Changes in the Asian monsoon climate during 1700–1850 induced by preindustrial cultivation

Abstract

Preindustrial changes in the Asian summer monsoon climate from the 1700s to the 1850s were estimated with an atmospheric general circulation model (AGCM) using historical global land cover/use change data reconstructed for the last 300 years. Extended cultivation resulted in a decrease in monsoon rainfall over the Indian subcontinent and southeastern China and an associated weakening of the Asian summer monsoon circulation. The precipitation decrease in India was marked and was consistent with the observational changes derived from examining the Himalayan ice cores for the concurrent period. Between the 1700s and the 1850s, the anthropogenic increases in greenhouse gases and aerosols were still minor; also, no long-term trends in natural climate variations, such as those caused by the ocean, solar activity, or volcanoes, were reported. Thus, we propose that the land cover/ use change was the major source of disturbances to the climate during that period. This report will set forward quantitative examination of the actual impacts of land cover/use changes on Asian monsoons, relative to the impact of greenhouse gases and aerosols, viewed in the context of global warming on the interannual, decadal, and centennial time scales.atmospheric water balance ͉ climate change ͉ historical land-cover change ͉ monsoon rainfall I n general, a monsoon is generated from a thermal contrast between land and ocean. Thus, the land's surface condition is an important factor in determining its climate. Monsoon Asia, where Ͼ50% of the world population is concentrated, has experienced large land cover/use changes due to agricultural development, particularly during the 18th and 19th centuries. In India and China between 1700 and 1850, extension of cultivation and habitation activities decreased the percentage of forested area from 40-50% to 5-10% of the entire territories between 1700 and 1850 (1).Changing the land cover/use from forest to croplands can affect the global and regional climate through changes in the energy and water balance at the earth's surface (2, 3). Among the various effects of vegetation change, 2 factors have been shown to have a major influence on the energy and water balance: (i) an increase in surface albedo leading to a reduction in solar energy absorption at the surface and (ii) a decrease in surface roughness, resulting in low-level wind speed intensification. As a consequence, the partitioning of turbulent heat fluxes into its sensible and latent heat fluxes would subsequently affect the planetary boundary layer and deep cumulus convection and, hence, the large-scale atmospheric phenomena (3). Previous modeling studies that investigated the impact of those effects used either a model of intermediate complexity with historical land cover changes (4, 5) or a general circulation model with a simplified setup in which the indigenous forests were totally and uniformly replaced by cultivated land. These latter studies have shown how different vegetation distributions affect the global surface energy-water balance...

Impacts of Land Use/Land Cover Change on Climate and Future Research Priorities

“…The change in these fluxes into the atmosphere will result in the alteration of a wide variety of climate variables, including the locations of major weather features. For example, Takata et al (2009) demonstrated the major effect of land use change during the period of 1700-1850 on the Asian monsoon. As land cover change accelerated after 1850 and continues into the future, LULCC promises to continue to alter the surface pattern of sensible and latent heat input to the atmosphere.…”

Seasonal modulation of the Asian summer monsoon between the Medieval Warm Period and Little Ice Age: a multi model study

“…Previous studies have only evaluated the effects of respective forcing on continental-scale, NH-mean, or global-mean climate features (e.g., Phipps et al 2013;Schurer et al 2013Schurer et al , 2014Otto-Bliesner et al 2016). Monsoon responses to historical land use changes (e.g., Takata et al 2009), aerosol forcing (e.g., Bollasina et al 2011;Polson et al 2014), and TSI (e.g., Shi et al 2014) should be further evaluated in a multi-model framework. Further modeling work may contribute to better understanding of the forced monsoon response and its internal variability on interannual, decadal, centennial, and millennial timescales.…”

“…This difference contributes partly to inter-model spread among simulation outputs. Varying land uses over time such as gradually increasing cropland and pasture area (Schmidt et al 2012) prescribed in these simulations can affect regional climate variability, including surface temperature and monsoon systems (Takata et al 2009;He et al 2014). Historical GHG concentrations (CO 2 , CH 4 and N 2 O) are derived from ice cores in Antarctica (Schmidt et al 2011).…”

The Effects of Forest Area Changes on Extreme Temperature Indexes between the 1900s and 2010s in Heilongjiang Province, China

“…Thus, because of changes in physical parameters such as surface albedo, roughness, and evapotranspiration, LUCC influences the transfer of energy between the land surface and the atmosphere, as well as water and momentum transmission, and the exchange of trace gases (such as CO 2 ) [3,4]. A number of researchers have utilized observational statistics and model simulations to verify these effects [5][6][7][8][9][10][11][12], as more-and-more frequent extreme weather events (e.g., heavy rainfall, heat waves, floods, and droughts) since the 1950s have caused natural disasters because of global warming [13][14][15][16]. Researchers around the world are increasingly focusing attention on the causes and mechanisms of extreme climate events.…”