The Intergovernmental Panel on Climate Change (IPCC) has projected that there would be increasing heat waves, longer warm seasons, and shorter cold seasons in the coming decades.
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According to the "Climate Change 2021: the Physical Science Basis" report, which was approved by 195 IPCC members, climate change is also intensifying the water cycle, bringing more intense rainfall and associated flooding, as well as more intense drought in many regions.
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 projected.
The report provided new estimates of the chances of crossing the global warming level of 1.5 degrees Celsius in the next decades, and found that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5 or even 2 degrees Celsius will be beyond reach.
Emissions of greenhouse gases from human activities are responsible for nearly 1.1 degrees Celsius of warming since 1850-1900. It found that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5 degrees Celsius of warming.
"Climate change is already affecting every region on Earth, in multiple ways," IPCC Working Group I Co-Chair Panmao Zhai said, adding that "the changes we experience will increase with additional warming."
Changes to the oceans, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been "clearly linked" to human influence.
Many of the changes observed in the climate are unprecedented in hundreds of thousands of years, and some changes already set in motion -- such as continued sea level rise -- are irreversible over hundreds to thousands of years.
However, strong and sustained reductions in CO2 emissions 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.
"This report is a reality check," said IPCC Working Group I Co-Chair Valerie Masson-Delmotte, adding that "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."