A Global Warming Pause That Didn’t Happen Hampered Climate Science

It was one of the biggest questions about climate change of the early 2000s: Has the planet’s rising fever stalled, even as humans pump more heat-trapping gases into Earth’s atmosphere? ?

By the turn of the century, scientific understanding of climate change was firmly entrenched. Decades of research have shown that carbon dioxide is building up in the Earth’s atmosphere, thanks to human activities such as burning fossil fuels and cutting down carbon-storing forests, and that global temperatures are rising as a result. . Yet weather records seem to show that global warming slowed between about 1998 and 2012. How could that be?

After extensive study, scientists found that the apparent pause was a problem in the data. The Earth had, in fact, continued to warm. This hiccup, however, prompted an outsized response from climate skeptics and scientists alike. It serves as a case study in how public perception shapes what science does, for better or for worse.

The mystery of what has come to be called the “global warming hiatus” has emerged as scientists accumulate year after year data on the planet’s average surface temperature. Several organizations maintain their own temperature data sets; each is based on observations collected at weather stations and from ships and buoys around the world. The actual amount of warming varies from year to year, but overall the trend is upward and peak years are becoming more frequent. the 1995 Intergovernmental Panel on Climate Change Reportfor example, noted that recent years had been among the warmest on record since 1860.

And then came the powerful El Niño of 1997-1998, a weather pattern that transferred vast amounts of heat from the ocean to the atmosphere. The planet’s temperature soared as a result – but then, according to weather records, it appeared to drop dramatically. Between 1998 and 2012, the global average surface temperature increased at less than half the rate it did between 1951 and 2012. It made no sense. Global warming is expected to accelerate over time as people increase the rate at which they add heat-trapping gases to the atmosphere.

Today’s ocean monitoring buoys (a NOAA buoy southeast of South Africa is shown) provide measurements of ocean surface temperatures that are more accurate than previous approaches.D. MacIntyre, NOAA

By the mid-2000s, climate skeptics had seized upon the narrative that “global warming has stopped”. Most professional climatologists did not study the phenomenon, as most believed the apparent pause was within the range of natural temperature variability. But public attention quickly caught up with them, and researchers began to investigate whether the break was real. It was a highly publicized shift in scientific focus.

“By studying this anomalous period, we learned a lot of lessons about both the climate system and the scientific process,” says Zeke Hausfather, a climatologist currently working for technology company Stripe.

In the early 2010s, scientists were actively working to explain why global temperature records appeared to be stagnating. Ideas included the contribution of cooling sulfur particles emitted from coal-fired power plants and the heat absorbed by the Atlantic and Southern oceans. Such studies have been the most focused attempt ever to understand the factors that determine temperature variability from year to year. They revealed how much natural variability can be expected when factors such as a strong El Niño are superimposed on a long-term warming trend.

Scientists have spent years investigating the alleged warming pause, devoting more time and resources than they otherwise might have had. So many articles were published about the apparent break that scientists started joking that the journal Natural climate change should change its name to nature break.

Then in 2015, a team led by researchers from the US National Oceanic and Atmospheric Administration published a stunning finding in the journal Science. The rise in global temperatures had not plateaued; on the contrary, incomplete data had obscured ongoing global warming. When more Arctic temperature records were included and biases in the ocean temperature data were corrected for, the NOAA dataset showed that warming was continuing. With the newly corrected data, the apparent global warming pause is gone. A study 2017 led by Hausfather confirmed and extended these findings, as did other reports.

Even after the studies were published, the hiatus remained a hot topic among climate skeptics, who used it to argue that concerns about global warming were overblown. Congressman Lamar Smith, a Republican from Texas who chaired the House Science Committee in the mid-2010s, was particularly angered by the 2015 NOAA study. He demanded to see the data under underlying while accusing NOAA of modifying them. (The agency denied falsifying the data.)

“In retrospect, it’s clear we focused too much on the apparent hiatus,” Hausfather says. It’s important to understand why global temperature records seemed to level off between 1998 and 2012, but it’s equally important to keep an overview of the broader understanding of climate change. The hiccup represented a short fluctuation in a much longer and much larger trend.

Science is all about testing hypotheses and questioning conclusions, but here’s a case where the search for an anomaly may have gone too far. This caused the researchers to doubt their conclusions and spend a lot of time questioning their well-established methods, says Stephan Lewandowsky, a cognitive scientist at the University of Bristol who has studied climatologists’ response to the pause. Instead, scientists studying the hiatus could have worked to provide clear information to policy makers about the reality of global warming and the urgency of addressing it.

Debates over whether or not the hiatus was real have fueled public confusion and undermined efforts to convince people to take aggressive action to reduce the impacts of climate change. This is an important lesson for the future, says Lewandowsky.

“My feeling is that the scientific community has moved on,” he says. “By contrast, the political operatives behind organized denial have learned a different lesson, which is that the ‘global warming has stopped’ meme is very effective at generating public complacency, and so they will use it at every opportunity. .”

Already, some climate deniers are talking about a new “pause” in global warming because not all of the past five years have set a new record, he notes. Yet the overall trend remains clear: global temperatures have continued to rise in recent years. The seven hottest years on record have all occurred since 2015, and every decade since the 1980s has been warmer than the last.

Teresa H. Sadler