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Private diaries are important sources of historical data for research on climate change. Their advantages include a high veracity and reliability, accurate time and location information, a high temporal resolution, seasonal integrity, and rich content. In particular, these data are suitable for reconstructing short-term, high-resolution climate series and extreme climatic events. Through a case study of Yunshan Diary, authored by Bi Guo of the Yuan dynasty of China, this article demonstrates how to delve into climate information in diaries, including species distribution records, phenological records, daily weather descriptions and personal experiences of meteorological conditions. In addition, this article considers how to use these records, supplemented by other data, to reconstruct climate change and extreme climatic events on various timescales, from multidecadal to annual or daily. The study of Yunshan Diary finds that there was a relatively low amount of precipitation in central and southern Jiangsu Province in the summer of 1309; the winter of 1308–1309 was abnormally cold in the Taihu Lake basin. In the early 14th century at the latest, the climate in eastern China had begun to turn cold, which reflects the transition from the Medieval Warm Period to the Little Ice Age.

To evaluate the climatic and ecological impacts of anthropogenic activities in global change research, it is essential to reconstruct historical land use and land cover change on regional and global scales. In this study, we reconstructed cropland areas for 54 provinces within the European part of Tsarist Russia (ETR) over the periods of 1500-1914 using historical data, including cropland area, population, grain consumption, and grain yield per unit area. The main results are as follows. (1) Total cropland areas and fractional cropland areas of ETR for 11 time sections (1500 AD, 1540 AD, 1585 AD, 1696 AD, 1719 AD, 1725 AD, 1763 AD, 1796 AD, 1856 AD, 1887 AD and 1914 AD) during 1500-1914 were reconstructed, respectively. The total cropland area of ETR increased from 4.26×104 km2 in 1500 AD to 147.40×104 km2 in 1914 AD. The fractional cropland area increased from 2.40% to 29.20%, and the per capita cropland area decreased from 2.58 ha to 1.13 ha during 1500-1914. (2) Cropland expanded from the central and southwest of ETR to the black soil region, surrounding area of the Volga River, Ukraine region, the new Russia region, and the vicinity of Ural for the increase and migration of population. While in the northern region of ETR, cropland area remained stable due to unfavorable climatic conditions throughout the study period. (3) In 1914 AD, the cropland area and fractional cropland area of each province varied from 0.16×104 km2 and 0.76% to 5.65×104 km2 and 76.68%, respectively. (4) The comparisons show that the cropland areas on the ETR in this study for 1500-1914 are higher than those of the HYDE 3.2 dataset. The main reason might come from the underestimation of per capita cropland areas in HYDE 3.2 dataset, which values remained about 1 ha from 1500 to 1920 in that dataset.

The effectiveness of adaptation to climate change depend on the social resilience. Historical case studies of climate change adaptations would be conducive to better understanding the preferred solution of people with different cultural background, and coping with the risk of the ongoing global climate changes. The relationship among climate change, adaptations and social resilience are analyzed based on the previous researches about famines, agricultural production, trade and migration in Germany during the 16th to the early 20th century. Differences in the primary choices and their effectiveness between Germany and China are also discussed from the perspective of food security. The results are as follows. (1) In the 16th and 17th centuries, the German agricultural system was quite sensitive to the cold and abrupt fluctuated climate, and poor harvests always accompanied by famines in which more than 30% were severe famines. After 1700AD, the severity of famine and its correlation with temperature declined gradually. About 29% famines were merely considered as dearth, and the only severe famine (1770-1772AD) occurred after a back-to-back harvest failure. However, the impact of rainfall extremes on harvest still existed. (2) Germany successfully escaped from famine after 1850AD due to four effective adaptations: ① Planting structure adjustment, like increasing the proportion of rye, was first thought of, but the effectiveness was limited until potatoes became widely accepted. ② The rapid increase in crop yield brought by ago-technology progress reversed the trend of social resilience decreasing with population growth, but was not enough to fully offset the impact of climatic deterioration. ③ The degree of dependence on grain import reached 20% in a short time, which improved the food availability and reduced the famine risk in German mainland. ④ Three emigration waves, following the drought (1844-1846AD) and cooling (1870-1890AD) might have partly alleviated food shortage, especially at a local scale. By 1900AD, German social resilience was nearly 20 times than the scenario of lacking adaptation. (3) In contrast to Germany entered a resilience increasing period since the early 18th century, China maintained the decline of resilience as population pressure increased. Differences might be attributed to their location and culture background. China had long been a unified and powerful empire in east Asia with large internal market and self-sufficient agricultural society, which made it more prone to reduce risk through domestic adjustments, such as internal migration and government relief. When the capacity for disaster relief efforts by the government failed to meet the needs of crisis management, social resilience would drop dramatically. Whereas Germany, located in the continent with a long history of division and amalgamation, had a commercial tradition and was close to the origin of the first industrial revolution, was more willing and likely to find new approaches for food supply ensurance or risk transfer in regional exchanges.