The dramatic transformations already underway in a warming world will only become more severe without drastic change — and time is running out to avoid increasingly severe consequences, according to a new United Nations report on climate change.
The major report from the U.N.’s Intergovernmental Panel on Climate Change released Monday found that the climate is changing in every region across the globe in unprecedented ways due to human activity, some of those changes will continue for centuries to come and growing impacts will only intensify with additional warming.
In Illinois, a changing climate looks wetter and warmer. A state-specific climate assessment released earlier this year, like the U.N. report, offered similarly stark warnings about the coming decades.
Earth has already warmed more than 1 degree Celsius, about 2 degrees Fahrenheit, since preindustrial times, driven by the burning of fossil fuels. Carbon dioxide concentrations in the atmosphere have reached the highest levels seen in at least 2 million years, according to Monday’s report. The last decade is likely the warmest in at least 100,000 years.
As temperatures climb, sea level rise is expected to continue, ice to disappear and extreme weather events to gain in frequency. The ripple effects of warming — with repercussions extending to people, agriculture and wildlife — are already widespread: extreme heat and heavy downpours have become more frequent and intense, while drought has also increased in some regions.
“The thing about this report, it gives you the global view,” said former state climatologist Jim Angel. But Illinois isn’t isolated from what’s happening in the rest of the world, Angel said.
“What impacts everybody else will impact us indirectly,” Angel said. “Sea level rise can have impacts on Illinois too. It doesn’t mean the ocean’s going to be lapping at the borders, but it does mean that things like exporting goods to other parts of the world could be hampered.”
In Illinois, the average daily temperature has increased throughout most of the state in the last century by 1 to 2 degrees. Some nighttime minimum temperatures have increased at three times the rate of daytime temperatures, leading to hot summer nights without relief, and also fewer freezing evenings in winter — the season that has seen the most warming. In some parts of the state, minimum winter temperatures have warmed by more than 3 degrees.
Even with measures to reduce emissions, changes in Illinois by 2100 could be grim: average annual temperatures warming beyond 4 degrees, a month of 95-degree or higher temperatures, 3 more inches of spring rain, more flooding, and compounding health risks from heat, waterborne pathogens and diseases carried by mosquitoes and ticks.
State climatologist Trent Ford said Monday’s report was more confident and direct compared with previous reports, especially in the attribution of extreme weather events to climate change.
“Previous reports had a very prophetic feel to them — if we don’t do something, this is what’s going to happen,” Ford said. “This report had the feel of — this is happening. We are in a mess of trouble. And we are going to continue to be in a mess of trouble irrespective of what we do. But if we don’t want to be in worse trouble — with extreme weather events, sea level rise, with global public health issues — we need to do something now.”
What’s happening on a global scale connects to what’s happening in Illinois, Ford said, including the impacts laid out in the state climate assessment. “The frequency and the intensity, the severity of those impacts, are largely determined by how much warming we have at a global level.”
In Illinois, last year’s variability was a strong example of future trends, Ford said. The wettest May on record in Chicago was followed by one of the driest Augusts.
Globally, some changes can be lessened or stopped if warming subsides, but others already in motion — especially related to warming oceans, melting glaciers and sea level rise — will continue for generations, scientists say.
Even with emission reductions, global surface temperature is expected to continue to rise through the next three decades, the report says. The 1.5 degrees Celsius warming threshold, which scientists have warned against passing to stave off the most severe consequences, is likely to be reached or surpassed in the next two decades.
“Unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting global warming to 1.5 degrees Celsius will be beyond reach,” said Valérie Masson-Delmotte, a co-chair of the report group, in a Monday news conference.
But if greenhouse gas emissions are rapidly reduced and net zero carbon dioxide emissions are achieved by 2050 — still a lofty goal — staying within 2 degrees of warming, and even dipping below 1.5 degrees, is likely. If emissions continue on recent paths, 2 degrees of warming could be reached by midcentury. In more extreme scenarios, 4 degrees of warming is possible by century’s end.
The first chapter of the latest assessment, Monday’s report is a comprehensive look at the latest in global climate science from more than 200 scientists — and the first since 2013. This chapter, focused on physical science, comes ahead of a U.N. climate summit in November.
The assessments draw from the findings of scientific studies throughout the world — Monday’s report considers more than 14,000 publications and is approved by 195 governments — and include the latest climate science, possible ways to adapt and options to minimize warming. The final parts of the report are expected to be released next year.
As warming becomes more pronounced, so do other extremes, the report says. Each half-degree Celsius of warming can boost the intensity and frequency of heat waves, heavy precipitation events, and agricultural and ecological droughts. Once-in-a-decade heat waves, for example, could occur four times in that same period with 1.5 degrees Celsius of warming.
The report is also clear about humans’ role in inducing climate change, saying it’s “unequivocal” that human action has led to warming at a rapid pace, and human activity is the main force behind extreme weather events, such as heat waves, heavy precipitation, droughts and tropical cyclones.
Earlier this year, when the Illinois climate assessment was released, Donald Wuebbles, a professor of atmospheric sciences at the University of Illinois and one of the lead authors of the Illinois assessment, said Illinois’ climate, “like the rest of the country and the rest of the world, is changing and is changing rapidly.
“And that has serious repercussions on the people of Illinois.”
