The new report by the Intergovernmental Panel on Climate Change (IPCC) lays out the basis for “the most up-to-date physical 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.”
The warnings are getting more and more dire, though the situation is not yet hopeless.
Earth is getting so hot that temperatures in about a decade will probably blow past a level of warming that world leaders have sought to prevent, according to a report released Monday that the United Nations called a “code red for humanity.”
“It’s just guaranteed that it’s going to get worse,” said report co-author Linda Mearns, a senior climate scientist at the U.S. National Center for Atmospheric Research. “Nowhere to run, nowhere to hide.”
But scientists also eased back a bit on the likelihood of the absolute worst climate catastrophes.
The authoritative Intergovernmental Panel on Climate Change (IPCC) report, which calls climate change clearly human-caused and “unequivocal” and “an established fact,” makes more precise and warmer forecasts for the 21st century than it did last time it was issued in 2013.
The 3,000-plus-page report from 234 scientists said warming is already accelerating sea level rise and worsening extremes such as heat waves, droughts, floods and storms. Tropical cyclones are getting stronger and wetter, while Arctic sea ice is dwindling in the summer and permafrost is thawing. All of these trends will get worse, the report said.
The report says that while some of the changes that have already occurred are irreversible, there are glimmers of hope that the worst case scenarios might be averted if action is taken now.
The report described five different future scenarios based on how much the world reduces carbon emissions. They are: a future with incredibly large and quick pollution cuts; another with intense pollution cuts but not quite as massive; a scenario with moderate emission cuts; a fourth scenario where current plans to make small pollution reductions continue; and a fifth possible future involving continued increases in carbon pollution.
In five previous reports, the world was on that final hottest path, often nicknamed “business as usual.” But this time, the world is somewhere between the moderate path and the small pollution reductions scenario because of progress to curb climate change, said report co-author Claudia Tebaldi, a scientist at the U.S. Pacific Northwest National Lab.
While calling the report “a code red for humanity,” U.N. Secretary-General Antonio Guterres kept a sliver of hope that world leaders could still somehow prevent 1.5 degrees of warming, which he said is “perilously close.”
Alok Sharma, the president of the upcoming climate negotiations in Scotland, urged leaders to do more so they can “credibly say that we have kept 1.5 degrees alive.”
Two things should be noted about this report. One is that the climate models are getting better and even more unequivocal about the human causes of the impending catastrophe.
The comprehensive assessment of climate science published on Monday, the sixth such report from the IPCC since 1988, has been eight years in the making, marshalling the work of hundreds of experts and peer-review studies. It represents the world’s full knowledge to date of the physical basis of climate change, and found that human activity was “unequivocally” the cause of rapid changes to the climate, including sea level rises, melting polar ice and glaciers, heatwaves, floods and droughts.
The other is the growth of attribution science that better enables us to draw a causal line blaming individual extreme weather events on climate change. (I had written just a week or so ago about how the relationship was statistical, preventing us from drawing such conclusions. The new report has changed things.)
The report highlights the stunning progress of a new field, attribution science, in quantifying the extent to which human-induced global heating increases the intensity and/or likelihood of a specific extreme weather event such as a heatwave, a hurricane or a wildfire.
Within weeks, for example, scientists established that the record-shattering heatwave that devastated British Columbia in June would have been “virtually impossible” without the influence of climate change.
The UN Secretary General did not mince words about the seriousness of the issue and the need for global action.
António Guterres, the UN secretary general, warned: “[This report] is a code red for humanity. The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk.”
He called for an end to new coal plants and to new fossil fuel exploration and development, and for governments, investors and businesses to pour all their efforts into a low-carbon future. “This report must sound a death knell for coal and fossil fuels, before they destroy our planet,” he said.
So will this report change the minds of skeptics? Unlike in the case of covid-19 vaccine skeptics whose minds may be changed by the sickness and deaths of those close to them, the serious consequences of climate change will be slower and more diffuse and thus enable some to refuse to acknowledge it. We can only hope that governments will take decisive action when representatives from 197 countries meet in November in Glasgow for UN climate talks called Cop26.