Summer monsoon rainfall is controlled by a number of factors but in general it is expected to intensify as the Earth becomes warmer. Rainfall is expected to be higher in South Asia, with the exception of Northwest India and Pakistan where drying is predicted. The Indian monsoon will be more prone to significant breaks. More cyclones are expected to make landfall in the Arabian Sea, while in East Asia typhoons will affect eastern China more. Rainfall is not expected to change greatly in China, but higher temperatures will result in more frequent drought especially in North China and the Tibetan Plateau where warming is strongest. Pollution will reduce rainfall, counteracting the effect of higher temperatures. Traditional small-scale farming is more effective at retaining soil moisture and may be more appropriate than large industrial agriculture in coping with the anticipated environmental changes. Sea-level rise is expected to rise approximately 36 cm by 2100, even assuming that CO2 emissions are capped. These rises are expected to more than double the occurrence of major tidal flooding, placing millions of people in jeopardy by the end of the century, especially in Bangladesh and Vietnam.

The Asian summer monsoon provides most of the moisture supply across Asia supporting large populations, controlling the natural vegetation and types of agriculture practiced. Colder conditions at the Glacial Maximum resulted in weaker summer precipitation, with the warmest, wettest conditions peaking around 6000–8000 years ago. We review how temperature, rainfall, changes in river load and course, and sea-level rise have intersected to create the unique agricultural landscape of Asia. Temperatures related to monsoonal pattern dictate the number of growing days for various critical crops, constraining where rice, millet, and wheat can be cultivated. The monsoon also provides water for the major rivers many of which originate in the Tibetan Plateau and which supply waters to the fertile floodplains across the region. Rapid glacial melting at 8200 years ago resulted a sharp drying of the climate in Asia lasting around 400 years. Rainfall particularly declined in peninsular India as well as in North China, now regions of dense population. This event can be used as an analog for potential future warming of the global climate into the twenty-first century.

The farmers who domesticated and grew rice throughout history developed expert knowledge that successfully allowed them to operate farming systems that are the most productive in terms of calories per hectare worldwide. Throughout both the historic and prehistoric record, Asian rice farmers have developed a dazzling array of techniques to deal with the climatic variations and changes in sea level and river evolution. Southern China is less impacted by changes in rainfall and precipitation than Northern China or South Asia. Humans have, however, constructed a unique niche for this aquatic plant, moving it into areas well outside of its natural range. This chapter outlines how humans first domesticated rice and controlled rivers and mastered the irrigation systems that support it.

Southwest Asia is one of the driest parts of the monsoon region with much of the precipitation concentrated toward the southeast, as well as along the front of the Himalayas. This chapter reviews how humans in Northwest India and Pakistan dealt with changes in precipitation and river course and developed agricultural strategies to mitigate fluctuating rainfall and river load. These strategies included increasing mobility or shifting settlement to areas with higher rainfall, diversification through use of different crops at one site or increasing investment in pastoralism. Finally, a wide variety of small-scale irrigation systems were likely employed that were uniquely attuned to their local environment. Some of the strategies, such as the adoption of arid adapted millets employed by these farmers, may represent useful adaptations for our future.

Agriculture in northern Asia is more rainfall controlled than seen further south. Changes in temperature were also critical to subsistence strategies in Northern China and Asia. This chapter charts changes in human subsistence patterns over a series of major climatic periods from the end of the last glacial maximum, a period of expansion of farming during the Holocene thermal maximum and a major downturn in temperature and aridification beginning at roughly 4000 y BP, which resulted in a major transition from millet to wheat and barley farming in Northern Asia and on the Tibetan Plateau.

The Asian summer monsoon is strongly heterogeneous across the continent, with maximum rainfall around the Bay of Bengal, contrasting with the strongest winds in the Arabian Sea. Its intensity reflects the temperature difference between the ocean and continent, which has been accentuated by the rise of high topography following the collision of India and Asia. The monsoon is also sensitive to orbital variability and oceanic phenomena, such as El Niño, which causes weak rainfall in South Asia. The South and East Asian monsoons show moderate differences on millennial timescales as reconstructed from a variety of terrestrial and marine proxies. These point to the Early Holocene as being a time of strong rainfall with a decline after around 4000–5000 years ago. High-resolution reconstructions are possible from tree rings, which show important differences between East and South Asia. A seventeenth-century drought in North China was not mirrored in South and Southeast Asia, while during the Strange Parallels Drought (1756–1768) the reverse was the case. Historical records in China indicate that the north of the country has experienced more droughts than the South, especially during the Little Ice Age.

The monsoon has changed significantly over the past century. In particular, Northwest India and Pakistan have dried in the latter part of the twentieth century along with northern China. The Indian Peninsula and South China have however become wetter. Some of the aridification is the result of increased aerosol concentrations due to industrialization as well as the southward migration of the Westerly Jet in northern China. The Indus basin is particularly susceptible to drying. Changes in atmosphere circulation have pushed typhoons away from the South China Sea and towards eastern China, although rainfall in South China has strengthened due to locally sourced storms. Dry years in South Asia resulted in significant reductions in the food production. Increased agriculture linked to deforestation has reduced soil moisture and has a negative impact on the climate, especially in Northwest India. Times of drought and poor food production push up prices and have resulted in civil disturbances exacerbated by policies introduced during the Green Revolution. Reduction in biodiversity on farms has reduced resilience to future climate change and caused more harm than changes in the environment over the recent past.