China's agriculture is expected to face challenges in the future mainly due to rising food demand and constraints of land and water resources. Although China has largely ensured its food security in the past 40 years, it has increasingly relied on international markets to ensure its food supply since 2004. With increasing population, higher income and constraints of resources, the pressure on China's food security is going to increase in the future. predicted that China's overall food self-sufficiency is likely to fall from 94.5% in 2015 to around 91% by 2025.  

Climate change will likely aggravate the challenges China faces on its food security in the future. China's annual average temperature has been rising significantly over the past six decades and the warming trend will continue under the future projections. It is generally accepted that the mechanism of climate change affecting China's agriculture is mainly through rising temperature and increasing fluctuation in precipitation.

The impacts of climate change on China's agriculture have been widely studied in the literature through biophysical models. For example, found that the negative impacts of climate change on wheat yield in China could reach up to 5.6–18.5% under A2 scenario1 by 2020s. Similarly,suggested that if the temperature increases by 1 °C, rice yield would decline by 6.1–18.6% even after considering the adaptation measures. predicted a moderate decrease in rice yield in the range of 4.9–8.6% in 2050s. Meanwhile, some other studies also provide the evidence on positive impacts of climate change on some of the crops. for example, concluded that irrigated maize yield would increase slightly by 2020 under B2 scenario1.

A major limitation of the biophysical models for assessing climate change impact is that they tend to overestimate adverse impacts of climate change on agriculture, as they fail to account for the underlying buffering capability of economic system, which the later attains through adjustments in production inputs and structure. For example, used a economic model to assess the climate change impacts on agriculture in China and found that the percentage decrease in production of rice, wheat, and maize in 2030 would be lower than the yield changes predicted by biophysical crop modelers. Using the global general (AGLINK), also found that climate change would cause China's total crop production to decrease only slightly (0.2–0.5%) in 2080. Some global studies on climate change do explicitly cover China while accounting for endogenous response of markets. Nevertheless, these studies either lack empirically based data on yield shocks for main crops in China or do not apply the detailed national economic model for China that can reflect China's agriculture market accurately.

International trade is also another important factor affecting China's food market but few studies have considered the role of trade while assessing climate change impacts on China. Around 2004, China turned a net importer of agriculture products form previously a net exporter, so much so that in 2016 > 80 million tons (Mt) of soybean was imported. At the same time, China became the world's largest importer of rice. There are several important global studies on the role of international trade in climate change on agriculture. For example, made the first attempt to discuss the role of international trade in assessing climate change impacts. Later, explored the potential for a more freely functioning global trading system to maintain improved food security in the long run (i.e. by 2050). More recently,suggested that global trade would continue to play a central role in assuring that global food system adapts to a changing climate in that it is likely to facilitate the movement of food from areas of surplus to areas of deficit. However, there is no China-focused study that assesses climate change impacts on China's agriculture while accounting for the role of international trade.

The overall purpose of this paper is to provide an updated and more reliable evidence on the impacts of climate change on China's production, prices, trade and self-sufficiency of major crops, with particular focus on the market and trade responses. Our study aims to give some perspective to the studies that (i) focus only on the impacts of climate change on national food markets (ii) use single region model and (iii) fail to consider the price transmission from the rest of world. Our study examines the climate change impacts on major crops towards 2050 under the worst climate change scenario (measured with representative concentration pathway, i.e., RCP 8.5) and the best climate change scenario RCP2.6. To achieve this purpose, we use the econometrically estimated projected changes in the yields of major crops in China, while we derive the projected crop yield changes for China's main trading partners from a process-based biophysical method. Next, we employ a widely-used agricultural partial equilibrium model (China Agriculture Policy Simulation Model, CAPSiM) of China to assess the climate change impacts on agriculture, thus considering the domestic market responses. Then we use the linked national and global equilibrium model (CAPSiM-GTAP) to assess the climate change impacts on agriculture, wherein we consider both the market and trade responses. The linked model approach effectively transmits the effects of foreign countries' climate shocks on agriculture to China via trade, while allowing us to use a more precise and detailed national economic model.

Our results show that the effects of climate change on crop production are significant but have large variations among crops. Under the worst climate change scenario i.e., RCP 8.5, among all crops in China, wheat yield is projected to experience the largest decrease of 9.4% by 2050. After taking into account the market response, production losses for most crop are dampened (e.g. wheat production loss reduces to only 4.3%) because of the growers' response to changes in agricultural prices under climate change. Moreover, if we consider the impacts of climate change from the rest of the world, which affect China's trade and therefore domestic production, the severity of climate change impacts on China's agricultural production will be further reduced, e.g. to around 4% for wheat. The study concludes that we need to learn more from farmers who respond to changing climate according to the market and trade signals, and further mainstream these lessons into national adaptation development plan.

The rest of the paper is organized as follows: Section 2 introduces data sources for yield changes under different climate change scenarios for China and its main trade partners. Section 3 describes the simulation methodology, baseline scenario and climate change scenarios. Section 4 presents and analyzes the results for climate change impacts on China's agriculture and the role of market and trade. Section 5 concludes the study with policy implications.

该文章以“Climate change impacts on China's agriculture The responses from market and trade”为题，发表在《China Economic Review》Volume 62, August 2020, 101256