Environment: August 2021 Current Affair | Environment & Additional Topics for State PSC Exams - BPSC (Bihar) PDF Download

 Page 1


 
49                                                                                                                                                        
5. ENVIRONMENT 
5.1. IPCC’S SIXTH ASSESSMENT REPORT  
Why in News? 
The Intergovernmental Panel on Climate Change 
(IPCC) recently released its Sixth Assessment Report 
(AR6). 
About the report 
• The IPCC prepares comprehensive Assessment 
Reports about the state of scientific, technical 
and socio-economic knowledge on climate 
change, its impacts and future risks, and 
options for reducing the rate at which climate 
change is taking place.  
• So far, five assessment reports have been 
produced, the first one being released in 1990.  
• This AR6 will be an update of the AR5 released in 2013.  
• Improvements since AR5: 
o Improvements in observation-based estimates and information from paleoclimate archives provide a 
comprehensive view of each component of the climate system and its changes to date.  
o New climate model simulations, new analyses, and methods combining multiple lines of evidence lead 
to improved understanding of human influence on a wider range of climate variables, including weather 
and climate extremes. 
Key Findings 
Observations Related Data and Statistics 
Current State of the Climate 
Human influence has unequivocally 
warmed the atmosphere, ocean and 
land:  
• Observed increases in well-mixed 
greenhouse gas (GHG) concentrations 
since around 1750 are unequivocally 
caused by human activities. 
• Human influence has been linked with 
widespread and rapid changes in the 
atmosphere, ocean, cryosphere and 
biosphere such as- 
o Global retreat of glaciers. 
o Sea level rise. 
o Drop in oxygen levels in many 
upper ocean regions. 
o Observed precipitation changes. 
o Changes in near-surface ocean 
salinity. 
o Global acidification of the surface 
open ocean. 
o Decrease in Northern Hemisphere 
spring snow cover. 
• Global surface temperature was 1.09 °C higher in 2011– 2020 than 
1850–1900, with larger increases over land (1.59 °C) than over the 
ocean (0.88 °C).  
• Each of the last four decades has been successively warmer than any 
decade that preceded it since 1850. 
• Human-caused global surface temperature increase from 1850–1900 
to 2010–2019 is estimated to be 1.07°C. 
• The Arctic Sea ice area has decreased (about 40% in September and 
about 10% in March) in between 1979–1988 and 2010–2019. 
• Global mean sea level increased by 0.20 m between 1901 and 2018, 
with average rate of sea level rise increasing from 1.3 mm yr between 
1901-1971 to 3.7 mm yr between 2006-2018. 
• Climate zones have shifted poleward in both hemispheres, and the 
growing season has on average lengthened by up to two days per 
decade since the 1950s in the Northern Hemisphere extratropics. 
 
About IPCC 
• Created in 1988 by the World Meteorological 
Organization (WMO) and the United Nations 
Environment Programme (UNEP), the objective of the 
IPCC is to provide governments at all levels with 
scientific information that they can use to develop 
climate policies.  
• The IPCC currently has 195 members including India.  
• In 2007, the IPCC and U.S. Vice-President Al Gore were 
jointly awarded the Nobel Peace Prize for their efforts 
to build up and disseminate greater knowledge about 
man-made climate change, and to lay the foundations 
for the measures that are needed to counteract such 
change. 
Page 2


 
49                                                                                                                                                        
5. ENVIRONMENT 
5.1. IPCC’S SIXTH ASSESSMENT REPORT  
Why in News? 
The Intergovernmental Panel on Climate Change 
(IPCC) recently released its Sixth Assessment Report 
(AR6). 
About the report 
• The IPCC prepares comprehensive Assessment 
Reports about the state of scientific, technical 
and socio-economic knowledge on climate 
change, its impacts and future risks, and 
options for reducing the rate at which climate 
change is taking place.  
• So far, five assessment reports have been 
produced, the first one being released in 1990.  
• This AR6 will be an update of the AR5 released in 2013.  
• Improvements since AR5: 
o Improvements in observation-based estimates and information from paleoclimate archives provide a 
comprehensive view of each component of the climate system and its changes to date.  
o New climate model simulations, new analyses, and methods combining multiple lines of evidence lead 
to improved understanding of human influence on a wider range of climate variables, including weather 
and climate extremes. 
Key Findings 
Observations Related Data and Statistics 
Current State of the Climate 
Human influence has unequivocally 
warmed the atmosphere, ocean and 
land:  
• Observed increases in well-mixed 
greenhouse gas (GHG) concentrations 
since around 1750 are unequivocally 
caused by human activities. 
• Human influence has been linked with 
widespread and rapid changes in the 
atmosphere, ocean, cryosphere and 
biosphere such as- 
o Global retreat of glaciers. 
o Sea level rise. 
o Drop in oxygen levels in many 
upper ocean regions. 
o Observed precipitation changes. 
o Changes in near-surface ocean 
salinity. 
o Global acidification of the surface 
open ocean. 
o Decrease in Northern Hemisphere 
spring snow cover. 
• Global surface temperature was 1.09 °C higher in 2011– 2020 than 
1850–1900, with larger increases over land (1.59 °C) than over the 
ocean (0.88 °C).  
• Each of the last four decades has been successively warmer than any 
decade that preceded it since 1850. 
• Human-caused global surface temperature increase from 1850–1900 
to 2010–2019 is estimated to be 1.07°C. 
• The Arctic Sea ice area has decreased (about 40% in September and 
about 10% in March) in between 1979–1988 and 2010–2019. 
• Global mean sea level increased by 0.20 m between 1901 and 2018, 
with average rate of sea level rise increasing from 1.3 mm yr between 
1901-1971 to 3.7 mm yr between 2006-2018. 
• Climate zones have shifted poleward in both hemispheres, and the 
growing season has on average lengthened by up to two days per 
decade since the 1950s in the Northern Hemisphere extratropics. 
 
About IPCC 
• Created in 1988 by the World Meteorological 
Organization (WMO) and the United Nations 
Environment Programme (UNEP), the objective of the 
IPCC is to provide governments at all levels with 
scientific information that they can use to develop 
climate policies.  
• The IPCC currently has 195 members including India.  
• In 2007, the IPCC and U.S. Vice-President Al Gore were 
jointly awarded the Nobel Peace Prize for their efforts 
to build up and disseminate greater knowledge about 
man-made climate change, and to lay the foundations 
for the measures that are needed to counteract such 
change. 
 
50                                                                                                                                                        
Scale of recent changes across the 
climate system are unprecedented.  
 
Human-induced climate change is already 
affecting many weather and climate 
extremes in every region across the 
globe: 
• It has been linked to extreme weather 
events such as heatwaves, heavy 
precipitation, droughts, and tropical 
cyclones etc. 
• Hot extremes (including heatwaves) have become more frequent and 
more intense across most land regions since the 1950s. 
• Marine heatwaves have approximately doubled in frequency since the 
1980s. 
• The frequency and intensity of heavy precipitation events have 
increased since the 1950s over most land area. 
• Tropical cyclone occurrence has increased over the last four decades. 
Human-caused net positive radiative 
forcing causes an accumulation of 
additional energy (heating) in the climate 
system.  
• Heating of the climate system has 
caused global mean sea level rise 
through ice loss on land and thermal 
expansion from ocean warming. 
• Human-caused radiative forcing of 2.72 W/m
2
 in 2019 relative to 1750 
has warmed the climate system. 
o Radiative forcing is the change in energy flux in the atmosphere 
caused by natural and/or anthropogenic factors of climate 
change. Positive radiative forcing means Earth receives more 
incoming energy from sunlight than it radiates to space. 
• Ocean warming accounted for 91% of the heating in the climate 
system, with land warming, ice loss and atmospheric warming 
accounting for about 5%, 3% and 1%, respectively. 
• Thermal expansion explained 50% of sea level rise during 1971– 2018, 
while ice loss from glaciers contributed 22%, ice sheets 20% and 
changes in land water storage 8%.  
• The equilibrium climate sensitivity (the global mean surface air 
temperature increase that follows a doubling of atmospheric carbon 
dioxide) is estimated to be 3°C. 
 
 
 
Page 3


 
49                                                                                                                                                        
5. ENVIRONMENT 
5.1. IPCC’S SIXTH ASSESSMENT REPORT  
Why in News? 
The Intergovernmental Panel on Climate Change 
(IPCC) recently released its Sixth Assessment Report 
(AR6). 
About the report 
• The IPCC prepares comprehensive Assessment 
Reports about the state of scientific, technical 
and socio-economic knowledge on climate 
change, its impacts and future risks, and 
options for reducing the rate at which climate 
change is taking place.  
• So far, five assessment reports have been 
produced, the first one being released in 1990.  
• This AR6 will be an update of the AR5 released in 2013.  
• Improvements since AR5: 
o Improvements in observation-based estimates and information from paleoclimate archives provide a 
comprehensive view of each component of the climate system and its changes to date.  
o New climate model simulations, new analyses, and methods combining multiple lines of evidence lead 
to improved understanding of human influence on a wider range of climate variables, including weather 
and climate extremes. 
Key Findings 
Observations Related Data and Statistics 
Current State of the Climate 
Human influence has unequivocally 
warmed the atmosphere, ocean and 
land:  
• Observed increases in well-mixed 
greenhouse gas (GHG) concentrations 
since around 1750 are unequivocally 
caused by human activities. 
• Human influence has been linked with 
widespread and rapid changes in the 
atmosphere, ocean, cryosphere and 
biosphere such as- 
o Global retreat of glaciers. 
o Sea level rise. 
o Drop in oxygen levels in many 
upper ocean regions. 
o Observed precipitation changes. 
o Changes in near-surface ocean 
salinity. 
o Global acidification of the surface 
open ocean. 
o Decrease in Northern Hemisphere 
spring snow cover. 
• Global surface temperature was 1.09 °C higher in 2011– 2020 than 
1850–1900, with larger increases over land (1.59 °C) than over the 
ocean (0.88 °C).  
• Each of the last four decades has been successively warmer than any 
decade that preceded it since 1850. 
• Human-caused global surface temperature increase from 1850–1900 
to 2010–2019 is estimated to be 1.07°C. 
• The Arctic Sea ice area has decreased (about 40% in September and 
about 10% in March) in between 1979–1988 and 2010–2019. 
• Global mean sea level increased by 0.20 m between 1901 and 2018, 
with average rate of sea level rise increasing from 1.3 mm yr between 
1901-1971 to 3.7 mm yr between 2006-2018. 
• Climate zones have shifted poleward in both hemispheres, and the 
growing season has on average lengthened by up to two days per 
decade since the 1950s in the Northern Hemisphere extratropics. 
 
About IPCC 
• Created in 1988 by the World Meteorological 
Organization (WMO) and the United Nations 
Environment Programme (UNEP), the objective of the 
IPCC is to provide governments at all levels with 
scientific information that they can use to develop 
climate policies.  
• The IPCC currently has 195 members including India.  
• In 2007, the IPCC and U.S. Vice-President Al Gore were 
jointly awarded the Nobel Peace Prize for their efforts 
to build up and disseminate greater knowledge about 
man-made climate change, and to lay the foundations 
for the measures that are needed to counteract such 
change. 
 
50                                                                                                                                                        
Scale of recent changes across the 
climate system are unprecedented.  
 
Human-induced climate change is already 
affecting many weather and climate 
extremes in every region across the 
globe: 
• It has been linked to extreme weather 
events such as heatwaves, heavy 
precipitation, droughts, and tropical 
cyclones etc. 
• Hot extremes (including heatwaves) have become more frequent and 
more intense across most land regions since the 1950s. 
• Marine heatwaves have approximately doubled in frequency since the 
1980s. 
• The frequency and intensity of heavy precipitation events have 
increased since the 1950s over most land area. 
• Tropical cyclone occurrence has increased over the last four decades. 
Human-caused net positive radiative 
forcing causes an accumulation of 
additional energy (heating) in the climate 
system.  
• Heating of the climate system has 
caused global mean sea level rise 
through ice loss on land and thermal 
expansion from ocean warming. 
• Human-caused radiative forcing of 2.72 W/m
2
 in 2019 relative to 1750 
has warmed the climate system. 
o Radiative forcing is the change in energy flux in the atmosphere 
caused by natural and/or anthropogenic factors of climate 
change. Positive radiative forcing means Earth receives more 
incoming energy from sunlight than it radiates to space. 
• Ocean warming accounted for 91% of the heating in the climate 
system, with land warming, ice loss and atmospheric warming 
accounting for about 5%, 3% and 1%, respectively. 
• Thermal expansion explained 50% of sea level rise during 1971– 2018, 
while ice loss from glaciers contributed 22%, ice sheets 20% and 
changes in land water storage 8%.  
• The equilibrium climate sensitivity (the global mean surface air 
temperature increase that follows a doubling of atmospheric carbon 
dioxide) is estimated to be 3°C. 
 
 
 
 
51                                                                                                                                                        
Possible Climate Futures: The report assesses the climate response to five scenarios based on the Shared Socioeconomic 
Pathways (SSPs), starting in 2015- 
• Scenarios with high and very high GHG emissions (SSP3-7.0 and SSP5-8.5) and CO2 emissions that roughly double 
from current levels by 2100 and 2050, respectively. 
• Scenarios with intermediate GHG emissions (SSP2-4.5) and CO2 emissions remaining around current levels until the 
middle of the century. 
• Scenarios with very low and low GHG emissions and CO2 emissions declining to net zero around or after 2050, 
followed by varying levels of net negative CO2 emissions (SSP1-1.9 and SSP1-2.6). 
• Global surface temperature will 
continue to increase until 2050 under 
all emissions scenarios.  
• With every increment of global 
warming, changes get larger in 
regional mean temperature, 
precipitation and soil moisture. 
• Continued global warming is 
projected to further intensify the 
global water cycle, including its 
variability, global monsoon 
precipitation and the severity of wet 
and dry events.  
• With increase in CO2 emissions, the 
ocean and land carbon sinks will 
become less effective at absorption of 
CO2 from the atmosphere.  
• Many changes due to past and future 
greenhouse gas emissions are 
irreversible, especially changes in the 
ocean, ice sheets and global sea level. 
• Global warming of 1.5°C and 2°C will be exceeded during the 21st 
century unless deep reductions in carbon dioxide (CO2) and other 
greenhouse gas emissions occur in the coming decades.  
 
Page 4


 
49                                                                                                                                                        
5. ENVIRONMENT 
5.1. IPCC’S SIXTH ASSESSMENT REPORT  
Why in News? 
The Intergovernmental Panel on Climate Change 
(IPCC) recently released its Sixth Assessment Report 
(AR6). 
About the report 
• The IPCC prepares comprehensive Assessment 
Reports about the state of scientific, technical 
and socio-economic knowledge on climate 
change, its impacts and future risks, and 
options for reducing the rate at which climate 
change is taking place.  
• So far, five assessment reports have been 
produced, the first one being released in 1990.  
• This AR6 will be an update of the AR5 released in 2013.  
• Improvements since AR5: 
o Improvements in observation-based estimates and information from paleoclimate archives provide a 
comprehensive view of each component of the climate system and its changes to date.  
o New climate model simulations, new analyses, and methods combining multiple lines of evidence lead 
to improved understanding of human influence on a wider range of climate variables, including weather 
and climate extremes. 
Key Findings 
Observations Related Data and Statistics 
Current State of the Climate 
Human influence has unequivocally 
warmed the atmosphere, ocean and 
land:  
• Observed increases in well-mixed 
greenhouse gas (GHG) concentrations 
since around 1750 are unequivocally 
caused by human activities. 
• Human influence has been linked with 
widespread and rapid changes in the 
atmosphere, ocean, cryosphere and 
biosphere such as- 
o Global retreat of glaciers. 
o Sea level rise. 
o Drop in oxygen levels in many 
upper ocean regions. 
o Observed precipitation changes. 
o Changes in near-surface ocean 
salinity. 
o Global acidification of the surface 
open ocean. 
o Decrease in Northern Hemisphere 
spring snow cover. 
• Global surface temperature was 1.09 °C higher in 2011– 2020 than 
1850–1900, with larger increases over land (1.59 °C) than over the 
ocean (0.88 °C).  
• Each of the last four decades has been successively warmer than any 
decade that preceded it since 1850. 
• Human-caused global surface temperature increase from 1850–1900 
to 2010–2019 is estimated to be 1.07°C. 
• The Arctic Sea ice area has decreased (about 40% in September and 
about 10% in March) in between 1979–1988 and 2010–2019. 
• Global mean sea level increased by 0.20 m between 1901 and 2018, 
with average rate of sea level rise increasing from 1.3 mm yr between 
1901-1971 to 3.7 mm yr between 2006-2018. 
• Climate zones have shifted poleward in both hemispheres, and the 
growing season has on average lengthened by up to two days per 
decade since the 1950s in the Northern Hemisphere extratropics. 
 
About IPCC 
• Created in 1988 by the World Meteorological 
Organization (WMO) and the United Nations 
Environment Programme (UNEP), the objective of the 
IPCC is to provide governments at all levels with 
scientific information that they can use to develop 
climate policies.  
• The IPCC currently has 195 members including India.  
• In 2007, the IPCC and U.S. Vice-President Al Gore were 
jointly awarded the Nobel Peace Prize for their efforts 
to build up and disseminate greater knowledge about 
man-made climate change, and to lay the foundations 
for the measures that are needed to counteract such 
change. 
 
50                                                                                                                                                        
Scale of recent changes across the 
climate system are unprecedented.  
 
Human-induced climate change is already 
affecting many weather and climate 
extremes in every region across the 
globe: 
• It has been linked to extreme weather 
events such as heatwaves, heavy 
precipitation, droughts, and tropical 
cyclones etc. 
• Hot extremes (including heatwaves) have become more frequent and 
more intense across most land regions since the 1950s. 
• Marine heatwaves have approximately doubled in frequency since the 
1980s. 
• The frequency and intensity of heavy precipitation events have 
increased since the 1950s over most land area. 
• Tropical cyclone occurrence has increased over the last four decades. 
Human-caused net positive radiative 
forcing causes an accumulation of 
additional energy (heating) in the climate 
system.  
• Heating of the climate system has 
caused global mean sea level rise 
through ice loss on land and thermal 
expansion from ocean warming. 
• Human-caused radiative forcing of 2.72 W/m
2
 in 2019 relative to 1750 
has warmed the climate system. 
o Radiative forcing is the change in energy flux in the atmosphere 
caused by natural and/or anthropogenic factors of climate 
change. Positive radiative forcing means Earth receives more 
incoming energy from sunlight than it radiates to space. 
• Ocean warming accounted for 91% of the heating in the climate 
system, with land warming, ice loss and atmospheric warming 
accounting for about 5%, 3% and 1%, respectively. 
• Thermal expansion explained 50% of sea level rise during 1971– 2018, 
while ice loss from glaciers contributed 22%, ice sheets 20% and 
changes in land water storage 8%.  
• The equilibrium climate sensitivity (the global mean surface air 
temperature increase that follows a doubling of atmospheric carbon 
dioxide) is estimated to be 3°C. 
 
 
 
 
51                                                                                                                                                        
Possible Climate Futures: The report assesses the climate response to five scenarios based on the Shared Socioeconomic 
Pathways (SSPs), starting in 2015- 
• Scenarios with high and very high GHG emissions (SSP3-7.0 and SSP5-8.5) and CO2 emissions that roughly double 
from current levels by 2100 and 2050, respectively. 
• Scenarios with intermediate GHG emissions (SSP2-4.5) and CO2 emissions remaining around current levels until the 
middle of the century. 
• Scenarios with very low and low GHG emissions and CO2 emissions declining to net zero around or after 2050, 
followed by varying levels of net negative CO2 emissions (SSP1-1.9 and SSP1-2.6). 
• Global surface temperature will 
continue to increase until 2050 under 
all emissions scenarios.  
• With every increment of global 
warming, changes get larger in 
regional mean temperature, 
precipitation and soil moisture. 
• Continued global warming is 
projected to further intensify the 
global water cycle, including its 
variability, global monsoon 
precipitation and the severity of wet 
and dry events.  
• With increase in CO2 emissions, the 
ocean and land carbon sinks will 
become less effective at absorption of 
CO2 from the atmosphere.  
• Many changes due to past and future 
greenhouse gas emissions are 
irreversible, especially changes in the 
ocean, ice sheets and global sea level. 
• Global warming of 1.5°C and 2°C will be exceeded during the 21st 
century unless deep reductions in carbon dioxide (CO2) and other 
greenhouse gas emissions occur in the coming decades.  
 
 
52                                                                                                                                                        
 
Climate Information for Risk Assessment and Regional Adaptation 
• Multiple climatic impact-drivers are projected to change in all regions of the world with changes being more 
widespread at 2°C compared to 1.5°C global warming.  
o Climatic impact-drivers (CIDs) are physical climate system conditions (e.g., means, events, extremes) that affect 
an element of society or ecosystem. 
• Low-likelihood outcomes, such as ice sheet collapse, abrupt ocean circulation changes, some compound extreme 
events and warming substantially larger than the assessed very likely range of future warming cannot be ruled out 
and are part of risk assessment. 
 
 
 
Page 5


 
49                                                                                                                                                        
5. ENVIRONMENT 
5.1. IPCC’S SIXTH ASSESSMENT REPORT  
Why in News? 
The Intergovernmental Panel on Climate Change 
(IPCC) recently released its Sixth Assessment Report 
(AR6). 
About the report 
• The IPCC prepares comprehensive Assessment 
Reports about the state of scientific, technical 
and socio-economic knowledge on climate 
change, its impacts and future risks, and 
options for reducing the rate at which climate 
change is taking place.  
• So far, five assessment reports have been 
produced, the first one being released in 1990.  
• This AR6 will be an update of the AR5 released in 2013.  
• Improvements since AR5: 
o Improvements in observation-based estimates and information from paleoclimate archives provide a 
comprehensive view of each component of the climate system and its changes to date.  
o New climate model simulations, new analyses, and methods combining multiple lines of evidence lead 
to improved understanding of human influence on a wider range of climate variables, including weather 
and climate extremes. 
Key Findings 
Observations Related Data and Statistics 
Current State of the Climate 
Human influence has unequivocally 
warmed the atmosphere, ocean and 
land:  
• Observed increases in well-mixed 
greenhouse gas (GHG) concentrations 
since around 1750 are unequivocally 
caused by human activities. 
• Human influence has been linked with 
widespread and rapid changes in the 
atmosphere, ocean, cryosphere and 
biosphere such as- 
o Global retreat of glaciers. 
o Sea level rise. 
o Drop in oxygen levels in many 
upper ocean regions. 
o Observed precipitation changes. 
o Changes in near-surface ocean 
salinity. 
o Global acidification of the surface 
open ocean. 
o Decrease in Northern Hemisphere 
spring snow cover. 
• Global surface temperature was 1.09 °C higher in 2011– 2020 than 
1850–1900, with larger increases over land (1.59 °C) than over the 
ocean (0.88 °C).  
• Each of the last four decades has been successively warmer than any 
decade that preceded it since 1850. 
• Human-caused global surface temperature increase from 1850–1900 
to 2010–2019 is estimated to be 1.07°C. 
• The Arctic Sea ice area has decreased (about 40% in September and 
about 10% in March) in between 1979–1988 and 2010–2019. 
• Global mean sea level increased by 0.20 m between 1901 and 2018, 
with average rate of sea level rise increasing from 1.3 mm yr between 
1901-1971 to 3.7 mm yr between 2006-2018. 
• Climate zones have shifted poleward in both hemispheres, and the 
growing season has on average lengthened by up to two days per 
decade since the 1950s in the Northern Hemisphere extratropics. 
 
About IPCC 
• Created in 1988 by the World Meteorological 
Organization (WMO) and the United Nations 
Environment Programme (UNEP), the objective of the 
IPCC is to provide governments at all levels with 
scientific information that they can use to develop 
climate policies.  
• The IPCC currently has 195 members including India.  
• In 2007, the IPCC and U.S. Vice-President Al Gore were 
jointly awarded the Nobel Peace Prize for their efforts 
to build up and disseminate greater knowledge about 
man-made climate change, and to lay the foundations 
for the measures that are needed to counteract such 
change. 
 
50                                                                                                                                                        
Scale of recent changes across the 
climate system are unprecedented.  
 
Human-induced climate change is already 
affecting many weather and climate 
extremes in every region across the 
globe: 
• It has been linked to extreme weather 
events such as heatwaves, heavy 
precipitation, droughts, and tropical 
cyclones etc. 
• Hot extremes (including heatwaves) have become more frequent and 
more intense across most land regions since the 1950s. 
• Marine heatwaves have approximately doubled in frequency since the 
1980s. 
• The frequency and intensity of heavy precipitation events have 
increased since the 1950s over most land area. 
• Tropical cyclone occurrence has increased over the last four decades. 
Human-caused net positive radiative 
forcing causes an accumulation of 
additional energy (heating) in the climate 
system.  
• Heating of the climate system has 
caused global mean sea level rise 
through ice loss on land and thermal 
expansion from ocean warming. 
• Human-caused radiative forcing of 2.72 W/m
2
 in 2019 relative to 1750 
has warmed the climate system. 
o Radiative forcing is the change in energy flux in the atmosphere 
caused by natural and/or anthropogenic factors of climate 
change. Positive radiative forcing means Earth receives more 
incoming energy from sunlight than it radiates to space. 
• Ocean warming accounted for 91% of the heating in the climate 
system, with land warming, ice loss and atmospheric warming 
accounting for about 5%, 3% and 1%, respectively. 
• Thermal expansion explained 50% of sea level rise during 1971– 2018, 
while ice loss from glaciers contributed 22%, ice sheets 20% and 
changes in land water storage 8%.  
• The equilibrium climate sensitivity (the global mean surface air 
temperature increase that follows a doubling of atmospheric carbon 
dioxide) is estimated to be 3°C. 
 
 
 
 
51                                                                                                                                                        
Possible Climate Futures: The report assesses the climate response to five scenarios based on the Shared Socioeconomic 
Pathways (SSPs), starting in 2015- 
• Scenarios with high and very high GHG emissions (SSP3-7.0 and SSP5-8.5) and CO2 emissions that roughly double 
from current levels by 2100 and 2050, respectively. 
• Scenarios with intermediate GHG emissions (SSP2-4.5) and CO2 emissions remaining around current levels until the 
middle of the century. 
• Scenarios with very low and low GHG emissions and CO2 emissions declining to net zero around or after 2050, 
followed by varying levels of net negative CO2 emissions (SSP1-1.9 and SSP1-2.6). 
• Global surface temperature will 
continue to increase until 2050 under 
all emissions scenarios.  
• With every increment of global 
warming, changes get larger in 
regional mean temperature, 
precipitation and soil moisture. 
• Continued global warming is 
projected to further intensify the 
global water cycle, including its 
variability, global monsoon 
precipitation and the severity of wet 
and dry events.  
• With increase in CO2 emissions, the 
ocean and land carbon sinks will 
become less effective at absorption of 
CO2 from the atmosphere.  
• Many changes due to past and future 
greenhouse gas emissions are 
irreversible, especially changes in the 
ocean, ice sheets and global sea level. 
• Global warming of 1.5°C and 2°C will be exceeded during the 21st 
century unless deep reductions in carbon dioxide (CO2) and other 
greenhouse gas emissions occur in the coming decades.  
 
 
52                                                                                                                                                        
 
Climate Information for Risk Assessment and Regional Adaptation 
• Multiple climatic impact-drivers are projected to change in all regions of the world with changes being more 
widespread at 2°C compared to 1.5°C global warming.  
o Climatic impact-drivers (CIDs) are physical climate system conditions (e.g., means, events, extremes) that affect 
an element of society or ecosystem. 
• Low-likelihood outcomes, such as ice sheet collapse, abrupt ocean circulation changes, some compound extreme 
events and warming substantially larger than the assessed very likely range of future warming cannot be ruled out 
and are part of risk assessment. 
 
 
 
 
53                                                                                                                                                        
Regional findings for India 
Following impacts are likely to be seen in India (South Asian region)- 
• Heatwaves and humid heat stress will be more intense and frequent during the 21st century all over South 
Asia. 
• Both annual and summer monsoon precipitation will increase during the 21st century, with enhanced 
interannual variability. 
• Increases in precipitation and rivers floods. 
• Fire weather seasons are projected to lengthen and intensify. 
• Covered areas and snow volumes will decrease in most regions of the Hindu Kush Himalaya during the 21st 
century and snowline elevations will rise and glacier volumes are likely to decline with greater mass loss in 
higher CO 2 emissions scenarios. 
• Regional-mean Sea level continues to rise and will contribute to more frequent coastal flooding and higher 
Extreme Total Water Level (ETWL) in low-lying areas and coastal erosion along sandy beaches. 
Way Forward 
According to the report, limiting human-induced global warming to a specific level requires limiting cumulative 
CO 2 emissions, reaching at least net zero CO 2 emissions, along with strong reductions in other greenhouse gas 
emissions. Strong, rapid, and sustained reductions in CH 4 emissions would also limit the warming effect resulting 
from declining aerosol pollution and would improve air quality. 
5.2. LAND DEGRADATION 
Why in news? 
The Desertification and Land Degradation Atlas of India for the year 2018-19 was recently released by Space 
Applications Centre (SAC), Ahmedabad (Indian Space Research Organization). 
Land degradation and Desertification 
• Land degradation is defined as a negative trend in land condition, caused by direct or indirect human-
induced processes including anthropogenic climate change, expressed as long-term reduction or loss of at 
least one of the following: biological productivity, ecological integrity, or value to humans.  
o Forest degradation is land degradation that occurs in forest land.  
o Land degradation within dryland regions (arid, semi-arid and dry sub-humid regions) is termed as 
Desertification, which turns fertile land into desert. 
• Its major drivers include natural processes such as wind and water erosion, water logging, salinity / 
alkalinity, mass movement, frost heaving and frost shattering etc. and anthropogenic activities such as land 
use change, mining/quarrying, livestock grazing, brick kiln, industrial effluents, pollution etc. 
Impacts of Land Degradation and Desertification 
• Socio-Economic impacts: 
o Reduces land productivity threatening food security and livelihoods of indigenous populations, small 
farmers etc. 
o Reduces the land’s ability to store water resulting in water scarcity. 
o Exacerbates existing societal tensions and forces migration. 
• Impact on Human health: 
o Creates ground for zoonotic disease, water- and food-borne diseases and respiratory diseases. 
o Higher threats of malnutrition from reduced food and water supplies. 
• Environmental impacts:  
o Causes extreme weather events, accelerates biodiversity loss and disruption of ecosystem services. 
o Contributes to Climate Change: Land degradation is a driver of climate change through emission of 
greenhouse gases (GHGs) and reduced ability of land to act as a carbon sink. 
? Since climate change also exacerbates the rate and magnitude of several ongoing land degradation 
processes and introduces new degradation patterns, this creates a positive feedback cycle.