Shazneen Mistry
The Intergovernmental Panel on Climate Change (IPCC) has indicated that glacial retreat, tropical cyclones, erratic monsoons, and heat stress are likely to impact India in recent years. Most of these impacts are irreversible and hence could not be remediated even if greenhouse gas emissions decline dramatically, the IPCC said.
A report released by them on Monday claimed that heatwaves and humid heat stress will be more intense and frequent during the 21st century over South Asia. It further added that the Indian Ocean, which includes the Arabian Sea and Bay of Bengal, has warmed faster than the global average. The oceans factsheet indicates that sea surface temperature over the Indian ocean is likely to increase by 1 to 2°C due to global warming.
The covering over the Himalayas has reduced since the early 21st century, and glaciers have thinned, retreated, and lost mass since the 1970s. They have also mentioned that snow-covered areas and snow volumes will continue to decrease during the 21st century. Rising global temperature and rain can increase the occurrence of glacial lake outburst floods and landslides.
One of the recent examples would be the flooding and landslide disasters in the high mountains of Uttarakhand and Himachal Pradesh. A glacier breach on February 7 in Uttarakhand triggered flash floods in the Rishiganga and Dhauliganga valleys, sweeping away the Rishiganga hydel project and National Thermal Power Corporation’s Tapovan Vishnugad project. The disaster is feared to have killed over 200 people.
Some climate impacts in India are irreversible:
Greenhouse gas emissions since 1750 have committed the global ocean to future warming, it said adding that based on multiple lines of evidence, upper ocean stratification (vertical changes in seawater density), ocean acidification (decrease in ph value of oceans), and ocean deoxygenation (low oxygen zones in the oceans) will continue to increase in the 21st century. The rate at which these intensify will depend on emission trends.
Mountain and polar glaciers will continue melting for decades or centuries, continued ice loss over the 21st century is virtually certain for the Greenland Ice Sheet and the Antarctic Ice Sheet
It is also certain that the global mean sea level will continue to rise over the 21st century. Over the next 2,000 years, the global mean sea level will rise by about 2 to 3m even if warming is limited to 1.5°C, 2 to 6m if limited to 2°C.
Highlights of IPCC report include:
• Climate change is intensifying the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.
• It is affecting rainfall patterns. In high latitudes, rainfall is likely to increase, while it is projected to decrease over large parts of the subtropics.
• Changes to monsoon rain are expected, which will vary by region.
• Coastal areas will see continued sea-level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion.
• Extreme sea-level events that previously occurred once in 100 years could happen every year by the end of this century.
• Further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets.
• Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been linked to human influence. These changes affect both ocean ecosystems and the people that rely on them, and they will continue throughout at least the rest of this century.
• For cities, some aspects of climate change may be amplified, including heat (since urban areas are usually warmer than their surroundings), flooding from heavy precipitation events, and sea-level rise in coastal cities.
How do we know climate change is due to human influence?
The increasing rates of the major greenhouse gases (carbon dioxide, methane, and nitrous oxide) are unprecedented over at least the last 800,000 years, the evidence clearly shows that these increases are the results of human activities.
The development of the latest generation climate models like weather forecasting models, climate models represent the state of the atmosphere on a grid and simulate its evolution over time-based on physical principle, this includes a representation of the ocean, sea ice, and the main processes important in driving climate and climate change. Results consistently show that such climate models can only reproduce the observed warming when including the effects of human activities in particular the increasing concentrations of greenhouse gases.
