Stockholm (NordSIP) – On Monday morning, August the 9th, the Intergovernmental Panel on Climate Change (IPCC) finally unveiled the first part of its highly anticipated AR6, the Sixth Assessment Report, Climate Change 2021: The Physical Science Basis. The report summarises the most up-to-date understanding of the climate system and climate change, bringing together the latest advances in climate science, and combining multiple lines of evidence from paleoclimate, observations, process understanding, and global and regional climate simulations.
“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 report states. Alarmingly, the scale of recent climatic changes is unprecedented. The scientists conclude “with high confidence” that these changes are human-induced.
There is hardly lack of evidence. Observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence, has strengthened in the less than a decade that has passed since the Fifth Assessment Report (AR5).
Climate change is already affecting every inhabited region across the globe. The scientifical evidence is easier than ever to observe thanks to a new tool introduced by AR6 working group, the Interactive Atlas. The tool’s Regional Information component provides access to climate change information from the main datasets used in the report, whereas its Regional Synthesis component allows the exploration of key synthesized assessments building on multiple lines of evidence across reference regions.
The report assesses the climate response to five illustrative scenarios that cover a range of possible future development of anthropogenic drivers of climate change. No matter which of these emissions scenarios plays out, however, the global surface temperature will continue to increase until at least 2050. It is clear, that global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.
Of particular concern to the scientists is the global water cycle. There is strengthened evidence since AR5 that it will continue to intensify as global temperatures rise, with precipitation and surface water flows projected to become more variable over most land regions within seasons and from year to year.
“Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level,” concludes the authors of the report in a special summary for policymakers.
There is, however, a way to limit the devastating effects of human-induced global warming. It involves limiting cumulative CO2 emissions drastically, as well as strong reductions in other greenhouse gas emissions. This would require enormous structural changes to the way the world produces electricity, heats buildings, moves around and produces food.
Commenting on the evidence presented by the AR6 report, António Guterres, the UN secretary general, called it “a code red for humanity”. “This report must sound a death knell for coal and fossil fuels, before they destroy our planet,” he concluded.