The First Ever Climate Change Assessment For India

-Rituraj Phukan |

The first ever climate change assessment for Indiahas presented a grim analysis of observed changes and future projections of warming impacts including precipitation changes, temperature rise, droughts, sea level rise and extreme weather events.

The ‘Assessment of Climate Change over the Indian Region- A Report of the Ministry of Earth Sciences, Government of India, published last month, was prepared by the Centre for Climate Change Research at the Indian Institute of Tropical Meteorology (IITM), Pune.

The report stated that the global temperature rise of 1°C since the industrial revolution, and the magnitude rate of warming, cannot be explained by natural variations alone. Emissions of greenhouse gases, aerosols and changes in land use and land cover have substantially altered the atmospheric composition, and consequently the planetary energy balance, and are thus primarily responsible for the present-day climate change.

Global climate models project a continuation of human-induced climate change during the twenty-first century and beyond. If the current GHG emission rates are sustained, the global average temperature is likely to rise by nearly 5°C, and possibly more, by the end of the twenty-first century. Even if all the commitments (called the “Nationally Determined Contributions”) made under the 2015 Paris agreement are met, it is projected that global warming will exceed 3°C by the end of the century.

However, temperature rise will not be uniform across the planet; some parts of the world will experience greater warming than the global average. Such large changes in temperature will greatly accelerate other changes that are already underway in the climate system, such as the changing patterns of rainfall and

Climate Change in India: Observed and Projected Changes

India is a vast country with many climate zones, and hence, local climate change and their causes can be quite complex. This assessment documents climate changes in different parts of India, with observed changes and future implications for different regions.

Rising Temperatures

India’s average temperature has risen by around 0.7°C during 1901–2018, largely on account of GHG-induced warming. By the end of the twenty-first century, the frequencies of occurrence of warm days and warm nights are projected to increase by 55% and 70%, respectively, relative to the reference period 1976-2005.

The frequency of summer (April–June) heat waves over India is projected to be 3 to 4 times higher by the end of the twenty-first century as compared to the 1976–2005 baseline period, under a high emissions scenario. The average duration of heat wave events is also projected to approximately double, but with a substantial spread among models. In response to the combined rise in surface temperature and humidity, amplification of heat stress is expected across India, particularly over the Indo-Gangetic and Indus river basins.

Rainfall Changes

The summer monsoon precipitation (June to September) over India has declined by around 6% from 1951 to 2015, with notable decreases over the Indo-Gangetic Plains and the Western Ghats.There has been a shift in the recent period toward more frequent dry spells (27% higherduring 1981–2011 relative to 1951–1980) and more intense wet spells during the summermonsoon season. Over central India, the frequency of daily precipitation extremes increased by about 75% during 1950–2015.

With continued global warming and anticipated reductions in anthropogenic aerosol emissions in the future, projections include increase in the mean and variability of monsoon precipitation by the end of the twenty-first century, together with substantial increases in daily precipitation extremes.

Increased Droughts

The overall decrease of seasonal summer monsoon rainfall during the last 6–7 decades has led to an increased propensity for droughts over India. Both the frequency and spatial extent of droughts have increased significantly during 1951–2016. Areas over central India, southwest coast, southern peninsula and north-eastern India have experienced more than 2 droughts per decade, on average, during this period. The area affected by drought has also increased by 1.3% per decade over the same period.

Climate model projections indicate a high likelihood of increase in the frequency (>2 events per decade), intensity and area under drought conditions in India by the end of the twenty-first century.

Warming Ocean

Sea surface temperature of the tropical Indian Ocean has risen by 1°C on average during 1951–2015, markedly higher than the global average warming of 0.7°C, over the same period. Ocean heat content of the Indian Ocean has also exhibited an increasing trend over the past six decades (1955–2015), with the past two decades (1998–2015) having witnessed a notably abrupt rise. During the twenty-first century, sea surface temperature and ocean heat content in the tropical Indian Ocean are projected to continue to rise.

Sea Level Rise

Sea levels have risen globally because of the continental ice melt and thermal expansion of ocean water in response to global warming. Sea-level rise in the North Indian Ocean occurred at a rate of 1.06–1.75 mm per year during 1874–2004 and has accelerated to 3.3 mm per year in the last two and a half decades (1993–2017), which is comparable to the current rate of global mean sea-level rise.

At the end of the twenty-first century, sea levels in the same area are projected to rise by approximately 300 mm, compared to the projected global mean rise of approximately 180 mm.

Tropical Cyclones

There has been a significant reduction in the annual frequency of tropical cyclones over the North Indian Ocean basin since the middle of the twentieth century (1951–2018). In contrast, the frequency of very severe cyclonic storms during the post-monsoon season has increased significantly (+1 event per decade) during the last two decades (2000–2018).

However, a clear signal of anthropogenic warming on these trends has not yet emerged.Climate models project a rise in the intensity of tropical cyclones during the twenty-first century.

Changes in the Himalayas

The Hindu Kush Himalayas (HKH) experienced a temperature rise of about 1.3°C during1951–2014. Several areas of HKH have experienced a declining trend in snowfall and alsoretreat of glaciers in recent decades. In contrast, the high-elevation Karakoram Himalayas have experienced higher winter snowfall that has shielded the region from glacier shrinkage.

By the end of the twenty-first century, the annual mean surface temperature over HKH isprojected to increase by about 5.2°C under the worst-case scenario. The projections also indicate an increase in annual precipitation but decrease in snowfall over the HKH region by the end of the twenty-first century, with large spread across models.

Conclusion

India has witnessed rising average temperatures,increased droughts, rising sea levels, precipitation changes and an increase in the intensity of severe cyclones since the middle of the twentieth century. There is compelling scientific evidence that human activities have influenced these changes in regional climate.Human-induced climate change is expected to continue apace during the twenty-first century. To improve the accuracy of future climate projections, particularly in the context of regional forecasts, it is essential to develop strategic approaches for improving the knowledge of Earth system processes, and to continue enhancing observation systems and climate models.

– Rituraj Phukan is an environmental writer with personal experience of climate change impacts at the polar regions. He believes in making a personal commitment to solving the biggest environmental crisis to humanity and has been vegan for years.