Linda Mearns (co-author of the report), a senior climate scientist at U.S. National Center for Atmospheric Research, stated that “it’s just guaranteed it’s going to worse.” “Nowhere to hide, no place to run.”
Scientists have also lowered their expectations of the worst climate disasters.
The authoritative Intergovernmental Panel on Climate Change report (IPCC), which declares climate change clearly human-caused, “unequivocal”, and “an established fact,” provides more accurate and warmer forecasts for 21st century than the 2013 version.
Each of five scenarios for the future, based on how much carbon emissions are cut, passes the more stringent of two thresholds set in the 2015 Paris climate agreement. Because of the rapid rise in problems after then, world leaders agreed to try and limit global warming to 1.5 degrees Celsius (2.7 degree Fahrenheit). Since then, the world has warmed by almost 1.1 degrees Celsius (2° Fahrenheit).
According to the report, each scenario would see the world surpass the 1.5-degree Celsius warming threshold in 2030s. This is earlier than many previous predictions. Warming has ramped up in recent years, data shows.
“Our report shows we must be ready for that level of global warming in the next decades. We can prevent further warming by reducing greenhouse gas emissions,” Valerie Masson Delmotte, co-chair of the report, said. She is a climate scientist at France’s Laboratory of Climate and Environment Sciences located at the University of Paris–Saclay.
The report stated that the world could also exceed 2 degrees Celsius (3.6 degree Fahrenheit) in three scenarios. This is in addition to the Paris goal, which is less strict, and with much worse heat waves, droughts, and flood-inducing rains, unless deep emissions cuts are made.
“This report tells me that recent climate changes are widespread, rapid and intense, unprecedented in thousands years,” stated Ko Barrett, IPCC Vice Chair and senior climate advisor for the U.S. National Oceanic and Atmospheric Administration.
With crucial international climate negotiations coming up in Scotland in November, world leaders said the report is causing them to try harder to cut carbon pollution. Anthony Blinken, U.S. Secretary-of-State, called it “a stark reminder.”
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. The strength and frequency of tropical cyclones is increasing, and the Arctic sea ice is shrinking in summer. Permafrost is also thawing. The report stated that all of these trends are likely to worsen.
According to the report, heat waves that were once common once in 50 years are now more frequent than ever. If the world gets another degree Celsius (1.8 degrees Fahrenheit), they will occur twice every seven years.
According to the report, as the planet heats up, more places will be affected by multiple climate catastrophes and not just extreme weather. That’s like what’s now happening in the Western U.S., where heat waves, drought and wildfires compound the damage, Mearns said. Extreme heat is also driving massive fires in Greece and Turkey.
The report stated that some climate change harms, such as shrinking ice sheets and rising sea levels, and changes in oceans as they lose oxygen or become more acidic, are “irreversible for centuries and millennia.”
Bob Kopp, a Rutgers University report co-author, stated that the world is “locked-in” to a rise of 15-30 centimeters (6-12 inches) in sea level by mid-century.
This message has been repeated by scientists for over three decades but the world still doesn’t listen, according to Inger Andersen, Executive Director of United Nations Environment Program.
For the first time, the report offers an interactive atlas for people to see what has happened and may happen to where they live.
Emissions of heat-trapping gases like carbon dioxide or methane can account for nearly all the global warming. The report stated that only natural forces and randomness can account for one to two-tenths or less of the warming.
Based on the world’s reduction of carbon emissions, five future scenarios were described in the report. These are: A future with rapid and dramatic pollution reductions; another scenario with more severe pollution cuts, but less drastic; a scenario that has moderate emissions cuts; a scenario in which current plans for small pollution reductions will continue; and a fifth scenario that would see an increase in carbon pollution.
Five previous reports showed that the world was still on the final hottest path. This is often called “business as usual” or “business as usual”. But, this time, Claudia Tebaldi (a scientist at U.S. Pacific Northwest National Lab) said the world is now somewhere in between the moderate path to small pollution reductions.
Although Guterres called the report “a code-red for humanity,” he expressed hope that world leaders would still be able to prevent 1.5 degrees of global warming. He said it is “perilously close.”
Alok Sharma, president of the forthcoming climate negotiations in Scotland, asked leaders to do more to “credibly claim that we have kept 1.5° alive.”
Tebaldi stated, “Anything we do to limit, slow down, or limit it, will pay off.” “And even if we can’t get to 1.5, it will be difficult, but it’s better to not give up.”
The report’s worst-case scenario suggests that the world will be 3.3 degrees Celsius (or 5.9 degrees Fahrenheit), hotter by the end century. However, this scenario seems increasingly unlikely, according to Zeke Hausfather (climate scientist and co-author of the report), climate change director at Breakthrough Institute.
Hausfather stated that it is less likely than we thought to be lucky and have less warming. “But, at the same time, our chances of getting in a worse place than we anticipated if we reduce our emissions are significantly lower.”
The report said that ultra-catastrophic catastrophes, also known as “tipping points”, such as ice sheet collapses or the sudden slowdown in ocean currents, are “low probability” but cannot be ruled. Kopp stated that the much-rumored shutdown of Atlantic ocean currents which would cause massive weather shifts is unlikely to occur in the next century.
Mason-Delmotte stated that scientists have made a “major breakthrough” in understanding how quickly the world heats with each ton carbon dioxide emitted. This allowed them to be more precise in their scenarios.
Scientists have highlighted how reducing the airborne methane levels, a powerful but short-lived greenhouse gas that has reached record levels, could reduce short-term warming. Natural gas leaks are a major source of methane. Large amounts of methane are also produced by livestock, with a large portion of it coming from cattle burps.
More than 100 countries have made informal pledges to achieve “net zero” human-caused carbon dioxide emissions sometime around mid-century, which will be a key part of the negotiations in Scotland. These commitments were deemed essential by the report.
Barrett stated that it is possible to prevent many of the most devastating impacts.
