Wildfires, heat waves, droughts, flooding, and more are no longer “natural” disasters exclusively, because humanity has a substantial role in making many of them more extreme. That’s a key takeaway from the latest comprehensive assessment from the world climate-science profession. The assessment — “Climate Change 2021: The Physical Science Basis,” released in August — is the first part of a larger report from the United Nations Intergovernmental Panel on Climate Change, or IPCC. It’s likely to shape negotiations during a crucial period in the fight against global warming.
1. What are the report’s key findings?
Humanity has raised global average temperatures by 1.1° Celsius since the end of the 19th century and has dumped enough greenhouse gas into the atmosphere to heat the planet by 1.5°C — the globally agreed-upon threshold after which global warming becomes more destructive. (The reason for the discrepancy is that fine-particle pollution from fossil fuels provides a cooling effect that masks some of the impact.) Global average temperatures are higher than at any point in 125,000 years. Carbon dioxide (CO2) levels are higher than at any point in 2 million years, and methane and nitrous oxide concentrations higher than in 800,000 years.
2. Was any of that surprising?
Yes. Close observers noted that the forceful language in the report’s 42-page summary for policy makers — which was agreed-upon unanimously by all 195 governments that make up the IPCC — gave the report added authority. “It is unequivocal,” the report says, “that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.” Scientists’ temperature projections, accurate for half a century, are further strengthened in this report with substantial new evidence from satellites and research into ancient climates. Just one of five scenarios spelled out in the report — and not the most likely one — suggests the world can meet the science-backed goal of zeroing out the impact of carbon dioxide pollution by 2050.
3. Is it too late for the world to act?
Scientists are adamant: It’s never too late to act. Some changes have already occurred, such as the rise in extreme weather. Others can be slowed tremendously even if they can’t be stopped, such as the rise in sea levels. The rate and amount of further greenhouse emissions determines how much danger is ahead of us and how quickly it comes. “Every tonne of CO2 emissions adds to global warming,” the authors state. A key finding in the report is that if emissions are curbed, heating will soon stop as well. (Some scientists had fretted that global heating might continue for a considerable amount of time in that scenario.) The report bolsters efforts to find ways to remove carbon dioxide directly from the air. Technologies to do so exist, and several high-profile startups have shown they can do it, but cost is a major hurdle for now.
4. What’s next?
Diplomats meet for the 26th annual climate negotiations. called COP26, in November in Glasgow, Scotland. In the runup to that meeting, the almost 200 countries that are part of the Paris Agreement on global warming are supposed to be updating their pledges — NDCs, for Nationally Determined Contributions. The findings of the IPCC report are sure to add urgency to that task. The report states with “high confidence” that nations are failing to meet their Paris goals.
5. Will the report change any minds?
Recent history suggests it might. A 2018 IPCC report that spelled out the impact of global warming of 1.5°C or higher sparked something of a frenzy among governments, companies and investors to end carbon-dioxide emissions by mid-century, a goal shorthanded as “net-zero by 2050.” In recent years, the most powerful evidence has been climate change itself. Small-island nations and coastal cities see the waters lapping further inland. Farmers see unprecedented losses from drought and heat. Infrastructure buckles and snaps because the climate it was built for no longer exists.