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Presented to The Unitarian Universalist Church of Ogden
September 17, 2006

1. Main Points of the Presentation

• Although I am not a climatologist or a climate modeler, as a professional geologist I possess credibility in terms of being able to compile and analyze complex data. Earth has a rich history of climate change, and I have studied the earth for more than three decades.
• As the ‘Third Rock from the Sun”, the Earth differs from its near neighbors. Venus has a runaway greenhouse effect, with surface temperatures too hot for life as we know it. Mars is too small to hold a permanent atmosphere and hydrosphere; its atmosphere is too thin for a significant greenhouse effect. Earth is the “Goldilocks planet”, where conditions are “just right” for evolving life. Earth is a natural greenhouse planet- our atmosphere can trap heat that would otherwise radiate back into space. Natural greenhouse gases include water vapor, carbon dioxide and methane. Carbon dioxide is particularly important in climate change, because it is closely correlated with atmospheric temperature.
• Earth’s atmosphere is very thin (like a coat of varnish on a classroom globe), and its thermochemical balances are delicate.
• Earth has experienced climate change numerous times during its existence, particularly during the past 2 million years. The later part of this period is known as “The Ice Age.” However, the RATE of climate change (increase in mean global temperature) that we have observed during the past century is unprecedented in the geologic record. The measured increase in mean global temperature during the last century is directly attributed to increased levels of carbon dioxide in the atmosphere, which have increased by about 30 percent during this time. The cause of the observed carbon dioxide increase is widely believed to be the burning of fossil fuels during the past 150 years of the industrial age.
• “Global Warming” is somewhat of a misnomer because not all places on Earth are getting hotter, even though the average atmospheric temperature has been increasing. Scientists generally prefer the term “Climate Change” rather than “Global Warming.”
• There is broad consensus among scientists (though not total agreement) that much of the recent climate change can be attributed to humans’ burning of fossil fuels.
• There are two main types of supporting data for climate change, both developed in the late 20^th century: Paleoclimatology (the study of ancient climates) and Climate Modeling (computer-generated, numerical models that quantitatively explain the forces at work in climate change).
• The most compelling paleoclimatological data are from ice cores drilled in Antarctica and Greenland. The ice cores give us a reliable record of temperature and carbon-dioxide levels in the atmosphere, going back more than 600,000 years. The ice layers were initially deposited as seasonal snowfall, which became compacted into glacial ice. Time is measured by counting the annual layers of ice deposition, much like tree-ring analysis. Past temperatures are calculated using measurements of the oxygen- and hydrogen- isotopic compositions of the yearly ice layers, which are very sensitive to air temperature at the time of deposition. Past carbon-dioxide levels are known by analyzing the tiny bubbles of air within the ice layers, trapped at the time of deposition.
• The most compelling results of climate modeling are that: (1) All credible climate models, though they may differ in detail and complexity, project future temperature increases (even if carbon dioxide levels remain unchanged from today); and (2) the climate models of today are strongly credible because they can numerically reproduce the observed temperature increase (and other changes) of the past 150 years. To achieve this concurrence between the models and historical observations requires the “climate forcing” of the observed 30 percent increased carbon dioxide in the atmosphere. This agreement of models and observations gives confidence that the models can accurately forecast future conditions. The forecasts unanimously indicate a future increase in mean global atmospheric temperature.
• In discussing climate change, it is important to acknowledge that uncertainties exist in the data and the interpretations. Scientists are generally comfortable with uncertainty, but politicians and their constituents may not be. Hence, uncertainties are commonly used as a tool to “derail” the arguments of scientists in support of climate change (global warming).
• My own understanding of current uncertainties would be something like this: “Climate change during the past 500,000 years, and the unprecedented rate of increase in mean global temperature during the past 150 years (the industrial age), is not at all uncertain. As we go back in time, the uncertainties increase, as is true of all historical data. The idea that human-induced carbon emissions have contributed to climate change during the past 150 years is not at all uncertain; the exact proportion of human vs. “natural” climate forcing is somewhat uncertain. The ability of climate models to project the future is somewhat uncertain, but all models project some measure of increased mean global temperature. Major uncertainty currently exists as to whether future climate change will involve gradual, centuries-spanning change, or whether the climate is being pushed to a dangerous tipping point. Growing evidence suggests that the ocean-atmosphere system controlling world climate can lurch from one state to another in a few decades. Scientists don’t yet know how close the system is to a critical threshold.
• Much of what passes for legitimate “debate” nowadays is little more than ideological blogging between liberals and conservatives.
• Our purpose should be to “Raise the Level of Debate.” This can be done by citing credible sources (see below). Thus, if someone says, “I think global warming is nonsense”, a suitable response might be, “Oh really? That’s not what respected scientists at the National Academies think. I suggest you go to their website for further information.”

2. Some web links and other references

References Compiled by: William R. Hackett, to support his presentation given at the Unitarian Universalist Church of Ogden, September 17, 2006.

Purpose: “To Raise the Level of Debate.” We all have varying degrees of credibility, and not all of us are scientists. We should avoid ideological discussions as proxies for scientific debate. Instead, we should point to original sources whose credibility is high or unquestioned, such as the National Academies, government scientific organizations, policy statements of professional societies, and original research publications in prestigious scientific journals.

__________

Here is a link for the Joint Science Academies statement on climate change, which summarizes many important observations and conclusions:

http://www.nationalacademies.org/morenews/20050607.html

A key idea in this statement is the following:

"Carbon dioxide levels have increased from 280 parts per million (ppm) in the year 1750, to over 375 ppm today -- higher than any previous levels that can be reliably measured (i.e., in the last 420,000 years)."

The gist of the statement is contained in its lead paragraph:

June 7 -- The U.S. National Academy of Sciences joined 10 other national science academies today in calling on world leaders, particularly those of the G8 countries meeting … in Scotland, to acknowledge that the threat of climate change is clear and increasing, to address its causes, and to prepare for its consequences. Sufficient scientific understanding of climate change exists for all nations to identify cost-effective steps that can be taken now to contribute to substantial and long-term reductions in net global greenhouse gas emissions that cause global warming. The statement echoes the findings and recommendations of several previous reports by the U.S. National Academies. __________

General information about climate change and human-induced global warming is provided by the Union of Concerned Scientists (UCS):

http://www.ucsusa.org/global_warming

The U.S. Global Change Research Information Office also provides comprehensive information on climate change and global warming:

http://www.gcrio.org/compendium/gcnews.html

__________

In his first broadcast interview as President of the American Association for the Advancement of Science, John Holdren told the BBC that the climate was changing much faster than predicted. He blamed President Bush not only for refusing to cut emissions, but also for failing to live up to his rhetoric on harnessing technology to tackle climate change.

"We are not starting to address climate change with the technology we have in hand, and we are not accelerating our investment in energy technology research and development," Professor Holdren observed. His comments can be found at: 
http://news.bbc.co.uk/2/hi/science/nature/5303574.stm

__________

Here is a link to a recent briefing from the President of the National Academy of Sciences to the U.S. Senate, on the subject of Climate Change Science and Economics:

http://www7.nationalacademies.org/ocga/testimony/Climate_Change_Science_and_Economics.asp

__________

The U.S. Environmental Protection Agency has published a number of reports on future sea-level rise and its potential to displace tens of millions of people worldwide. The following link is a good place to begin further research:

http://yosemite.epa.gov/OAR/globalwarming.nsf/content/ResourceCenterPublicationsSeaLevelRiseIndex.html#future

http://yosemite.epa.gov/oar/globalwarming.nsf/content/ResourceCenterPublicationsSeaLevelRiseIndex.html

Here is a supporting comment from an old friend and respected colleague, Dr. Robert C. Walter. Bob is a geologist who has used radiometric age-dating to understand the progress of human evolution, including the fossil remains of the famous east-African hominid, “Lucy.” Bob says,

“I've studied climate change for my human-evolution research, and it is well documented that in the last 500,000 years Earth has experienced the most severe and sudden climate shifts since the end of the Mesozoic. The modern "ice age", which began around 2.5 million years ago, did not fully develop until about 500,000 years ago. To document the close, positive correlation between mean global temperature and atmospheric CO2, and to know that we are at the highest level of CO2 in the last 420,000 years is alarming. This means that we now have the potential to exceed the highest known mean global temperatures in the last 420,000 years. For example, during the last interglacial period 125,000 years ago (a warm, interglacial period similar to the modern Holocene), global temperatures were slightly higher than exist today and persisted for a longer duration, resulting in sea levels rising ~ 6 m higher than current levels. If the modern temperature and CO2 levels continue to rise and persist for a period of time, sea levels will rise.”

Dr. Robert C. Walter, Professor, Dept of Earth & Environment, Franklin and Marshall College

__________

The American Geophysical Union (AGU), of which I am a supporting life member, issued the following policy statement, Human Impacts on Climate:

http://www.agu.org/sci_soc/policy/climate_change_position.html

The American Geological Institute’s (AGI) 1999 policy statement supporting scientific research on climate change is: http://www.agiweb.org/gapac/climate_statement.html

The American Association of Petroleum Geologists (AAPG) issued this contrarian policy. The AAPG is virtually alone among geoscientific societies in its lack of support for human-induced global warming: http://dpa.aapg.org/gac/papers/climate_change.cfm

__________

Climate change has characterized the past 2 million years of Earth history, and particularly the past 500,000 years. However, the rate and the magnitude of increased mean global temperature during the past 150 years (the industrial age), and particularly the past 30 years, is unprecedented in the geologic record. Atmospheric CO2 has increased approximately 30 percent during the industrial age as a result of our burning of fossil fuels. Following are some links that provide detailed information on the strong correlation between carbon dioxide in the atmosphere, human activities, and the increase in average global temperature:

http://www.whoi.edu/institutes/occi/viewArticle.do?id=9986

(Woods Hole Oceanographic Institute, WHOI)

http://www.ncdc.noaa.gov/oa/climate/globalwarming.html

(National Oceanic and Atmospheric Administration, NOAA)

http://www.ncdc.noaa.gov/paleo/globalwarming/paleostory.html

(NOAA paleoclimatology summary; especially see the Final Word)

__________

Climate modeling is consistent with the data from the Antarctic and Greenland ice cores. Modeling shows that mean global temperatures are closely correlated with CO2 (a greenhouse gas) in the atmosphere. The validity of climate modeling, with all of its complexities and uncertainties, is further demonstrated by the ability of current models to closely reproduce the observed changes in mean global temperature that have been measured during the past 150 years, as a result of increased atmospheric CO2 from human sources.

Climate models differ in complexity (zero-, 1, 2, 3, 4 dimensions) and sophistication (e.g., ability to account for feedback mechanisms; ability to accurately incorporate the effects of clouds and aerosols). NONE OF THE MODELS PROJECT CONSTANT OR DECREASED MEAN GLOBAL TEMPERATURE FOR THE FORESEEABLE FUTURE. That is, all of the models project a temperature increase, although the magnitudes and the detailed geographic patterns of the temperature changes may differ among the models.

For supporting data and conclusions, see the WHOI and NOAA links given above.

__________

For a recent peer-reviewed, sophisticated, state-of-the-art climate model published in a prestigious international scientific journal, see:

James Hansen and others, 2005, Earth’s Energy Imbalance: Confirmation and Implications, Science, v. 308, p. 1431-1435 (June 3, 2005 issue).

__________

An excellent report from the Pew Center on Global Climate Change, entitled The Science of Climate Change, can be viewed and downloaded from: http://www.pewclimate.org/global-warming-basics/basic_science/wigley.cfm

__________

An excellent and readable source of general information is:

Al Gore, An Inconvenient Truth, Rodale Press, Emmaus, PA, 325 p.

ISBN-10: 1-59486-567-1 

Note: a movie of the same title will be issued on DVD in November 2006, with a kit of reference and study materials. The movie and reference materials are available at a reasonable cost from the web site: http://www.an-inconvenient-truth.com/get.html

(Thank you for your interest in this subject- pass it on. Bill Hackett)

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