James Hansen and Colleagues Advance the Timetable

Our regular columnist, Dr. Bruce Johansen, has written his newest What's HOT in Global Warming? article about the most recent study done by climate scientist Dr. James Hansen and his colleagues. Dr. Hansen, the world's most famous climate scientist, is coming to Omaha to deliver a free public lecture Friday evening April 29th at the Mike and Josie Harper Center on the Creighton University campus at 602 North 20th Street at 7:00 p.m. titled, “Energy and Climate Change: How Can Justice Be Achieved for Young People?”

By Bruce E. Johansen

As our presidential campaign drowns in insults and trivia, here’s the real news: the world’s coastal cities are on a carbon-dioxide clock. As the Earth has experienced its warmest winter and early spring in recorded history, exceeding records in the 121-year instrumental record by an astounding margin, the scientific debate no longer dwells on whether present levels of greenhouse-gas emissions in the atmosphere will drown the coasts. The question is when, and by how much.

During the last few months, an intense El Nino and rising greenhouse-gas levels have launched temperatures to nearly 5 degrees F. above 20th-century averages. In December, 2015; January, 2016; and February 2016 (the meteorological winter season), temperatures not only set world records, but did so by the largest margins (anomalies) since record-keeping began about 1880. February's global temperature was 1.35 degrees C. above the 1951-1980 average—exceeding the previous record anomaly set in January of 1.13 degrees C., according to NASA's Goddard Institute for Space Studies. December, 2015 was 1.11 degrees C. above the same set of averages.

"The departures are what we would consider astronomical," said NOAA climate scientist Jessica Blunden. "It's on land. It's in the oceans. It's in the upper atmosphere. It's in the lower atmosphere. The Arctic had record low sea ice. Everything everywhere is a record this month, except Antarctica," Blunden said. "It's insane." Georgia Tech climate scientist Kim Cobb added: “When I look at the new February 2016 temperatures, I feel like I'm looking at something out of a sci-fi movie. In a way we are: it's like someone plucked a value off a graph from 2030 and stuck it on a graph of present temperatures. It is a portent of things to come, and it is sobering that such temperature extremes are already on our doorstep.”

Advancing the Timetable for Sea-level Rise

As radical rises in worldwide temperatures startled scientists early in 2016, James Hansen and 18 co-authors published a study in the open-access journal Atmospheric Chemistry and Physics (from the European Geophysical Union), making a case that several meters in sea-level rise could take place within a century—not the several hundred years projected by many scientists. This conclusion is based on a study of paleoclimate during the Eemian period 120,000 years ago, a situation analogous to today (except that temperature increases occurred less rapidly then than now).

During the Eemian, Hansen and colleagues assert that excess heat in the deep oceans rapidly eroded ice in Antarctica and Greenland at an accelerating pace. This melting was accelerated by a slowing of the Atlantic Ocean’s meridional circulation that usually distributes heat through the world ocean. The slowing of ocean circulation caused stagnation of relatively warm water in some areas in and near the Arctic.

The authors of this study point to maps of worldwide warming during the winter of 2015-2016 indicating that the only areas with below-average temperatures were over oceans adjacent to Greenland and Antarctica, where rapid melting of ice influences the water’s temperature level. “My interpretation is that this is the beginning,” Hansen said. “And it’s one or two decades sooner than in our model” (Gillis, 2016). “I think almost everybody who’s really familiar with both paleo [climatic] and modern [observations] is now very concerned that we are approaching—if we have not passed—the points at which we have locked in really big changes for young people and future generations,” Hansen said.

The 2 Degree C. Limit “Dangerous”

Limiting global temperature rise to 2 degrees C. (3.6 F.) over pre-industrial levels (as recommended by recent diplomatic efforts such as the 2015 Paris accords) will not prevent climate-driven changes forcing evacuation of many coastal cities, Hansen and colleagues warned.

Hansen and colleagues hypothesized that: “Mass loss from the most vulnerable ice, sufficient to raise sea level several meters, is better approximated as exponential than by a more linear response. Doubling times of 10, 20 or 40 years yield multi-meter sea level rise in about 50, 100 or 200 years. These climate feedbacks aid interpretation of events late in the prior interglacial, when sea level rose to +6–9 meters with evidence of extreme storms while Earth was less than 1° C warmer than today. [Climate] modeling, paleoclimate evidence, and ongoing observations together imply that 2° C global warming above the pre-industrial level could be dangerous, [including] growing sea level rise, reaching several meters over a timescale of 50–150 years.”

“Some of the claims in this paper are indeed extraordinary,” said Michael E. Mann, a climate scientist at Penn State University. “They conflict with the mainstream understanding of climate change to the point where the standard of proof is quite high.” However, noting that Hansen and colleagues often have presaged consensus, Mann said: “I think we ignore James Hansen at our peril,” Mann said (Gillis, 2016).

Bruce E. Johansen is Jacob J. Isaacson University Research Professor in the School of Communication, University of Nebraska at Omaha. He is presently completing a 3-volume encyclopedia on climate change for ABC-CLIO.


Gillis, Justin. “Scientists Warn of Perilous Climate Shift Within Decades, Not Centuries.” New York Times, March 22, 2016. http://www.nytimes.com/2016/03/23/science/global-warming-sea-level-carbon-dioxide-emissions.html

Hansen, J., M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, E. Rignot, I. Velicogn. B. Tormey, B. Donovan, E. Kandiano, K. von Schuckmann, P. Kharecha, A.N. Legrande, A. M. Bauer, and K.-W. Lo. “Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations That 2 °C Global Warming Could be Dangerous.” Atmospheric Chemistry and Physics 16(March 22, 2016), 3,761-3812. doi:10.5194/acp-16-3761-2016.

Mooney, Chris. “We Had All Better Hope These Scientists Are Wrong about the Planet’s Future.” Washington Post, March 22, 2016 https://www.washingtonpost.com/news/energy-environment/wp/2016/03/22/we-had-all-better-hope-these-scientists-are-wrong-about-the-planets-future/?wpmm=1&wpisrc=nl_evening

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