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The IPCC Assessment Reports

Why are they significant in
understanding climate change?

Introduction
Every few years, the Inter-governmental Panel on Climate Change (IPCC), which was set up in 1988 by the World Meteorological Organisation (WMO) and the UN Environment Programme (UNEP), produces assessment reports (ARs) that are the most comprehensive scientific evaluations of the state of earth’s climate. So far, six assessment reports have been produced, the first one being released in 1990. The sixth assessment report was released on August 09 in the run up to the climate change conference – Conference of Parties 26 or COP 26 – in Glasgow, Scotland.
Who Creates Ars?
The IPCC does not itself engage in scientific research; instead, it asks scientists from around the world to go through all the relevant scientific literature related to climate change and draw up the logical conclusions. So, the IPCC reports are created by three working groups of scientists.
Working Group-I: deals with the scientific basis for climate change. The sixth AR, to which over 750 scientists who reviewed over 14,000 scientific publications have contributed, has been prepared by this Working Group;
Working Group-II: looks at the likely impacts, vulnerabilities and adaptation issues; and
Working Group-III: deals with actions that can be taken to combat climate change.
Significance of Ars
IPCC assessments provide a scientific basis for governments at all levels to develop climate-related policies.
They underlie negotiations at the UN Climate Conference – the United Nations Framework Convention on Climate Change (UNFCCC).
The assessment reports are the most widely-accepted scientific opinion about climate change. They form the basis for government policies to tackle climate change, and also provide the scientific foundation for the international climate change negotiations.
Here is what the ARs have said to date:
First Assessment Report (1990)
Ø Emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases.
Ø Global temperatures have risen by 0.3 to 0.6 degree Celsius in last 100 years. In business-as-usual scenario, temperatures are likely to increase by 2 degree Celsius compared to pre-industrial levels by 2025, and 4 degree Celsius by 2100
Ø Sea-level likely to rise by 65 cm by 2100
This report formed the basis for negotiation of the UN Framework Convention on Climate Change in 1992.
Second Assessment Report (1995)
Ø Revises projected rise in global temperatures to 3 degree Celsius above pre-industrial levels by 2100, sea-level rise to 50 cm, in the light of more evidence.
Ø Global rise in temperature by 0.3 to 0.6 degree Celsius since late 19th century, “unlikely to be entirely natural in origin”.
This report was the scientific underpinning for Kyoto Protocol in 1997.
Third Assessment Report (2001)
Ø Revises projected rise in global temperatures to 1.4 to 5.8 degree Celsius by 2100 compared to 1990. Projected rate of warming unprecedented in last 10,000 years.
Ø Rainfall will increase on an average. The report also predicted that by 2100, the sea level could rise by as much as 80 cm from 1990 levels. Glaciers to retreat during the 21st century.
Ø Frequency, intensity and duration of extreme weather events to increase.
Ø Presents, new and stronger evidence to suggest that global warming is mostly attributable to human activities.
Fourth Assessment Report (2007)
Ø Greenhouse gas emissions increased by 70 percent between 1970 and 2004.
Ø Atmospheric concentrations of CO2 in 2005 (379 ppm) the maximum in 650,000 years.
Ø In worst-case scenario, global temperatures could rise 4.5 degree Celsius by 2100 from pre-industrial levels. Sea-levels could be 60 cm higher than 1990 levels.
The report won the 2007 Nobel Peace Prize for IPCC and was the scientific input for the 2009 Copenhagen climate meeting.
Fifth Assessment Report (2014)
Ø More than half the temperature rise since 1950 attributable to human activities.
Ø Atmospheric concentrations of carbon dioxide, methane and nitrous oxide “unprecedented” in the last 800,000 years.
Ø Rise in global temperatures by 2100 could be as high as 4.8 degree Celsius from pre-industrial times
Ø More frequent and longer heat waves “virtually certain”.
Ø “Large fraction of species” face extinction. Food security would be undermined.
This report formed the scientific basis for negotiations of the Paris Agreement in 2015.
Sixth Assessment Report (2021)
Ø The world has already warmed 1.1 degrees more than 1850-1900. The 1.5 degrees is likely to be reached in a couple of decades, which means more heat waves and longer warm seasons.
Ø Unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach.
Ø Warming of Indian Ocean will result into rise in sea levels causing more frequent and severe coastal flooding across low-level areas.
Ø It will also result into intense and frequent heat waves and humid heat stress in the 21st century in South Asia.
Ø Even if the temperature is limited 1.5 degree Celsius from pre-industrial levels, extreme weather events will be witnessed.
Ø Heatwaves, heavy rainfall events, and melting of glaciers are going to happen frequently.
Ø Developed countries need to undertake immediate, deep emission cuts and decarbonisation.
Analysis of Sixth AR
Eight years in the making, authored by the world’s leading climate scientists and approved by 195 national governments, the report confirmed the meaning of the evidence before our eyes: the cumulative impact of human activity since the Industrial Revolution is “unequivocally” causing catastrophic changes to the climate. The future that environmental scientists foresaw with alarm, when the IPCC produced its first report three decades ago, has arrived.
Without an accelerated reduction in greenhouse gases during the next decade, the ambition of the 2015 Paris climate agreement to limit global heating to 1.5°C will not be met. The price of failure will be a world vulnerable to irreversible and exponential effects of global heating: there will be worse floods more often, more terrible and frequent heatwaves and devastating droughts.
The science is irrefutable. Less certain is the strength of political will to act upon it. An awesome burden of responsibility now rests upon this generation of leaders as humanity finds itself at a fork in the road. The actions taken or foregone during the next 10 years will define the parameters of the possible for future generations. A step-change is required, but across the world, green rhetoric continues to translate into policymaking at a pace which is fatally slow.
As alarming as it is, the report still leaves room for hope. Aggressive, rapid and widespread emissions cuts, beginning now, could limit the warming beyond 2050, which can save the world in the remainder of the century from catastrophic consequences.
This is not some far-off dystopian threat—climate change is here and if emissions are not curbed, its devastation will start showing very soon, with poorer countries sure to be the worst hit. It is hoped that this terrifying report will propel the world into action.

The writer is an Advocate of High Courts.