At a glance
- 2017 was the third warmest year worldwide since records began.
- The 20 warmest years worldwide since 1850 occurred after 1990.
- The Paris Climate Agreement stipulates that the increase in global temperature should be limited to well below 2 °C above pre-industrial levels, and even to 1.5 °C.
Climate change manifests itself as an increase in the global average surface temperature. But we are also seeing increases in climate variability and risks of extreme weather events such as heavy precipitation, heat waves and droughts.
Germany as well has become warmer over the years. Consequently, the number of hot days are increasing (cf. 'Hot days' indicator). The increase in average temperatures is also changing the duration of individual seasons. As of yet we have only a rudimentary understanding of the complex effects of these seasonal shifts on plants and animals.
The global average temperature for one year alone is not very significant. We obtain more information from a given year's global mean deviation from the average for a longer period in the past. This shows whether one year was warmer or cooler than the climatological average. The internationally accepted ‘climate normal period’ 1961 to 1990 is normally used as the reference period.
The 'German Strategy of Adaptation to Climate Change' envisages climate impact monitoring (BReg 2008). Climate change impacts and adaptation in different areas are published in a monitoring report which is updated every four years (UBA 2015, in German only).
Assessing the development
To prevent dangerous interference to the climate system, the aim is to limit the temperature increase to well below 2 degrees Celsius (°C) above pre-industrial levels, and even to 1.5 °C. This is the agreement adopted by the global community at the 2015 Climate Conference in Paris (UNFCCC 2015). To achieve this target, global greenhouse gas emissions must be reduced rapidly and substantially (cf. 'Greenhouse gas emissions' indicator).
According to calculations by the Hadley Centre, in 2017 the global average near-surface temperature was approximately 0.54 °C above the average for the 1961 to 1990 period. This makes 2017 the third hottest year on record. The 20 warmest years since records began have all occurred since 1990.
The Hadley Centre's temperature data form part of an internationally recognised body of temperature datasets. As with other available datasets, the global average surface temperature is based on measurement data from meteorological stations. The global average surface temperature is calculated from worldwide measurements using a combination of calculation rules and interpolations. More detailed information about the Hadley Centre calculations can be found in a paper which describes the HadCRUT4 model (Morice et al. 2012).
More detailed information: 'Trends der Lufttemperatur' (in German only).