One of the biggest challenges in preparing for a warming world is the uncertainty. With so many factors at play—temperature, rainfall, sea rise, weather—the best scientists can do is to map multiple climate futures using computer models, which try to simulate the complex processes that govern oceans and wind and the likelihood that each will occur. It’s enough to make you wish you had a crystal ball.

Barring that option, federal land and resource management agencies led by the U.S. National Park Service (NPS) are now turning to an unconventional tool: scenario planning. Developed by the military and used extensively by big businesses such as Shell Oil and the United Parcel Service, it's a planning technique that has long been used to prepare for the unlikely—and sometimes the unthinkable.

Now, the NPS is using scenario planning to better address the variety of challenges and management decisions that climate change will usher in. It’s proven especially useful for getting past what NPS ecologist Gregor Schuurman calls "analysis-paralysis"—the inability for most of us to consider a variety of possible futures. "It's very difficult for us as humans to consider more than one future in an effective way, and if there's an emotional component involved, we just shut down," Schuurman says. "Scenario planning comes out of an environment where that's not an option."

According to Jonathan Star, founder of the consulting firm Scenario Insight, scenario planning can be traced back to the U.S. military in the 1950s. It was championed in particular by Herman Kahn, a political scientist, military strategist and futurist at RAND Corporation. Kahn used scenario planning to map out the likely consequences of thermonuclear war—including how to win it, or barring that, how to survive it. Kahn’s penchant for “thinking about the unthinkable” attracted the attention of filmmaker Stanley Kubrick, who modeled his infamous character Dr. Strangelove in part on Kahn himself.

"Kahn said we may not think this is likely, but it is extremely important for us to at least go through the full experiment of imagining a surprising or difficult situation, because we will be better prepared if something like this happens," Star says.

Scenario planning took off in the commercial sector in the 1970s, when the oil and gas company Royal Dutch Shell (commonly known as Shell) began incorporating the tool into their planning process. "Until the late 1960s, the oil industry was very stable. There was not a great deal of turbulence or gyrations in the price of oil," Star says. "But with the rise of oil nationalism and OPEC"—the Organization of the Petroleum Exporting Countries—“in the late 1960s, Shell realized that they couldn't plan in the same linear way because their industry was getting buffeted by very unpredictable forces."

Using the tool, the company was able to successfully react to the oil price crises of the 1970s better than their competitors. Their experience inspired other companies including Morgan Stanley, Johnson & Johnson, and Proctor & Gamble to do the same, says Star. Recently, the use of scenario planning by UPS helped the global shipping company weather disrupted operations when Iceland's Eyjafjallajökull volcano erupted in 2010, its ash halting flights across Europe for several days.

The UPS had been planning not for a volcanic eruption but for the possibility of an Avian flu pandemic—which illustrates a key point about the scenario planning process, Star says. It's not necessary to get the future precisely right. "It's not a game of prediction. It's a game of preparation," Star says. "Going through exercises where you're asking 'What if?' tends to make organizations more flexible to deal with surprises and shocks when they come along."

In 2010, Leigh Welling, the first director of the agency’s Climate Change Response Program, had a hunch that scenario planning might be useful in the context of resource management. So she approached Star, who was at the time a scenario planner for Global Business Network, a consulting firm started by planning managers from Shell. "Leigh's insight was that scenario planning could be a really useful communication and translation device between climate change scientists and park managers," Star says.

The concept caught on. Scenario planning has spread throughout the NPS and to other federal land management and natural resource agencies such as the National Oceanic and Atmospheric Administration (NOAA). The NPS now holds regular scenario planning workshops with park managers to work through possible futures for natural and cultural treasures.

"Scenario planning allows situations to be explored that you might not explore, because they seem implausible," says Welling, who now manages the agency’s Shared Beringian Heritage Program in Alaska. "People tend to get stuck in their own mental models, and to think about things the way they have happened. We don't often spend time to think, 'what are the external forcings?' and 'how could they play out?'"

Welling recalls several eerie instances when her group was "scooped by reality." In 2012, for instance, her team used scenario planning to map out what might happen if the greater New York City area was pummeled by a combination of high tides and a severe storm. Months later, Hurricane Sandy struck, and NYC’s subway system was flooded just as the team predicted. “It was really fascinating,” Welling says. “We’ve had several experiences [like that] now.”

One example where the NPS has used scenario planning is a recent project exploring climate change effects to South Dakota's Badlands National Park, the site of one of the world's richest fossil beds and home to bison, bighorn sheep and other iconic species.

In 2015, Schuurman and the other experts visited the Badlands to observe the plants, animals, and other natural and cultural resources that would be impacted. "Then we went away for about half a year and developed climate change scenarios that were really relevant to those resources," Schuurman says. For example, soil moisture is important for grazing animals, so Schuurman and his team translated projected changes in temperature and precipitation from computer models into soil moisture futures.

After doing this for several variables, the group met again to paint distinct climate futures for Badlands. One called "The Jungle" is characterized by high temperature and precipitation increases, and has the longest growing season of all the scenarios. Another, called "Awfully Dry," has a reasonable amount of warming but decreased precipitation, resulting in a relatively short growing season. The group explored each scenario in detail, asking how each resource will be altered.

The answers are often surprising and subtle. "For example, in 'The Jungle' scenario, Badlands National Park will be a wetter place," Schuurman says. "Well, right now, the resource managers use water as an attractant to help round up buffalo in the late summer and early fall. But if the world is full of water, then that's not going to work. That's a nuanced translation of a climate future into an implication for a particular resource."

Star says the participatory aspect of scenario planning workshops is a key part of the exercises. “When people are involved in the creation of the scenarios, they are invested in the ideas that come out of them and are therefore probably more likely to continue to take action as a result of them. It’s the difference between having information delivered to you and discovering things for yourself.”