The Washington Post-Why Septembers record-warm temperatures have scientists so worried
September 23, 2023 5 min 1022 words
这篇报道引起了我对全球气温升高的严重担忧。尤其是在今年9月，气温暴涨，接近工业化前水平高出近2摄氏度，这一全球变暖的阈值正是全球领袖力求避免的。科学家们认为这一趋势使2023年成为地球有史以来最热的一年的几率极高，这也加剧了全球范围内极端气象事件的威胁。 这种异常气温很可能与深化的厄尔尼诺气候模式有关，也是温度将在未来一年继续超越以往标准的迹象。厄尔尼诺气候模式开始在今年春季出现，以释放太平洋海洋热量进入大气而提高全球气温而著称。 报告中指出，科学家的评估基于几乎实时的气候分析，类似于气象预测模型，但是它们是向后看的，而不是向前看的。这些分析得到了广泛的信任，因为它们与NASA和美国国家海洋和大气管理局（NOAA）在事后数周和数月内进行的例行全球气候评估相吻合。 文章提到，如果长期全球平均温度升高2摄氏度（3.6华氏度）以上，将可能引发对地球上所有生命的不可逆后果。尽管在已经经历了这些升温水平的地球上的热点地区，这些最严重和广泛的后果可能需要数年持续升温才能触发，但这个目标已经接近实现。科学家们表示，最新的高温激增凸显了气候行动的重要性。 报道中指出，这些温度异常之所以引人注目，是因为它们比7月和8月全球范围内观察到的极端高温还要离谱。这个夏季被欧洲气象科学家称为“有记录以来最热的三个月”，比近两个世纪前的温度记录高出0.71摄氏度。 考虑到当前的气温异常持续下去，可能会首次在年度基础上超过1.5摄氏度的工业化前平均温度，不过作者认为这“非常不可能”。 这一温度异常的增加与绝对值上的全球降温相反，因为9月23日的秋分标志着北半球秋季的开始。由于北半球包含更多陆地，而陆地升温和降温比海洋快，因此北半球的条件对全球平均气温有更大的影响。然而，科学家认为厄尔尼诺模式可能是这一温暖趋势的主要驱动因素。 报道还提到了其他一些可能导致气温升高的因素，如船只减排减少，允许更多阳光照射到海洋中；2022年南太平洋海底火山Hunga Tonga的喷发，释放大量水汽进入大气层；以及太阳活动的持续增长，略微增加了太阳对地球的升温效应。 总的来说，这篇报道突显了气候行动的紧迫性，提醒我们必须采取迅速和大胆的行动来减少温室气体排放，以尽可能减少气温升高和其带来的影响。气候变化已经不再是未来的问题，而是我们当前和未来都必须应对的挑战。
2023-09-21T14:29:09.748Z
After months of record planetary warmth, temperatures have become even more abnormal in recent weeks — briefly averaging close to 2 degrees Celsius above preindustrial levels, a global warming threshold leaders are seeking to avoid.
“I thought we had seen exceptional temperatures back in July,” said Zeke Hausfather, climate research lead for the payment company Stripe. “What we’ve seen this week is well above that.”
The trend adds to near-certainty that 2023 will be Earth’s warmest on record, and heightens threats of the extreme conditions the heat could fuel around the world.
The warmth is likely to be the fingerprints of a deepening El Niño climate pattern and a sign that temperatures will continue to accelerate beyond old norms in the year ahead, scientists said. El Niño, which began to appear this spring, is known for raising global temperatures by releasing vast stores of Pacific Ocean heat into the atmosphere.
“The El Niño won’t peak until later this year and there is plenty more heat waiting in the wings,” Michael McPhaden, a senior scientist at the National Oceanic and Atmospheric Administration, said in an email. “So expect more records to be set in the coming months.”
Scientists’ assessments are based on near real-time climate analyses that use weather observations to estimate global averages, much like a weather prediction model — only one that looks backward in time, rather than forward. Trust in such analyses has grown as they line up with the routine global climate assessments that NASA and NOAA perform weeks and months after the fact.
One such analysis produced by the Japanese Meteorological Agency shows that, this month, global temperatures have persistently diverged from 1991-2020 averages by 1 degree Celsius (1.8 degrees Fahrenheit).
Hausfather said that the 1991-2020 average is, itself, about 0.9 degrees warmer than levels observed before the Industrial Revolution and the widespread burning of fossil fuels. That means temperatures are inching closer, at least briefly, to warming thresholds that global leaders have pledged to avoid.
The past few days in September have been extraordinarily warm globally, with the warmest anomalies that we've seen all year in the JRA-55 reanalysis product (more than 1C over the 1991-2020 baseline): pic.twitter.com/TkHNhE3NDh
— Zeke Hausfather (@hausfath) September 20, 2023
Scientists have warned that if long-term global average temperatures rise 2 degrees Celsius (3.6 degrees Fahrenheit) above preindustrial levels, it could unleash irreversible consequences for all life on Earth. It would take years of such sustained warming to trigger the most dire and widespread consequences, though in the planet’s hottest spots that have already experienced those levels of warming, the effects have been catastrophic.
Already, the planet is on the brink of the most ambitious climate target, to limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial averages. Scientists have said it is not out of reach, however, and said the latest spike of heat underscores the importance of climate action.
“Decades of burning fossil fuels and deforestation have pumped heat-trapping gases in the atmosphere, and the vast majority of that heat is absorbed by the oceans. We’re now seeing the wrath of that heat as it’s unleashed back to the atmosphere,” Jennifer Francis, a senior scientist at the Woodwell Climate Research Center, wrote in an email. “We must act swiftly and boldly to reduce emissions of these gases to prevent as much warming as possible and the impacts of that heat.”
The temperature anomalies are remarkable for being even more aberrant than the extreme heat observed around the world in July and August. “By a large margin” of 0.71 degrees, this summer was the planet’s warmest three-month stretch in record books going back nearly two centuries, European climate scientists said earlier this month.
Hausfather called it “a foregone conclusion” that September marks a third consecutive month of record-setting average global temperatures.
If temperatures remain as abnormally warm as they are now, the planetary average could for the first time on an annual basis surpass 1.5 degrees Celsius of warming above preindustrial temperatures, Hausfather calculated, though he called that “very unlikely.”
The temperature anomalies have grown even as, in absolute terms, the planet is cooling ahead of the Sept. 23 equinox, which marks the start of fall in the Northern Hemisphere. Conditions in the Northern Hemisphere have a larger effect on planetary averages because it contains more land than the Southern Hemisphere, and land warms and cools more quickly than oceans do.
El Niño is nonetheless likely a major driver behind the warm trend because it creates Pacific trade wind patterns that encourage more heat to be released from the ocean and trapped by greenhouse gases in the atmosphere. With that El Niño pattern only expected to strengthen, reaching a peak during the Northern Hemisphere winter, that warmth may become even more anomalous over the coming year, said Michael Mann, a climate scientist and professor at the University of Pennsylvania.
El Niño is known for boosting planetary temperatures by one to two tenths of a degree Celsius. The last strong El Niño pushed 2016 to the current record for average global warmth, and also triggered a rise in extreme heat and storms.
Other factors may be contributing to the warming, Hausfather said: Reduced emissions from shipping liners, allowing more sunlight to reach the oceans; the 2022 eruption of the South Pacific underwater volcano Hunga Tonga, which sent vast amounts of water vapor into the atmosphere; and an ongoing upswing in solar activity, slightly increasing the sun’s warming effect on Earth.
But Claudia Tebaldi, an earth scientist at the Pacific Northwest National Laboratory, said the latest surge in temperature anomalies could be a sign that human influences and natural fluctuations are acting in concert to raise global temperatures.
During a stretch of the early 2000s when rates of global warming appeared to slow, Tebaldi said, natural fluctuations had a cooling effect that acted to dampen human-caused warming. That appears to have changed.
“It is not surprising that the pendulum is now oscillating in the other direction,” she wrote in an email.