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Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study

Ozan Eruygur, Selin Özokcu.

Abstract
In this study, the impacts of climate related variables such as temperature, maximum temperature, precipitation, solar radiation on wheat yield are estimated by using a regional panel data (NUTS2) for Turkey. The estimated coefficients are used to simulate the impacts of climate change on wheat yield in Turkey until 2100. The humidty coefficient (nks) of Aydeniz climate classification, July Maximum Temperature and August Maximum Temperature are also used in the estimations. The regional effects (for seven regions of Turkey) are estimated separately for each decade. Apart from point estimation, the upper and lower bounds of the estimations are also provided. The "average scenario" points out a decline of about 8% in the wheat yields. In the "worst scenario" the decline enlarges to about 23%. However, the "best scenario" based on the statistically significant lower bound estimation values shows only a 1% of decline in the wheat yields of Turkey. This large interval can be explained by the high varance of the estimations and long forecasting period until 2100. In the study, to take into account the non-stationarity of variables and cross-sectional dependence of panel data, the heterogenus panel data estimation method of AMG (Augmented Mean Group Estimator) is preferred. The AMG estimator of Eberhardt is robust to the cross-sectional dependence of panel series. We argue that this feature makes AMG a good estimator for climate change estimations based on panel data. The residuals of Fixed Effect, Random Effect, FGLS and PCSE estimators are found to be non-stationary pointing unhealthy estimations results.

Key words: Turkey, Climate Change, Wheat Yield, Panel Data, Heterogeneous Panel, Augmented Mean Group estimator, AMG, Common Correlated Effects Mean Group estimator, CCEMG. JEL Codes: Q54, Q10, C23.



Türkiye’de İklim Değişikliğinin Buğday Verimi Üzerine Etkileri: Bir Heterojen Panel Çalışması

Özet
Bu çalışmada, buğday veriminin sıcaklık, maksimum sıcaklık, yağış, güneşlenme gibi iklimsel değişkenlerle olan ilişkisi bölgesel veriler kullanılarak ekonometrik yöntemlerle tahmin edilmiş ve sonrasında iklim değişikliğinin ülkemiz buğday verimi üzerindeki etkileri kestirilmiştir. Aydeniz iklim sınıflamasında hesaplanan nemlilik katsayısı (nks), Temmuz Maksimum Sıcaklık ve Ağustos Maksimum Sıcaklık değişkenleri modelde kullanılmıştır. Ortalama senaryoda 2100 yılına gelindiğinde yedi bölgede buğday veriminde ortalama olarak %8 civarında bir düşme yaşanacağı tahmin edilmektedir. Diğer taraftan en kötü senaryoda 2100 yılında buğday veriminde ortalama olarak %23 civarında bir düşme kestirilmektedir. Dolayısıyla azalmanın istatistiksel olarak anlamlı üst sınırı %23’ler civarındadır. Diğer taraftan istatistiksel olarak anlamlı alt sınır en iyi senaryoda %1’lere kadar düşebilmektedir. Bu durum tahmin sonuçlarının varyanslarının yüksek olmasıyla açıklanabilir. Çalışmada "Genişletilmiş Ortalama Grup ” tahmincisi (AMG) kullanılmıştır. AMG tahmincisi yatay kesitler arasında bağıntı olmasına dirençli bir tahmincidir. Bu özelliğiyle iklim değişikliği konusunda özellikle karşılaşılan bir soruna çözüm getirmektedir. Ayrıca iklim değişikliğini tahmin ederken kullanılan veri setindeki zaman boyutunun da uzun olması iklim değişikliğine ilişkin zaman içindeki değişimleri yakalayabilmek açısından önemlidir. Ancak zaman boyutu arttıkça verilerde durağan-olmama problemi ortaya çıkmakta ve bu durum dikkate alınmadığında hatalı tahminler yapılabilmektedir. Çalışmada temel alınan AMG tahmincisi durağan-olmama durumlarında da etkin olan bir tahmincidir.

Anahtar Kelimeler: Türkiye, İklim Değişikliği, Buğday Verimi, Panel Veri, Heterojen Panel, Genişletilmiş Ortalama Grup Tahmincisi, AMG, Ortak Bağıntılı Etkiler Ortalama Grup tahmincisi, CCEMG. JEL Kodları: Q54, Q10, C23.


 
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How to Cite this Article
Pubmed Style

Eruygur O, Ozokcu S. [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. Ekonomik Yaklasim. 2016; 27(101): 219-255. Turkish. doi:10.5455/ey.35944



Web Style

Eruygur O, Ozokcu S. [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. www.scopemed.org/?mno=238210 [Access: March 25, 2017]. Turkish. doi:10.5455/ey.35944



AMA (American Medical Association) Style

Eruygur O, Ozokcu S. [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. Ekonomik Yaklasim. 2016; 27(101): 219-255. Turkish. doi:10.5455/ey.35944



Vancouver/ICMJE Style

Eruygur O, Ozokcu S. [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. Ekonomik Yaklasim. (2016), [cited March 25, 2017]; 27(101): 219-255. Turkish. doi:10.5455/ey.35944



Harvard Style

Eruygur, O. & Ozokcu, S. (2016) [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. Ekonomik Yaklasim, 27 (101), 219-255. Turkish. doi:10.5455/ey.35944



Turabian Style

Eruygur, Ozan, and Selin Ozokcu. 2016. [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. Ekonomik Yaklasim, 27 (101), 219-255. Turkish. doi:10.5455/ey.35944



Chicago Style

Eruygur, Ozan, and Selin Ozokcu. "[Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]." Ekonomik Yaklasim 27 (2016), 219-255. Turkish. doi:10.5455/ey.35944



MLA (The Modern Language Association) Style

Eruygur, Ozan, and Selin Ozokcu. "[Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]." Ekonomik Yaklasim 27.101 (2016), 219-255. Print.Turkish. doi:10.5455/ey.35944



APA (American Psychological Association) Style

Eruygur, O. & Ozokcu, S. (2016) [Impacts of Climate Change on Wheat Yield in Turkey: A Heterogeneous Panel Study]. Ekonomik Yaklasim, 27 (101), 219-255. Turkish. doi:10.5455/ey.35944



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