NEW DELHI: Four Indian coastal cities — Kolkata, Mumbai, Surat and Chennai — will be severely threatened due to sea level rise while several others in the north India will be exposed to acute water crisis due to melting of Himalayan glaciers by the end of the century, a UN body on climate change hinted on Wednesday.Sea levels, rising faster than ever before, are on course to rise one metre higher due to melting of ice in the business-as-usual scenario by 2100, severely affecting over 1.4 billion people globally, a special report on “oceans and cryosphere” released by the Intergovernmental Panel on Climate Change (IPCC) warned on Wednesday.Four Indian cities are among 45 such coastal port cities globally where even an increase of sea level by 50cm will lead to flooding. In fact, the extreme sea level events that used to happen once a century in the past will occur every year by mid-century in many regions, increasing risks for many low-lying coastal cities and small islands.Sounding another alarm for urgent action to slow down the pace of global warming, a new IPCC report released in Monaco on Wednesday said increasing warming of the oceans and accelerated sea level rise would lead to widespread death of marine life leading to a seafood crisis and increasingly destructive cyclones. Marine heatwaves have likely doubled in frequency between 1982 and 2016, the report said, warning that the pace of change was accelerating.The IPCC report, which referenced nearly 7,000 research papers, warns that sea levels are rising faster than previously thought due to accelerating rates of ice melt. It said that sea levels would rise globally by around 30-60cm by the end of this century even if emissions of GHG are sharply reduced and global warming is limited to well below 2 degree Celsius.But, oceans will rise by around 60-110cm if humans continue to emit increasing amounts of GHGs — in a scenario where the collective mitigation targets of all countries under the Paris Agreement would lead to global average temperature rise of over 3 degree Celsius by 2100.The report showed that the seas have actually risen globally by around 15cm during the 20th century while “it is currently rising more than twice as fast — 3.6mm per year — and accelerating”.Though the IPCC doesn’t release city or country-specific data in these special reports, the published scientific researches cited by it while preparing the report have some indications for Asia and south Asia region.On key takeaways for India, IPCC report co-author Anjal Prakash noted that around 240 million people of the entire Hindu Kush Himalayan (HKH) regions — an area covering all the high mountain chains of central, south and inner Asia — would be affected due to changes in the cryosphere as it may affect the “world’s largest renewable supplies of fresh water”.Referring to rising temperature and very high global warming scenario (3.5-6 degree Celsius) by 2100, Prakash said, “This will lead to significant losses in glacier volume, from 36% to 64%, depending on the warming scenario, and impact timing of water flows and water availability (in the HKH regions). So, the rate of risk is extremely high in the present emission scenario”.But amid all these alarms there is a silver lining, provided nations scale up their collective mitigation targets and work for adaptation. “If we reduce emissions sharply, the consequences for people and their livelihoods will still be challenging, but potentially more manageable for those who are most vulnerable,” said Hoesung Lee, chair of the IPCC, underlining the importance of building resilience as part of adaptation exercises.Adaptation has to be part of the solution, Prakash added. “The mantra for solution is to adapt, adapt and adapt. There are many ways in which it could be done through policy changes and planning and to create climate resilient infrastructure”.