This year broke records in all the wrong ways. That’s the chilling conclusion of a special report on climate change published in the journal Bioscience.
"Life on planet Earth is under siege,” said William Ripple, a distinguished professor of ecology at Oregon State University and a lead author on the report. The annual State of the Climate analysis aims to provide a succinct and accessible overview of the global warming impacts the world has experienced over the past year, and how we can mitigate them.
One of the strangest things in this year’s report was just how hot 2023 has been. Before 2000, for example, global average daily temperature never went higher than 1.5 Celsius above pre-industrial levels. Since the start of the current millennium, the world has only occasionally exceeded that temperature in a given year. By Sept. 12, the cut-off for when data was collected, Earth had already seen 38 days that exceeded daily average temperatures of 1.5 C, more than in any other year.
The 1.5 C threshold has become symbolic because countries agreed in the 2015 Paris Agreement to try and keep global average temperatures increases under that limit and "well below” 2 C. So far the world has warmed roughly 1.2 C. Research has shown that the difference between 1.5 C and 2 C of warming is significant. At 1.5 C, the world will likely have some coral reefs and summer ice in the Arctic. At 2 C both will disappear.
Ever tenth "of a degree of warming that we can avoid can save a huge amount of suffering and will save many, many lives,” Ripple said.
The days that exceeded 1.5 C in 2023 were part of a broader trend toward record-breaking temperatures both on land and in the ocean. June and July of this year were the warmest period ever recorded. July was not only the hottest month in over 170 years of record-keeping, but likely the hottest month in over 100,000 years.
The El Nino phenomenon, which typically causes warmer weather, has been often cited as a reason for this year’s heat. But it’s hard to explain 2023’s extreme warming with just El Nino, says Zeke Hausfather, a research scientist at Berkeley Earth who was not involved in the report. That "suggests one of two things,” said Hausfather. "Either this El Nino is behaving differently than previous ones. Or there’s other factors on top of the El Nino events that are contributing to the extreme warmth we’re seeing.”
Researchers have been delving into possible causes, including an uptick in the 11-year solar cycle and last year’s volcanic eruption in Tonga, which put an unusual amount of water vapor — another greenhouse gas — into the air. While each contributed a bit to warming, "it still seems like there's a bit of a gap there between what you'd expect with El Nino and underlying warming,” Hausfather said. "The world is much warmer than expected and we’re not sure why.”
As temperatures rose this year, so did the number of disasters. The State of the Climate report includes a timeline of calamities, from the Canadian wildfires to tropical cyclones in Myanmar and heavy rainfall in Japan and India that led to landslides, floods and deaths. "Some people are just starting to recover from one climate related disaster or extreme weather event and another is starting to take place,” said Ripple. "There isn’t even recovery time.”
Climate change can lead to compounding disasters, says Christine Shield, a project scientist at the National Center for Atmospheric Research, who was not involved in the research. For example, a drought followed by a series of heavy storms can be devastating because the dry ground is less able to absorb the moisture, increasing the risks of landslides and floods.
And yet, even as climate change impacts are being increasingly felt, efforts to curb climate change lag behind. Worldwide greenhouse gas emissions continue to rise along with coal use, especially in China and India. Similarly, Russia’s invasion of Ukraine has helped some European countries speed up their energy transition away from fossil gas and towards renewables, but it has led other countries to pivot back to coal.
The report points out that the world’s continued release of greenhouse gas emissions is also an issue of equity. "The Global South is much more vulnerable to climate change,” Ripple said. "And that’s a climate justice issue because most of the historical emissions have come from the Global North.”