Observations demonstrate that climate change has affected many sectors in Asia in the past decades (medium confidence).
Evidence of impacts of climate change, variability and extreme events in Asia, as predicted in the Third Assessment, has emerged. The crop yield in most countries of Asia has been observed to be declining, probably partly attributable to rising temperatures. As a likely consequence of warming, the retreat of glaciers and thawing of permafrost in boreal Asia have been unprecedented in recent years. The frequency of occurrence of climate-induced diseases and heat stress in Central, East, South and South-East Asia has increased with rising temperatures and rainfall variability. Observed changes in terrestrial and marine ecosystems have become more pronounced [10.2.3].
Future climate change is expected to affect agriculture through declining production and reductions in arable land area and food supply for fish (medium confidence).
Projected surface warming and shifts in rainfall in most countries of Asia will induce substantial declines in agricultural crop productivity as a consequence of thermal stress and more severe droughts and floods [10.4.1]. The decline in agricultural productivity will be more pronounced in areas already suffering from increasing scarcity of arable land, and will increase the risk of hunger in Asia, particularly in developing countries [10.4.1]. Subsistence farmers are at risk from climate change. Marginal crops such as sorghum and millet could be at the greatest risk, both from a drop in productivity and from a loss of crop genetic diversity [10.4.1]. In response to climate change, it is expected that changes will occur in fish breeding habitats and food supply for fish, and ultimately the abundance of fish populations [10.4.1].
Climate change has the potential to exacerbate water-resource stresses in most regions of Asia (high confidence).
The most serious potential threat arising from climate change in Asia is water scarcity. Freshwater availability in Central, South, East and South-East Asia, particularly in large river basins, is projected to decrease due to climate change which, along with population growth and increasing demand arising from higher standards of living, could adversely affect more than a billion people by the 2050s [10.4.2]. Changes in seasonality of runoff due to rapid melting of glaciers and in some areas an increase in winter precipitation could have significant effects on hydropower generation and on crop and livestock production [10.4.2].
Increases in temperature are expected to result in more rapid recession of Himalayan glaciers and the continuation of permafrost thaw across northern Asia (medium confidence).
If current warming rates are maintained, Himalayan glaciers could decay at very rapid rates errata (Figure TS.11). Accelerated glacier melt would result in increased flows in some river systems for the next two to three decades, resulting in increased flooding, rock avalanches from destabilised slopes, and disruption of water resources. This would be followed by a decrease in flows as the glaciers recede [10.6.2]. Permafrost degradation errata can result in ground subsidence, alter drainage characteristics and infrastructure stability, and can result in increased emissions of methane [10.4.4].
Figure TS.11. Projected future changes in the northern Asia permafrost boundary under the SRES A2 scenario for 2100. [F10.5]
Asian marine and coastal ecosystems are expected to be affected by sea-level rise and temperature increases (high confidence).
Projected sea-level rise could result in many additional millions of people being flooded each year [10.4.3.1]. Sea-water intrusion could increase the habitat of brackish-water fisheries but significantly damage the aquaculture industry [10.4.1]. Overall, sea-level rise is expected to exacerbate already declining fish productivity in Asia [10.4.1]. Arctic marine fisheries would be greatly influenced by climate change, with some species, such as cod and herring, benefiting at least for modest temperature increases, and others, such as the northern shrimp, suffering declining productivity [10.4.1].
Climate change is expected to exacerbate threats to biodiversity resulting from land-use/cover change and population pressure in most parts of Asia (high confidence).
Increased risk of extinction for many flora and fauna species in Asia is likely as a result of the synergistic effects of climate change and habitat fragmentation [10.4.4]. Threats to the ecological stability of wetlands, mangroves and coral reefs around Asia would also increase [10.4.3, 10.6.1]. The frequency and extent of forest fires in northern Asia is expected to increase in the future due to climate change and extreme weather events that could likely limit forest expansion [10.4.4].
Future climate change is likely to continue to adversely affect human health in Asia (high confidence).
Increases in endemic morbidity and mortality due to diarrhoeal disease primarily associated with floods and droughts are expected in East, South and South-East Asia, due to projected changes in the hydrological cycle associated with global warming [10.4.5]. Increases in coastal water temperature would exacerbate the abundance and/or toxicity of cholera in South Asia [10.4.5]. Natural habitats of vector-borne and water-borne diseases are reported to be expanding [10.4.5].
Multiple stresses in Asia will be further compounded in the future due to climate change (high confidence).
Exploitation of natural resources associated with rapid urbanisation, industrialisation and economic development in most developing countries of Asia has led to increasing air and water pollution, land degradation, and other environmental problems that have placed enormous pressure on urban infrastructure, human well-being, cultural integrity, and socio-economic settings. It is likely that climate change will intensify these environmental pressures and impinge on sustainable development in many developing countries of Asia, particularly in the South and East [10.5.6].