Global warming has given rise to unprecedented extreme events such as cyclones, floods, heatwaves and droughts in India. Why are these threats increasing?

Dr Aradhana Yaduvanshi, a hydro meteorologist at W-CReS (The WOTR Center for Resilience Studies) talks to India Water Portal about her study on the implications of global warming for India titled ‘Impacts of 1.5 °C and 2 °C global warming on regional rainfall and temperature change across India’ published in the journal Environmental Research Communications and what can be done to cope with these changes.

What is the phenomenon of global warming and why is it increasing the world over?

In simple words, global warming is an increase in the planet’s average temperature due to an increase in emission of greenhouse gases. The process of absorption and radiation of heat by the atmosphere is the natural greenhouse gas effect, which is essential for life on earth. Since 1750, after the industrial revolution, concentrations of methane and carbon dioxide gases have increased substantially into our atmosphere.

This unprecedented and rapid rise in greenhouse gas emissions has led to a rapid change in climate, causing irreversible events such as glaciers melting, a rise in sea levels, submergence of coastal areas, frequent cyclones, heat waves and extinction of species, to name a few. Moreover, the frequency of occurrence of changes has increased; climatic changes that used to happen over thousands  of years, are now happening in the span of just a mere decade. 

What are the implications for India and what is the situation in India? Why is it worrying for India?

India is a developing country with the second largest population in the world. Deadly heatwaves - similar to the one in 2015 that killed thousands of people in India - could soon become the norm. In 2018-19, as many as 2,400 people in India lost their lives to extreme weather events such as floods and cyclones, according to the Environment Ministry. The Indian Meteorological Department (IMD) says these events are increasing in both frequency and intensity.

Extreme events may be the most tangible and immediate impact of climate change, but another more long-term and equally dangerous effect is rising temperatures and change in rainfall patterns that will have serious implications on agriculture and overall economy.

What was the focus of your study and why did you undertake it?

At Watershed Organisation Trust (WOTR), we strive to connect science with practice on ground for the betterment of society in a more sustainable way. This study was a product of IDRC and DFID funded project, Adaptation at Scale in Semi-Arids (ASSAR) which was part of the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA).

Global temperatures are projected to increase to 4°C by the end of this century, if we carry on as we are. The Paris agreement resolved to maintain the rise in average global temperatures to a level of 2.0°C or an aspirational level of 1.5°C compared to pre-industrial levels. This goal is dependent on the commitment of member countries to the Paris agreement, to cut down on emissions. The impact of each increment of 0.5°C need not necessarily be linear and there is much uncertainty on how extreme events would unfold.

Also there is limited understanding of what an increase in global average temperature means at a regional scale. An increase of 2°C global temperature need not be the same at regional level. It could be higher or lower. India, with its diverse agro-climatic zones, would surely face severe implications. Therefore, the present study is an attempt to find changes in mean temperature and rainfall (both annual and seasonal) of Indian states.

What did your study find?

The study found that at different warming levels, as we move from 1.5°C to 2°C increase in average temperatures, there is an increase in regional rainfall, temperatures and climate extremes in semi-arid regions of India, which are already hot places to live. Relative to pre-industrial period, majority of the states have shown the maximum increase in temperature of 2.1 °C and 2.8 °C under the threshold of 1.5 °C and 2 °C respectively.

The most severe temperature change is expected to occur in the presently colder Northern most states of India such as Jammu and Kashmir, Himachal Pradesh and Uttaranchal (2.0 °C - 2.2 °C at 1.5 °C and 2.5 °C - 2.8 °C at 2.0 °C) in both RCP4.5 and RCP8.5 (business as usual scenario). In addition, maximum increase in annual rainfall is expected in the North East region of the country, especially during the pre-monsoon and monsoon seasons.

What are the long term implications of your study for India and its states?

In both warming levels of 1.5 and 2.0°C, there would be increased melting of snow and glaciers in the Himalayas. High rainfall in the North East would increase river flows, which will in turn increase the vulnerability of people residing in the deltaic regions of the Ganga and Brahmaputra rivers to severe flooding by the year 2038.

The agriculture sector is particularly vulnerable to climate change, and will bear the maximum impact of increased climate variability and extremes. States in which agriculture could potentially be affected by increased temperature rise (in post monsoon and winter) include Haryana, Punjab and Rajasthan, which account for the highest wheat and paddy growing areas in the country.

The implications of projected increases in rainfall and temperatures in the future could lead to risks at a larger biophysical level (e.g. in the form of increased river flows and consequent floods) or at farm level production activities (e.g. impact on crop productivity).

What steps do you think need to be undertaken to cope with them?

The problems of temperature rise need to be seen in totality as there is already an increased incidence of land use land cover changes, groundwater decline, pests attack, frequently occurring heat waves etc. and these are only expected to increase in future. Increase in rainfall projections in pre-monsoon season indicate a need for change in farm management practices such as early land preparation and sowing activities.

It is important for the current national and respective state action plans on climate change and adaptation to be more sensitive as well as responsive to the different scenarios at the global level (4 °C, 2 °C and 1.5 °C) in order to take more informed policy decisions as well as develop strategies that benefit the regional or local populace. The state action plan for climate change and adaptation needs to take cognizance of increased frequency of such extreme events.