"Climate researchers often use a scenario approach," says Dr. Klaus Keller, assistant professor of geosciences, Penn State. "Nevertheless, scenarios are typically silent on the question of probabilities."
The Intergovernmental Panel on Climate Change, which is in its third round of climate assessment, uses models that scenarios of human climate forcing drive. These forcing scenarios are, the researchers say, overconfident.
"One key question is which scenario is likely, which is less likely and which they can neglect for practical purposes," says Keller who is also affiliated with the Penn State Institutes of Energy and the Environment. "At the very least, the scenarios should span the range of relevant future outcomes. This relevant range should also include low-probability, high-impact events."
The researchers provide evidence that the current practice neglects a sizeable fraction of these low probability events and results in biased outcomes. Keller; Louis Miltich, graduate student; Alexander Robinson, Penn State research assistant now on a Fulbright Fellowship in Berlin, and Richard Tol, senior research officer, Economic and Social Research Institute, Dublin, Ireland, developed an Integrated Assessment Model to derive probabilistic projections of carbon dioxide emissions on a century time scale. Their results extended far beyond the range of previously published scenarios, the researchers told attendees today (Dec. 15) at the fall meeting of the American Geophysical Union in San Francisco.
Noting that overconfidence is an often observed effect, Keller cites a study reviewing estimates of the weight of an electron as an example. The reported range for the weight of an electron from 1955 to the mid-1960s did not include the weight considered correct today. On a more closely related topic, the range of energy use projections in the 1970s typically missed the observed trends.
"We need to identify key sources of overconfidence and critically reevaluate previous studies," says Keller.
According to their study, past scenarios of carbon dioxide emissions can miss as much as 40 percent of probabilistic projection, missing a large number of low-probability events. The omitted scenarios may include low-probability, high-impact events.
"If low-probability, high-impact events exist, such as threshold responses of ocean currents or ice sheets, omitting these scenarios can lead to poor decision making," says Keller. "We need to see the full range of possible scenarios, because the actual outcome may not be contained in the central estimate.
"New tools and faster computers enable a considerably improved uncertainty analysis," he adds. "If you do not tell how likely the probability of a scenario is, people are left to guess. A sound scientific analysis can at least tell how consistent these guesses are with the available observations and simple, but transparent assumption."
A'ndrea Elyse Messer | EurekAlert!
The unintended consequences of dams and reservoirs
14.11.2018 | Uppsala University
Earth's magnetic field measured using artificial stars at 90 kilometers altitude
14.11.2018 | Johannes Gutenberg-Universität Mainz
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
14.11.2018 | Materials Sciences
14.11.2018 | Health and Medicine
14.11.2018 | Life Sciences