Domino-effect of climate events could move Earth into a ‘hothouse’ state

Leading scientists warn that passing such a point would make efforts to reduce emissions increasingly futile[0]

[0]futile: actions that are futile are useless because they have no chance of being successful 无用的；徒劳的

A domino-like cascade of[一系列] melting ice, warming seas, shifting currents and dying forests could tilt the Earth into[1] a “hothouse” state beyond which human efforts to reduce emissions will be increasingly futile[徒劳的], a group of leading climate scientists has warned.

[1]tilt: /tɪlt/ if an opinion or situation tilts, or if something tilts it, it changes so that people start to prefer one person, belief, or action to others （使）倾向于，（使）偏向于

Crisis situations tend to tilt the balance of power in favour of the president.

危急形势总是会把权力天平倾向于总统。

[+toward/towards]

Government tax policy has tilted toward industrial development.

政府的税收政策已经向工业发展倾斜。

This grim[2] prospect is sketched out in a journal paper that considers the combined consequences of 10 climate change processes, including the release of methane[甲烷] trapped in Siberian permafrost and the impact of melting ice in Greenland on the Antarctic.

[2]grim

1) A situation or piece of information that is grim is unpleasant, depressing, and difficult to accept. 严酷的; 令人沮丧的

There was further grim economic news yesterday. 

昨天有更令人沮丧的经济新闻。

2) A place that is grim is unattractive and depressing in appearance. (地方) 阴沉的

The city might be grim at first, but there is a vibrancy and excitement. 

这个城市也许一开始沉闷，但它有一种活力和激情。

Climate cascade: feedback loops could amplify[3] one another, pushing Earth towards ‘hothouse’ state, warn scientists

[3]amplify:

1) to make sound louder, especially musical sound  放大〔声音，尤指音乐声〕

an amplified guitar

带有扩音设备的电吉他

2) to increase the effects or strength of something formal  增强

These stories only amplified her fears.

这些故事徒增了她的恐惧感。

3) to explain something that you have said by giving more information about it formal  详述，（进一步）阐述

Would you care to amplify that remark?

请你把那句话解释一下好吗？

The authors of the essay, published in Proceedings of the National Academy of Sciences, stress their analysis is not conclusive, but warn the Paris commitment to keep warming at 2C above pre-industrial levels may not be enough to “park” the planet's climate at a stable temperature.

They warn that the hothouse trajectory[轨迹] “would almost certainly flood deltaic[4] environments, increase the risk of damage from coastal storms, and eliminate coral reefs (and all of the benefits that they provide for societies) by the end of this century or earlier.”

[4]delta: Δ 三角洲

the Mississippi delta 密西西比河三角洲

deltaic (adj.) 三角洲的；三角形的

“I do hope we are wrong, but as scientists we have a responsibility to explore whether this is real,” said Johan Rockström, executive director of the Stockholm Resilience Centre. “We need to know now. It’s so urgent. This is one of the most existential questions in science.”

Rockström and his co-authors are among the world's leading authorities on positive feedback loops, by which warming temperatures release new sources of greenhouse gases or destroy the Earth's ability to absorb carbon or reflect heat.

Their new paper asks whether the planet's temperature can stabilise at 2C or whether it will gravitate[4] towards a more extreme state. The authors attempt to assess whether warming can be halted or whether it will tip towards a “hothouse” world that is 4C warmer than pre-industrial times and far less supportive of human life.

[4]gravitate: If you gravitate toward a particular place, thing, person, or activity, you are attracted by it and go to it or get involved in it. 受吸引

You naturally gravitate toward people with shared values. 

你自然而然地被具有共同价值观的人吸引。

New feedback loops are still being discovered. A separate paper published inPNAS reveals that increased rainfall – a symptom of climate change in some regions - is making it harder for forest soils to trap greenhouse gases such as methane.

Previous studies have shown that weakening carbon sinks[5] will add 0.25C, forest dieback[森林梢枯病] will add 0.11C, permafrost thaw[永冻土融化] will add 0.9C and increased bacterial respiration[细菌呼吸作用] will add 0.02C. The authors of the new paper also look at the loss of methane hydrates[甲烷水合物] from the ocean floor and the reduction of snow and ice cover at the poles.

[5]carbon sink: a large area of forest that is believed to help the environment by taking in carbon from the air so that the effects of global warming are reduced   碳汇，碳吸存〔被认为能够吸收空气中的碳从而缓解全球变暖的大面积森林〕

Rockström says there are huge gaps in data and knowledge about how one process might amplify another. Contrary to the Gaia theory, which suggests the Earth has a self-righting tendency, he says the feedbacks could push the planet to a more extreme state.

As an example, the authors say the loss of Greenland ice could disrupt the Gulf Stream ocean current, which would raise sea levels and accumulate heat in the Southern Ocean, which would in turn accelerate ice loss from the east Antarctic. Concerns about this possibility were heightened earlier this year by reports that the Gulf Stream was at its weakest level in 1,600 years.

Currently, global average temperatures are just over 1C above pre-industrial levels and rising at 0.17C per decade. The Paris climate agreement set actions to keep warming limited to 1.5C-2C by the end of the century, but the authors warn more drastic action may be necessary.

Another climate scientist – who was not involved in the paper – emphasised the document aimed to raise questions rather than prove a theory. “It’s rather selective, but not outlandish[古怪的；奇异的],” said Prof Martin Siegert, co-director of the Grantham Institute. “Threshold and tipping points[临界点] have been discussed previously, but to state that 2C is a threshold we can’t pull back from is new, I think. I’m not sure what ‘evidence’ there is for this – or indeed whether there can be until we experience it.”

Rockström said the question needed asking. “We could end up delivering the Paris agreement and keep to 2C of warming, but then face an ugly surprise if the system starts to slip away,” he said. “We don’t say this will definitely happen. We just list all the disruptive events and come up with plausible[貌似合理的]occurrences … 50 years ago, this would be dismissed as alarmist, but now scientists have become really worried.”

“In the context of the summer of 2018, this is definitely not a case of crying wolf, raising a false alarm（“狼来了”的故事）: the wolves are now in sight,” said Dr Phil Williamson, a climate researcher at the University of East Anglia. “The authors argue that we need to be much more proactive in that regard, not just ending greenhouse gas emissions as rapidly as possible, but also building resilience in the context of complex Earth system processes that we might not fully understand until it is too late.”（适用于写作）

节选自：The Guardian

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