时间:2024-09-20 01:01:52 来源:网络整理编辑:探索
A new study extends global average surface temperature records back to 2 million years ago, further
A new study extends global average surface temperature records back to 2 million years ago, further back in time than any previous climate research. The research suggests that global warming from human emissions of greenhouse gases will cause far more warming, up to 9 degrees Celsius, or 16.2 degrees Fahrenheit, during the next several millennia than previously expected.
However, prominent climate researchers refuted that more disturbing conclusion in interviews with Mashable.
The study, published Monday in the scientific journal Nature, uses nearly five dozen ocean sediment cores to develop a record of Earth's global average surface temperature dating back to 2 million years.
The study's author, Carolyn Snyder, a scholar at Stanford University and an official at the U.S. Environmental Protection Agency, used these sediment cores to create more than 20,000 climate reconstructions from specific points in the ocean.
SEE ALSO:Climate change poses a major security risk to the U.S. today, intelligence report warnsLike a forensic investigator examining a crime scene, Snyder used a variety of methods -- in this case statistics and modeling -- to extend the temperature reconstructions to land areas as well.
"Previously, the longest continuous global temperature reconstruction was only 22,000 years long," Snyder told Mashable. "Before that in time, only a few isolated individual windows in time had global temperature reconstructions."
While outside scientists praised the temperature reconstruction as a valuable addition to climate science, several researchers contacted for this article were critical of how Snyder used the temperature reconstructions to infer the climate's sensitivity to changing ice sheets, carbon dioxide levels, and other factors.
In this Jan. 26, 2015 photo, pieces of thawing ice are scattered along the beachshore at Punta Hanna, Livingston Island, South Shetland Island archipelago, Antarctica.Credit: Natacha Pisarenko/APThe study estimates what is known as the "Earth system sensitivity," which encompasses a variety of feedbacks within the climate system, from the response of the atmosphere and oceans to fluctuations in greenhouse gases to the ways that ice sheet expansion or melting can alter global temperatures.
However, this metric is a correlation between events, and doesn't pinpoint whether one event caused another. Still, the study estimates an Earth system sensitivity of 9 degrees Celsius, or 16.2 degrees Fahrenheit, per a doubling of atmospheric carbon dioxide levels over millennium timescales.
In more simple terms, this means that over the long, long-term, our planet will see its global average surface temperature increase by up to 9 degrees Celsius if greenhouse gases in the atmosphere were to double, which they are currently on course to do.
The study found that if all greenhouse gas emissions were to cease today, the climate would still warm by about 5 degrees Celsius, or 9 degrees Fahrenheit, during the next several centuries.
However, the Earth system sensitivity metric is not the same as the similarly named, but altogether different, scientific metric known as climate sensitivity. That metric is defined as how much the globe would warm if greenhouse gas concentrations in the atmosphere were to double.
Climate sensitivity considers the influence of greenhouse gases, such as carbon dioxide, alone, while Earth system sensitivity involves a variety of feedbacks between the land, oceans and atmosphere, some of which are not well understood.
With climate sensitivity, carbon dioxide and other greenhouse gases are in the driver’s seat, whereas with Earth system sensitivity, there are many drivers, with cars going in different directions and sometimes colliding head on.
Estimates of climate sensitivity tend to be much lower than 9 degrees Celsius, closer to about 3 degrees Celsius.
The problem, Snyder as well as several outside scientists told Mashable, is that it's not clear exactly what was driving temperature changes during some time periods in the past.
"[Earth system sensitivity] is a useful metric that summarizes a combination of interactive feedbacks in the climate system (including temperature, greenhouse gases, ice sheets, vegetation, and dust)," Snyder said in an email.
"But it is a correlation observed in the past, not a test of causation," she said.
Via GiphyMichael Mann, a climate researcher at Penn State University who has published influential studies on the planet's climate history, said he views the new study as "somewhat of an outlier." Mann was not involved in the new research.
"The estimate of earth system sensitivity (9C for CO2 doubling) is so much higher than the prevailing estimates (5-6C) that one has to consider it somewhat of an outlier, and treat it with an appropriate level of skepticism," he told Mashablein an email.
One major problem with the study, Mann said, is that the sensitivity estimate is dominated by glacial and interglacial cycles during the past 800,000 years, and it's tough to untangle the roles played by carbon dioxide in such variations.
This is because carbon dioxide both causes and responds to temperature changes that are driven by other factors, such as variations in Earth's orbit around the sun.
"It is unclear that an estimate of the relationship between global temperature and carbon dioxide under those circumstances is an appropriate measure of the response of temperature when carbon dioxide alone is the major driving force, as it true today," Mann said.
"So I regard the study as provocative and interesting, but the quantitative findings must be viewed rather skeptically until the analysis has been thoroughly vetted by the scientific community."
Gavin Schmidt, a climate scientist who directs NASA's Goddard Institute for Space Studies in New York, was more blunt in his views on the new publication.
"The temperature reconstruction is great, but the claims about sensitivity are just wrong," Schmidt, who was not involved in the new research, said in an email. "This is not an argument about methods or what to present in public or whether you like models or observations, it is just wrong."
The U.S. will no longer have the final say on internet domain names2024-09-20 01:01
反轉?媒體人:淄博有人私自更改合同 俱樂部損失超137萬2024-09-20 00:59
江蘇隊中場張曉彬加盟中甲武漢三鎮 曾入選三級國家隊2024-09-20 00:18
AKS上海杯足球錦標賽重燃戰火 60支青少年球隊報名參賽2024-09-19 23:56
MashReads Podcast: What makes a good summer read?2024-09-19 23:25
藍衣崛起!意大利23場不敗 曼奇尼1成就比肩裏皮2024-09-19 23:24
西班牙解析 :平民鬥牛士 水爺布教授最後的倔強2024-09-19 22:59
英超官方:2021/22賽季8月14日開啟 次年5月22日結束2024-09-19 22:46
Here's what 'Game of Thrones' actors get up to between takes2024-09-19 22:38
吉翔已赴泰山隊報到參加合練 27日熱身上海海港2024-09-19 22:23
Despite IOC ban, Rio crowds get their political messages across2024-09-20 00:51
巴薩晴天霹靂!法蒂庫鳥賽季報銷 均需第三次手術2024-09-20 00:07
前中甲聯賽MVP加盟青島隊 司職邊鋒曾留洋法乙兩年2024-09-19 23:56
武磊評吐槽大會:體育非娛樂 足球應當是團結一心榮辱與共2024-09-19 23:54
WhatsApp announces plans to share user data with Facebook2024-09-19 23:36
媒體人談中超開賽:感覺4月20日開始的概率越來越小2024-09-19 23:29
反轉?媒體人:淄博有人私自更改合同 俱樂部損失超137萬2024-09-19 22:55
前中甲聯賽MVP加盟青島隊 司職邊鋒曾留洋法乙兩年2024-09-19 22:51
Make money or go to Stanford? Katie Ledecky is left with an unfair choice.2024-09-19 22:23
意大利前瞻:欲延續首戰不敗 博努奇迎百場裏程碑2024-09-19 22:21