Jingyun Zheng

Temperature variation through 2000 years in China: An uncertainty analysis of reconstruction and regional difference

Twenty-three published proxy temperature series over China spanning the last 2000 years were selected for an uncertainty analysis in five climate regions. Results indicated that, although large uncertainties are found for the period prior to the 16th century, high level of consistency were identified in all regions during the recent 500-years, highlighted by the two cold periods 1620s-1710s and 1800s-1860s, and the warming during the 20th century. The latter started in Tibet, Northwest and Northeast, and migrated to Central East and Southeast. The analysis also indicates that the warming during the 10-14th centuries in some regions might be comparable in magnitude to the warming of the last few decades of the 20th century which was unprecedented within the past 500 years. Citation: Ge, Q.-S., J.-Y. Zheng, Z.-X. Hao, X.-M. Shao, W.-C. Wang, and J. Luterbacher (2010), Temperature variation through 2000 years in China: An uncertainty analysis of reconstruction and regional difference, Geophys. Res. Lett., 37, L03703, doi: 10.1029/2009GL041281.

Impacts of climate warming on plants phenophases in China for the last 40 years

Based on plant phenology data from 26 stations of the Chinese Phenology Observation Network of the Chinese Academy of Sciences and the climate data, the change of plant phenophase in spring and the impact of climate warming on the plant phenophase in China for the last 40 years are analyzed. Furthermore, the geographical distribution models of phenophase in every decade are reconstructed, and the impact of climate warming on geographical distribution model of phenophase is studied as well. The results show that (i) the response of phenophase advance or delay to temperature change is nonlinear. Since the 1980s, at the same amplitude of temperature change, phenophase delay amplitude caused by temperature decrease is greater than phenophase advance amplitude caused by temperature increase; the rate of phenophase advance days decreases with temperature increase amplitude, and the rate of phenophase delay days increases with temperature decrease amplitude. (ii) The geographical distribution model between phenophase and geographical location is unstable. Since the 1980s, with the spring temperature increasing in the most of China and decreasing in the south of Qinling Mountains, phenophases have advanced in northeastern China, North China and the lower reaches of the Changjiang River, and have delayed in the eastern part of southwestern China and the middle reaches of the Changjiang River; while the rate of the phenophase difference with latitude becomes smaller.

Phenological responses of plants to climate change in an urban environment

Global climate change is likely to alter the phenological patterns of plants due to the controlling effects of climate on plant ontogeny, especially in an urbanized environment. We studied relationships between various phenophases (i.e., seasonal biological events) and interannual variations of air temperature in three woody plant species (Prunus davidiana, Hibiscus syriacus, and Cercis chinensis) in the Beijing Metropolis, China, based on phenological data for the period 1962–2004 and meteorological data for the period 1951–2004. Analysis of phenology and climate data indicated significant changes in spring and autumn phenophases and temperatures. Changes in phenophases were observed for all the three species, consistent with patterns of rising air temperatures in the Beijing Metropolis. The changing phenology in the three plant species was reflected mainly as advances of the spring phenophases and delays in the autumn phenophases, but with strong variations among species and phenophases in response to different temperature indices. Most phenophases (both spring and autumn phenophases) had significant relationships with temperatures of the preceding months. There existed large inter- and intra-specific variations, however, in the responses of phenology to climate change. It is clear that the urban heat island effect from 1978 onwards is a dominant cause of the observed phenological changes. Differences in phenological responses to climate change may cause uncertain ecological consequences, with implications for ecosystem stability and function in urban environments.

Spatiotemporal dynamics of reclamation and cultivation and its driving factors in parts of China during the last three centuries

Different from other similar studies, in this paper, most of the data were excerpted from historical archives and documents, and were used to study the spatiotemporal dynamics of cultivated land resources in China during the last 300 years. It is clear that these data may help reveal land use change dynamics and its regional differences, but they may be problematic due to the constraints of the original data in the Ming Dynasty, Conversion of Land Area for the purpose of collecting land taxes, and the deliberate or inadvertent omission of cultivated land area during land surveys, therefore, such data were adjusted to our need. In processing the data, we made great efforts to analyze the historical context of their sources and reduced the possible errors. The results show that the cultivated land area increased most quickly in the early Qing Dynasty, and slowed down after the middle Qing Dynasty, and then was stable in the late Qing Dynasty until 1949, and has been decreasing since then. It is also found that the cultivated land use varied greatly in different regions. The east of the country was cultivated much more heavily than the west, but in some western provinces cultivated land area increased more quickly. It is considered that the driving factors of such cultivated land area change include the increase of the population, the political issues, and the impacts of wars. Natural environmental factors and the introduction of new crops might also have affected the cultivated land use change in the past 300 years.

General characteristics of climate changes during the past 2000 years in China

The general characteristics of climate changes over the past 2000 years in China, regional differences and uncertainties were analyzed based on the recently peer-reviewed high time-resolution climatic reconstructions. The results showed that there exists four warm periods of the temperature variation in China since the Qin Dynasty, including the western and eastern Han Dynasties (200 BC-AD 180), the Sui and Tang dynasties (541–810), the Song and Yuan dynasties (931–1320), and the 20th century, and three cold phases involving the Wei, Jin, and North-South Dynasties (181–540), the late Tang Dynasty (811–930), and the Ming and Qing dynasties (1321–1920). The Song and Yuan warm period is consistent with the Medieval Warm Period over the Northern Hemisphere, and the cold phases of the North-South Dynasties and the Ming and Qing dynasties are paralleled to the Dark Ages Cold Period and the Little Ice Age, respectively. The 13th-15th century could be a shift to the wet condition of the climate, and the low precipitation variability is exhibited in western China prior to 1500. In the context of the climate warming, the pattern of the drought in north and flood in south is prevalent over the eastern China. In addition, the published reconstructions have a high level of confidence for the past 500 years, but large uncertainties exist prior to the 16th century.

Warming/cooling effects of cropland greenness changes during 1982-2006 in the North China Plain

This study analysed the changes in cropland greenness during 1982-2006 in the North China Plain (NCP) and investigated the warming/cooling effects of the greenness changes. The results show that while spring cropland greenness increased, early summer cropland greenness substantially decreased from 1982 to 2006. In contrast to the cooling and wetting effects of the greenness increase in spring, the greenness reduction in early summer had warming and drying effects. The cooling/warming effects of cropland greenness changes accounted for similar to 47% of the spatial variance of daily maximum temperature (T-max) change in spring and similar to 44% in early summer. The wetting/drying effects of cropland greenness changes accounted for similar to 48% of the spatial variance of daily minimum specific humidity (SPHmin) change in spring and similar to 19% in early summer. The cooling-wetting/warming-drying effects mainly resulted from the distinct partitioning of surface net radiation between surface latent heat flux and sensible heat flux over cropland with different greenness. Canopy transpiration plays a dominant role. The increased (decreased) cropland greenness corresponds to high (low) transpiration rate, less (more) sensible heat flux and high (low) humidity, and consequently cooling-wetting (warming-drying) effects. In comparison, there was little change in surface net radiation, although surface albedo and emissivity had changed with greenness change.

Famine, migration and war: Comparison of climate change impacts and social responses in North China between the late Ming and late Qing dynasties

The human-climate-ecosystem interactions in the past were valuable for today’s human beings who face the challenge of global change. The multi-proxy reconstruction of climate change impacts and social responses and the comparative study between typical periods form an effective tool for elucidating the mechanisms of the interactions. In this paper, with a reconstruction of the proxy series of famine, migration and wars, the most typical social consequences related to climate change and disasters (flood/drought) in North China in 1470–1911 were quantitatively described, and two typical periods of human-climate interaction with similar climate change backgrounds (cold periods of the ‘Little Ice Age’), which were the late Ming dynasty (1560–1644) and late Qing dynasty (1780–1911), were selected and compared. It is determined that the climate deterioration (rapid cooling and increasing extreme disasters) in the late 16th and 18th centuries both resulted in severe social consequences characterized by more famine and popular unrest. The differences were that the climatic impacts in the late Ming were much more serious, and interregional migration, which was an effective responsive measure in the late Qing, was not important in the late Ming; they were primarily influenced by three factors based on the analytical framework of the impacts of historical climate change and social responses: (1) climate deterioration in the late Ming was more severe (more rapid cooling and more extreme disasters), (2) social system were more sensitive to climate change in the late Ming because of its mode of agricultural production (especially cropping system and crop species), and (3) the capacity of social response to climate disaster, especially disaster relief and refugee settlement, was considerably greater in the late Qing.

A 170 year spring phenology index of plants in eastern China

Extending phenological records into the past is essential for the understanding of past ecological change and evaluating the effects of climate change on ecosystems. A growing body of historical phenological information is now available for Europe, North America, and Asia. In East Asia, long-term phenological series are still relatively scarce. This study extracted plant phenological observations from old diaries in the period 1834–1962. A spring phenology index (SPI) for the modern period (1963–2009) was defined as the mean flowering time of three shrubs (first flowering of Amygdalus davidiana and Cercis chinensis, 50% of full flowering of Paeonia suffruticosa) according to the data availability. Applying calibrated transfer functions from the modern period to the historical data, we reconstructed a continuous SPI time series across eastern China from 1834 to 2009. In the recent 30 years, the SPI is 2.1–6.3 days earlier than during any other consecutive 30 year period before 1970. A moving linear trend analysis shows that the advancing trend of SPI over the past three decades reaches upward of 4.1 d/decade, which exceeds all previously observed trends in the past 30 year period. In addition, the SPI series correlates significantly with spring (February to April) temperatures in the study area, with an increase in spring temperature of 1°C inducing an earlier SPI by 3.1 days. These shifts of SPI provide important information regarding regional vegetation-climate relationships, and they are helpful to assess long term of climate change impacts on biophysical systems and biodiversity.

Agriculture development-induced surface albedo changes and climatic implications across northeastern China

To improve the understandings on regional climatic effects of past human-induced land cover changes, the surface albedo changes caused by conversions from natural vegetation to cropland were estimated across northeastern China over the last 300 years, and its climatic effects were simulated by using the Weather Research and Forecasting (WRF) model. Essential natural vegetation records compiled from historical documents and regional optimal surface albedo dataset were used. The results show that the surface albedo decreased by 0.01–0.03 due to conversions from grassland to cropland in the Northeast China Plain and it increased by 0.005–0.015 due to conversions from forests to cropland in the surrounding mountains. As a consequence, in the Northeast China Plain, the surface net radiation increased by 4–8 W/m2, 2–5 W/m2, and 1–3 W/m2, and the climate was therefore warmed by 0.1°C–0.2°C、0.1°C–0.2°C、 0.1°C–0.3° in the spring, autumn and winter, respectively. In the surrounding mountain area, the net radiation d °C ecreased by less than 1.5 W/m2, and the climate was therefore cooled too slight to be detected. In summer, effects of surface albedo changes on climate were closely associated with moisture dynamics, such as evapotranspiration and cloud, instead of being merely determined by surface radiation budget. The simulated summer climatic effects have large uncertainties. These findings demonstrate that surface albedo changes resulted in warming climate effects in the non-rainy seasons in Northeast China Plain through surface radiation processes while the climatic effects in summer could hardly be concluded so far.

Key points on temperature change of the past 2000 years in China

Temperature change of the past 2000 years in China is discussed based on the winter half-year temperature series of the past 2000 years in eastern China reconstructed recently, and other related studies. The main conclusions are as follows: ( 1) The Little Ice Age (LIA) in China began in the early of the 14th century (1320s) and ended in the beginning of the 20th century (1910s), which was composed of four evident cold stages and three short warming stages. The cold period in the Wei, Jin and South-North dynasties (210ssimilar to560s) was the only one comparable with LIA for the past 2000 years. (2) The Medieval Warm Period (MWP) in China began in the 930s and ended in the 1310s, which was composed of two warm stages over 100 years and a cold stage less than 100 years. (3) The climate in the Sui and Tang dynasties should be divided into two stages: the climate in the 570ssimilar to770s was as warm as that in the 20th century; while the temperature in the 780ssimilar to920s was lower than that in the 1950ssimilar to1970s. (4) In eastern China as a whole, winter half-year temperature variation with over 1 degreesC occurred between the cold and warm stages on centennial scale, while the changing rate exceeded 1.0 degreesC per century. (5) There exists an about 1350-year periodicity in the historical temperature change. Inferred from the periodicity, the most likely historical analogue for the warming in the 20th century is the warm stage of the Sui and Tang dynasties (570ssimilar to770s), instead of the Medieval Warm Period. (6) Although it was critically warm, the temperature of the 20th century in eastern China is still within the threshold of the variability of the last 2000 years.