Each of the last four decades has been successively warmer than any decade that preceded it since 1850, according to a just-released report from the Intergovernmental Panel on Climate Change.
Scientists are observing changes in the Earth’s climate in every region and across the whole climate system, and some of the changes already set in motion—such as continued sea-level rise—are irreversible over hundreds to thousands of years, the report says.
That’s according to the Intergovernmental Panel on Climate Change in a just-released report.
The report is nothing but bad news for winegrape growers in California and other regions.
In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years, it says, and global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years.
Late summer Arctic sea ice area was smaller than at any time in at least the past 1000 years, the report says, adding that the global nature of glacier retreat, with almost all of the world’s glaciers retreating synchronously, since the 1950s is unprecedented in at least the last 2000 years.
“It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s, while cold extremes (including cold waves) have become less frequent and less severe, the report says. It adds “with high confidence” that human-induced climate change is the main driver of these changes
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.
The Working Group I report is the first installment of the IPCC’s Sixth Assessment Report (AR6), which will be completed in 2022.
Faster warming
The report sounds a note of urgency, warning that the chances of crossing the global warming level of 1.5°C in the next decades are significant. 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, it says.
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 missions.
“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 Zhai.
The report projects that in the coming decades climate changes will increase in all regions. For 1.5°C (34.7F) of global warming, there will be increasing heat waves, longer warm seasons and shorter cold seasons, the report says. At 2°C (35.6F) 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, the report says. 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. For example:
● 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.
A more detailed journalistic summary (which we did not use in preparing teh above) can be found here.
