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Indicator Assessment
Modelled number of tropical nights over Europe during summer (June-August) 1961-1990 and 2071-2100
Note: Reference period (1961-1990) (left), scenario period (2071-2100) (centre) and change between periods (right)
Dankers, R. and Hiederer, R., 2008. Extreme Temperatures and Precipitation in Europe: Analysis of a High-Resolution Climate Change Scenario. EUR 23291 EN. Office for Official Publications of the European Communities Luxembourg. 66 pp.
European annual average temperature deviations, 1850-2008, relative to the 1850-1899 average (in ºC). The lines refer to 10-year moving average, the bars to the annual 'land only' European average
Annual and seasonal average
The average temperature has increased 1.3oC and 1.0oC for the European land area and European land & ocean area , respectively, comparing the trend towards 2008 with pre-industrial times (CRU, 2007) (Fig. 3). As such Europe has warmed slightly more than the global average (i.e. 0.9oC and 0.7oC for land and land & ocean). Considering the European land, nine of the 12 years between 1997 and 2008 were among the warmest years since 1850' in Europe with 2007 as warmest year (1.5oC higher than pre-industrial), closely followed by 2000, 2006 and 2008.
Seasonally, Europe warmed more in winter than in summer (Fig. 4). Remarkably, autumn saw almost no warming. Geographically, particularly significant warming has been observed in the past 50 years over the Iberian Peninsula, in central and north-eastern Europe and in mountainous regions (Bohm et al., 2001; Klein Tank, 2004). In the past 30 years, warming was strongest over Scandinavia, especially in winter, whereas the Iberian Peninsula warmed in summer
The annual average temperature for Europe is projected to increase by 1.0-5.5oC (comparing 2080-2100 with the 1961-1990 average). This range takes into account the uncertainties in future socio-economic development by including two of the IPCC-SRES scenarios (the high emissions A2 and the medium emissions A1b), and the uncertainties in the climate models (IPCC, 2007b). The warming is projected to be greatest over eastern Europe, Scandinavia and the Arctic in winter (December to February), and over south-western and Mediterranean Europe in summer (June to August) (Giorgi et al., 2004; IPCC, 2007a). The temperature rise in parts of France and the Iberian Peninsula may exceed 6oC, while the Arctic could become on average 6oC and possibly 8oC warmer than the 1961-1990 average (IPCC, 2007a,b; ACIA 2007).
Temperature extremes in Europe
High-temperature extremes like hot days, tropical nights, and heat waves have become more frequent, while low-temperature extremes (e.g. cold spells, frost days) have become less frequent in Europe (Klein Tank, 2004; IPCC 2007a, Fig. 5). The average length of summer heat waves over Western Europe doubled over the period 1880 to 2005 and the frequency of hot days almost tripled (Della-Marta et al, 2007).
Extreme high temperature events across Europe, along with the overall warming, are projected to become more frequent, intense and longer this century (Schar et al., 2004, Tebaldi et al., 2006, IPCC, 2007a,b; Beniston et al., 2007). Likewise, night temperatures are projected to increase considerably, possibly leading to additional health problems and even mortality (Halsnćs et al, 2007, Sillman and Roekner, 2008), at least partly compensated by reduced mortality in winter (Fig. 6).
Geographically, the maximum temperature during summer is projected to increase far more in southern and central Europe than in northern Europe, whereas the largest reduction in the occurrence of cold extremes is projected for northern Europe (Kjellstrom et al., 2007; Beniston et al., 2007, Sillman and Roekner, 2008). Under the A2 scenario, central Europe, for example, is projected to experience by the end of the 21st century the same number of hot days as are currently experienced in Spain and Sicily (Beniston et al., 2007).
Global annual average temperature deviations, 1850-2008, relative to the 1850-1899 average (in ºC). The lines refer to 10-year moving average, the bars to the annual 'land and ocean' global average.
The Earth has experienced considerable temperature increases in the last 100 years, especially in the most recent decades. These changes are unusual in terms of both magnitude and rate of change. The temperature increase up to 2008 was about 0.7oC (land & ocean) compared to pre-industrial (defined as 1850-1899 average), about 1/3 of the EU 'sustainable' target of limiting global average warming to not more than 2oC above pre-industrial levels (Fig. 1). The increase over the global land area has been 0.9oC. Eleven of the last 12 years (1997-2008) rank among the warmest years in the instrumental record (the exception being 1996), and 2005 and 1998 were the warmest two years than any other year (Jones and Moberg, 2003; IPCC, 2007a). Note that 1998 experienced a strong El Nino, a warm water event in the eastern Pacific Ocean that adds warmth to global temperatures. In 2005 was about equally warm as 1998 without an El Nino event. 2008 was about 0.7oC above pre-industrial values. As such 2008 is set to be cooler globally than recent years. This is mainly due to the development of a strong La Nina in the tropical Pacific Ocean and changes in solar activity that limited the warming trend of the global climate. Despite these developments, 2008 is still one of the top ten warmest years.
The rate of change in the global average temperature is accelerating from 0.1oC per decade over the last 100 years, to 0.13oC per decade over the past 50 years up to 0.16oC per decade over the last 10 years (all values represent land & ocean area) (IPCC, 2007a) (Fig. 2). As such the indicative target of 0.2oC per decade becomes close.
The global and European average temperature is projected to continue to increase. Globally, the projected increase in this century is between 1.8 and 4.0oC (best estimate), and is considered likely (66 % probability) to be between 1.1 and 6.4oC for the six IPCC SRES scenarios and multiple climate models (IPCC 2007a), comparing the 2080-2100 average with the 1980-1999 average. These scenarios assume that no additional policies to limit greenhouse gas emissions are implemented (IPCC 2007). The range results from the uncertainties in future socio-economic development and in climate models. The EU 'sustainable' target of limiting global average warming to not more than 2.0oC above pre-industrial level is projected to be exceeded between 2040 and 2060, for the all six IPCC scenarios.
These recent projections are more advanced -as they provide best estimates and an assessed likelihood range for each of the marker scenarios- and now rely on a larger number of climate models of increasing complexity and realism, as well as new information regarding the nature of feedbacks from the carbon cycle and constraints on climate response from observations.
This indicator shows absolute changes and rates of change in average near-surface temperature for the globe and for a region covering Europe. Near-surface air temperature gives one of the clearest and most consistent signals of global and regional climate change, especially in recent decades. It has been measured for many decades or even centuries at some locations and a dense network of stations across the globe, and especially in Europe, provide regular monitoring of temperature, using standardised measurements, quality control and homogeneity procedures.
This indicator provides guidance for the following policy-relevant questions:
Global average annual temperature deviations, ‘anomalies’, are discussed relative to a ‘pre-industrial’ period between 1850 and 1899 (beginning of instrumental temperature records). During this time, anthropogenic greenhouse gases from the industrial revolution (between 1750 and 1850) are considered to have a relatively small influence on climate compared to natural influences. However it should be noted that owing to earlier changes in the climate due to internal and forced natural variability there was not one single pre-industrial climate and it is not clear that there is a rigorous scientific definition of the term ‘pre-industrial climate’.
Temperature changes also influence other aspects of the climate system which can impact on human activities, including sea level, intensity and frequency of floods and droughts, biota and food productivity and infectious diseases. In addition to the global average target, seasonal variations and spatial distributions of temperature change are important, for example to understand the risks that current climate poses to human and natural systems and to assess how these may be impacted by future climate change.
Units are degrees Celsius (°C) and degrees Celsius per decade (°C/decade).
Baseline period
Global average annual temperature is expressed here relative to a ‘pre-industrial’ baseline period of 1850 to 1899, and this period coincides with the beginning of widespread instrumental temperature records. During this time anthropogenic GHGs (greenhouse gases) from industrial activity before 1850 had a relatively small influence on climate compared to natural influences. However, it should be noted that there is no rigorous scientific definition of the term ‘pre-industrial climate’ because climate also changed prior to 1850 due to internal and forced natural variability. Other studies sometimes use a different climatological baseline period, such as the 1971-2000 period used in parts of the IPCC Working Group One contribution to the Fifth Assessment Report (IPCC, 2013).
This indicator provides guidance for the following policy-relevant questions:
The absolute change and rate of change in global average temperature are both important indicators of the severity of global climate change. Temperature changes also influence other components of the climate system which can impact on human activities, including the hydrosphere with oceans and the cryosphere.
To avoid serious climate change impacts, the European Council proposed in its Sixth Environmental Action Programme (6EAP), reaffirmed by the Environment Council and the European Council of 22-23 March 2005 (Presidency Conclusions, section IV (46)) and later in the Seventh Environmental Action Programme (7EAP, 2014) , that the global average temperature increase should be limited to not more than 2 0 C above pre-industrial levels. Furthermore the UNFCCC 15th conference of the parties (COP15) recognised in the Copenhagen Accord (UNFCCC, 2009) the scientific evidence for the need to keep global average temperature increase below 2 0C above pre-industrial levels. In addition, some studies have proposed a 'sustainable' target of limiting the rate of anthropogenic warming to 0.1 to 0.2 0 C per decade.
The target for absolute temperature change (i.e. 2 0C) was initially derived from the variation of global mean temperature during the Holocene, which is the period since the last ice age during which human civilization has developed. Further studies (IPCC, 2007;Vautard, 2014) have pointed out that even a global temperature change of below the 2 0C target would still result in considerable impacts. Vulnerable regions across the world, in particular in developing countries (including least developed countries, small developing island states and Africa), would be most strongly affected. The UNFCCC Copenhagen Accord (2009) therefore foresees a review in 2015 of the scientific evidence for revising the global temperature target to 1.5°C.
Mainstreaming climate change adaptation in EU policies is one of the pillars of the EU Adaptation strategy. In the Europe 2020 strategy for smart, sustainable and inclusive growth, the following is stated on combating climate change: “We must also strengthen our economies, its resilience to climate risks, and our capacity for disaster prevention and response”.
Various data sets on trends in global and European temperature have been used for this indicator:
Global and European average time series for monthly temperature
In the original source the long-term annual and monthly mean HadCRU global temperatures were calculated from 4349 stations for the entire period of the record. There is an irregular distribution in the time and space of available stations (i.e .denser coverage over the more populated parts of the world and increased coverage after 1950). Maps/tables giving the density of coverage through time are given for land regions by Jones (2003). The gridding method was climate anomaly method (CAM), which means the station temperature data have been converted to the anomalies according to the WMO standards (baseline period 1961-1990 and at least 15 years of station data in the period) and grid-box values have been produced by simple averaging of the individual station anomaly values within each grid box.
GISS surface temperatures were calculated using around 7200 stations from Global Historical Climatology Network, United States Historical Climatology Network (USHCN) data, and SCAR (Scientific Committee on Antarctic Research) data from Antarctic stations. Additionally satellite SST has been included for the period after 1980. Temperatures were transformed into anomalies using station normalisation based on the 1951 to 1980 baseline period. Gridding has been done with reference station method using 1200 km influence circle (Hansen et al. 2006).
Surface temperature mean anomalies from Global Historical Climatology Network-Monthly (GHCN-M) has been produced at the NCDC from 2,592 gridded data points based on a 5° by 5° grids for the entire globe. The gridded anomalies were produced from GHCN-M bias corrected data. Gridded data for every month from January 1880 to the most recent month is available. The data are temperature anomalies in degrees Celsius (Jones, 2003).
Other global climate datasets are used by the climate research community, often with a specific purpose or audience in mind, for example processed satellite Earth-observations, and climate reanalyses. Although these are not specifically constructed for climate indicator monitoring, they do show the same temperature trends described here. Recently one new global temperature dataset has been developed especially for understanding temperature trends. This is the Berkeley Earth temperature record: http://berkeleyearth.org/
Daily climate information
Although Europe has a long history in collecting climate information, datasets containing daily climate information across the continent are scarce. Furthermore, accurate climate analysis requires long term time series without artificial breaks. The objective of the ECA project was to compile such a data set, consisting of homogeneous, long-term daily climate information. To ensure a uniform analysis method and data handling, data were centrally collected from about 200 meteorological stations in most countries of Europe and parts of the Middle East. Furthermore the data were processed and analysed at one institute (i.e. KNMI) (Klok et.al. , 2008).
In order to ensure the quality of the ECA&D climate data set:
Global and European average time series for monthly temperature
Grid values of HadCRUT, GISTEMP and GHCN data sets have been gridded using different interpolation techniques. Each grid-box value for the HadCRUT dataset is the mean of all available station anomaly values, except that station outliers in excess of five standard deviations are omitted (Brohan et al., 2005). GISTEMP temperature anomaly data are gridded into 8000 grid cells using reference station interpolation method with 1200 km influence circle (Hansen et al. 2006). GHCN monthly data consists of 2,592 gridded data points produced on a 5° by 5° basis for the entire globe (Jones, 2003).
No methodology references available.
The observed increase in average air temperature, particularly during recent decades, is one of the clearest signals of global climate change.
Temperature has been measured over the centuries. There is a range of different methodologies which give similar results suggesting that uncertainty is relatively low. Three data sets have been presented here for the global temperature indicator. Global temperatures from HadCRUT, GISTEMP, and GHCN have been homogenized to minimise the effects of changing measurement methodologies and location.
Each observation station follows international standards for taking observations set out by WMO. Each National Meteorological Service provides reports on how its data are collected and processed to ensure consistency. This includes recording information about the local environment around the observation station and any changes to that environment. This is important for ensuring the required data accuracy and performing homogeneity tests and adjustments. There are additional uncertainties because temperatures over large areas of the Earth are not observed as a matter of routine. These elements are taken into account by factoring the uncertainty into global average temperature calculations, thereby producing a temperature range rather than one uniquely definite figure (WMO, 2013). The uncertainty of temperature data has decreased over recent decades due to wider use of agreed methodologies and denser monitoring networks. Uncertainty of the temperature data comes from sampling error, temperature bias effect and from the effect of the limited observation coverage. Annual values of global and European temperature are approximately accurate to +/- 0.05 degrees C (two standard errors) for the period since 1951. They are about four times as uncertain during the 1850s, with the accuracy improving gradually between 1860 and 1950 except for temporary deteriorations during data-sparse, wartime intervals. Estimating accuracy is difficult as the individual grid-boxes are not independent of each other and the accuracy of each grid-box time series varies through time (although the variance adjustment has reduced this influence to a large extent). The issue is discussed extensively by Jones et al. (2003), Brohan et al. (2005), and Hansen et al. (2006).
According to the IPCC 4th Assessment Report (IPCC, 2007), there is very high confidence that the net effect of human activities since 1750 has been one of warming. Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations. Moreover, it is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period (IPCC, 2013).
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/global-and-european-temperature/global-and-european-temperature-assessment-2 or scan the QR code.
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