By Rakesh Kumar Sinha, Indian Institute of Technology Bombay, Mumbai, India
Intergovernmental Panel on Climate Change (IPCC) was set by the UNEP (United Nation Environmental Programme) and the World Meteorological Organization (WMO) in 1988. This is the international body for investigating climate change impacts to provide policymakers regarding its impacts and future risk as well as an option for adaptation and mitigation. Every few years (5 to 7), IPCC produces such kind of comprehensive scientific report but IPCC itself does not have involved in any scientific research and analysis in their centre. However, they ask scientists all over the globe to review the scientific paper related to climate change which was published recently. The complete IPCC report will be developed by three working groups. Working Group-I that report published on 09th of August 2021 (Monday) which is the first part of IPCC sixth assessment report called Climate Change 2021: A Physical Science Basis. This report explained the scientific basis of climate change which happens around the world. The second part of the report which will be developed by working group-II, likely deals with impacts vulnerabilities and adaption part. However, Working Group-III is likely to deal with which kind of actions should be taken to combat climate change in the future. Over 240 scientists reviewed more than 1400 pieces of literature to contribute to the Working Group-I report.
Till now sixth assessment report has been released:
First Assessment Report of IPCC (1990):
- The first report of IPCC formed underpinning for negotiation of United Nation Framework Convention on Climate change in 1992.
- As per the first IPCC, report temperature has risen by 0.3 to 0.6 degrees Celsius in the last 100 years and is likely to increase by 2 degrees Celsius in 2025 and 4 degrees Celsius by 2100 in comparison to pre-industrial level in business-as-usual conditions.
- Sea level is likely to rise by 0.65 m by 2100 in comparison to the pre-industrial level.
Second Assessment Report of IPCC (1995):
- This report formed the basis of the Kyoto protocol which was held in 1997.
- In the second IPCC report, revised projected rise in global temperature by 3 degrees Celsius above in comparison to pre-industrial levels by 2100.
Third Assessment Report of IPCC (2001)
- As per this report revise global temperature rise by 1.4 to 5.8 degrees Celsius by 2100 in comparison to 1990.
Fourth Assessment Report of IPCC (2007)
- This report Won Novel Peace Prize in 2007 (IPCC and Al Gore) and formed the basis with the help of scientific inputs of the Copenhagen Climate meeting in 2009.
- As per this report temperature could rise by 4.5 degrees Celsius by 2100 in comparison to pre-industrial time in worse conditions.
Fifth Assessment Report of IPCC (2014)
- This report makes scientific inputs for the international negotiation of the Paris agreement which was held in 2015. As per this report, global temperature could rise by 4.8 degrees Celsius in comparison to pre-industrial time till 2100.
Six Assessment Report of IPCC (2021)
The Sixth Assessment Report (AR6) of IPCC was finalized on the sixth of August 2021 by Working Group I on the 54th session of IPCC. Please note that all statements in the AR6 report based on scientific literature are accepted for publication by 31 January 2021.
Global change as per IPCC AR6 report
- As per the sixth assessment report of IPCC (AR6) ‘Climate Change 2021: A Physical Science Basis’ the average global temperature will rise by 1.5°C in the coming next 20 years and emissions of greenhouse gases from anthropogenic activities are responsible for approximately 1.1°C in comparison to 1850-1900. Since 1850, each of the last four decades was warmer than any decade that preceded.
- In the 21st century, the first two-decade (2001 to 2020) was 0.99 °C more in comparison to 1850-1900. However, when compared with the first decade (2001-2010), it was 0.99 °C with a larger increase in land surface than ocean areas. The total human-induced increase in global surface temperature was 1.07 °C from 2010 – 2019 in comparison to 1850-1900.
- For global average rainfall, it is likely to increase since 1950 and faster rate since the 1980s with medium confidence.
- The global mean sea level increased by 0.20 m from 1901 to 2018 and the average rise of mean sea level was 1.3 mm per year between 1901 to 1971 while it increased 1.9mm per year between 1971 to 2006 and further increased to 3.7 mm per year between too6 to 2018.
- The atmospheric CO2 concentration in 2019 was higher than at least any time in 2 million years with high confidence and concentrations of CH4 and N2O were higher than at any time in at least 800,000 years with very high confidence.
- The annual average arctic sea ice area reached its lowest level since 1850 in 2011 to 2020 with high confidence.
Changes over South Asia and India as per IPCC AR6 report
- As per observation, scientists found that South Asia and Southeast Asian monsoon has weakened in the second half of the 2oth century but as per the AR6 report the Southeast and Asian Monsoon and East Asian summer monsoon rainfall will increase in the future for the long term period.
- For particularly South Asia, as per the AR6 report, both summer and annual monsoon rainfall will increase during the 21st century with an increase of inter-annual and inter-seasonal variability monsoon patter will be very difficult to predict from one year to next year.
- The glacier volume of the Hindu-Kush Himalayan region will decline said with high confidence and due to this runoff may decrease due to the loss of glaciers in this region. The precipitation will increase across the whole Tibetan and the Himalayan region in the 21st century.
- Heatwave and humid heat will more intense and frequent in Southeast Asia and on the other hand heatwave will increase and cold waves will decrease in the 21st century,
- The Indian Ocean, which includes the Arabian Sea and Bay of Bengal, has warmed faster than the global average, the IPCC said with “very high confidence”.
- The report warns that with a 7,517 km coastline, India will face significant threats from rising seas. Across six Indian port cities like Chennai, Kochi, Kolkata, Mumbai, Surat, and Visakhapatnam, 28.6 million people will be exposed to coastal flooding if sea levels rise 50cm.
Some irreversible change due to climate change in the 21st century
- Upper Ocean Stratification (means a vertical change in seawater density)
- Ocean acidification (means decrease of Ph value of ocean water)
- Ocean deoxygenation (decrease of oxygen level in oceanic water)
- Sea level rise (means increase of sea level height may cause flood in the coastal city of the world in the future)
- Increase in heat and cold wave
- Increase in heavy rainfall (both amount and frequency)
The report will release in future
AR6 Climate Change 2022: Impacts, Adaptation, and Vulnerability by the Working Group II
AR6 Climate Change 2022: Mitigation of Climate Change by the Working Group III
AR6 Synthesis Report (SYR) will come in September 2022. Check from below link