The IPCC warns: “climate change is widespread, fast and intensifying”

Scientists are observing changes in Earth’s climate in all regions and across the climate system, according to the latest Report of the Intergovernmental Panel on Climate Change (IPCC), released today. Many of the observed changes in climate are unprecedented in thousands, if not hundreds of thousands of years, and some of the changes that have already been put in place, such as continued sea level rise, are irreversible for hundreds or thousands of years.

However, strong and sustained reductions in emissions of carbon dioxide (_CO2) and other greenhouse gases 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 IPCC Working Group I report, Climate Change 2021: The Foundation of Physical Science, approved Friday by 195 IPCC member governments. , through a virtual approval session that took place over two weeks starting July 26.

The Working Group I report is the first installment 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, chair of the IPCC. “The innovations in this report, and the advances in climate science it reflects, provide a valuable contribution to climate negotiations and decision-making.”

Faster heating

The report provides new estimates of the chances of crossing the global warming level of 1.5°C in the coming decades and finds that, unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to about 1.5°C or even 2°C will be out of reach.

The report shows that greenhouse gas emissions from human activities are responsible for about 1.1°C of warming from 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 progress in scientific understanding of the climate system’s response to man-made 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 to understanding where we are headed, what can be done and how we can prepare.”

Each region faces increasing changes

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, global warming is greater than the global average and is more than double in the Arctic.

“Climate change is already affecting all regions of the 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 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 most often reach tolerance thresholds critical to 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 increase with further warming. These include changes in humidity and dryness, winds, snow and ice, coastal areas, and oceans. For example:

• Climate change is intensifying the water cycle. This brings heavier rainfall and associated flooding, as well as more intense drought in many regions.
• Climate change is affecting rainfall patterns. At high latitudes, precipitation is likely to increase, while it is forecast to decrease in large parts of the subtropics. Changes in monsoon rainfall are expected, which will vary by region.
• Coastal areas will see continued sea level rise throughout the twenty-first century, which will contribute 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 the melting of permafrost and the loss of seasonal snow cover, the melting of glaciers and ice sheets, and the 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 affect both ocean ecosystems and the people who depend on them, and will continue for at least the rest of this century.
• For cities, some aspects of climate change can be amplified, including heat (given that urban areas tend to be warmer than their surroundings), flooding from heavy rainfall, and sea level rise in coastal cities.

For the first time, the Sixth Assessment Report provides a more detailed overview of regional climate change assessment, 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 into 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 newly developed Interactive Atlas interactivo-atlas.ipcc.ch, as well as in the regional fact sheets, technical summary and underlying report.

Human influence on past and future climate

“It has been clear for decades that Earth’s climate is changing and the role of human influence on the climate system is indisputable,” Masson-Delmotte said. However, the new report also reflects important advances in the science of attribution: understanding the role of climate change in intensifying specific weather and climate phenomena, such as extreme heat waves and heavy rainfall.

The report also shows that human actions still have the potential to determine the future course of the 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.

“Climate stabilization 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 both health and climate benefits,” Zhai said.

Source: Retema