In 2002, the National Academy of Sciences published “Abrupt Climate Change: Inevitable Surprises,” a valuable report examining whether and how the building human influence on the climate system might lead to disruptive jolts. The most important finding, in a way, was that this was an area sorely in need of intensified research.
Most of the “monsters behind the door,” to use an apt phrase from Stephen W. Pacala of Princeton, were plausible rather than probable. There were signs they’d escaped before (evidence of past abrupt changes), but only faint scratching could be heard now.
Now there’s a new report from the Academy’s National Research Council. The title reflects advances in understanding: “Abrupt Impacts of Climate Change: Anticipating Surprises.” The findings laid out below reinforce the reality that the biggest impacts of greenhouse-driven global warming still lie several generations in the future.
Given humanity’s focus on the near and now, the greatest challenge posed by global warming is figuring out how to spur meaningful changes in energy norms based on a risk with this time scale.
With that in mind, the new report also looks at abrupt change in societies as well as the climate system. Read more on that below from one of the authors.
This excerpt from a summary nicely summarizes the basic findings:
Abrupt change is already underway in some systems [summer Arctic sea ice and extinction rates], and large scientific uncertainties about the likelihood of other abrupt changes highlight the need for further research. However, with recent advances in understanding of the climate system, some potential abrupt changes once thought to be imminent threats are now considered unlikely to occur this century.
The report sees evidence of moderate risk of abrupt shifts in this century in these areas:
– Increases in intensity and frequency of heat waves and extreme precipitation events (a category in which it includes droughts, floods, hurricanes and major storms)
– Decrease in ocean oxygen
– Rapid state changes in ecosystems, species range shifts, and species boundary changes
Among the abrupt shifts that the report says have a low probability of occurring in this century but pose higher risks after 2100 are the following:
– Disruption to Atlantic Meridional Overturning Circulation (the ocean current shifts that were caricatured in “The Day After Tomorrow“)
– Changes to patterns of climate variability (such as the Pacific temperature shifts (such as El Niño La Niña)
– Increasing release of carbon stored in soils and permafrost and methane from seabed methane hydrates
– Sea level rise from ice sheet destabilization
I reached out to Richard Alley of Pennsylvania State University, who was an author of both the 2002 report and this one, asking him to characterize what’s been learned. Here’s his reply:
The first report knew, and commented on, the possibilities of gradual climate change pushing ecosystems or economies over thresholds and triggering abrupt responses, but the new report focuses on such tipping points in our societies and environment.
The very strong evidence from Greenland ice and other sources of large, rapid, widespread climate changes in the past, and the fairly clear evidence that freshening of the north Atlantic could trigger a large climate shift, had raised LOTS of big questions, and at the time of Inevitable Surprises, many of those questions were poorly answered. By now, enough of the hard work of measuring and modeling has been done to provide high scientific confidence that while we are and will affect the north Atlantic with climate change, and this will have consequences, it is very unlikely that there will be a huge and abrupt change in the coming decades. A similar story applies to giant methane belches changing the climate — as knowledge of the huge stores of frozen and free methane in the sea floor was first developed, and the carbon frozen in Arctic soils, we couldn’t quantify the possibility of a large, rapid release. Now we can, and while such stored carbon is likely to amplify our warming, it is not likely to do so both greatly and rapidly.
But, Katrina’s high waters just made it over the levee, and the difference between “just over” and “not quite over” proved to be a lot of billions of dollars and human disruption. The Arab Spring surprised many people, including some who had expertise, and while attribution of such an event to a particular cause is probably impossible, there are people (as written up in The Economist, for example) who link at least some of the causation to food prices, and there in turn people who link at least some of the food-price swings to climate change. It is easy to see such linkages occurring, and strengthening, in a greatly warmed future climate when many of our crops are already grown at temperatures above their optimum.
The report observes that knowledge of vulnerabilities can be used to reduce them, and that we have the capability to identify and reduce such vulnerabilities, helping us.
One valuable section is a call for an “Abrupt Change Early Warning System.” Here’s a summary released with the report:
Some surprises in the climate system may be inevitable, but with improved scientific monitoring and a better understanding of the climate system it could be possible to anticipate abrupt change before it occurs and reduce the potential consequences. Building this ability will require careful monitoring of climate conditions, improved models for projecting changes, and the interpretation and synthesis of scientific data using novel analysis techniques. To address these needs, the committee believes that action is needed to develop an abrupt change early warning system.
Such a system would be part of an overall risk management strategy, providing information for hazard identification and risk assessment. These data would help identify vulnerabilities to assist in tailoring risk mitigation and preparedness efforts and to ensure warnings result in appropriate protective actions, with the ultimate goal or preempting catastrophes.
Much is already known about the design, implementation, and sustainability of early warning systems. Planning for an abrupt change early warning system would benefit from leveraging the experience and knowledge gained as part of existing early warning programs, such as the National Integrated Drought Information System or the Famine Early Warning System.
Network. Providing a complete roadmap to a successful abrupt change early warning system was beyond the scope of this report, but the committee has outlined its initial thoughts on what would make such a system successful:
Monitoring: An abrupt change early warning system should expand upon existing monitoring networks, protect and/or augment important networks that are already in place, and develop new ones as needed. Maintaining and expanding these monitoring networks in an era of budget cuts is an area of concern….
Modeling: A successful abrupt change early warning system must consistently iterate between data collection, model testing and improvement, and model predictions that suggest better data collection….
Synthesis: A necessary part of an abrupt change early warning system is synthesizing knowledge to avoid the trap of data collection without continuing and evolving data analysis and model integration. This will require dedicated teams of researchers, improved collaborative networks, enhanced educational activities, and innovative tools for data analysis and modeling techniques.
To implement an abrupt change early warning system, it will be important to integrate the various components of the project, pay attention to stakeholder priorities, and build the ability to be flexible and adaptive. Thus, designing and implementing an abrupt change early warning system will need to be an iterative process that is revisited and refined as understanding of abrupt climate change, impacts, and social vulnerabilities evolves.
The organizational structure of an abrupt change early warning system would capitalize on existing programs, but will also need to capture the interconnectedness of climate and human systems. Although it could eventually be run as a large, overarching program, such a system might better be started through the coordination, integration, and expansion of existing and planned smaller programs. Careful coordination—to reduce duplication of efforts, maximize resources, and facilitate data and information sharing—will be essential to a successful abrupt change early warning system.
Abrupt climate changes present substantial risks to society and nature. Although there is still much to learn, to ignore the threat of abrupt change would lead to more costs, loss of life, suffering, and environmental degradation. The time is here to be serious about the threat of tipping points, so as to better anticipate and prepare ourselves for the inevitable surprises.