The Sandpiper

June 2008 issue

A Rising Ocean Affects Us All
June 2008| by Betty Wheeler

Polar bears live far away, but Del Marians share something important with this Arctic species: The prospect of significant habitat change because of global warming. Two-thirds of the world's polar bears are predicted to disappear within 50 years because of Arctic ice decline, say USGS scientists. Jeff Severinghaus, a Scripps Institution of Oceanography scientist who studies ice-core samples to learn what causes abrupt climate change like one that occurred 8,000 years ago, says that best estimates are that global warming will cause sea rise of three feet, plus or minus 18 inches, in the next 100 years. Because of the force of waves, each inch of sea rise results in about 100 inches of bluff retreat. Del Mar's beaches and bluffs will be protected or lost in direct proportion to global success in reducing CO 2 emissions in a 50-100 year window.

Severinghaus made several key points in a recent Sandpiper interview about sea rise. First, “Ignore the deniers.” That humans are causing climate change, he said, is as scientifically established as the link between smoking and cancer, industry-funded naysayers notwithstanding. Second, because the ocean takes a long time to warm, we are already committed to some sea rise. “We've realized 1°F increase in ocean temperature in the last 50 years, and we're already committed to 2 degrees”; what we aren't already committed to, he says, is “whether our grandchildren live with 20 feet of sea level rise, or 5 feet."* If we stay on course with CO 2 emissions, we are guaranteeing the eventuality of a Greenland ice slide that would produce 20-foot sea rise sometime in the next 500 years, though predicting the timing of ice sheet slides is like predicting earthquakes. Even five years ago, glaciologists believed ice sheets were unlikely to contribute to sea level rises; that glacier slides as well as ice melt are major contributors, he says, has been a big wake-up call.

What should we be doing? “Personal action,” he notes, “while important, is not sufficient.” Plug-in hybrids, solar, wind and other alternative energy sources and CO 2 sequestration are key, he says, as are top-down government regulation and coordinated global action to level the playing field so corporations aren't disadvantaged by reducing CO 2 emissions. Take key individual actions, he says, but also urge Congress to support a coordinated national and global response.

*Correction: In the print edition, the reference to five feet was erroneously expressed as five inches.

Additional reading:

Publications by Jeffrey Severinghaus are listed here, with links to PDF versions of many of the articles:

http://icebubbles.ucsd.edu/Publications/pubs.html

Dr. Severinghaus's links on climate change are here:

http://icebubbles.ucsd.edu/Links/links.html

Powerpoint Presentation:

An excellent Powerpoint Presentation of the 2008 Jim Arnold Lecture, "Global Climate Change: A Paleoclimate Perspective from the World's Highest Mountains", given on May 9, 2008 at UC San Diego by Lonnie G. Thompson, University Distinguished Professor, School of Earth Sciences & Byrd Polar Research Center, The Ohio State University, is available here:

http://calspace.ucsd.edu/casgc/JArnoldLecture/
Powerpoints/Global%20Climate%20Change--
Lonnie%20Thompson%205-9-08.pdf

It includes numerous images relating to climate change, ice core research and related expeditions, glacial retreat, the Larson B ice shelf collapse, and more. The abstract of the presentation follows:

ABSTRACT: Glaciers are among the first responders to global warming, serving both as indicators and drivers of climate change. Over the last 30 years the Ice Core Paleoclimate Research Group at The Ohio State University has been engaged in a program of systematic recovery of ice cores from high-elevation, low-latitude ice fields. The resulting climate records, along with other proxy data, have produced three primary lines of evidence for past and present abrupt climate change. First, high-resolution time series of stable oxygen isotopes (temperature proxies) and net balance (precipitation proxies) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for at least the last two millennia. Second, the continuing retreat of most mid to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, there is strong evidence within and around glaciers for a widespread and spatially coherent abrupt event ~5.2 ka that marked the transition from early Holocene warmth to cooler conditions that occurred through much of the world and was coincident with structural changes in several civilizations. Together, these three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in many areas for at least 5000 years. Specific evidence of recent acceleration in the rates of ice loss of glaciers will be presented. The current melting of these ice fields is consistent with model predictions of both high latitude and vertical amplification of temperatures in the tropics. The ongoing rapid, global-scale retreat of mountain glaciers is not only contributing to global sea level rise, but threatening fresh water supplies in many of the world's most populous regions. The current and present danger posed by ongoing climate change and the human response will be discussed. Professor Thompson's Ice Core Paleoclimatology Research Group website can be found at: http://bprc.osu.edu/Icecore/

“Target Atmospheric CO2: Where Should Humanity Aim?”, James Hansen, Makiko Sato, Pushker Kharecha, David Beerling, Valerie Masson-Delmotte, Mark Pagani, Maureen Raymo, Dana L. Royer, James C. Zachos

The lead author of this scientific paper, published on Columbia University 's website, is James Hansen of NASA/Goddard Institute for Space Studies. Examining available data to consider what our target atmospheric CO2 should be, the paper concludes:

“Humanity today, collectively, must face the uncomfortable fact that industrial civilization itself has become the principal driver of global climate. If we stay our present course, using fossil fuels to feed a growing appetite for energy-intensive life styles, we will soon leave the climate of the Holocene, the world of prior human history. The eventual response to doubling preindustrial atmospheric CO 2 likely would be a nearly ice-free planet. Humanity's task of moderating human-caused global climate change is urgent. Ocean and ice sheet inertias provide a buffer delaying full response by centuries, but there is a danger that human-made forcings could drive the climate system beyond tipping points such that change proceeds out of our control. The time available to reduce the human-made forcing is uncertain, because models of the global system and critical components such as ice sheets are inadequate. However, climate response time is surely less than the atmospheric lifetime of the human-caused perturbation of CO 2 . Thus remaining fossil fuel reserves should not be exploited without a plan for retrieval and disposal of resulting atmospheric CO 2 . Paleoclimate evidence and ongoing global changes imply that today's CO 2 , about 385 ppm, is already too high to maintain the climate to which humanity, wildlife, and the rest of the biosphere are adapted.… We suggest an initial objective of reducing atmospheric CO 2 to 350 ppm, with the target to be adjusted as scientific understanding and empirical evidence of climate effects accumulate… This target must be pursued on a timescale of decades… A practical global strategy almost surely requires a rising global price on CO 2 emissions and phase-out of coal use except for cases where the CO 2 is captured and sequestered. The carbon price should eliminate use of unconventional fossil fuels, unless, as is unlikely, the CO 2 can be captured. A reward system for improved agricultural and forestry practices that sequester carbon could remove the current CO 2 overshoot. With simultaneous policies to reduce non-CO 2 greenhouse gases, it appears still feasible to avert catastrophic climate change. Present policies, with continued construction of coal-fired power plants without CO 2 capture, suggest that decision-makers do not appreciate the gravity of the situation. We must begin to move now toward the era beyond fossil fuels. Continued growth of greenhouse gas emissions, for just another decade, practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects. The most difficult task, phase-out over the next 20-25 years of coal use that does not capture CO 2 , is herculean, yet feasible when compared with the efforts that went into World War II. The stakes, for all life on the planet, surpass those of any previous crisis. The greatest danger is continued ignorance and denial, which could make tragic consequences unavoidable.

The full paper can be read here:

http://www.columbia.edu/~jeh1/2008/TargetCO2_20080407.pdf