Getting a feel for the feedback threat

The prospects of abrupt climate change are mixed, a new report finds, with dangerous feedback loops likely further down the track but their scope broader than previously thought.

A new report from the US National Research Council offers some encouraging news about several widely discussed worries often associated with abrupt climate change. But that message comes with a big dollop of some pretty troubling possibilities down the road a ways.

If you were coaching or playing for an athletic team, it might be a bit like rejoicing about your performance during regulation, only to find out that the overtime looks quite problematic.

First the good news: The NRC’s Abrupt Impacts of Climate Change: Anticipating Surprise finds that “some abrupt changes, widely discussed in the scientific and popular literature as potential threats, are unlikely to take place over the near term”. The scientists in this case are talking about “near term” as being 100 years. They say we can all breathe a bit easier – and for a while longer than previously thought – when it comes to prospects for a rapid shutdown of the Atlantic Meridional Overturning Circulation, AMOC. That’s the current that moves warm waters from upper levels of the Atlantic northward and brings colder water south. Probability of that over the next century “is now understood to be low”, they say.

That goes also for potential rapid “belches” of carbon stored in permafrost soils in high-latitude regions of the world or in methane-rich ices. Those carbon inventories still “are poised to play a significant amplifying role in the century-scale buildup of greenhouse gases in the atmosphere – but are unlikely to do so abruptly”, the NRC committee said in summarising its report.

So do the carrot and stick dabbles of good news about abrupt climate change offset continuing worries about longer term impacts of a warming climate?

Responding to that question during an NRC webinar, Anthony Barnosky of the University of California, Berkeley, a study panel participant, responded that in driving a vehicle down a highway drivers generally have something of a chance to see what lies out in front of them. With abrupt climate change, “the road suddenly drops out in front of you”, he cautioned.

In weighing abrupt versus more gradual climate change impacts, study chair James W.C. White, of the University of Colorado, Boulder, replied: “If there were a third option, I would take it.” He, Barnosky, and Penn State scientist Richard Alley, a panel member and remote webinar participant, repeatedly emphasised a need now to begin managing potential impacts and risks posed by both abrupt and more gradual climate change. And, again, the impacts. They encouraged increased modeling and monitoring of abrupt climate change impacts just as one would monitor to better understand where one's assets and valuable resources may be most vulnerable.

Key concerns go beyond climate system alone

And so the researchers moved on to less cheerful recommendations coming from their study, using this language in the report’s introduction:

What has become clearer recently is that the issue of abrupt change cannot be confined to a geographical discussion of the climate system alone. The key concerns are not limited to large and abrupt shifts in temperature or rainfall, for example, but also extend to other systems that can exhibit abrupt or threshold-like behaviour even in response to a gradually changing climate. The fundamental concerns with abrupt change include those of speed – faster changes leave less time for adaptation, either economically or ecologically – and of magnitude – larger changes require more adaptation and generally have greater impact. This report offers an updated look at the issue of abrupt climate change and its potential impacts, and takes the added step of considering not only abrupt changes to the climate system, but also abrupt impacts and tipping points that can be triggered by gradual changes in climate.

“It’s really a question of pace,” White said at one point, saying that Miami “would be largely dysfunctional” if a three-foot (91cm) sea-level rise were to occur over the next 30 years. The same rise over a 100-year period won’t be a walk on the beach either, he suggested, but the additional time would at least be useful in making better risk management decisions.

Abrupt impacts ‘already underway’ and more to come

“We’re already seeing abrupt impacts, and we’re going to see more,” Barnosky said at the November 3 briefing releasing the new study. He pointed to “a dramatic stair step” in the increase in fires across the American west over the past 25 years and said, “we’re already at that new normal”, with an expectation of more and more fires “on the horizon with very high confidence”.

Among the abrupt climate change impacts “already underway”, the committee pointed to higher Arctic temperatures triggering rapid decline in sea ice over the past decade. It said declining sea ice “could potentially have large and irreversible effects on various components of the Arctic ecosystem, as well as substantial impacts on Arctic shipping and resource extraction, with significant geopolitical ramifications”.

Also among the abrupt climate change impacts highlighted by the new report are increased pressures on plant and animal species extinctions. “The current pace of climate change is probably as fast as any warming event in the past 65 million years, and the rate is projected to increase over the next 30 to 80 years,” it said, adding that “some species can neither move nor adapt fast enough…already putting some species at greater risk of extinction".

Along with calls for more research, more modeling, and more monitoring concerning abrupt climate change and resulting impacts, the NRC committee also said “action is needed to develop an abrupt climate change early warning system” as part of an overall risk management strategy. Such a system, it said, could “assist in tailoring risk mitigation and preparedness efforts and to ensure warnings result in appropriate protective actions, with the ultimate goal of preempting catastrophes”.

The panel members addressing the webinar specifically called for an early and strong role for social scientists and communications experts in such an early-warning effort. They urged early efforts also to coordinate and standardise in consistent formats the relevant risk management information already existing and yet to be utilised.

‘Low and slow’ urged for upper bounds and for pace of change

White told the webinar session he had been approached by a computer systems analyst wanting to know what the maximum ambient temperature might be in 30 years, saying computers must be designed and built to operate at that maximum temperature.

“But what if we exceed that temperature in 15 years while the company amortises it over 30 years?” he asked. He said such social and economic considerations involving abrupt climate change impacts could well be the trigger for improved public understanding and more effective personal and policy responses.

“There’s no doubt that we want to keep the upper boundary and the rate of change low and slow,” Barnosky added. Alley chimed in that the situation may be analogous to saving for one’s retirement: “All delay is costly, but it helps whenever you start,” he said, adding that each additional degree of global warming imposes more societal costs than the previous degree.

Carrying the analogy over to sea-level rise, White said that excessive increases could mean “It’s no more Delaware …. The first state in [the union] could be the first one out.” As in FIFO/First In-First Out.

Addressing risks of melting permafrost and releases of methane, he said, “it won’t come out abruptly, but over time we’ll still need to adapt.” Methane calthates “don’t come out as one big belch”, based on current understanding, but instead “it starts in years and it happens over decades and centuries”.

Among the major take-home messages from the committee’s new report and the three committee members’ presentation at the meeting releasing it:

– Society already is seeing impacts from abrupt climate change, and we’ll see more and more in coming years.

– Some of those most widely discussed in popular media in recent years – the AMOC and sudden “belches” of stored carbon and methane – appear less likely over the next 100 years but still significant issues after that period.

– And it’s not just abrupt climate change impacts themselves that pose concerns, but also the societal, ecological, and economic impacts of those changes, impacts that can be triggered even by more gradual or phased-in warming: “Abrupt impacts of ongoing changes that, when certain thresholds are crossed, can cause abrupt impacts for society and ecosystems.”

“Science gives and science takes away,” White acknowledged at one point in commenting on the “good news” and “bad news” findings in the committee’s report. But he and fellow committee members Alley and Barnosky agreed that the time is now to better understand, anticipate, and prepare not only for the risks and adverse impacts posed by a gradually warming climate, but also for those posed by abrupt climate change and its own set of likely impacts … over whatever short- or long-term time frame they might be manifested.

One particularly interesting and readily accessible resource provided in the committee’s full report is a table (S.1, beginning on page 11) describing a range of potential abrupt climate change issues or related impacts and examples of the consequences of each. The chart reports current trends, outlook over the balance of this century, outlook beyond 2100, relative levels of scientific understanding (low/moderate/high, etc), and critical research and monitoring needs for abrupt changes in the oceans, in the atmosphere, at high latitudes, and in ecosystems.

Asked during a Q&A session about the “Anticipating Surprises” wording in the title of the report, White said that as a scientist he is hopeful that continuing research and improved understanding will help society foresee and mitigate some potential surprise developments.

“But as a realist, I’m pretty sure we’re going to be blindsided,” he added, saying he hopes to keep the blindsiding at a manageable level.

This article was originally published on The Yale Forum on Climate Change & The Media. Republished with permission.

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