Global Warming and its Impact on the Agricultural Sector○Akira Hibiki * ・ Huey-Lin Lee * *and Yasuaki Hijioka * * *１ ． Introduction
The Intergovernmental Panel on Climate Change (IPCC) reports global surface
temperature change for the end of the 21st century is likely to exceed 2 ℃ for RCP 8.5
and that warming will not be regionally uniform (IPCC, 2013). The impact of thetemperature rise exceeding 2 ℃ on the production of the major crops (wheat, rice andmaze) in Tropical and Temperate regions is likely to negative. (IPCC, 2014)
There are many previous studies to estimate the impact of temperature onagricultural sectors(Mendelsohn,et. al(1994), Exenberger et al. (2014) etc). However,they did not consider the impact of the temperature rise on the agricultural sector via
international trade. The international trade affects the impact on the agricultural
sector via change in comparative advantage resulting from the productivity change.
There are limited studies to consider how international trade affects the impact ofclimate change (Reily and Hohmann(1993), Costinot et al (2016)). They mainly
identified how the impact of climate change on the agricultural sector affected GDP
under consideration of international

trade. Costinot et al (2016)) show thatinternational trade reduced substantially the negative impact of climate change on
global GDP. It is important to examine the impact of climate change on the agricultural
sector at the country level especially for the developing countries since the income in
the agricultural sector is lower.
In this study, firstly we explore how temperature affect the land productivity(crop yield) in the agricultural sector by estimating the land productivity function andsimulate the impact of temperature rise in 2050 on the productivity using projection
by MIROC5, an atmosphere–ocean general circulation model. Secondly, we investigate
how change in productivity due to temperature change affects the agricultural sector
and GDP of each country/region via change in trade using the GTAP model.
2. Methodology
2.1 Estimation of Land Productivity Model and Impact of the Temperature RiseIn our study, we estimate the agricultural land productivity function using theTohoku University (E-mail: hibiki@tohoku.ac.jp)
National Chengchi University* * National Institute for Environmental Studies***

country level panel data expressed as follows.
ln(𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑖𝑖𝑖𝑖 )= 𝛼𝛼1 ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 ) + 𝛼𝛼2 ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 ) ∗ ln(𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑖𝑖𝑖𝑖 )+ 𝛼𝛼3 {ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 )} ∗ 𝐷𝐷𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑖𝑖 + 𝛼𝛼4 ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 ) ∗ 𝐷𝐷𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐&𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑖𝑖+ 𝛼𝛼5 ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 ) ∗ 𝐷𝐷𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑖𝑖 + 𝛼𝛼6 {ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 )}2+ 𝛼𝛼7 {ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 )}2 ∗ 𝐷𝐷𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑖𝑖 + 𝛼𝛼8 {ln(𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑢𝑢𝑟𝑟𝑟𝑟𝑖𝑖𝑖𝑖 )}2 ∗ 𝐷𝐷𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐&𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑖𝑖+ 𝛼𝛼9 {ln 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑖𝑖𝑖𝑖 }2 ∗ 𝐷𝐷𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑖𝑖 + 𝛼𝛼10 ln(𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑖𝑖𝑖𝑖 ) + � 𝛽𝛽𝑘𝑘 𝑋𝑋𝑘𝑘 + 𝜇𝜇𝑖𝑖 + 𝜀𝜀𝑖𝑖𝑖𝑖

We collected unbalanced panel data with 186 countries/regions for 24 years(1991-2014). We obtained all the agricultural data from the Food and Agricultural
Organization’s FAOSTAT data base (www.fao.org/faostat/en/#data ) and the country
level climate data such as temperature and precipitation from Climate Change
Knowledge

PortaloftheWordBank(http://sdwebx.worldbank.org/climateportal/index.cfm?page=downscaled_data_downlo
ad&menu=historical). Using these panel data, we estimated the fixed effect model.
Then using the significant variables and projection of the temperature by MIROC5model under RCP85 scenario, we calculated the impact of the temperature rise in 2050
relatively to 2010 on the land productivity.
2.2 Simulation of the Impact of the Productivity Change on the Agricultural Sector
We constructed the computable general equilibrium model (GTAP model) with
12 sectors including agricultural sector and 68 countries/regions. Then we calculated
the change in the productivity of each countries/regions affect the agricultural sector
and real GDP via international trade due to change in comparative advantage.
3. Main Findings
Our main findings are as follows(1)The analysis of 2.1 shows that the temperature rise raises productivity in the cooltemperate zone countries (3.2～ 6.7%) but reduces productivity in temperate zone (－0.1~－ 3.4%) and in tropical zone (－ 0.1~－ 6.8%).
(2)The analysis 2.2 shows that ① the positive impacts of temperature rise on US andCanada after trade adjustment, +4.51% and +6.07% respectively are larger than thepositive impacts on the productivity, 6.34% and 13.1 % respectively, ② the negativeimpact after trade adjustment is smaller than the negative impact on the productivity
for many countries, ③ the negative impact after trade adjustment is larger than thenegative impact on the productivity for some countries such as Japan, Germany, Egypt,
Cote d’Ivoir.