ClimateChange 2021: the Physical Science Basis – provides the most updated physical understanding of the climate system and #climatechange, combining the latest advances in climate science, and multiple lines of evidence.
Read below the Press Release issued by Intergovernmental Panel on Climate
Change (IPCC) about its latest Report.
Climate change widespread, rapid, and intensifying – IPCC
GENEVA, Aug 9 – Scientists are observing changes in the Earth’s climate in every region and
across the whole climate system, according to the latest Intergovernmental Panel on Climate
Change (IPCC) Report, released today.
Many of the changes observed in the climate are unprecedented in thousands, if not hundreds of thousands of years, and some of the changes already set in motion—such as continued sea level rise—are irreversible over hundreds to thousands of years.
However, strong and 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 stabilize, according to the IPCC Working Group I
report, Climate Change 2021: the Physical Science Basis, 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.
The Working Group I report is the first instalment of the IPCC’s Sixth Assessment Report (AR6),
which will be completed in 2022.
“This report reflects extraordinary efforts under exceptional circumstances,” said Hoesung Lee,
Chair of the IPCC. “The innovations in this report, and advances in climate science that it reflects,
provide an invaluable input into climate negotiations and decision-making.”
The report provides new estimates of the chances of crossing the global warming level of 1.5°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°C or even 2°C will be beyond reach.
The report shows that emissions of greenhouse gases from human activities are responsible for
approximately 1.1°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°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.
“This report is a reality check,” said IPCC Working Group I Co-Chair Valérie Masson-Delmotte. “We
now have 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.”
Every region facing increasing changes
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.
“Climate change is already affecting every region on Earth, in multiple ways. The changes we
experience will increase with additional warming,” said IPCC Working Group I Co-Chair Panmao
The report projects that in the coming decades climate changes will increase in all regions. For
1.5°C of global warming, there will be increasing heat waves, longer warm seasons and shorter cold
seasons. At 2°C of global warming, heat extremes would more often reach critical tolerance
thresholds for agriculture and health, the report shows.
But it is not just about temperature. Climate change is bringing multiple different changes in different
regions – which will all increase with further warming. These include changes to wetness and
dryness, to winds, snow and ice, coastal areas and oceans.
● 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.
For the first time, the Sixth Assessment Report provides a more detailed regional assessment of
climate change, including a focus on useful information that can inform risk assessment, adaptation,
and other decision-making, and a new framework that helps translate physical changes in the
climate – heat, cold, rain, drought, snow, wind, coastal flooding and more – into what they mean for
society and ecosystems.
This regional information can be explored in detail in the newly developed Interactive Atlas
interactive-atlas.ipcc.ch as well as regional fact sheets, the technical summary, and underlying
Human influence on the past and future climate
“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 the new 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.
“Stabilizing 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 Zhai.