The Intergovernmental Panel on Climate Change (IPCC) released the first part of its Sixth Assessment Report (AR6), titled Climate Change 2021: The Physical Science Basis on August 9, 2021. It was prepared by more than 750 scientists of Working Group-I, after reviewing over 14,000 scientific publications. The remaining two parts would be released in 2022. The report assesses scientific, technical, and socio-economic information concerning climate change. Created by the UN Environment Programme (UNEP) and the World Meteorological Organisation (WMO), the IPCC, currently has 195 member countries.
The IPCC brings out scientific assessment reports in every six to seven years which are the most comprehensive scientific evaluations of the state of the earth’s climate. These reports are the most widely-accepted scientific opinion about climate change, and form the basis for government policies to handle climate change. These reports are prepared by three working groups of scientists—Working Group-I deals with the scientific basis for climate change; Working Group-II works at the likely impacts, vulnerabilities, and adaptation issues; whereas Working Group-III looks at actions to be taken to control it. The report is supported by a task force on national greenhouse gas inventories that prepares methodologies for measuring emissions and removals.
Key Highlights of the Report
Some of the key highlights of the WG-I study are as follows:
- The average surface temperature of the earth will cross 1.5 °C, over pre-industrial levels by 2040 and 2 °C by the middle of the century without sharp reduction of emissions.
(In 2018, the IPCC’s Special Report on Global Warming had estimated that the two-fifths of the global population lived in regions with warming above 1.5 °C which could be saved from further heat by 2040 if emissions are controlled.
- The last decade was hotter than any period of time in the past 1,25,000 years. Global surface temperature was 1.09 °C higher in the decade between 2011–2020 than between 1850–1900.
- The 1.5 °C warming was inevitable even in the best-case scenario.
- Carbon dioxide (CO2) concentrations are the highest in at least two million years. Humans have emitted 2,400 billion tonnes of CO2since the late 1800s. A major factor for this increase is human activities, particularly the burning of fossil fuels. These activities have caused warming of the climate at a rate unprecedented in 2,000 years. The world has already depleted 86 per cent of its available carbon budget.
- As a result, sea-level rise has tripled compared with 1901–1971. The loss of summer Arctic sea ice is the lowest in 1,000 years.
- Due to continued sea-level rise throughout the 21st century, coastal erosion will occur leading to more frequent and severe flooding in low-lying areas.
- Thermal expansion is the main cause of about 50 per cent sea level rise as the heated water expands and occupies more space.
- Every additional 0.5 °C of warming will enhance hot extremes, extreme precipitation and drought. The extra warming will also weaken the earth’s carbon sinks available in plants, soils, and the ocean.
- Heat extremes have increased causing cold extremes to decrease. These trends will continue over the coming decades over Asia.
- Global warming will also impact mountain ranges across the world, including the Himalayas. These changes will affect and result in freezing level of mountains, retreating snowlines, and melting glaciers in the coming decades. If this happens, it must be taken as an alarm as this can cause a change in the water cycle, the precipitation patterns, increased floods, and an increased scarcity of water in the future, particularly in the states across the Himalayas. Rise in temperature in the mountains and glacial melt is unprecedented in 2,000 years.
- A new element in this report is the discussion over ‘compound events’, i.e., two or more climate change-induced events happening one after another, triggering each other, or occurring at the same time. (For instance, recent events including heavy rainfall, landslides, snow avalanche, and flooding in Uttarakhand.)
- India is expected to see rise in frequency and severity of hot extremes. Incidents of forest fire may increase due to heat-waves. Rainfall may increase more severely over the southern part of the country, may reach 20 per cent more in the southwest coast, compared to 1850–1900 level.
- Changes in both annual and summer monsoon precipitation are also projected to increase. The south-west monsoon has undergone decline in the past few decades due to the increase of aerosols, which may bring heavy monsoon rainfall.
- Glacial-lake outbursts, floods and landslides over moraine-dammed lakes can increase.
- Snowline elevations will increase leading to the decline of glacier volumes. Regional mean sea level will continue to rise in South Asia. Snow volumes may decrease in most regions of the Hindu Kush Himalaya during the 21st century.
- The Indian Ocean, including the Arabian Sea and Bay of Bengal, has warmed faster than the global average. The sea surface temperature over Indian ocean may rise by 1 °C to 2 °C in case global warming increases from 1.5 °C to 2 °C. The sea temperature is getting warm at a higher rate than other areas, which may influence other regions.
- A global net-zero emission by 2050 would not be possible without India.
- As per the report, in six Indian port cities—Chennai, Kochi, Kolkata, Mumbai, Surat, and Visakhapatnam—28.6 million people could face severe coastal flooding.
- According to the report, currently, climate change is widespread, rapid, and intensifying, and some trends are now irreversible.
Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change, set up in 1988, is an international body which assesses the science related to climate change. It was set up by the World Meteorological Organization (WMO) and United Nations Environment Programme (UNEP) to provide policymakers with regular assessments of the scientific basis of climate change, its impacts and future risks, and options for adaptation and mitigation. It provides a scientific basis for governments at all levels to develop climate-related policies, and also underlies negotiations at the United Nations Framework Convention on Climate Change.
Net-Zero Emissions
Net-zero emissions means that all man-made greenhouse gas emissions must be removed from the atmosphere through reduction measures so that the earth’s net climate balance may be reduced to zero through natural and artificial sink.
Experts’ Views
Responding to the report, Oxfam Climate Policy Lead, Nafkote Dabi, said: “Amid a world in parts burning, in parts drowning and in parts starving, the IPCC today tables the most compelling wake-up call yet for global industry to switch from oil, gas and coal to renewables. Governments must use law to compel this urgent change. Citizens must use their own political power and behaviours to push big polluting corporations and governments in the right direction. There is no Plan B.”
While articulating India’s position and response to the report, environmentalist Bhupender Yadav said, “The report reaffirms India’s position that historical cumulative emissions are the source of the current climate crisis. The report is a clarion call for the developed countries to undertake deep emission cuts and decarbonisation of their economies.”
As per Professor Bala Govindasamy, Centre for Atmospheric and Oceanic Sciences, Bengaluru, the crux of the problem is not the headline statements, containing mostly the average or mean values, but the extremities of these predictions. For example, in a 2 °C warmer world, not every day would be 2 °C warmer than pre-industrial times. Some days can be 6 °C to 8 °C, or even 10 °C warmer. That is how global warming will manifest at the local levels.
Conclusion
The menace of climate change has been described by many as a far greater threat to humanity than SARS CoV-2 pandemic due to its irreversible impacts. Many of the impacts such as sea level rise and melting of glaciers will continue for many years. The need of the hour is—drastic and immediate cut in carbon emissions. All nations, especially the G20 and other major emitters, must join hands to reach the net-zero emissions, reinforce their commitments with credible, concrete, and enhanced nationally determined contributions and policies before COP26.
Findings of Previous Reports in a Nutshell
1st Assessment Report (1990): Emissions due to human activities are substantially increasing the atmospheric concentrations of the greenhouse gases. Global temperatures have risen by 0.3 °C to 0.6 °C in the past 100 years. If continued as usual, temperatures may increase by 2 °C compared to pre-industrial levels by 2025, and 4 °C by 2100. Sea level may rise by 65 cm by 2100.
2nd Assessment Report (1995): Revises projected rise in global temperatures to 3 °C above pre-industrial levels by 2100, sea-level rise to 50 cm, in light of more evidence. Global rise in temperature by 0.3 to 0.6 °C since late 19th century, “unlikely to be entirely natural in origin”.
3rd Assessment Report (2001): Revises projected rise in global temperatures to 1.4 to 5.8 °C by 2100 compared to 1990. Projected rate of warming unprecedented in last 10,000 years. Rainfall will increase on an average. By 2100, the sea level may rise by as much as 80 cm from 1990 levels. Glaciers to retreat during the 21st century. Frequency, intensity, and duration of extreme weather events to increase. Presents new and stronger evidence to suggest that global warming is mostly anthropogenic (due to human activities).
4th Assessment Report (2007): Greenhouse gas emissions increased by 70 per cent between 1970 and 2004. Maximum atmospheric concentrations of CO2 in 2005 in 6,50,000 years. In worst-case scenario, global temperatures could rise 4.5 °C by 2100 from pre-industrial levels. Sea levels could be 60 cm higher than 1990 levels.
5th Assessment Report (2014): More than half the temperature rise since 1950 is anthropogenic. Atmospheric concentrations of CO2, methane, and nitrous oxide “unprecedented” in the last 8,00,000 years. By 2100, global temperatures could be as high as 4.8 °C from pre-industrial times. More frequent and longer heat waves are “virtually certain”. “Large fraction of species” is facing extinction.
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