The observed climate change is unprecedented by thousands, if not hundreds of thousands of years, and some of the changes already set in motion, such as continual sea level rise, are irreversible over hundreds or thousands of years.
Scientists are observing changes in the Earth’s climate in every region and throughout the climate system, according to the latest report from the Intergovernmental Panel on Climate Change (IPCC). released today.
However, strong and lasting reductions in carbon dioxide (CO2) and other greenhouse gas emissions would limit climate change. While the air quality benefits would come quickly, it may take 20-30 years for global temperatures to stabilize, according to the report by IPCC Working Group I, Climate Change 2021: the Physical Science Basis, approved on Friday by 195 member governments of the IPCC, through a virtual approval session that took place over two weeks starting from 26 July.
The Working Group I report is the first part of the IPCC’s Sixth Assessment Report (AR6), which will be completed in 2022.
“This report reflects extraordinary efforts in exceptional circumstances,” said Hoesung Lee, president of the IPCC. “The innovations in this report, and the advances in climate science it reflects, make an invaluable contribution to climate negotiations and decision making.”
Climate change with faster warming
The report provides new estimates of the chances of overcoming the level of global warming of 1.5 ° C in the coming decades and notes that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, the goals of limiting warming to around 1.5 ° C or even 2 ° C will be unattainable.
The report shows that greenhouse gas emissions from human activities are responsible for around 1.1 ° C of warming from 1850-1900 and notes that, on average over the next 20 years, global temperatures are expected to reach or exceed 1.5 ° C. of heating. This assessment is based on improved observational datasets to assess historical warming, as well as advances in scientific understanding of the climate system’s response to greenhouse gas emissions. man-made.
“This report is a reality check,” said the co-chair of IPCC Working Group I, Valérie Masson-Delmotte. “We now have a much clearer picture of the past, present and future climate, which is essential to understand where we are headed, what can be done and how we can prepare.”
Many characteristics of climate change are directly dependent on the level of global warming, but what people experience is often very different from the global average. Eg, terrestrial warming is greater than the global average and it is more than double in the Arctic.
“Climate change is already affecting every region of the Earth, in different ways. The changes we experience will increase with further warming, ”said Panmao Zhai, co-chair of IPCC Working Group I.
The report predicts that in the next few decades climate change 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, extremes of heat would more often reach critical tolerances for agriculture and health, the report shows.
But it’s not just about temperature. Climate change is bringing multiple different changes in different regions, which will all increase with further warming. These include changes in humidity and drought, winds, snow and ice, coastal areas and oceans. For instance:
Climate change is intensifying the water cycle. This results in more intense rainfall and related floods, as well as more intense droughts in many regions. Climate change is affecting rain patterns. At high latitudes, precipitation is likely to increase, while they are expected to decrease over most of the subtropical areas. Changes in monsoon rainfall are expected, which will vary by region.
Coastal areas will see continuous sea level rise throughout the 21st century, contributing to more frequent coastal flooding and severe in flat areas and coastal erosion. Extreme sea level events that previously occurred once every 100 years could occur every year by the end of this century.
Further heating will amplify thawing of the permafrost and the loss of seasonal snow cover, the melting of glaciers and ice sheets, and the loss of summer Arctic sea ice.
Changes in the ocean, including warming, more frequent marine heat waves, ocean acidification, and reduced oxygen levels have certainly been linked to human influence. These changes affect both ocean ecosystems and the people who rely on them e they will continue at least for the rest of this century.
For cities, some aspects of climate change can be amplified, including heat (as urban areas are generally warmer than their surroundings), the floods due to heavy rainfall and rising sea levels in coastal cities.
For the first time, the sixth evaluation 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 processes, and a new framework that helps translate physical changes in the climate; heat, cold, rain, drought, snow, wind, coastal flooding and more, in what they mean for society and ecosystems.
This regional information can be explored in detail in the interactive Atlas new concept as well as in the regional fact sheets, in the technical summary and in the report below.