Global sea levels could rise by two meters and displace tens of millions of people by the end of the century, according to new projections that double the UN's benchmark estimates.
The vast ice sheets of Greenland and Antarctica contain enough frozen water to lift the world's oceans a dozen of meters. The expansion of water as oceans warm also contributes to sea level rise.
The United Nations' Intergovernmental Panel on Climate Change (IPCC) said it's 2013 Fifth Assessment Report that under current emissions trajectories – a "business-as-usual" scenario known as RCP8.5 – would likely rise by up to one meter by 2100.
That prediction has since been viewed as conservative, as the levels of planet-warming greenhouse gas emissions continue to rise year on year, and satellites show accelerated rates of melt-off from massive ice sheets atop Antarctica and Greenland.
A group of the world's leading ice scientists this week released an expert judgment on the situation, drawing on their own experience and observations.
While there was still a significant margin of error, they found it "plausible" that under the business-as-usual emissions scenario, sea-level rises could exceed two meters by 2100.
遭到影响的人数会高出大约200倍 – 估量将导致约1.8亿人无家可归。
The authors said the area of land lost to the ocean could be equivalent to that of France, Germany, Spain and Britain combined and would displace more than 180 million people. "A sea-level rise of this magnitude would clearly have profound consequences for humanity," they said.
'The true risks'
The Paris climate deal, struck between nations in 2015, aims to limit global temperature rises to well below two degrees Celsius (3.6 Fahrenheit) and encourages countries to work towards a 1.5C cap.
In October, the IPCC released a landmark climate report that called for a drastic and immediate drawdown in coal, oil and gas consumption in order to arrest the rapid rise in the levels of greenhouse gases in the atmosphere.
That report, however, did not include revised estimates of sea level rise. Earth has already heated 1C since pre-industrial times, contributing roughly 3mm to sea levels each year. The authors of the new study, released Monday in the journal Proceedings of the National Academy of Sciences, argue that the IPCC's sea-level rise prediction was too constrained by focusing on what was "likely" to happen.
At wider probabilities – five-95 percent likelihood – they found that under 2C of warming seas could rise 36-126 cm by 2100. In a world that has warmed by 5C – unlikely but certainly not impossible given projected fossil fuel demand in the coming decades – they calculated a five percent risk of sea levels surpassing two meters higher, topping out at 238 cm.
Willy Aspinall, from the University of Bristol's School of Earth Sciences, said he hoped the study could provide policymakers with a more accurate worst-case scenario "crucial for robust decision making."
"Limiting attention to the 'likely' range, as was the case in the IPCC Fifth Assessment Report, may be misleading and will likely lead to a poor evaluation of the true risks," he added.
写作格局攻略是记者编写、修改和英语运用的规范参照。在《卫报》新的攻略中， “气候变化” （climate change）被替换为“气候紧急状况/危机/崩盘”（climate emergency, crisis or breakdown），而“全球变暖”（global warming）的表述也得到了强化，变为“全球加热”（global heating ）。
When it comes to climate coverage, the Guardian is also making headlines by changing its language in order to more accurately reflect the science and the extent to which climate issues escalate and worsen. The move, though seen as polarizing by observers, recommends using a more critical language, and less passive and gentle terms describing the environment in its recently updated style guide, such as "climate emergency, crisis or breakdown" instead of "climate change," and "global heating" rather than "global warming.”
上一年 12 月，担任英国气象局气候研讨的理查德·贝茨( Richard Betts )教授表明，“全球加热” 是一个比“全球变暖” 更精确的术语。而在政界，英国国会议员最近同意了工党宣告的“气候紧急状况”。