The latest report from the Intergovernmental Panel on Climate Change (IPCC) makes sober reading. Here are five of the most alarming takeaways:
1. We will reach 1.5 degrees Celsius over pre-industrial levels by the early 2030s
The last IPCC report, published seven years ago, estimated that we would reach a global warming level of 1.5 degrees Celsius within the range of 2030 to 2052, assuming a continued, constant rate of warming. The best of available science now estimates that we will cross the 1.5 threshold “in the early 2030s.”
2. Global surface temperature has increased faster since 1970 than in any other 50-year period in the last 2000 years
Each of the last four decades has been successively warmer than any decade since 1850. At the same time, global mean sea level has continued to increase, and it has risen faster since 1900 than over any preceding century in the last 3000 years.
3. In 2019, atmospheric carbon dioxide concentrations were higher than at any time in the last 2 million years
In 2019, atmospheric concentrations of greenhouse gases methane and nitric oxide were also higher than at any time in the last 800,000 years.
“Strong, rapid and sustained reductions” are needed, starting immediately, both to mitigate climate change and to “improve air quality.”
4. Many of the changes associated with greenhouse gas emissions are irreversible for centuries to millennia
One of the most alarming messages from the 2021 Report is that “many changes due to past and future greenhouse gas emissions” are now “irreversible for centuries to millennia”—especially changes in the ocean, ice sheets and to global sea level.
Under every scenario of emissions reduction considered in the Report, global surface temperature will continue to increase until at least 2050, and we will exceed the Paris Climate Agreement cap of two degrees Celsius unless we secure immediate "deep reductions" in carbon dioxide and other greenhouse gas emissions.
5. COVID-19 has caused only temporary emissions reductions
COVID-19 with its restricted movement and industry has resulted in temporary emissions reductions, but these reductions remain only temporary. “The scale of recent changes across the climate system as a whole and the present state of many aspects of the climate system” are unprecedented, and will remain so “over many centuries to many thousands of years.”
In short, the Report is a clarion call. Action must be taken immediately, and it must be comprehensive and significant. Achieving Net Zero emissions is not enough—we must strive to be carbon negative. This will not be easy, and it may be expensive, but it is no longer a choice.
(Image acknowledgement: National Oceanic and Atmospheric Administration (NOAA))