can’t see the forest

Global Warming for the Skeptical, or the Merely Inquisitive

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Last month the Intergovernmental Panel on Climate Change (that’s an international group of peer-reviewed scientists—not cabinet ministers, congressmen, or oil lobbyists, n.b.) released the summary of its fourth assessment report on the topic of global climate change. The analysis is both quantitative and qualitative, discussing how much is changing, what is changing, and why it is changing.

The latest report takes advantage of both more precise physical observations and data collection as well as a better understanding of the data provided by computer models. It is the most sophisticated and circumspect collection of analyses and projections available to humanity.

You can view the summary here (PDF). Below I’ve extracted some of the information that I found most interesting and revelatory.

What does all of this data mean? I’m not in a position to pontificate, although I have wildly gesticulated in the past.

I will merely say that it seems to me that common sense dictates:

  • Global warming is a matter which is of concern to our generation not only because of the immediate manifestations of its effects—which are felt most harshly in the less-developed world, not in air-conditioned suburbia—but because of future manifestations. This is because the industrial activity of today generates the climatic fallout of tomorrow. It is precisely because of this slow-motion reaction that the danger is so easy to ignore. In this respect, response to global warming can be viewed as an extremely important test of the ability of humanity to organize and act on behalf of future generations. This is a skill which is altogether foreign to the capitalist/imperialist ideal, and a skill which has never before been of such urgent importance to the well-being of life on Earth.
  • It is important for citizens to petition their governments to act decisively in enforcing regulations on industries which contribute to global warming and pollution. Will these regulations restrict economic activity in certain sectors? Will jobs be lost? Absolutely. Is that too high a price to pay for the continuation of an environment which is conducive to complex life? Hardly. We are faced with a situation in which we must bear unpleasant responsibility for a cultural dysfunction for which we are not personally responsible in the generative sense. It’s strange that this sort of altruism is the basis for much proud flag-waving and militarism when it is perverted to the uses of nationalist profiteering pursuits such as warfare, wherein it is lauded as “proud sacrifice” or something similar, and yet is viewed by many as hardly worthwhile when it needs to be applied to the future health of the entire planet.
  • Even more important is individual responsibility and accountability in developing sustainable lifestyles. Clearly the automobile-driven lifestyle is a primary culprit in hydrocarbon emissions, so the elimination of unnecessary fuel consumption and participation in biopowered transportation and public transit are helpful. Likewise, opting for low-energy devices in the home and the pursuit of local, unprocessed foodstuffs and other goods are positive contributions that the average person can make. Furthermore, raising the issue as widely and as intelligently as possible is one of the most productive enterprises in which one can engage. Don’t look to the government for solutions. Create your own, and be proud of them. Make some noise; then the government will react and take credit for the initiative.

Let’s have a look at some of this data.

The most reliable data on atmospheric conditions before the period when such data began to be measured in real time comes from Antarctic ice cores. Just as geologists can tell much about conditions on Earth in a given geologic period by examining the differences in strata of rock, climatologists can also discern, with a surprisingly high degree of precision, the climate conditions from a given period by examining strata of unexposed ice which are known to have been deposited at a given rate. Through this type of analysis, climatologists have been able to reconstruct temperature and atmospheric composition data for the past several hundreds of thousands of years.

The graph below is a composite of changes in atmospheric greenhouse gas levels as recorded in the ice cores over the past ten thousand years, and as recorded by active human measurement of atmospheric levels over the past several years. The red lines show the contemporary data collected from real time atmospheric sampling; the other colors represent various interpretations of the ice core data and so naturally extend back much further in time. Note that, while the ice core-derived values from the different studies vary slightly, they coincide with one another remarkably as to the general trend of increase. Pictured are carbon dioxide levels (parts per million) and methane and nitrous oxide levels (parts per billion):

Greenhouse Gas Levels - Ice Core/Active Measurement Composite

Since the graphs cover a large expanse of time, the last several centuries of activity are presented in exploded views. You can see that carbon dioxide levels, for instance, have risen from roughly 300 to about 375 parts per million in the last century, compared to a net increase of about thirty parts per million over the previous ten thousand years.

The following graph shows changes in average temperature, sea level, and snow cover in the northern hemisphere from various periods ending in 2000. The changes are relative to averages from the period of 1961-1990.

Temperature, Sea Level, and Snow Cover Changes, 1961-1990, Northern Hemisphere

The solid black lines represent decadal averages of values; the circles indicate plotted annual values and the blue shaded regions represent reasonable uncertainty resulting from these discrepancies. This data was obtained entirely from real time human measurement.

Next, a depiction of changes in regional average temperature changes from 1900 to 2000 is presented. The black lines represent decadal averages of actual observations of temperatures. Here is the important twist: the pink shaded areas represent ranges of values derived from computer models which included anthropogenic forcing of climate shift (models which accounted for industrial activity.) The blue shaded areas represent ranges of values derived from computer models which did not include human industrial activity. You can see that, particularly from about 1950 forward, the actual observations follow models which included human industrial activity much more closely than those which did not. This means that, according to an array of a total of 33 simulations, it is virtually certain that the rises in temperature experienced throughout the past half-century to century are explicitly associated with human industrial activity. Put another way, absent of human emissions of greenhouse gases, we could expect to have seen temperature changes within the blue shaded areas. Unfortunately this has not been the case, as the trajectories of the black lines clearly denote.

Regional Temperature Changes

Now, let’s talk about the future. This last graph represents a variety of predictions of changes in surface temperature from the present up through the year 2100, based on computer simulations of several different scenarios, each scenario reflecting a different projection of rates of increase in atmospheric greenhouse gases based on projections of increasing economic/industrial activity, population increases, and other variables. The orange line represents values from an experiment at which greenhouse gas concentrations were frozen at the levels observed in the year 2000.

Multi-model Averages for Temperature Change through 2100

Please review the assessment report summary (link at top) for a description of each of these projected scenarios (page 18/18). Based on these values, it is reasonable to project an increase in average global surface temperature of 4-6º C by the year 2200 or of 6-8º C by the year 2300 if human emissions are not drastically and permanently reduced in the immediate future. Such temperature increases and the associated climatic changes, if not prevented, will very likely result in massive depopulation and extinction of thousands of species of plant and animal life. This prediction is based on climate change alone, without consideration of environmental compositional degradation (pollution, urban sprawl) associated with human industrial activities and population increase.

Here are some various observations/predictions based on the IPCC’s fourth assessment:

  • Eleven of the past twelve years (1995 – 2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850.) … Urban heat island effects are real but local, and have a negligible influence (less than 0.006º C per decade) on these values.
  • The average atmospheric water vapour content has increased since at least the 1980s over land and ocean as well as in the upper troposhere. The increase is broadly consistent with the extra water vapour that warmer air can hold.
  • Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system. Such warming causes seawater to expand, contributing to sea level rise.
  • Average Arctic temperatures increased at almost twice the global average rate in the past 100 years.
  • It is virtually certain that the 21st Century will be marked by warmer and fewer cold days and nights over most land areas.
  • It is virtually certain that the 21st Century will be marked by warmer and more frequent hot days and nights over most land areas.
  • It is very likely that the 21st Century will be marked by an increasing frequency in heat waves over most land areas.
  • It is very likely that the 21st Century will be marked by an increasing frequency in heavy precipitation events over most land areas [such as the extreme snow accumulations experienced in the eastern U.S. this winter -ed].
  • It is likely that in the 21st Century the geographical areas affected by drought will increase in size.
  • It is likely that in the 21st Century there will be an increase in intense tropical cyclone activity.
  • It is likely that in the 21st Century there will be an increased incidence of extreme high sea levels, excluding those which can be accounted for by tsunamis.
  • Average northern hemisphere temperatures during the second half of the 20th Century were very likely higher than during any other 50-year period in the last 500 years and very likely the highest in at least the past 1300 years.
  • It is likely that increases in greenhouse gas concentrations alone would have caused more warming than observed because volcanic and anthropogenic aerosols have offset some warming that would otherwise have taken place.
  • The observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that the global climate change of the past fifty years can be explained without external forcing and very likely that it is not due to known natural causes alone.
  • Warming tends to reduce land and ocean uptake of atmospheric carbon dioxide, increasing the fraction of anthropogenic emissions that remains in the atmosphere.
  • Increasing atmospheric carbon dioxide concentrations leads to increasing acidification of the oceans.
  • Snow cover is projected to contract.
  • Sea ice is projected to shrink in both the Arctic and Antarctic under all SRES scenarios. In some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st Century.
  • Climate carbon cycle coupling is expected to add carbon dioxide to the atmosphere as the climate system warms, but the magnitude of this feedback is uncertain … Based on current understanding of climate carbon cycle feedback, model studies suggest that to stabilize at 450 ppm CO2, could require cumulative emissions over the 21st Century to be reduced from an average of approximately 670 GtC to approximately 490 GtC.
  • Contraction of the Greenland Ice Sheet is projected to continue to contribute to sea level rise after 2100.
  • Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium, due to the timescale required for removal of this gas from the atmosphere.

The Working Group of the IPCC which prepared this report is composed of more than fifty independent authors. [correction—in addition to the authors referenced on the summary frontispiece, the working group contains hundreds of additional researchers and representatives of industry and government bodies.]

Through the Ice


After one look at this planet any visitor from outer space would say
“I want to see the manager.”

William S. Burroughs


When the well’s dry, we know the worth of water.

– Benjamin Franklin

Peter Norvig’s Experiment on the Climate Change Consensus

Global Warming Facts: Top 50 Things to Do to Stop Global Warming

Union of Concerned Scientists – ExxonMobil’s Disinformation Campaign on Global Warming Science

Sierra Club of Canada – 10 Popular Myths About Global Warming

National Arbor Day Foundation – Differences in US Hardiness Zones as Evidence for Global Warming (animation)

UNEP – World Environment Day 2007

The Ecologist Online – How Mankind Is Sleepwalking to the End of the Earth

An Inconvenient Truth –

The Guardian – Arctic Ocean May Lose All Its Ice by 2040, Disrupting Global Weather

The Los Angeles Times – Why We’re More Scared of Gay Marriage and Terrorism Than a Much Deadlier Threat

The Boston Review – Phaeton’s Reins – The human hand in climate change

BBC: The Stern Review at a Glance

Environmental Defense – Shifting Gears: Cars and Global Warming

Center for Biological Diversity – Bush Administration Issues Polar Bear Gag Order

EcoBridge – Causes of Global Warming – Interview with David Suzuki

Foreign Policy in Focus – Going Green

State of the Cryosphere

Wired News – New Carbon Dioxide Tracking Developed

Wikipedia – Martin Durkin (producer, The Great Global Warming Swindle)

Greenpeace – The Energy Revolution

Yahoo! News – Canadian Activist Given Hearing on Global Warming/Human Rights

Bill McKibben – The Gospel vs. Global Warming

Carbon Footprint – Calculate Your Carbon Footprint

Project Earth – Tour the Wounded Earth

EMagazine – Australia to Phase Out Incandescent Lightbulbs

Carbon Neutral Journal

Pew Center – Climate Change 101


7 Responses

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  1. ellemay said, on 3/22/07 at 5:36 pm

    Thank you for writing this complete and convincing article – you’re fab! :)

  2. […] wanted to walk through the empty streets And feel something constant under my feet, But all the news reports recommended that I stay indoors Because the air outside will make Our cells divide at an alarming rate Until our shells simply […]

  3. Curtis said, on 3/23/07 at 9:33 am

    Thanks very much for your interest, ellemay…but the real thanks are due to the dedicated scientists who are working so hard to understand climate change!

  4. Curtis said, on 3/23/07 at 1:24 pm

    Pursuant to this post’s thread on, I wanted to add some (hopefully helpful) information.

    Digg user M0b1u5 writes:

    The IPCC hockey stick has been well and truly debunked numerous times. They still keep using it. Bad data and worse analysis does not make a convincing case. Buried as inaccurate.

    First of all, the MBH98 construction (“hockey stick graph”) is not proprietary of the IPCC. It does feature prominently in the AR4 report. Secondly, it has not been “well and truly debunked” even once.

    MBH stands for Mann, Bradley, and Hughes, the authors of the study which produced this graph of temperature/composition data. Their methods focused on records from coral, the ice cores, and tree rings in addition to the contemporary instrumental record. While the MBH study has been constructively criticised on methodological and statistical grounds, never has it been “debunked.”

    One of the studies most critical of MBH98 was conducted by Stephen McIntyre (a consultant to the minerals industry) and Ross McKitrick (an economist). Their biggest criticism of MBH98 was that it exaggerated 20th Century warming by using data sets which suppressed climatic variations over the past 1000 years, specifically the “Medieval Warm Period” and the later “Little Ice Age.”

    The US Congress commissioned evaluations of MBH98 based largely on the McInture/McKitrick paper. One evaluation conducted by the National Research Council found that, while there were problems with the methodology used by Mann et al., the overall aberrations resulting from these uncertainties were “small in effect.”

    The other major study into MBH was commissioned by Representative Joe Barton (R), an outspoken global warming skeptic. Conducted by the Committee on Energy and Commerce (red flag?) and known as the “Wegman Report,” this report supported the M/M paper from a statistical angle. However, the Wegman Report has been criticized in that it was never subject to formal peer review; that studies employing different methodologies from those used in MBH98 produced similar results; and that fixing the errors alleged by the Wegman Report did not produce markedly different results.

    The IPCC would hardly place such great value in MBH98 if it were the only study of its kind. The IPCC is, after all, not a research body but a reviewing body. Numerous studies based on similar data and on computer models of varying configurations have, to varying extents, confirmed its findings.

    There is certainly room for constructive criticism of MBH98, and future IPCC reports and studies by other organizations will likely improve upon the methodologies involved in such studies. But to claim that MBH98 has been debunked is to invoke polemics inconsistent with the scientific consensus and inconsistent even with critical statements from dissenters. To call MBH98 “bad data” without further qualification is, at best, a bit obtuse. As to the quality of analysis, well, that’s up in the air. Constructive criticism is certainly welcome.

    User MacGregor writes:

    Civilizations have risen and fallen for thousands of years due to climate change. No need to sacrifice the virgin because we don’t recognize this. Mars is having a climate change right now also. It’s not us.

    This is an awfully stoic viewpoint, founded on what I would consider a straw man argument that is itself without historical basis. Civilizations have risen and fallen for thousands of years, but to what extent did “climate change” play a role in any of these scenarios? Misallocation of resources, warfare, and disease are more persistent culprits in civilizational collapses. Climate change almost certainly played a role in species extinction in the past, but we’re discussing the potentials of human-accelerated or aggravated climate change on a much shorter timescale.

    The idea that Mars is experiencing “climate change” that parallels that potentially occurring on Earth is increasingly widespread but unfounded. This argument is based on observations of instability in the southern polar cap; this instability is well-documented and is known to fluctuate in a much more volatile way than we observe on Earth. The implication of this argument is that this polar instability is a new discovery; it is not, and it is associated with regional climate peculiarities that are endemic to Mars and without a clear analogy on Earth. See this article at

    User Newbee70 had this crypticism to offer:

    Still claiming global warming with Fantasy Science. The Alarmists will not admit their crying wolf; they can’t afford to keep losing the arguments: first global cooling; now global warming.

    This is a faulty analogy and a possible case of post hoc ergo propter hoc. Global cooling was indeed a major concern in the press through the 1970s, but never had a scientific consensus behind it to rival those which support theories of human-accelerated global warming. Furthermore, there have been major improvements in climatological methodologies and understanding since the 1970s. It is true that the sensationalist fanfare in the press which surrounded global cooling provide a valuable caveat which is applicable to global warming, in that press depictions of global warming science are generally absent of the predicating precautions which are present in scientific reporting on the subject. Concern over global warming is centered on its manifestations in future centuries; the global cooling “scare” was associated with faulty datasets taken out of context, specific to the period from roughly 1945-1970.

    User magicjava posted a thorough set of denunciations of the IPCC reports and methodologies. Some of this is constructive criticism, and some of it is polemical lambasting. It is essential to recognize the uncertainties and discontinuities in research methods behind such documentation as the IPCC AR4, and to recognize that the politicization of science is certainly not limited to either side of the debate. But regurgitating dissenting opinions does not transform them into the representation of a credible majority—all available evidence indicates that global warming skeptics remain a small minority in the scientific community at large.

  5. balkanbalkan said, on 4/4/07 at 3:54 pm

    Thank you very much for this very good article.!

  6. Ray said, on 4/8/07 at 12:00 pm

    Record cold temps today. Oh wait, I thought we were warming?

  7. Bluebear2 said, on 4/13/07 at 3:47 pm

    Very good report. I never cease to be amazed at how those who who try to debunk it look at very short range evidence as their source of proofs.

    General warming will create cooling in some areas due to changes in weather patterns caused by shifts in the jet stream and ocean currents.

    If the Gulf stream continues to slow due to dilution of the sea waters by the melting ice pack at its northern subduction zone, northern Europe will cool as a result.

    While it is true that warming and cooling have occurred throughout history with carbon dioxide levels following those temperature swings, it is the rate of increase that points to other than natural causes.

    One scenario not much publicized involves the methane ice at the bottom of the deep oceans. It will take only a small rise in deep ocean temperature to cause this methane to be released adding significantly to the greenhouse gas levels.

    It is just such releases that are theorized to be at the root of the Bermuda Triangle ship sinkings and aircraft disappearances. (The bubbles released cause ships to lose bouancy and methane in the air intake of aircraft engines has been shown to stall them even in very low concentrations.)

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