By Zeke Hausfather
Originally published in The New York Times
Staggering. Unnerving. Mind-boggling. Absolutely gobsmackingly bananas.
As global temperatures shattered records and reached dangerous new highs over and over the past few months, my climate scientist colleagues and I have just about run out of adjectives to describe what we have seen. Data from Berkeley Earth released on Wednesday shows that September was an astounding 0.5 degree Celsius (almost a full degree Fahrenheit) hotter than the prior record, and July and August were around 0.3 degree Celsius (0.5 degree Fahrenheit) hotter. 2023 is almost certain to be the hottest year since reliable global records began in the mid-1800s and probably for the past 2,000 years (and well before that).
While natural weather patterns, including a growing El Niño event, are playing an important role, the record global temperatures we have experienced this year could not have occurred without the approximately 1.3 degrees Celsius (2.3 degrees Fahrenheit) of warming to date from human sources of carbon dioxide and other greenhouse gas emissions. And while many experts have been cautious about acknowledging it, there is increasing evidence that global warming has accelerated over the past 15 years rather than continued at a gradual, steady pace. That acceleration means that the effects of climate change we are already seeing — extreme heat waves, wildfires, rainfall and sea level rise — will only grow more severe in the coming years.
I don’t make this claim lightly. Among my colleagues in climate science, there are sharp divisions on this question, and some aren’t convinced it’s happening. Climate scientists generally focus on longer-term changes over decades rather than year-to-year variability, and some of my peers in the field have expressed concerns about overinterpreting short-term events like the extremes we’ve seen this year. In the past I doubted acceleration was happening, in part because of a long debate about whether global warming had paused from 1998 to 2012. In hindsight, that was clearly not the case. I’m worried that if we don’t pay attention today, we’ll miss what are increasingly clear signals.