氣候變遷對台灣小農生產之經濟分析：李嘉圖模型之應用

The Impacts of Climate Change on Small Farm's Production: The Application of Ricardian Approach

黃盈甄(Ying-Chen Huang)

指導教授 ： 魏國棟

國立臺北大學/社會科學學院/經濟學系/碩士(2009年)

摘要

本文採用Mendelsohn, Nordhaus and Shaw(1994)的李嘉圖方法論(Ricardian Approach)進行氣候變遷對台灣農業損害之評估。本文沿用MNS(1994)的架構，修正MNS(1996)的靜態模型，以利潤最大為目標函數，並將環境變數的設定由外生給定，修正成內生，並以動態方式引入模型中，以判斷氣候變遷對台灣農業產值變動的影響因素為何。目前台灣無法影響二氧化碳排放量，因此模型假設比較適用於農業大國且其溫室氣體排放量占全球排放總量高的國家，但本文利用李嘉圖模型，將環境變數內生化確實是一項新的嘗試。
本研究採用最適控制動態模型(Optimal Control Method)，並依循MNS(1994)中所做的三項假設：1.不論是要素市場或產品市場皆為完全競爭架構、2.假設農夫在特定地點將氣候變數視為給定，且調整其對應的投入與產出、3.經濟體系在給定的氣候下為完全性調整機制(Completely Adapted)。推導出廠商為投入防治溫室效應相關設備所需花費的資金的收斂路徑，與資金及二氧化碳累積方程式，證實其存在一個全域穩定均衡點，故可將影響臺灣農業利潤的變數列出。
　　在實證分析的資料處理上，本文採用1984~2003年，共計20年的縣市年資料進行分區整理，11項自變數分成氣候變數(一、四、七、十月的平均溫度及總雨量)、經社變數(人口密度、農業所得)及土壤變數(耕地面積)，因變數則為農業產值。所有的資料來源，僅人口密度取自中華民國統計年鑑外，其餘皆取自台灣農業年報。
本研究利用追縱資料( Panel Data )的方法進行實證分析，先將變數取自然對數，以消除個別變數的單位限制，再採橫斷面固定效果模型(Cross Section Fixed Effect Model)推估，且利用Coefficient Covariance Method修正後，取得台灣的農業損害函數估計式。
損害函數中，並非每一個係數皆為顯著，但發現十月份平均溫度及總雨量、農家每人所得、耕地面積的變動，有利於農業產值提升外，其餘自變數的變動，皆不利於農業產值的提升。本研究亦利用IPCC所設定的A1B情境，即經濟快速成長、技術研發效率愈來愈快，且人口成長趨緩的情境，模擬預測未來二氧化碳集中度( CO2 Concentration)的濃度變化，會如何改變台灣平均溫度與總雨量，進而評估對台灣農業產值的影響；結果發現，平均溫度上升會顯著的降低農業產值，而總雨量的變動，會使農業產值小部份的提升，因此未來氣候快速的變化，的確對台灣農業造成不利的影響。

關鍵字

氣候變遷,李嘉圖模型,損害函數

並列摘要

This study employs the Ricardian Approach derived from Mendelsohn, Nordhaus and Shaw’s model (1994) to estimate the impact of climate change on the sales of Taiwan’s agricultural industry. It is assumed that both of agricultural product and input markets are perfect competition. And the Taiwanese economy plays as a complete adaptor when the climate status is changed. But, this study modifies the MNS static model (1994) to a dynamic optimal control model. And, this study also defines the ratio of CO2 concentration as an endogenous variable. It is proved that the theoretical model has a stable solution, thus, the agricultural damage function can be derived.
The empirical model defines 11 different independent variables that include average temperatures and total rainfalls for four seasons, population density, average farmers income, and cultivated area. The only dependent variable is the sales of agricultural products. The panel data for four different areas (north, central, south, and east) of Taiwan from 1984 to 2003 are selected from Taiwan Agriculture Report. This study employs cross section fixed effect model and coefficient covariance adjusting method to evaluate the damage function of climate change for Taiwan agricultural industry.
This study concludes that the increase of winter’s average temperature and total rainfalls, average farmers income and cultivated area have positive effects for the sales of agricultural products. But, the other independent variables have negative effects for the sales of agricultural products. By applying the A1B status, that are the highly economic growth, efficient technological innovation, and slowly population growth, of IPCC model, this study simulates the change of CO2 concentration rate in the near future. And the assessment of the change of agricultural products sales can be evaluated. It is concluded that the rise of four seasons’ average temperatures have significant negative impacts on the sales of Taiwanese agricultural products. But, the increases of four seasons’ total rainfalls only have slightly positive effects for agricultural products. Thus, this study believes that the severe climate change definitely has negative impact on Taiwanese agricultural industry.

並列關鍵字

Climate Change, Ricardian Approach, Agriculture Damage Function

參考文獻

柳中明、王維強、吳明進(1994)，「台灣地區未來氣候變遷之評估」，1994年3月18-19日台灣地區氣候變遷因素及影響研討會，台灣大學全球變遷研究中心。

魏國棟(2003)，「氣候變遷與因應經濟政策工具：文獻回顧」，經濟研究(Taipei Economic Inquiry)，39：1，27-69。

Kelly, D. L., C. D. Kolstad and G. T. Mitchell (2005), “Adjustment Costs from Environmental Change,” Journal of Environmental Economics and Management, 50, 468-495.

Bosello, F. and R. Roson (2007), “Estimating a Climate Change Damage Function through General Equilibrium Modeling,” Working Paper, Department of Economics, University of Venice, Ca’ Foscari.

Chang, C. C. (2002), “The Potential Impact of Climate Change on Taiwan’s Agriculture,” Agriculture Economics, 27, 51-64.