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Transcript
BIOSPHERIC FEEDBACK LOOPS
AND RAPID GLOBAL CLIMATE
CHANGE
John Cairns, Jr.
University Distinguished Professor of Environmental Biology Emeritus
Department of Biological Sciences
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061, U.S.A.
June 2010
POSITIVE AND NEGATIVE FEEDBACK LOOPS
 A positive feedback loop makes an existing process speed up – for example,
release of stored carbon dioxide into the atmosphere accelerates global
warming.
 A negative feedback loop decreases the impact of an existing process – for
example, removal (i.e., sequestering) of carbon dioxide from the atmosphere by
marine ecosystems reduces the rate of global warming but my cause harm by
making the oceans acidic.1
SOURCES AND SINKS FOR GREENHOUSE
GASES
 A source emits carbon dioxide or other greenhouse gases.
 A sink retains and stores carbon dioxide or other greenhouse gases.
 A sink can become a source when climate changes – for example, permafrost
stores carbon dioxide but releases it when the permafrost thaws, and trees
remove carbon dioxide from the atmosphere but release it when a forest fire
occurs.
CARBON IS A BASIC UNIT OF LIFE FORMS AND IS
STORED (E.G., SINKS) IN VARIOUS PARTS OF THE
BIOSPHERE.2
 Atmosphere – 578* (as of 1700), 766 (as of 1999)
 Soil organic matter – 1,500 to 1,600
 Oceans – 38,000 to 40,000
 Marine sediments and sedimentary rocks – 66,000,000 to 100,000,000
 Terrestrial plants – 540 to 610
 Fossil fuel deposits – 4,000
* values are billions of metric tons
THE OCEANS ARE A MAJOR SINK FOR CARBON
DIOXIDE (AN ESTIMATED 25 – 30 %), BUT, WHEN CO2
DISSOLVES IN SEAWATER, CARBONIC ACID IS
FORMED.3
 Ocean acidification decreases the ability of many marine organisms to build their
shells and skeletal structures.3
 Acidification is already causing major shifts in marine ecosystems.
 The same gas, carbon dioxide, that is contributing to global warming and other
types of climate change is also affecting oceanic ecosystems.
UNTIL THE INDUSTRIAL REVOLUTION,
ATMOSPHERIC GREENHOUSE GASES, INCLUDING
CARBON DIOXIDE, WERE NOT A PROBLEM, BUT NOW
CARBON DIOXIDE EMISSIONS ARE COMING FROM
50,000 COAL-FIRED POWER PLANTS.4
 At present, more carbon dioxide exists than the biosphere can assimilate, and the surplus
remains in the atmosphere.
 On a per capita basis, Australians produce about 11 tons, Americans 9 tons, Chinese 2 tons,
and Indians 0.5 ton of carbon dioxide per year.4
 “Globally, power generation emits nearly 10 billion tons of CO2 per year.”4
 “Economists have estimated these ‘social costs’ at anywhere from $8 per ton to as high as
$100 per ton of CO2.”4
IN THE 21ST CENTURY, CONCERN HAS BEEN
ESCALATING ABOUT POSITIVE FEEDBACK RELEASE OF
CARBON DIOXIDE.
 Rising temperatures have caused emissions from Arctic permafrost to increase by
almost one-third in just five years.5
 Warming caused by released methane emissions will release more methane in a
classic positive feedback loop.
 “After water vapor and carbon dioxide, methane is the third most important
greenhouse gas in the atmosphere, and researchers warn that this unforeseen
flux of gas into the atmosphere could alter the global climate in unexpected
ways.”6
THROUGHOUT HISTORY ATTACKS HAVE BEEN MADE ON
SCIENCE AND SCIENTISTS – IN THE 21ST CENTURY, THESE
ATTACKS HAVE FREQUENTLY BEEN BASED ON THE UNCERTAINY
IN SCIENCE – PARTICULARLY GLOBAL CLIMATE CHANGE.
 Uncertainty exists in all aspects of living – politics, finances, football games, etc. –
uncertainty is not unique to science.
 Science is based on probability supported by evidence.
 Of course, dealing with circumstances (e.g., global climate change) is problematical when
the terms are complicated.
 Humankind’s creativity is not energized by contentment but the excitement of
understanding how nature “works.”
 Of course, people are most content when they are confident and certain – but then came
the global financial meltdown.
A GOOD EXAMPLE OF UNCERTAINTY IS THE
METHANE POSITIVE FEEDBACK FROM OCEANIC,
FROZEN, HYDRATED METHANE AND MELTING
PERMAFROST.7
 Are these emissions new or just newly observed?
 Will these releases of heat-trapping methane destabilize the global climate system?
 An extensive monitoring program over a considerable span of time will be essential to
answer these two questions.
 However, can global decisions on anthropogenic greenhouse gas emissions wait until
robust data are available to answer the above questions?
“IN FIGHTING FOR SCIENCE, WE SUBSCRIBE TO A
COMFORTING ILLUSION: THAT PEOPLE CAN BE
SWAYED BY THE FACTS.”8
 “No level of evidence can shake the growing belief that climate science is a conspiracy….”8
 “The attack on climate science is now widening to an all-out war on science.” 8
 However, even as the volume of evidence increases, fewer people believe climate change is
a significant problem.
 The global financial meltdown, loss of jobs, foreclosures on homes, and governmental
deficits have almost certainly contributed to this alteration in the list of global problems.
REGRETTABLY, NO SHORT-TERM SOLUTION EXISTS
FOR IMPROVING PUBLIC RESPECT FOR SCIENCE.
 Scientists are usually viewed as members of a different culture from the average citizen.
 Neither scientists nor their organizations have effectively explained to the general public
how the scientific process works.
 If scientists spend much of their time informing the public more persuasively, their
research my suffer.
 Most scientific disciplines have a special “tribal” language (i.e., “jargon” in layperson’s
terms) that is not understood by the general public and sometimes rarely understood by
scientists in other fields of research.
ULTIMATELY, IF “BUSINESS AS USUAL” CONTINUES,
MANY CATASTROPHES MAY OCCUR THAT HAVE BEEN
PREDICTED BY THE SCIENTIFIC LITERATURE.
 Positive feedback loops resulting from release of stored carbon into the atmosphere is one
likely scenario.
 Catastrophes should be avoided whenever possible, but most research scientists are not
skilled in communicating complex information about dynamic, complex systems to the
general public.
 Since positive feedback loops may increase the rate of climate change dramatically, time
for social change may be too short.
IF EACH SCIENTIFIC/PROFESSIONAL ORGANIZATION WOULD
ALTER ITS POSITION PAPER ON CLIMATE CHANGE TO SERVE AS
AN OP-ED FOR THE NEWS MEDIA, THIS CHANGE WOULD HAVE
A GREAT EFFECT.
 For example, the Australian Medical Association refers to “our life-support system.”9
 The American Chemical Society states: “The costs of unchecked climate change in
economic loss, human misery, and loss of ecosystem services are likely to be enormous.”10
 The National Academies of the G8 + 5 (Brazil, Canada, China, France, Germany, India, Italy,
Japan, Mexico, Russia, South Africa, United Kingdom, United States,) report: “It is
unequivocal that the climate is changing, and it is very likely that this is predominantly
caused by the increasing human interference with the atmosphere. These changes will
transform the environmental conditions on Earth unless counter-measures are taken.”11
ALL POSSIBLE PRECAUTIONS MUST
BE TAKEN NOW TO AVOID
INCREASING THE EFFECT OF THE
POSITIVE FEEDBACK LOOPS TO AVOID
RUNAWAY CLIMATE CHANGE.
Acknowledgments. I am indebted to Darla Donald for transcribing the
handwritten draft and for editorial assistance in preparation for publication
and to Valerie Sutherland for converting it to Power Point.
References