Climate Change In South Asia

Climate change is particularly important in Asia, as the continent accounts for the majority of the human population. Warming since the 20th century is increasing the threat of heatwaves across the entire continent. Heatwaves lead to increased mortality, and the demand for air conditioning is rapidly accelerating as the result. By 2080, around 1 billion people in the cities of South and Southeast Asia are expected to experience around a month of extreme heat every year. The impacts on water cycle are more complicated: already arid regions, primarily located in West Asia and Central Asia, will see more droughts, while areas of East, Southeast and South Asia which are already wet due to the monsoons will experience more flooding.Shaw, R., Y. Luo, T. S. Cheong, S. Abdul Halim, S. Chaturvedi, M. Hashizume, G. E. Insarov, Y. Ishikawa, M. Jafari, A. Kitoh, J. Pulhin, C. Singh, K. Vasant, and Z. Zhang, 2022
Chapter 10: Asia
I
Climate Change 2022: Impacts, Adaptation and Vulnerability
.-O. Pörtner, D. C. Roberts, M. Tignor, E. S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.) Cambridge University Press, Cambridge, United Kingdom and New York, New York, US, pp. 1457–1579 , doi=10.1017/9781009325844.012.

The waters around Asia are subjected to the same impacts as elsewhere, such as the increased warming and ocean acidification. There are many coral reefs in the region, and they are highly vulnerable to climate change, to the point practically all of them will be lost if the warming exceeds . Asia's distinctive mangrove ecosystems are also highly vulnerable to sea level rise. Asia also has more countries with large coastal populations than any other continent, which would cause large economic impacts from sea level rise. Water supplies in the Hindu Kush region will become more unstable as its enormous glaciers, known as the "Asian water towers", gradually melt. These changes to water cycle also affect vector-borne disease distribution, with malaria and dengue fever expected to become more prominent in the tropical and subtropical regions. Food security will become more uneven, and South Asian countries could experience significant impacts from global food price volatility.

Historical emissions from Asia are lower than those from Europe and North America. However, China has been the single largest emitter of greenhouse gases in the 21st century, while India is the third-largest. As a whole, Asia currently accounts for 36% of world's primary energy consumption, which is expected to increase to 48% by 2050. By 2040, it is also expected to account for 80% of the world's coal and 26% of the world's natural gas consumption. While the United States remains the world's largest oil consumer, by 2050 it is projected to move to third place, behind China and India. While nearly half of the world's new renewable energy capacity is built in Asia, this is not yet sufficient in order to meet the goals of the Paris Agreement. They imply that the renewables would account for 35% of total energy consumption in Asia by 2030.

Climate change adaptation is already a reality for many Asian countries, with a wide range of strategies attempted across the continent. Important examples include the growing implementation of climate-smart agriculture in certain countries or the "sponge city" planning principles in China. While some countries have drawn up extensive frameworks such as the Bangladesh Delta Plan or Japan's Climate Adaptation Act, others still rely on localized actions that are not effectively scaled up.

Greenhouse gas emissions

Historical emissions from Asia are lower than those from Europe and North America. However, China has been the single largest emitter of greenhouse gases in the 21st century, while India is the 3rd-largest, Russia is 4th, while Japan and South Korea rank 5th and 7th. Around 70% of India's energy comes from fossil fuels, while this figure reaches 80-90% in China, Japan and the Republic of Korea. As a whole, Asia currently accounts for 36% of world's primary energy consumption, which is expected to increase to 48% by 2050. By 2040, it is also expected to account for 80% of the world's coal and 26% of the world's natural gas consumption. While the United States remains the world's largest oil consumer, by 2050 it is projected to move to third place, behind China and India.

After 2040, Asia would likely account for over half of the world's electricity consumption, and around 40% will likely be generated from coal burning. Asia is expected to import more oil and gas in the future than it does now, and would likely account for 80% of the global energy market in 2050. In particular, there are 11 developing countries in Asia which have a large energy consumption yet also lack energy security.

Impacts

Warming

Starting from the 20th century, there has been clear warming across the entire continent. The frequency of cold days and nights decreased, which had also lowered the need for heating. Yet, the demand for air conditioning had increased far more as the frequency of hot days and warm nights had also grown, which had also increased the strain on power grids. Hot temperature extremes appear to have increased the most in Central and West Asia, while heatwaves in East and South Asia are becoming longer, more frequent and more severe.

In 2016 and 2018, Asia has already experienced extreme heat that would have been statistically impossible without climate change. New Delhi broke an all-time record when it reached in 2018. North Asia has the coldest climate due to its proximity to the Arctic, but it also experiences greater relative warming due to what is known as the arctic amplification. This has led to permafrost thaw, which acts as a climate change feedback and also places large quantities of infrastructure at risk of collapse.

All of these trends are expected to continue in the future. There will be greater frequency of extreme heatwaves across the continent and heat stress would become more persistent across South Asia. Under the mid-range climate change scenario, parts of West and South Asia would reach "critical health thresholds" for heat stress during the 21st century, and this would also occur in parts of East Asia under the high-emission scenario. Growing urbanization in Asia would also subject more people to the urban heat island effect: for instance, Hyderabad will likely be the hottest city in the world at the end of the century, with an average annual temperature around . Yet, many rural people are agricultural workers, who are some of the most vulnerable to increasing heat. The demand for air conditioning would continue to increase and managing it would become more challenging for the energy infrastructures, which are often already prone to blackouts in many countries on the continent. In the Southeast Asia, heat-related deaths under a high-warming scenario could increase by 12.7% by 2100.

Water availability

Precipitation trends are more complex than temperature trends. While climate change is generally expected to increase precipitation due to greater evaporation from the oceans, the large increase in anthropogenic sulfate aerosols during most of the 20th century (sometimes described as global dimming) has had an opposite impact, as sulfates cause clouds to retain water for longer before rainfall occurs. Rainfall associated with the Monsoon of South Asia and East Asian Monsoon had decreased by the end of the 20th century, and this is likely associated with aerosol pollution: there is already evidence of monsoon recovery when the aerosol concentrations decline. Because some clouds from South and East Asia go on to Central Asia, they could increase rainfall there with the same moisture they did not shed during the monsoon, and some evidence supports that.

However, this effect isn't very strong, as the overall rainfall in West and Central Asia had decreased, while drought likelihood had increased. The frequency and intensity of dust storms had increased in this region as well, although this is partly caused by poor land use practices. At the same time, ''heavy'' precipitation events (defined as 400 mm or more in a day) had increased in South, Southeast and East Asia during the 21st century. Over a third of the cities in Asia, with a combined population of around 932 million, are considered at high risk of flooding.

Future warming is expected to substantially increase annual precipitation across most of the continent. Monsoon regions would experience more heavy and even ''intense'' precipitation (defined as 50mm or more in an hour), making floods substantially more frequent. 100-year extremes in vapor transport (directly related to extreme precipitation) would become 2.6 times more frequent under of global warming, yet 3.9 and 7.5 times more frequent under and . While there has been no significant change in tropical cyclone (TC) frequency in Asia since the 1950s, category 4-5 TCs are likely to become more frequent under high warming and generate more rainfall.

On the contrary, drought frequency is expected to increase in the West and Central Asia. Even in the regions where precipitation increases, plants' water losses to evapotranspiration may increase even more, which could still increase the overall agricultural drought frequency. Across the continent, drought conditions would on average increase by between 5% to 20% by 2100. Around 2050, populations living in the Amu Darya, Ganges and Indus may be faced with severe water scarcity due to both climate and socioeconomic reasons.

Glaciers in the Hindu Kush region feed the water basin of over 220 million people. In the Indus River basin alone, they contribute to up to 60% of irrigation outside of the monsoon season. These glaciers have already experienced melting in the 21st century, and it would continue in the future, as up to two-thirds of glacier ice may melt by 2100 under high warming. While glacier water supply would likely increase until 2050, it would be permanently diminished afterwards. Although the increases in monsoon strength may offset these losses, agriculture in the region would still become more reliant on it than ever before, while hydropower generation would become less predictable and reliable.

Sea level rise

Between 1901 and 2018, average global sea level rose by , an average of per year.IPCC, 2019
Summary for Policymakers
In
IPCC Special Report on the Ocean and Cryosphere in a Changing Climate
.-O. Pörtner, D. C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N. M. Weyer (eds.) Cambridge University Press, Cambridge, UK and New York, New York, US. https://doi.org/10.1017/9781009157964.001. This rate accelerated to /yr for the decade 2013–2022. While the rate of sea level rise in Asia is usually similar to the global average, it has been around 10% faster in the Indo-Pacific region since the 1990s. Future sea level rise on Japan's Honshu Island would be up to 25 cm faster than the global average under RCP8.5, the intense climate change scenario.

Asia has the largest population at risk from sea level. As of 2022, some 63 million people in East and South Asia were already at risk from a 100-year flood. This is largely due to inadequate coastal protection in many countries. This will get much worse in the future. Bangladesh, China, India, Indonesia, Japan, Pakistan, the Philippines, Thailand and Vietnam alone account for 70% of people exposed to sea level rise during the 21st century. This is due to the dense population on the region's coasts. 2019 research indicated that globally, 150 million will be under the water line during high tide and 300 million will live in zones with flooding every year. By the year 2100, those numbers differ sharply depending on the emission scenario. In a low emission scenario, 140 million will be under water during high tide and 280 million will have flooding each year. In high emission scenario, the numbers reach up to 540 million and 640 million, respectively. Large parts of Ho Chi Minh City, Mumbai, Shanghai, Bangkok and Basra could be inundated. These figures are, on average, triple that of past estimates, and the increases are even larger for certain Asian countries.

Modeling results predict that Asia will suffer direct economic damages of US$167.6 billion at 0.47 meters of sea level rise. This rises to US$272.3 billion at 1.12 meters and US$338.1 billion at 1.75 meters. There is an additional indirect impact of US$8.5, 24 or 15 billion from population displacement at those levels. China, India, the Republic of Korea, Japan, Indonesia and Russia experience the largest economic losses. Nations like Bangladesh, Vietnam and China with extensive rice production on the coast are already seeing adverse impacts from saltwater intrusion. High-emission RCP8.5 scenario would see the loss of at least one third of Japanese beaches and 57–72% of Thai beaches.

Sea level rise in Bangladesh may force the relocation of up to one third of power plants by 2030. A similar proportion would have to deal with increased salinity of their cooling water. Recent search indicates that by 2050 sea-level rise will displace 0.9-2.1 million people. This would require the creation of about 594,000 new jobs and 197,000 housing units in the areas receiving the displaced persons. It would also be necessary to supply an additional 783 billion calories worth of food. Another paper in 2021 estimated that sea-level rise would displace 816,000 people by 2050. This would increase to 1.3 million when indirect effects are taken into account. Both studies assume that most displaced people would travel to the other areas of Bangladesh. They try to estimate population changes in different places.

By 2030, major Indian cities such as Mumbai, Kolkata, Cuttack and Kochi are expected to end up with much of their territory below the tide level. In Mumbai alone, failing to adapt to this would result in damages of US$112–162 billion by 2050, which would nearly triple by 2070. Thus, the authorities are carrying out adaptation projects like the Mumbai Coastal Road, even at the likely expense of local coastal ecosystems and fishing livelihoods. Out of the 20 coastal cities expected to see the highest flood losses by 2050, 13 are in Asia. Nine of these are the so-called sinking cities, where subsidence (typically caused by unsustainable groundwater extraction in the past) would compound sea level rise. These are Bangkok, Guangzhou, Ho Chi Minh City, Jakarta, Kolkata, Nagoya, Tianjin, Xiamen and Zhanjiang.

By 2050, Guangzhou would see 0.2 meters of sea level rise and estimated annual economic losses of US$254 million – the highest in the world. One estimate calculates that in the absence of adaptation, cumulative economic losses caused by sea level rise in Guangzhou under RCP8.5 would reach about US$331 billion by 2050, US$660 billion by 2070 and US$1.4 trillion by 2100. The impact of high-end ice sheet instability would increase these figures to about US$420 billion, US$840 billion and US$1.8 trillion respectively. In Shanghai, coastal inundation amounts to about 0.03% of local GDP. But this would increase to 0.8% by 2100 even under the "moderate" RCP4.5 scenario in the absence of adaptation. The city of Jakarta is sinking so much (up to per year between 1982 and 2010 in some areas) that in 2019, the government had committed to relocate the capital of Indonesia to another city.

Natural environment

Multiple biomes in Asia have already experienced visible shifts in response to climate change. These include changes in growing season length, habitat losses (particularly of the amphibian species) or greater invasive species frequency. Many animal species have been observed to move into warming areas to the north. In Siberia, tundra extent shrinks as it is gradually replaced by boreal forest (taiga). At the same time, wildfires have also become more severe in Siberia, although this is partly connected to increased pressure from mineral exploration and illegal logging

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