To a significant extent, the issue of climate change revolves around the elevation of the commonplace to an ominous omen. In a world where climate change has been the norm, it's now taken as punishment for sinful levels of consumption. In a world where we experience temperature changes of tens of degrees in a single day, we treat changes of a few tenths of a degree in some statistical residue, known as the globally averaged temperature anomaly or GATA, as portents of disaster.
Earth has had ice ages and warmer periods. Ice ages have occurred in a 100,000-year cycle for the past 700,000 years, and there have been previous interglacial periods that appear to have been warmer than the present, despite lower carbon-dioxide levels. More recently, we have had the medieval warm period and the little ice age.
For small changes in the GATA, there is no need for any external cause. The earth never is exactly in equilibrium. The motions of the massive oceans, where heat is moved between deep layers and the surface, provide variability. Examples include El Niño, the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation, etc. Recent work suggests that this variability is enough to account for all change in the GATA since the 19th century. To be sure, man's emissions of carbon dioxide must have some impact. The important question, however, is how much.
A generally accepted answer is that a doubling of carbon dioxide in the atmosphere (it turns out that one gets the same value for a doubling regardless of what value one starts from) would perturb Earth's energy balance about 2 percent and this would produce about 2 degrees Fahrenheit warming in the absence of feedbacks. The observed warming over the past century, even if it were all because of increases in carbon dioxide, would not imply any greater warming.
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However, climate models predict that a doubling of carbon dioxide might produce more warming: 3.6 degrees to 9 degrees Fahrenheit or more. They do so because within these models the far more important radiative substances, water vapor and clouds, act to greatly amplify whatever an increase in carbon dioxide might do. This is known as positive feedback. Thus, if adding carbon dioxide reduces Earth's ability to cool itself by emitting thermal radiation to space, the positive feedbacks will further reduce this ability.
It is acknowledged that such processes are poorly handled in current models, and there is substantial evidence the feedbacks may be negative rather than positive. For example: 2.5 billion years ago, the sun's brightness was 20 percent to 30 percent less than it is today, yet the oceans were unfrozen and the temperatures appear to have been similar to today's.
This was referred to by Carl Sagan as the "early faint sun paradox." For 30 years, there has been an unsuccessful search for a greenhouse gas resolution of the paradox, but it turns out a modest negative feedback from clouds is entirely adequate. With the positive feedback in current models, the resolution would be essentially impossible.
Interestingly, according to the United Nations' Intergovernmental Panel on Climate Change, the greenhouse forcing from manmade gases is already about 86 percent of what one expects from a doubling of carbon dioxide (with about half coming from methane, nitrous oxide, freons and ozone). Thus, these models should show much more warming than has been observed. But they have arbitrarily removed the difference and attributed this to essentially unknown aerosols.
The IPCC's claim that most of the warming since the 1950s is because of man as- sumed that cur- rent models adequately accounted for natural internal variability. The failure of these models to anticipate that there has been no statistically significant warming for the past 14 years or so contradicts this assumption.
However, the modelers chose not to stress this. Rather, they suggested that the models could be further corrected, and that warming would resume by 2009, 2013, or even 2030.
Global warming enthusiasts have responded to the recent absence of warming by arguing that the past decade has been the warmest on record. We are still speaking of tenths of a degree, and the records have come into question. But since we are, according to these records, in a relatively warm period, it is not surprising the past decade was the warmest on record.
Given that the evidence suggests that anthropogenic warming has been greatly exaggerated, so is the basis for alarm. But this basis would be weak even if anthropogenic global warming were significant. Polar bears, arctic summer sea ice, regional droughts and floods, coral bleaching, hurricanes, alpine glaciers, malaria, etc., all depend not on GATA, but on a regional variables including temperature, humidity, cloud cover, precipitation, direction and magnitude of wind, and the state of the ocean.
This is not to say disasters will not occur as they always have. Fighting global warming with symbolic gestures certainly will not change this. However, history tells us that greater wealth and development can profoundly increase our resilience.
One may ask why there has been the astounding upsurge in alarmism in the past four years. When an issue such as global warming is around for more than 20 years, agendas are developed to exploit it. The interests of the environmental movement in acquiring power, influence and donations are reasonably clear.
So, too, are the interests of bureaucrats who seek control of carbon dioxide. After all, carbon dioxide is a product of breathing itself. Politicians see the possibility of taxation that will be happily accepted to save the earth. Nations see exploiting the issue to gain competitive advantages. So do private firms.
Take the case of Texas energy firm Enron. Before disintegrating from unscrupulous manipulation, Enron was one of the most intense lobbyists for the Kyoto Protocol. It had hoped to become a trading firm dealing in carbon-emission rights. This was no small hope. These rights are likely to amount to trillions of dollars, and the commissions will run into many billions.
It is probably no accident Al Gore is associated with such activities. The sale of indulgences is in full swing, with organizations selling offsets to one's carbon footprint while sometimes acknowledging that the offsets are irrelevant. The possibilities for corruption are immense.
Finally, there are well-meaning individuals who believe that in accepting the alarmist view of climate change, they are displaying intelligence and virtue. For them, psychic welfare is at stake.
Clearly, the possibility that warming may have ceased could provoke a sense of urgency. For those committed to the more venal agendas, the need to act soon, before the public appreciates the situation, is real. However, the need to resist hysteria courageously is equally clear. Wasting resources on symbolically fighting ever-present climate change is no substitute for prudence.
Lindzen is the Alfred P. Sloan professor of atmospheric science at the Massachusetts Institute of Technology.
THE FREE LANCE-STAR (FREDERICKSBURG, VA.)