Intergovernmental Panel on Climate Change (IPCC) Reports on Irreversible Global Climate Change

Publication of first instalment of the IPCC’s Sixth Assessment Report (AR6), which will be completed in 2022.

The latest Intergovernmental Panel on Climate Change (IPCC) report finds that scientists are observing unprecedented changes in the Earth’s climate in every region and across the whole climate system. Many of the changes observed in the climate are unprecedented, and some – such as continued sea level rise – are irreversible over hundreds to thousands of years.

Climate Change 2021: the Physical Science Basis 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. 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.

In additional to rising temperatures, the effects of climate change also include:

  • Intensifying the water cycle, bringing more intense rainfall and associated flooding, as well as more intense drought in many regions
  • 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

The report also finds 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.

“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.”

(This report was the subject of a RESEARCHconnect Newsflash.)