【】
作者:焦點 来源:探索 浏览: 【大中小】 发布时间:2024-11-23 16:09:41 评论数:
The next time someone tells you that we can’t tie an individual weather event to climate change, you should tell them that’s partly to mostly bullshit. Not only can we say a whole lot about an event’s ties to climate change, but some events could not have occurred without global warming’s assistance.
Let this sink in for a second.
Global warming is bringing us newly possible extremes, from the 2016 global average surface temperature milestone (it was number one, baby), to a stifling heat wave in Southeast Asia that set numerous all-time high temperature records.
SEE ALSO:Emmanuel Macron lures top U.S. climate scientists fleeing from Trump research cutsThe reason we know this tipping point in extreme weather and climate events has been passed is because of a growing sub-field within climate science, known as detection and attribution research. Scientists who work in this field are the climate equivalent of CSI investigators, probing for clues about what may have led to an extreme event soon after it occurs.
Global temperature anomalies averaged from 2012 through 2016 in degrees Celsius compared to the 20th century average.Credit: nasa gissFor the past six years, scientists have published the equivalent of a greatest hits album of extreme weather events and their possible ties to climate change. These reports, published in the Bulletin of the American Meteorological Society, or BAMS, analyze events that took place all over the globe during the past year. They employ different methodologies and are typically chock full of cautious statements about what phenomena can and cannot be attributed to climate change.
Scientists tend to shy away from bold pronouncements. But this year's report is different.
On Wednesday, at the American Geophysical Union’s Annual Meeting in New Orleans, which this week has become a temporary global headquarters of earthquake, space, weather, and climate geeks, contributors to 2016’s edition threw much of that typical caution to the increasingly gusty wind.
A boy cools himself in a public water fountain in downtown Seoul, South Korea, in July, 2016.Credit: Lee Jin-man/AP/REX/ShutterstockThe message of the 2016 attribution issue is that a sea change has occurred in our understanding of what we, by burning fossil fuels for energy, are doing to our weather. In short, we're now manufacturing our own extremes, scientists said.
It can no longer be said that we are simply raising the odds of particular events, or making them more severe, or both. In fact, we’re now pushing the climate into new territory entirely, researchers said.
In other words, instead of realizing the sci-fi fantasy of controlling our weather, we’ve done everything possible to push the atmosphere toward a new, more malevolent form of chaos.
Out of the 27 extreme events examined in the peer reviewed report, investigators looking into three of them — the 2016 global heat record, a deadly heat wave in Southeast Asia, and “marine hot spots” that led to devastating coral bleaching — concluded that the events could not have occurred without the influence of human-caused global warming.
We’re now pushing the climate into new territory entirely.
In other words, take away global warming, and these things probably wouldn't have happened.
"This report marks a fundamental change," says Jeff Rosenfeld, a meteorologist who is the editor-in-chief of BAMS, in a press release.
“For years scientists have known humans are changing the risk of some extremes. But finding multiple extreme events that weren’t even possible without human influence makes clear that we're experiencing new weather, because we've made a new climate.”
Ironically, this was a predictable milestone, given that with enough warming, unprecedented heat events become likelier to occur. Climate scientists refer to this statistically as tail extremes of a probability distribution becoming far more likely the more the distribution shifts in a given direction.
However, our new climate era’s arrival is jarring, and feels as if the already capricious atmosphere has turned more violent, due to our own activities.
Credit: NASA GISSRegarding the 2016 global temperature record, scientists concluded that at least part of the warmth was due to a strong El Niño event, but that most of the warm temperature record was due to human-caused climate change during the past 100 years.
When the researchers ran state of the art computer models with natural climate factors only, versus simulations including the high levels of greenhouse gases we now have, only the simulations that included observed greenhouse gas concentrations in the atmosphere were able to capture the global temperature milestone.
Another consequential event during 2016 was record warm Arctic temperatures during the November 2015 through December 2016 time period. A study tracing the contributors to this also concluded that it "most likely would not have been possible without a long-term warming contribution from anthropogenic [human-caused] forcing."
One important caveat from both of these, and indeed most of the attribution studies in the BAMS issues over the years, is that they rely on computer models to simulate conditions and determine if they can replicate the extreme event with or without human-caused global warming. This introduces uncertainties involved with simulating a complex system such as the climate, but a growing accumulation of evidence is all pointing in one direction: It's us.
"Climate change was a necessary condition for some of these events in 2016. Necessary in order for them to happen,” Rosenfeld said. “They were impossible in the old climate."
Another study in the BAMS issue found that extreme heat in Southeast Asia, particularly India and Thailand, near the end of 2016 "would not have been possible without climate change." The study did note, though, that the El Niño contributed to regional warm extremes in some parts of Asia, but found that it could not explain the record-shattering triple-digit temperatures that killed hundreds continent-wide. "All of the risk of the extremely high temperatures over Asia in 2016 can be attributed to anthropogenic [human-caused] global warming," the study found.
"This is actually evidence for new events only possible because we have created a new climate," said Stephanie Herring, lead author of the BAMS report and a climate scientist at the National Oceanic and Atmospheric Administration (NOAA).
The Arctic had its warmest year on record in 2016.Credit: climate.gov"We have evidence now that climate change is pushing events past thresholds that could have been achieved with natural variability alone," Herring said. "These are not likely the first events of their kind."
"Statistically speaking we've likely crossed that threshold already, and we're just finding evidence for it in this report," Herring said, noting that scientists have only studied a small set of extreme events.
These three particular studies could be flawed or contain greater uncertainty than indicated, depending on subsequent work to duplicate the results. However, for now at least, it appears that just two years after the negotiation of the Paris Climate Agreement, we have entered a new relationship with nature. It is one in which we are the dominant player, with consequences that are bouncing back and hitting us smack in the face.
And if we're already here in the year 2017, one must ask the unsettling question of where we'll be in 2050, after several more decades of warming that is already baked into the climate system, let alone the year 2100.
Featured Video For You
Biggest die-off of corals ever recorded on Great Barrier Reef