On Monday, August 9th, the Intergovernmental Panel on Climate Change (IPCC) released the first of their newest set of climate reports. The report, titled Climate Change 2021: The Physical Science Basis, focuses on the physics and science of climate change, bringing together thousands of the most up to date studies and research available to form a single, comprehensive report. Two similar reports will follow in 2022 that will focus more on impacts, adaptation, and mitigation, all coming together to form the IPCC’s Sixth Assessment Report, or AR6.
While this physical science report does not present anything significantly new or unexpected, it does depart from previous IPCC reports in its strength of language and confidence of results. The very first chief finding exemplifies this: “It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.” The Secretary-General of the United Nations, António Guterres, calls the report a “code red for humanity” constituting deafening alarm bells and irrefutable evidence.
Many of the findings of the report, while not new, back up these claims of severity. A warming of up to 1.5° C is nearly guaranteed in all possible futures, whereas a 2° C future increase can be avoided with “deep reductions in CO2 and other greenhouse gas emissions [GHG]… in the coming decades.” Sea level rise will continue through at least the end of the century, with a low-likelihood possibility of nearly 2 meters of rise under the worst, high-emission future. The Arctic could become “practically ice-free” after 2050 under the higher-emission scenarios that do not include drastic GHG cuts. Ocean acidity could continue to increase at its current rate, reaching up to four times the already observed amount of acidification by 2100.
These possible futures are what is in store for the planet if emissions reductions do not happen in drastic ways under immediate timescales, such as net-zero carbon emissions by 2050. Fortunately, there are no new bombshells revealing our situation as worse than previously thought, even the prospect of reaching 1.5° C of warming, but what we already knew is enough to necessitate great action. The report gives us even stronger justification to take that knowledge, and subsequent necessity of action, as fact. There is no denying that the alarm has been rung.