Global Change

 Global Warming
    1. - Great Experiment on Planet Earth
    2. - Kyoto & Its Implications
    3. - The Rise of CO2 & Warming
    4. - The Scientific Assessment
    5. - Controversy & Debate
    6. - Scientific Background
    7. - Predicting the Future
    8. - Predictions for California
    9. - About this Site
    10. - Sources of Information

 The Greenhouse Effect
 The Keeling Curve

GLOBAL WARMING: Controversy & Debate

There is much resistance to accepting the explanation that most of the observed warming of the last fifty years is indeed a result of release of greenhouse gases to the atmosphere, by human activities. A Wall Street Journal editorial from April 17, 2001 described the Kyoto Protocol as “ill-conceived and the science highly dubious”, adding that it was an “ineffective and misguided proposal.” Another editorial from the same publication on March 17, 2001 stated, “There remains, for example, no consensus on what global warming really means for the earth, much less whether restricting CO2 is really a solution.” The Wall Street Journal may be assumed to reflect (or attempting to reflect) the view of the business community. The concern is that dealing with the CO2 problem will interfere with the health of the economy. Thus there is a reluctance to admit that there is a problem in the first place.

We should be clear on one point: admitting that there is a problem is not the same as endorsing a proposed solution.

It is disturbing that many commentators seem to miss this point.

Many newspapers have commented on cold spells in recent years, implying they weaken the case for global warming (for example, a cartoon similar to this one appeared in the Columbus Dispatch on January 9, 2001). Global warming refers to a long-term trend. Short-term events are interesting but have no bearing on the problem.
Not all the critics of the global warming consensus are non-scientists. A small group of vocal scientists (known collectively as “climate contrarians” or “greenhouse skeptics”) keep emphasizing the well-known uncertainties in all climate assessment. One of these contrarians is a distinguished meteorologist at MIT. He thinks that humanity’s impact on climate is negligible and insists that carbon dioxide doubling will bring about only a 0.4 degree Celsius rise in global temperature rather than the 1.5 to 5.8 degree increase predicted by the climate modelers reporting to the IPCC. Another critic of global warming, a physicist and former director of the U.S. Weather Satellite Service, issued the following warning,

The United States and other industrialized nations are on the brink of adopting policies that will ruin national economies, and drive manufacturing and other industries into less developed and less regulated countries ... all to mitigate "disasters" that exist only on computer printouts and in the feverish imagination of professional environmental zealots.

This same critic equated the Kyoto Protocol to a vampire: “You need to drive a stake through its heart. Otherwise it'll keep coming back and causing problems.”

How should we view the pronouncements of the “contrarians”?

In the face of uncertainty there is, of course, room on the fringe. However, there is such a thing as scientific consensus, that is, a judgment arrived at by the great majority of those concerned. While there is no guarantee that the majority has the correct view (science is not done by voting), it is probably unwise to disregard that view without good evidence forcing us to do so.

Those who stand away from the climate consensus often cite the following points:
  1. Computer modeling is unreliable. For example, the models do not resolve small-scale processes, such as local atmospheric convection. In addition, it is difficult to integrate processes that operate on different time-scales – as when the models try to couple the atmosphere to the ocean.
  2. Atmospheric physics is not well understood, largely due to our gaps in understanding of how the climate system deals with cloud feedback.
  3. Climate reconstruction is unreliable since it is done, in part, by incorporating statistical behavior of questionable reliability.
These points are not without merit. However they do nothing to decrease the risks inherent in the Great Experiment. They merely point to the fog ahead, but say nothing about whether we are likely to run up on a reef.

Indeed, different computer models do give different results, in detail. However, they also agree on some things. Where they agree is in showing an overall warming in response to greenhouse gas increase. This warming is greater in high latitudes than in low latitudes. In low latitudes, increased cloud cover presumably provides for increased shading, slowing the warming.

Admittedly, also, cloud physics is poorly understood. Dr. Richard Somerville, a meteorologist and professor at UC San Diego, is an expert on this subject. In his book, “The Forgiving Air,” he explains, “Clouds contribute to the greenhouse effect, by trapping heat, while at the same time contributing to the Earth’s albedo, by reflecting sunlight away. In the present climate…the cooling dominates, but both effects are strong. Clouds have, in other words, powerful, competing effects on the heat balance of the Earth.” So to get things right, we have to consider circumstances and we have to know what types of clouds are involved.

Lastly, different reconstructions of past climate do give different results. But they do agree on some things, for instance, an unusually warm early Middle Ages (during which time Viking settlements were founded in Iceland and Greenland). This was followed by the onset of cooling after AD 1200 and the start of the so-called “Little Ice Age” that lasted from roughly 1350 to 1850 – a chilly period whose origins are still unknown.

The large error bars on the temperature calculations and climate reconstructions make the prediction of future developments quite difficult.

How, then, can one proceed with the risk assessment that is necessary to make informed policy decisions?

The risks of scaling back on carbon-based energy are quite different for different nations, as are the potential benefits of reducing emissions. The nations where risks of emission reduction outweigh the potential benefits will insist that more studies are needed before decisions can be made. The larger the region occupied by a nation, the greater the resilience to possible problems. Thus, we would expect the USA, Russia, China, India, Canada, and Australia to be less interested in the problem than for example Egypt, Bangladesh and the Pacific island nations.

Ultimately, however, these competing levels of concern – which have their basis in geography, politics and economics – should not be allowed to get in the way of the strictly scientific question: Is the Earth warming and are anthropogenic greenhouse gas emissions to blame? And, if so, what consequences are to be expected for further warming?

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