Climate change in South Asia is having significant impacts already which are expected to intensify as global temperatures rise due to climate change. The South Asia region consists of the eight countries: Afghanistan, Pakistan, India, Nepal, Bhutan, Bangladesh, the Maldives and Sri Lanka. In the 2017 edition of Germanwatch's Climate Risk Index, Bangladesh and Pakistan ranked sixth and seventh respectively as the countries most affected by climate change in the period from 1996 to 2015, while India ranked fourth among the list of countries most affected by climate change in 2015. The Indian subcontinent is one of the most vulnerable regions globally to a number of direct and indirect effects of climate change, including sea level rise, cyclonic activity, and changes in ambient temperature and precipitation patterns. Ongoing sea level rise has already submerged several low-lying islands in the Sundarbans region, displacing thousands of people.
Among the countries of South Asia, Bangladesh is likely to be the worst affected by climate change. This is owing to a combination of geographical factors, such as its flat, low-lying, and delta-exposed topography, and socio-economic factors, including its high population density, levels of poverty, and dependence on agriculture. Its sea level, temperature, and evaporation are increasing, and the changes in precipitation and cross-boundary river flows are already beginning to cause drainage congestion. There is a reduction in freshwater availability, disturbance of morphological processes, and a higher intensity of flooding.
Greenhouse gas emissions
Bangladesh only contributes 0.21% of the world's emissions yet it has 2.11% of the world's population. In contrast, the United States makes up about 4.25 percent of the world's population, yet they produce approximately 15 percent of the pollution that causes global warming.
According to data from 2020, China, the United States, India, and Russia are the world's biggest emitters of .
Impacts on the natural environment
Temperature and weather changes
Regarding local temperature rises, the IPCC figure shows that mean annual value of temperature rise by the end of the century in South Asia is 3.3 °C with the min-max range as 2.7 – 4.7 °C. The mean value for Tibet would be higher with mean increase of 3.8 °C and min-max figures of 2.6 and 6.1 °C respectively, which implies harsher warming conditions for the Himalayan watersheds.
Extreme weather events
Increased landslides and flooding are projected to have an impact upon states such as Assam. Ecological disasters, such as a 1998 coral bleaching event that killed off more than 70% of corals in the reef ecosystems off Lakshadweep and the Andamans, and was brought on by elevated ocean temperatures tied to global warming, are also projected to become increasingly common.
Sea level rise
The global average sea level rose by 3.1 mm per year from 1993 to 2003. More recent analysis of a number of semi empirical models predict a sea level rise of about 1 metre by the year 2100.
Ongoing sea level rises have already submerged several low-lying islands in the Sundarbans, displacing thousands of people. Temperature rises on the Tibetan Plateau are causing Himalayan glaciers to retreat. It has been predicted that the historical city of Thatta and Badin, in Sindh, Pakistan would have been swallowed by the sea by 2025, as the sea is already encroaching 80 acres of land here, every day.
Some territories in India were already evacuated due to increase in tidal flooding. Large part of some Indian cities will be below tide-level by 2030: Mumbai, Kolkata, Cuttack, Kochi and more. Navi Mumbai will be below this level almost entirely.
In October 2019, a study was published in the Nature Communications journal. The journal claims that the number of people who will be impacted from sea level rise during 21st century is 3 times higher than the previous expected number. By 2050, 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. 70% of these people will live in 8 countries in Asia: China, Bangladesh, India, Indonesia, Thailand, Vietnam, Japan, and the Philippines. Large parts of Ho Chi Minh City, Mumbai, Shanghai, Bangkok and Basra could be inundated.