Describing it as a "stark assessment of the frightening future that awaits us if we fail to act", scientists across the globe on Monday said, many of the changes observed in the climate are unprecedented in thousands, if not hundreds of thousands of years.
Moreover, some of the changes already set in motion -- such as a continued sea-level rise -- are irreversible over hundreds to thousands of years, the scientists said, adding, they are observing changes in the Earth's climate "in every region and across the whole climate system".
In simplest terms: The climate has always changed but warming like that of recent decades has not been seen for millennia or longer. It is warming almost everywhere on the globe -- Australia, Asia, Europe, or North America; it is warming rapidly -- Iceland lost 750 sq kms of glaciers in the last two decades; the warming reversed a long-term cooling, and it has been a long time since it has been this warm.
It is unequivocal that human influence has warmed the atmosphere, ocean, and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred. However, strong, sustained reductions in emissions of carbon dioxide (CO2) and other greenhouse gases would limit climate change; while benefits for air quality would come quickly, it could take 20-30 years to see global temperatures stabilise, they said.
This clangorous proclamation was made in the latest Intergovernmental Panel on Climate Change (IPCC) Report released at a virtual global media conference held at Geneva.
The report from the Working Group I -- Climate Change 2021: the Physical Science Basis' -- is the first instalment of the IPCC's Sixth Assessment Report (AR6), which will be completed in 2022. This report was approved on Friday by 195-member governments of the IPCC, through a virtual approval session that was held over two weeks starting on July 26. For the first time, it has provided detailed regional assessment too.
The report provides new estimates of the chances of crossing the global warming level of 1.5 degree C in the next decades, and finds that unless there are immediate, rapid, and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5 degree C or even 2 degree C will be beyond reach.
The report shows that emissions of greenhouse gases from human activities are responsible for approximately 1.1 degree C of warming since 1850-1900, and finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5 degree C of warming. This assessment is based on improved observational datasets to assess historical warming, as well progress in Scientific Understanding of the response of the climate system to human-caused greenhouse gas emissions, an IPCC statement said.
- Climate change is intensifying the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.
- Climate change is affecting rainfall patterns. In high latitudes, precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon precipitation are expected, which will vary by region.
- Coastal areas will see continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion. Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.
- Further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice.
- Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been clearly linked to human influence. These changes affect both ocean ecosystems and the people that rely on them, and they will continue throughout at least the rest of this century.
- For cities, some aspects of climate change may be amplified, including heat (since urban areas are usually warmer than their surroundings), flooding from heavy precipitation events and sea level rise in coastal cities.
"The innovations in this report, and advances in climate science that it reflects, provide an invaluable input into climate negotiations and decision-making," said Chair of the IPCC Hoesung Lee.
Climate negotiations and decision-making that Lee referred to is the Conference of Parties (COP26) of the United Nations Framework Convention for Climate Change (UNFCCC) that is to be held at Glasgow, London in November to work out low-emission pathways by all countries to keep the global temperature rise in check.
Stating that the report offers a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare, IPCC Working Group I Co-Chair Valrie Masson-Delmotte reminded, "This report is a reality check".
Many characteristics of climate change directly depend on the level of global warming, but what people experience is often very different to the global average. For example, warming over land is larger than the global average, and it is more than twice as high in the Arctic. Or for that matter, the average global temperature increases by 1.5 degree C on the plains and 2.5 degree C for the Himalayan states.
The report projects that in the coming decades climate changes will increase in all regions. For 1.5 degree C of global warming, there will be increasing heat waves, longer warm seasons, and shorter cold seasons. At 2 degree C of global warming, heat extremes would more often reach critical tolerance thresholds for agriculture and health, the report shows.
The Working Group I report addresses the most updated physical understanding of the climate system and climate change, bringing together the latest advances in climate science, and combining multiple lines of evidence from paleoclimate, observations, process understanding, global and regional climate simulations. It shows how and why climate has changed to date, and the improved understanding of human influence on a wider range of climate characteristics, including extreme events.
The scrupulous AR6WGI report has been prepared by 234 authors from 66 countries and 517 contributing authors. There were over 14,000 cited references and a total of 78,007 expert and government review comments. There is a greater focus on regional information that can be used for climate risk assessments. Scientists said the Ministry of Earth Science's 2020 publication 'Assessment of Climate Change over the Indian Region' helps fill the data gap in many ways. There are a few Indian authors too who have contributed to the tome.
"It has been clear for decades that the Earth's climate is changing, and the role of human influence on the climate system is undisputed," said Masson-Delmotte. Yet this latest report also reflects major advances in the science of attribution -- understanding the role of climate change in intensifying specific weather and climate events such as extreme heat waves and heavy rainfall events.
The report also shows that human actions still have the potential to determine the future course of climate. The evidence is clear that carbon dioxide (CO2) is the main driver of climate change, even as other greenhouse gases and air pollutants also affect the climate.
"Stabilising the climate will require strong, rapid, and sustained reductions in greenhouse gas emissions, and reaching net zero CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have benefits both for health and the climate," said IPCC Working Group I Co-Chair Panmao Zhai.
Even when the governments that approved the AR6WGI report are yet to come out with reactions, the non-profits and the climate action groups responded soon with their thoughts.
Dr Stephan Singer, senior advisor, Climate Action Network International (CAN International) said, "Governments must interpret the findings of the latest IPCC report as an alarm bell to phase-out of fossil fuels and drastically reduce emissions within this decade. This report must serve as a large nail in the coffin of the fossil fuel industry."
The latest IPCC report shows we currently have the highest carbon dioxide concentrations in the atmosphere and the highest amounts of marine acidification since at least two million years, he said and suggested: "Phasing out fossil fuels, massively deploying renewables, investing in energy efficiency, and halting ecosystem destruction is the only obvious political course of action for a liveable planet. This report also implies that extreme weather events will continue at current rates of warming. This means stronger support is urgently needed for adaptation and loss and damage, particularly for vulnerable communities in poor countries."
Dr Kristina Dahl, Senior Climate Scientist, Union of Concerned Scientists said, "This report offers a wealth of scientific information that should be elevated and heeded. While this report underscores the urgent need for climate action, prior IPCC reports and countless other studies, as well as our lived experience, have already given us more than enough evidence to know that we're amid a crisis brought to us largely by the fossil fuel industry and their political allies. The continued dithering to address climate change is no longer about the lack of scientific evidence, but rather directly tied to a lack of political will."