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Rational Inquiry -Volume 12 Number 3

GLOBAL WARMING
A scientist looks back

By Edvard A. Hemmingsen
Emeritus Professor of Physiology at UCSD

Fifty years ago this summer, while I was at Oslo University, I co-authored a scientific paper with Lawrence Coachman and Per Scholander entitled "Gas Enclosures in a Temperate Glacier." (1) Behind this innocuous title laid a broader idea that was first proposed by Per, namely, can clues about past atmospheric air composition be obtained from gas bubbles trapped in glacier ice centuries or millennia ago?

Our glacier study in Norway was the first step in a series of investigations that would lay the ground work for answering this intriguing question. Information about past air composition would have many interesting inferences. For example, were the vast quantities of carbon dioxide that were being added to the atmosphere by our modern, industrialized societies having an impact on the carbon dioxide content of the atmosphere? Foremost on our minds was the scientific paper on the atmospheric greenhouse effect published by Svante Arrhenius sixty years earlier. He showed that carbon dioxide had a very strong greenhouse effect and calculated that a doubling of this gas in the atmosphere could increase the Earth’s mean temperature by more than 5ºC, which would cause much havoc. Some greenhouse effect is beneficial for life if maintained within very narrow limits. Indeed, it is this effect which has made the Earth livable for organisms for billions of years. Without it, the mean temperature on the Earth’s surface would be far below freezing. Now it is about 14ºC. For comparison, our planetary neighbor, Venus, has 95 percent carbon dioxide, and a surface temperature of 477ºC. Although Venus is moderately closer to the sun, the difference in distance accounts for very little of the difference in temperature between the two planets.

After finishing our studies in Norway, we organized a multinational ship expedition to West Greenland. Its primary objective was to attempt to find old air samples in ice released from glaciers in the form of large icebergs. Ice samples were collected, the extracted gas bubbles were analyzed and radio-carbon dated for age, and the ratios of oxygen-18 to oxygen-16 isotopes in the ice were measured in order to assess the temperature at the original precipitation location. This is possible because the ratio is a specific function of the temperature, and the deviation in the ratio from a reference temperature gives us the unknown temperature. This relationship has been calibrated at numerous locations worldwide.

Our endeavor had some successes. However, as was pointed out in the scientific report from our expedition (2), all of the ice samples which we collected appeared to have undergone some melting before breaking loose from the ice cap, or somehow had been exposed to liquid water. This could have affected the composition of the gas in the trapped bubbles, but would not be of consequence for the radio-carbon date determinations. It was clear that ice samples that would provide all of the desired information had to be obtained from the main ice caps of Northern Greenland or Antarctica because even in the summer temperatures stay well below freezing.

In the decades that followed other groups took up this research in international collaborations, developed coring drilling techniques that yielded the desired samples from the deeper parts of the ice caps. New methods were used to examine these samples, taking advantage of many advances made in recent decades both with gas and isotope analytical techniques. These studies on the trapped air bubbles would prove to be very important.

Concurrently with our glacier ice studies, soon-to-be academic colleagues at Scripps Institution of Oceanography in La Jolla, Charles "Dave" Keeling, persuaded and encouraged by Roger Revelle, began monitoring accurately the carbon dioxide content in present day air. Dave persistently carried out this monitoring project for nearly fifty years, until he passed away in 2005, providing precious data. We may find it amazing today, although it is not surprising to scientists in general who are familiar with arbitrary nonsensical decisions by bureaucrats, Dave at times had to struggle to obtain funds from government agencies to continue his important work. He expressed his frustration to me on many occasions.

Keeling’s results (3) are now famous and astonishingly important. He found that the carbon dioxide content in air increased gradually and relentlessly for every year of his study. It started out at 0.0315 percent in 1958, and reached 0.0380 percent in 2005. To a person not familiar with the field, this may seem like a small increase, but it is large when compared with various other data that now have been obtained for past atmospheres. Foremost of interest here are the ancient air samples extracted from ice cores taken from the icecaps in Greenland and Antarctica (Vostok Station). In particular, the ice cores from Vostok have yielded some startling information (4). For more than half a million years prior to our industrial age, the carbon dioxide content of the atmosphere changed relatively little, and always remained below the level characteristic of the early 1900s, namely about 0.028 percent. By the end of the 1900s, the carbon dioxide level had risen substantially above this pre-industrial level. The concomitant temperature record for this period was determined from the oxygen and hydrogen isotopes in the gas from the ice cores. These show that there have been cyclical changes in the temperature over time. But these changes until the last century have remained within the range of +/-2ºC, and occur in precise unison with the changes in the carbon dioxide content. These temperature fluctuations have been confirmed for the last 1000 years by such methods as studies of tree rings, lake sediments and historical data. Altogether, we know that there has been about a one degree rise in global mean temperature just in the last hundred years. But from the current rate of increase in atmospheric carbon dioxide, it has been estimated that its content probably will more than double in the next hundred years, leading to a mean global temperature rise of several to as much as 10ºC, the latter being more than that predicted by Arrhenius.

In the most recent decades, the warming has been directly determined by measurements, for example, from satellites and by probes placed in the oceans and on land. It is also visible to anyone who cares to look: glaciers are rapidly receding worldwide, the icecaps of Antarctica and Greenland are shrinking, the Arctic polar sea ice cap is thinner and more open water is present in the summer, the permafrost of the Arctic is thawing, causing highly visible damage to buildings and other structures, including oil pipelines.

The continuous record of temperatures that we now have is based on unassailable scientific measurements and statistical analyses. Virtually all geophysicists, climatologists and other experts with competence to evaluate the various scientific data agree that (a) there has been a sharp increase in the carbon dioxide level in the last decades, (b) there has been a concomitant increase in the surface temperature of the Earth, and (c) both parameters are increasing at an accelerated rate because of carbon dioxide pollution from human activities. The correlations among the different sets of data are far too strong to be fortuitous. Those who denied the warming trend just a few years back have largely conceded it is occurring or, belatedly, have drifted into obscurity. The only issue still being challenged by a few, mostly politicians, bureaucrats and others with little or no scientific expertise, is whether or not the warming is caused by atmospheric carbon dioxide. They even question that human activities are the source of the carbon dioxide buildup. They reject all of the solid scientific data that exist to support the scientists’ conclusions. Data with confidence levels of 95 percent are summarily dismissed. These deniers often claim that "proof" is missing. Indeed, if actions taken were dependent on scientific proofs, we still would be in the Medieval age. Only mathematics deals with absolute proofs; science deals with probabilities.

Whereas the deniers may raise their unwarranted, even irrational objections, rational people have for many years had cause for alarm. Even in the sixties when the direct empirical evidence for systematic warming was far more skimpy and our understanding of many climatic processes was very limited, a number of scientists expressed concern about the carbon dioxide pollution and the climatic effects it may have, simply by knowing that billions of tons of carbon dioxide were put into the atmosphere every year. Such quantities added a substantial amount to the total carbon dioxide content naturally present on Earth. It was rational to predict that this was bound to have consequences.

It is an undeniable fact that water vapor and carbon dioxide will reflect some of the solar radiation back towards the Earth’s surface, preventing it from escaping into space, and as a result causing a general warming trend such as we are observing now. The energy in the form of heat just cannot disappear. Yet, some have sought to ascribe warming to natural cyclical variations in the radiation emitted by the sun, in the Earth’s distance from the sun, in the reflections from clouds, etc., but no credible evidence has been offered to show that any of these processes — or any other one — are large enough to contribute significantly to the observed rate of warming. Our greatest concern now should be that we have superimposed an increase in the greenhouse effect upon the normal variability, leading to conditions that have not existed for hundreds of thousands of years, or longer. That is, we have added a new warming factor to those which caused climatic changes in the past.

The long range consequences of these new conditions are unknown, but could be very serious, even catastrophic. The many problems that we are likely to be faced with in the not so distant future have been extensively dealt with in both the scientific literature and the public media, and much of this information can be found by Internet searches. Also, a documentary movie on global warming, featuring Al Gore, An Inconvenient Truth (Director David Guggenheim), was released recently. This movie gives a largely correct picture of the future events which likely will occur as a result of the warming. It is faithfully based on the existing scientific knowledge, although some details are arguable and the timing for disasters could be off by two or three decades. However, the thrust of the message of the film is definitely on target.

There are factors that may make conditions worse than anticipated. These are the "feedback loops" that may accelerate events and cause runaway warming. One is the loss of light reflection from shrinking polar ice masses. Others have barely surfaced in the public debate. For example, large quantities of greenhouse gases may be released from melting and decaying permafrost. The decrease in gas solubility which occurs with increasing temperatures in the oceans is another factor that will furnish more carbon dioxide to the atmosphere. Methane gas, which has a strong greenhouse effect, may be released from the vast deposits of solid methane hydrates (clathrates) that exist in many places on the ocean floor if there is an elevation of just a few degrees in water temperature. These scenarios would all add to the greenhouse effect generated by burning fossil fuels.

We are now at a critical point with respect to the degree of warming that societies worldwide will be able to accommodate later in this century. Perhaps we have already missed the juncture for making a truly meaningful, positive impact. It must be recognized that due to the ocean’s large buffering capacity for both temperature and gases, what already has been added to the system no doubt will influence the climate for decades and possibly centuries to come. Thus, even if we could reduce the carbon dioxide emissions to a trickle now, the global warming trend would stay with use for a long time. But we should, indeed must for the sake of our descendants, try to do the best we can.

How did we get on this calamitous course? There is enough blame to dispense. Politicians and special interest groups as well as an apathetic public deserve major blame. Perhaps scientists were not strong enough in communicating their findings to the public. For a number of years it has been evident that the early warnings about climatic changes, with global warming, were justified. But few of our leaders cared to listen to this message, and hardly anybody took it seriously. With some rare exceptions, this ignorance has continued until today. No administration in this country has ever engaged in any real efforts to mitigate the warming process, even though the evidence showing that the process potentially could be very harmful. Certainly, the scientific evidence has been convincing for more than a decade. The situation, which has progressed from levels of doubt to reckless neglect, has been particularly exasperating during the years of our current administration.

Some obvious steps could have been taken — and still can be — to blunt the warming problem, but they would require a serious national program beyond the effort and cost level of the moon-landing project. The emission of carbon dioxide has to be reduced substantially — now! Equally important, the use of available non-polluting energy generating technologies must be vastly expanded, and new ones must be developed. These include power systems using nuclear technologies, photovoltaic solar cells, and wind driven turbines. It is essential that new non-polluting technologies be developed; the costs for this must not be a barrier. Radically reducing the rate of population growth around the world, and hence, the ever increasing energy demands, clearly would contribute to solving the problem in a big way. It would be necessary that the other industrialized countries, as well as those to be, participate in the reduction of pollution and the developments. They now produce three quarters of the total carbon dioxide emission in the world.

Are such actions likely to be implemented? In other countries with emerging industrial capabilities, probably not for a long while. In this country, not until we get a new type of leadership in the White House as well as in Congress. We need leaders who will place the welfare of the country and its people above their own personal interests. And this will not occur until the public becomes more informed, more concerned — and outraged.

References

1. Tellus, No. 4 (1956): 415-423.

2. Medelelser om Grønland, Vol. 165 (1962): 1-26.

3. Annual Review of Energy and Environment, Vol. 23 (1998): 25-82.

4. Nature, Vol. 399 (1999): 429-436.

Dr. Edvard Hemmingsen is Emeritus Professor of Physiology at the University of California, San Diego.


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