This week the Senate began considering legislation to combat global warming. A carbon dioxide emissions “cap-and-trade” system, it seems to have little chance of becoming law. It is, however, a welcome sign that our government is beginning to come to grips with a problem that has the entire world worried. In this week’s column I would like to step back and consider the science behind the mess we’ve gotten ourselves into. We as a nation cannot hope to implement the sort of changes necessary to achieve a sustainable world if we as citizens do not clearly understand the nature of the problem we face.
So how did we get into this mess? In a nutshell, we grew into it. The 20th Century has been characterized by the unbridled use of resources to fuel growth, with no thought to pollution or future scarcity. If we are going to deal with global warming, it seems to me important that we take a careful, detailed and unvarnished look not only at global warming, but also at other ways we are modifying our planet. How we have successfully delt with other problems may suggest how we could best approach this one.
Our planet is changing in many undesirable ways as we enter the new century, some very obvious, others less so. Here I would like to examine four. They are by no means the only problems the global ecosystem faces, but a close look at them reveals common elements that I suspect apply very broadly. The four sorts of global change I would like to consider are: 1. the ozone hole; 2. acid rain; 3. global warming; and 4. unsuspected chemical pollution. The first two represent problems that we have solved, the last two, not. Thus the comparison can be very instructive.
1. the ozone hole. I am sure most of you are familiar with the ozone depletion story. It is useful to start with it, as several aspects will prove important in other global change problems. Here the story starts with a scientific invention in the 1920s, a class of miracle chemicals called chloroflurocarbons (CFCs) soon used worldwide as coolants in air conditioners and refrigerators, as the gas in aerosol dispensers, and as the foaming agent in styrofoam. Very stable, almost all the CFC molecules made for 80 years are still around. Where are they? Released into earth’s atmosphere. Then atmospheric scientists reported in the 1980s that the accumulating CFCs were depleting the earth’s ozone shield. By now, after 20 years, the drop in ozone worldwide is over 3%, and has led to a 20% increase in lethal melanoma skin cancer. Fortunately, the world community has acted in a concerted way to phase out the manufacture of most CFCs. The situation now appears to be improving, and computer models suggest the Antarctic ozone hole should recover in another 50 years.
The problem in a nutshell: chemical pollution, allowed because the chemical (CFCs) was felt to be harmless.
2. acid rain. A very similar picture is seen when we consider another form of worldwide atmospheric pollution, that which leads to acid rain and snow. Here the scientific innovation was the invention in Britain in the mid-1950s of tall smokestacks. When high-sulfur coal is burned in powerplants with such tall stacks, the stinky smoke with its high concentrations of sulfur dioxide is delivered high into the atmosphere, its stench undetectable at ground level. Winds disperse and dilute it, carrying the sulfates far away. The problem, of course, is that the sulfates are not in fact harmless chemicals. In the atmosphere SO2 (sulfur dioxide ) combines with H2O (water) to form H2SO4 (sulfuric acid). By 1970 scientists began reporting that these acids were having drastic effects far downwind. Lakes and forests in northern Europe and in the eastern United States and Canada were literally dying, the acid killing the soil fungi called mycorrhizae needed by tree roots to live. Over 1.4 million acres of forest have been affected. In recent years, clean air legislation has gone a long way towards improving the situation, with chemical “scrubbers: being installed on smokestacks.
The problem in a nutshell: chemical pollution, allowed because the chemical (SO2) was felt to be harmless.
3. global warming. In recent years the most talked-about aspect of planet modification has been climate change, more simply and directly referred to as global warming, the direct result of another form of worldwide atmospheric pollution. The scientific advance that has led to global warming was the industrial revolution: more than two centuries of widespread burning of fossil fuels (coal, oil, gasoline, all of them the highly compressed remains of ancient plants) to obtain energy. Fossil fuels are the remains of plants that have been squashed under high pressure for a long time. A plant body is composed largely of woody stuff — what a chemist calls cellulose and hemicellulose — basically, molecules that are long chains of sugars linked together like pearls on a necklace. All that is left after all that squishing are short bits, a black gooy mix we call petrolium. The burning of petrolium and the so-called fossil fuels made from it is a process a chemists calls “oxidation”– in essence, the energy of their many C-H chemical bonds is released as heat, and the left-over carbon molecules (C) are combined with oxygen gas (O2) to form carbon dioxide (CO2). As the decades passed, the levels of CO2 released into earth’s atmosphere continually increased. The unanticipated problem is that CO2 is a greenhouse gas — The C-O chemical bonds absorb longer wavelengths of sunlight, readmitting them as heat, much as the glass of a greenhouse does. If our earth did not have CO2 in its atmosphere, it would be much colder here — about minus 20 degrees C, instead of today’s plus 15 degrees C. But we are now getting too much of a good thing. Current estimates are that increases in the amounts of greenhouse gasses like CO2 may increase average global mean temperatures as much as 4 degrees in this century, an enormous amount that will raise sea levels as ice caps and glaciers melt, will alter global rain patterns, and will seriously affect agriculture. Global efforts to abate CO2 emmissions have so far been thwarted by the failure of major industrial powers like the United States to cooperate, and by lack of inclusion of fast developing countries like China and India. That the United States Senate has awoken to the need for action is a very encouraging sign.
The problem in a nutshell: chemical pollution, allowed because the chemical (CO2) was felt to be harmless.
4. unsuspected chemical pollution. The pollution of the world’s air and water by industrial and agricultural wastes is not a new story to any of you. Automobile-induced smog in big cities is certainly not a new thing. When the problem became acute in California and other parts of the United States, legislation putting catalytic converters onto car exhausts has gone a long way toward solving the problem. The more serious problem, as I see it, isn’t this sort of chemical pollution, where the effect is obvious and the issue is effective policy. The more serious problem is chemical pollution where the effects are not obvious. I want to discuss just one, as it provides a good example of just how scary this sort of pollution can be: breast cancer and a chemical called bis-phenol A.
An estimated 213 thousand new cases of invasive breast cancer occured in the United States during 2007, less than 2 thousand of them among men — over 99% of the new breast cancer victims were women. Similarly, of 40,870 breast cancer deaths that year, all but 460 of them were women. It is impossible not to wonder, why so few men? An obvious answer would be that men don’t have breasts, but men do have breast tissue, it just isn’t as developed as a woman’s. So we are back to the same question: why so few men?
While 5% of breast cancers are due to inherited genetic mutations (BRCA1 and BRCA2), the cause of 95% — the overwhelming majority — remains a mystery. Hormone differences seem the most promising place to start, as the female sex hormone estrogen controls breast development in women; men, by contrast, lack physiologically significant amounts of estrogen. A logical suggestion is that in breast cancer patients the effect of estrogen on breast cells is being altered by exposure to a so-called “endocrine disruptor.” Endocrine disruptors are man-made chemicals that mimic hormones. By sheer chance, their molecules are perfectly shaped to fit particular hormone receptors. In this case, the culprit would be a chemical mimic of estrogen that promotes cancerous growth in breast cells.
One logical candidate is bisphenol A (BPA), a molecule which like estrogen has carbon rings at each end tipped with OH groups. Used to form the plastic packaging of many foods and drinks, as well as the clear plastic liners of metal food and beverage cans, BPA is a chemical to which all of us are exposed daily. Six billion pounds are produced worldwide each year.
It has been known since 1938 that BPA promotes excess estrogen production in rats. Alarmingly, in 1993 (15 years ago!) BPA was shown to have the same effects on human breast cancer cells growing in culture. What was alarming was that the effect could be measured at concentrations as low as 2 parts per billion, not much above the levels to which we humans are routinely exposed.
Does BPA in fact induce breast cancer? Dr. Ana Soto of Tufts University School of Medicine did a simple experiment in 2006 to find out, exposing laboratory rats to BPA and looking for evidence of increased breast cancer. She found that exposure to even low levels of bisphenol A induced ductal hyperplasias (precursors of breast cancer) in her laboratory rats, suggesting the rather alarming conclusion that BPA, a chemical to which we are all exposed every day, may indeed cause breast cancer. While the study is small and a rat is not a human, a new draft report released this spring by the National Toxicology Center of the National Institutes of Health says low levels of exposure to BPA can also cause changes to mammary gland tissue in human infants, indicating potential long term risks of breast cancer in humans as well. Acting on the precautionary principle, Canada has now banned BPA. Most government-funded breast cancer research in the United States has focused on the search for more effective breast cancer treatments; far less money is spent on searching for the causes of breast cancer. More should be.
The problem in a nutshell: chemical pollution, allowed because the chemical ((BPA) wasa felt to be harmless.
You can see the pattern emerging from these four examples of planet modification. Each is the result of chemical pollution, allowed because the chemical was felt — mistakenly — to be harmless. Now, with this general picture as a background, I would like to talk for a minute about the role science has to play in addressing these sorts of problems, and others we have not yet recognized.
The first and key role of science is to identify the problem. As those who have struggled to increase public awareness of global warming know only too well, identifying a problem is not the same thing as recognizing it. Science’s role in this regard is that of watchdog, to sound an alarm when scientific data suggest a serious problem may have arisen. Lets look at our four cases of chemical pollution to see how this works:
ozone depletion. The impact of CFCs on ozone became great enough to begin the ozone hole in 1975, as judged by satellite photos. It as first noticed by atmospheric researchers in Antarctia four years later, in 1979. Within four years after that, by 1983, 180 countries had signed an international agreement to phase out the manufacture of CFCs. Not bad. Four years for scientists to identify the problem and four years to recognize and address it, NGOs and policy planners goading government to action.
acid precipitation. The first tall stacks were built in the mid-1950s. The impact of acid rain and snow on forests and lakes was first reported in the early 1970s and became impossible to ignore by 1980. In the United States the problem was addressed by the Clean Air Act revisions of 1990 mandating abatement (basically, scrubbers on the stacks to remove the SO2). So eight years to identify the problem and ten more years to recognize and address it.
global warming. Starting in the 1980s, a sharp rise was noted by geoscientists in global mean temperature; looking at past records, it immediately became clear that the rise represented an acceleration of a general increase since the 1950s. It was not long before parallel increases in atmospheric carbon dioxide levels were noted. UCSD scientist Charles Keeling reported in 1955 that levels of COs were rising in air samples each year, and were now 30% higher than in pre-industrial times. The possibility of a relationship leaps out when you compare the two sets of data: if you plot CO2 concentration on a graph vs. global mean temperature, you get a nice line — the two variables are highly correlated. Responding to this, many scientists argued on the grounds of precautionary principle that governments worldwide should immediately institute CO2 emission caps.
But — and this is one of the most sticky points of science — correlation is not causation. Because two things tend to occur at the same time does not prove that one causes the other. The proof came a decade ago, when a British statistician showed that the variance (a measure of the amount of random scatter in data) in annual global mean temperature is strongly correlated with the variance in atmospheric CO2 levels — because scatter is random, this can only be true if the two variables are indeed entrained, one directly linked to the other. Any scientific controversy ceased with this report: increasing CO2 is causing global warming.
So, ten years for scientists to clearly identify the problem. As I speak, twelve years after this identification, the world is still in the process of recognizing and addressing the problem, although with international protocols, last year’s Nobel Prize, and this week’s action in the United States Senate, we seem well on our way. Although China, and India, with the U.S. the world’s principle releasers of CO2, are not yet taking action, there is reason to hope they will soon begin to move in this direction.
breast cancer. While bis phenol A was linked to estrogen levels in human breast cells in 1993, the link to breast cancer was not established until 2006, and is not yet firm. Much additional research will be required before scientists are sure. Until then, the identification of this problem must be considered preliminary, and its recognition by countries like Canade precautionary.
The second role of science is to provide ways to solve the problem. So as we confront planetary climate change, I think its important to be optimistic. The general pattern we see in these four instances convinces me that global warming is a souble problem — while more complex, not intrinsically different from the other three. With ozone, the solution was relatively simple, a safe chemical substitute for CFCs and legislation to mandate the change. With BPA the solution can be anticipated to be much the same, also a straightforward chemical substitution. With acid rain, the solution was again direct, scrubbers to remove the SO2 from coal smoke before it is released into the atmosphere, and clean air legislation to mandate their use. Global warming demands a more complex solution — basically we need to shift to alternative energy sources that do not increase the atmosphere’s carbon load. The mix will certainly include nuclear, solar, and wind power. It must not include the burning of coal, no matter that coal may plentiful, as coal is simply a hard form of fossil fuel and its burning adds CO2 directly to the atmosphere just as burning petrolium does. As automobiles are an important contributor to atmospheric CO2 pollution, it will be important to find a carbon-neutral substitute for gasoline as soon as possible. While solar, electric, and hydrogen powered cars are all being explored, I feel strongly that a transitional solution will be required, and that biofuels like ethanol and methanol offer a very promising possibility. In this regard, it is important to understand two things:
1. Burning biofuels does not add extra carbon dioxide to the atmosphere. Burning ethanol obtained by fermenting plant tissue simply releases into the atmosphere CO2 just removed from it by photosynthesis; there is no net increase in CO2.
2. Biofuels have nothing to do with food. Or at least they certainly should not. Corn kernals, rich in starch, are currently being used in the United States as the principle source of ethanol. A starch molecule is a long chain of glucose (a 6-carbon sugar) molecules. To get ethanol, the chain is cleaved by enzymes into individual glucose units, which are then fermented by yeasts to make ethanol, just like making beer. But there is no reason, other than making money for corn producers, to use starch to make ethanol. Starch is only 40% of a commercial corn plant’s biomass, and less than 10% of the biomass of most plants. The bulk of a corn plant — indeed of any plant — is composed of cellulose (chains of 6-carbon sugars like starch, but linked together differently) and hemicellulose (the same kind of chains, but of 5-carbon sugars). The reason you can’t eat grass is that you don’t have the enzyme necessary to break the chemical bonds linking the sugars of cellulose and hemicellulose. Termites do, which is why they can eat wood. Bioengineers have succeeded in transferring the necessary enzymes from termites into yeasts, which then can ferment all of the plant to ethanol. So rather than using farmland the world need to produce food, biofuels can be made from plants like switchgrass, which grows with high productivity on poor soils not suited for agriculture. They can even be made from municiple dumps, wich are 80% cardboard and paper! The United States should be devoting major resources to develop the process engineering required to up-scale this cellulosic ethanol process from the labatory to the market place.
It is easy to become discouraged when considering the world’s many environmental problems, but do not lose track of the single most important conclusion that emerges from our examination here of these problems — the fact that each is soluble. What is required is a clear understanding of the problem in each instance and a commitment to doing something about it. Because these problems are global in nature, we cannot simply assume they are too complex for solution, or wait for other countries to solve them. All countries will have to work effectively together as we set out designing and implementing workable solutions. The consideration of approaches to combat global warming by the U.S. Senate this week is a welcome first step. It cannot be the last.
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