IPCC: Widespread, rapid and intensifying climate change


Unless the world acts quickly to reduce carbon emissions, limiting warming to nearly 1.5 ° C or even 2 ° C will be out of reach, latest report warns

Scientists have issued a grim warning about current changes in Earth’s climate, saying they can be observed in all regions and across the climate system.

According to the latest report from the Intergovernmental Panel on Climate Change (IPCC), released on Monday, August 9, many of the observed changes in the climate are unprecedented for thousands, if not hundreds of thousands of years, and some of the changes already defined in motion, such as continuous sea level rise, are irreversible over hundreds or even thousands of years.

IPCC Working Group I report, Climate change 2021: the basis of physical science, provides new estimates of the chances of crossing the global warming level of 1.5 ° C over the next several decades, and finds that unless there are immediate, rapid and large-scale reductions in emissions greenhouse gas emissions, limiting warming to nearly 1.5 ° C or even 2 ° C will be out of reach.

The report shows that greenhouse gas emissions from human activities have been responsible for about 1.1 ° C of warming since 1850-1900, and finds that on average 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 as advances in scientific understanding of the climate system’s response to human-made greenhouse gas emissions.

Reality check

However, strong and sustained reductions in carbon dioxide (CO2) and other greenhouse gas emissions would limit climate change. While the benefits to air quality would come quickly, it could take 20 to 30 years for global temperatures to stabilize, according to the report.

The Working Group I report, prepared by 234 authors from 66 countries and 517 contributing authors, is part one 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, Chairman 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. “

“This report is a reality check,” says Valérie Masson-Delmotte, co-chair of IPCC Working Group I. “We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are going, what can be done and how we can prepare.”

Each affected region

Many characteristics of climate change depend directly on the level of global warming, but what people experience is often very different from the global average. For example, land warming is greater than the global average, and it is more than twice as high in the Arctic.

“Climate change is already affecting all regions of the Earth in multiple ways. The changes we are experiencing will increase with further warming, ”said IPCC Working Group I co-chair Panmao Zhai.

The report predicts that over the next decades, climate change will increase in all regions. For every 1.5 ° C of global warming, there will be increasing heat waves, longer hot seasons and shorter cold seasons. At 2 ° C of global warming, extreme heat would more often reach critical tolerances for agriculture and health, according to the report.

But it’s not just a question of temperature. Climate change is causing multiple different changes in different regions – all of which will increase with warming. These include changes in humidity and drought, winds, snow and ice, coastal areas and oceans. For example:

  • Climate change is intensifying the water cycle. This results in more intense rainfall and associated flooding, as well as more intense drought in many areas.
  • Climate change affects precipitation patterns. In high latitudes, precipitation is likely to increase, whereas it is expected to decrease over large parts of the subtropics. Changes in monsoon precipitation are expected, which will vary by region.
  • Coastal areas will experience continuous 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 every 100 years could occur every year by the end of this century.
  • Further warming will amplify permafrost thaw and loss of seasonal snow cover, melting glaciers and ice caps, and loss of arctic sea ice in summer.
  • Changes in the ocean, including warming, more frequent marine heat waves, ocean acidification, and reduced oxygen levels have been clearly linked to human influence. These changes are affecting both ocean ecosystems and the people who depend on them, and they will continue for at least the rest of this century.
  • For cities, some aspects of climate change may be magnified, including heat (since urban areas are generally warmer than their surroundings), flooding from heavy rainfall, and sea level rise in coastal towns. .

“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,” says 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.

Human action

The report also shows that human actions still have the potential to determine future climate change. It is clear that carbon dioxide (CO2) is the main driver of climate change, although 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 the achievement of zero net CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have both health and climate benefits, ”Zhai explains.

In Asia, some of the common regional changes are as follows:

  • The observed increase in mean surface temperature clearly fell outside the range of internal variability from 1850-1900. Extreme heat has increased while extreme cold has decreased, and these trends will continue for decades to come.
  • The relative sea level around Asia has risen faster than the global average, with loss of coastal areas and retreat of the coastline. The regional mean sea level will continue to rise.
  • Average and abundant precipitation will increase over much of Asia.
  • Marine heat waves will continue to increase.
  • The fire seasons will lengthen and intensify, especially in parts of North Asia.
  • Average surface wind speeds have decreased and will continue to decrease in central and northern parts of Asia.

The IPCC is the United Nations body responsible for assessing the science related to climate change. It was created by the United Nations Environment Program (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide political leaders with periodic scientific assessments regarding climate change, its implications and risks, as well as to propose adaptation and mitigation strategies. In the same year, the United Nations General Assembly endorsed the action of WMO and UNEP by jointly establishing the IPCC. It has 195 member states.

The report of Working Group I was approved Friday August 6 by 195 member governments of the IPCC, during a virtual approval session held over two weeks from July 26.

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