Lokman Hakan Tecer 1 Orhan Cerit 2 1 Department of Environmental Engineering, Balikesir University, Balikesir, Turkey. 2 Department of Environmental Engineering, Cumhuriyet University, Sivas, Turkey. Research Article Temperature Trends and Changes in Rize, Turkey, for the Period 1975 to 2007 There is increasing evidence that the global climate is changing as a result of anthro- pogenic activity. Short-term mean, maximum, and minimum temperatures of the city Rize located at the Eastern Black Sea Coast of Turkey were analyzed to reveal trends, change points, significant warming (cooling) periods, and trend rates per year. An increasing trend of approximately 1.278C/33 years (a = 0.001) in the annual mean temperatures is found during the period from 1975 to 2007. Two periods, aver- aging 13.78 and 14.668C, respectively, were detected from fluctuation in the annual mean temperatures. The trend of the first period (1975 – 1993) is towards a cooler cli- mate, whereas the trend of the second period (1994 – 2007) is towards a warmer cli- mate. Summer, autumn and, particularly, the spring mean temperatures have tended to increase strongly, whereas the winter mean temperatures have increased slightly over the whole period. For the winter mean temperature, the trend rate indicates a slight increase, which is insignificant. Maximum temperatures have dramatically increased with 1.618C(a = 0.001) over the last 33 years. However, annual minimum temperatures have increased by 0.998C(a = 0.01) over the same period. Keywords: Air temperature; Change point; Climate; Climate change; Trend rate; Received: January 28, 2008; revised: March 4, 2008; accepted: March 13, 2008 DOI: 10.1002/clen.200800021 1 Introduction There is increasing evidence that the global climate is changing as a result of anthropogenic activity (IPCC, Climate change 2001: Scien- tific basis. www.grida.no/climate/ipcc_tar/ available date: January 20, 2008). Measurements of surface temperature, primarily over land region, show an approximately 0.68C warming of global tem- peratures over the past century [1]. Global circulation models used to study the effects of greenhouse gase concentrations on the earth's climate predict the changes in temperature, in the amount and dis- tribution of precipitation, and other climatic parameters [2]. The Intergovernmental Panel on Climate Change (IPCC) established by WHO and UNEP to assess information relevant for the understand- ing of climate change showed an increase in the temperature of 0.6 l 0.28C over the 20th century, with most of the warming occur- ring over the past 20 years, while the decade of the 1990s was warm- est since 1861 (IPCC, Climate change 2001: Scientific basis. www.gri- da.no/climate/ipcc_tar/ available date: January 20, 2008). In addi- tion, the IPCC Fourth Assessment Report (AR4) reports an 100 year linear trend (1906 – 2005) of 0.748C, which is larger than the corre- sponding trend of 0.68C (1901 – 2000) given in the Third Assessment Report (TAR). The temperature increase is widespread over the globe and is greater at higher northern latitudes. One of the characteristics of global warming is that in many locations around the globe, the dif- ference between the maximum and minimum daily temperature is decreasing [3]. Significant changes in many physical and biological systems are reported by AR4, together with surface air temperature changes over the period of 1970 to 2004. The average temperature in Europe has increased by 0.958C over the past 100 years (EEA Signals 2004, http://reports.eea.europa.eu/signals-2004/en/ENSignals2004- web.pdf available date: January 24, 2008). Figure 1 shows an 0.2 to 1.08C increase of the air temperature over the period 1970 to 2004 for the continental regions including Turkey (Intergovernmental Panel on Climate Change Fourth Assessment Report, Climate Change 2007: Synthesis Report. http://www.ipcc.ch/ipccreports/ar4-syr.htm available date: January 24, 2008). Türkes et al. [4] have reported changes for most of the regions of Turkey. The mean diurnal temperature range in winter is con- trolled greatly by changes in the minimum temperature. On the basis of the results from other studies, a general decrease was domi- nant in annual and seasonal mean surface temperature series over much of Turkey. Nevertheless, this situation has begun to change in about the last ten years in Turkey, particularly during the warm period of the year [5 – 7]. It was shown that cooling trends in mean and maximum temperature series have been weakening and been less significant [8]. In addition, a change in climate has been docu- mented on many locations throughout the world. To detect and quantify climate change, much emphasis has been placed on the analysis of variability of temperature and precipitations in recent years [9 – 11]. The minimum temperature increased almost every- where, and the maximum and mean temperature increased in northern and central Europe, in the Russian Federation, Canada [12], and in Australia and New Zealand [13]. Correspondence: Dr. L. H. Tecer, Department of Environmental Engi- neering, Balikesir University, 10165 Balikesir, Turkey. E-mail: lhtecer@balikesir.edu.tr Abbreviations: VC, Variation coefficients i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com 150 Clean 2009, 37 (2), 150 – 159