI, 2003; Oldenborg and Van Ulden, 2003). There are scientific suspicions that these are associated with the cooling of the high atmosphere as a result of ozone breakdown and the greenhouse effect (KNMI, 2003; Hartmann, 2000).
Technical note
The temperatures recorded in De Bilt are adjusted for the effects of changes in measurement locations, the height of measurements and the effect of urbanisation (KNMI). The progressive average in each year is calculated as a weighted average for the 15 most recent years.
References
- Hartmann, D.L., et al. (2000). Can ozone depletion and global warming interact to produce rapid climate change? Proc. Nat. Acad. Sci., 97, 1412-1417.
- Jones, P.D., et al. (1999). Surface air temperature and its changes over the past 150 years. Rev. Geophys., vol. 37, pp 173-199. Data of the Climate Research Unit (CRU) in Great Britain.
- Jones, P.D. and A. Moberg (2003). Hemispheric and large-scale surface air temperature variations: an extensive revision and an update to 2001, Journal of Climate, 16, 206-223, 2003.
- KNMI (2003). De toestand van het klimaat in Nederland 2003. Royal Netherlands Meteorological Institute, De Bilt, 32 pp.
- Oldenborgh, G.J. and A. van Ulden (2003). On the relationship between global warming, local warming in the Netherlands and changes in circulation in the 20th century, International Journal of Climatology, in press.
Relevant sections and indicators in the Environmental Data Compendium
- Environmental pressure, theme of Climate change: introduction and Climate change: policy
- See the 'Environmental pressure, theme of Climate change (greenhouse effect)' guide for the emissions of substances that affect the climate.
- Trends in precipitation in the Netherlands, 1906-2002
- Length of the growing season in the Netherlands, 1900-2002
- Sea levels on the Dutch coast, 1900-2002
- Overview 'environmental themes and impact on nature', with a reference to four indicators about the relationship between the greenhouse effect and nature.
Relevant information outside of the Environmental Data Compendium
- Information about the Climate Treaty and the Kyoto protocol can be found on the website of the United Nations Framework Convention on Climate Change (UNFCCC).
- Information about Dutch climate policy can be found on the website of the Ministry of Housing, Spatial Planning and the Environment.
- More information about the effects of climate change on the weather can be found on the website of the Royal Netherlands Meteorological Institute.
- More information about climate change and concentrations of greenhouse gases can be found on the websites of the IPCC (Intergovernmental Panel on Climate Change) and ETC/ACC (European Topic Center on Air and Climate Change).
- Information about current and future developments for the Kyoto Protocol can be found in Environmental Balance 2003 and National Environmental Outlook 2000-2030, both of which are RIVM publications.
