Introduction to Global Warming:
Greenhouse warming has existed for quite some time, arguably since Earth was first formed. Greenhouse gases, or gases conducive to the greenhouse effect, act like a blanket or the panes of glass in a greenhouse’s walls; they reflect the heat the earth would radiate into space back down towards the earth, holding it in. You see, the balance of heat on earth is maintained by different processes. Solar radiation approaches the earth, and clouds and the atmosphere reflect some of it back into space.
More radiation is absorbed by the atmosphere, clouds, and the surface of the earth. Then the earth radiates the heat back as infrared radiation. To maintain a certain, constant temperature, the rate that Earth emits energy into space must equal the rate it absorbs the sun’s energy. The greenhouse effect’s refusal to allow a certain amount of this terrestrial radiation to pass keeps the Earth’s average surface temperature at about 60°F (15°C). If there were no greenhouse gases in the atmosphere, most of the heat radiated by the Earth’s surface would be lost directly to outer space, and the planet’s temperature would be 0°F (-18°C), too cold for most forms of life (Greenhouse).
There are several atmospheric gases that act as greenhouse gases (GHGs). The most infamous is carbon dioxide, which is emitted through the respiration of humans and animals, the burning of fossil fuel, deforestation, and other changes in land use. Carbon dioxide is the main focus of many greenhouse gas sanctions, since it is the greenhouse gas that has most been released into the atmosphere. However, some other gases may have a greater effect upon climate than CO2. If one examines research into the possible warming effect of other GHGs relative to CO2, one finds that over a 100-year period, there are gases present in far smaller amounts that have a much more concentrated effect. Methane, a gas produced by livestock (flatulence), oil and gas production, coal mining, solid waste, and wet rice agriculture, has 11 times more warming potential per volume than CO2 (Science), or 25 times more per molecule (Clarkson). Nitrous oxide, produced mainly in connection with current agricultural practices, has 270 times more warming potential per volume over this period than CO2 (Science). Chlorofluorocarbons (CFCs), the gases used as refrigerants and in aerosol spray dispensers that were banned some time back due to their ozone depletion potential, have 3400-7100 times more warming potential per volume than CO2 (Science). Hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), the CFC substitutes, have a slightly smaller warming potential at 1200-1600 times larger per volume than CO2 (Science).
And so, as one might infer, studies are showing that additions of GHGs may cause the earth to get warmer than it naturally would. This is what is referred to as anthropogenic (human-caused) global warming. Many times, the terms global warming and climate change are used interchangeably. (We will do the same, for continuity’s sake.) But, this is not correct and the concepts are different. Climate change includes precipitation, wind patterns, and temperature. It also refers to the whole climate, not just weather conditions of one place. Global warming is an indication of climate change. It is an example of a climate change that has the atmosphere’s average temperature increase. Earth has experienced much warming and much cooling throughout its history. There is a great deal of debate as to whether or not the earth is experiencing a globally warming climate change and, if it is, whether the underlying causes are man-made or natural. Different research has given different results.
However, even when greenhouse gases were arguably at a stable level, before the onset of the Industrial Revolution, Earth’s climate tended to fluctuate widely. A period from 5,000 to 3,000 BC (when civilization began) is called the Climatic Optimum and another period from 900 – 1200 AD is called the Little Climatic Optimum or the Medieval Climatic Optimum, both so named for their unusually warm temperatures. Likewise, a period from 1550 to 1850 is known as the Little Ice Age for its unusually cold temperatures (Pidwirny). At this time, glaciers in southern Norway reached their greatest extent in 9000 years (Keigwin). With such large variations possible, it is difficult to know where the next natural fluctuation could take us. Perhaps those who find that global climate is warming are simply measuring a natural fluctuation. Or perhaps a natural fluctuation is masking the real effect of GHGs on the globe.
Global Warming: Big Questions, Big Research
As mentioned previously, there is a great debate over whether or not humans are causing global warming. Some activists and researchers have resorted to name-calling or accusing the opposing side of having “sold out” to one special interest or another. As mentioned previously, we have attempted to cut away the personal attacks between the opposing sides, search for the kernel of truth (or logic, where truth cannot be discerned), and get down to the heart of the matter.
In order to properly read any of the reports or research on global climate change, one must keep in mind that nothing (or almost nothing) is certain. Everything has a certain degree of uncertainty, a certain flavor of the unknown. There really is no conclusive evidence of global warming, and many scientists in favor of the global warming hypothesis say that it will be a decade or more before it is possible to develop any substantial evidence. As an anonymous senior climate modeler has said about global warming, “The more you learn, the more you understand that you don’t understand very much” (Kerr – Greenhouse Forecasting). Global climate is by nature always fluctuating, and that only adds to the confusion about anthropogenic global warming. If there were an anthropogenic global warming, we couldn’t be sure what temperature we were supposed to be at, as climate shifts are a natural part of life on Earth. Compounding that confusion is natural variability, which is always working to confuse researchers just as they come close to attributing a perceived change in average temperature to some external factor, such as atmospheric composition (GHGs) or solar variation. One reason for this variability is the long adjustment time of the oceans’ heat storage and current systems. It is estimated to take several hundred years for water to circulate from the deepest portions of the oceans back to the surface. This means that if, for example, a pool of extra cold water is singled out and stored in the depths by some freak mechanism, it could stay there a century or two before resurfacing and producing a local, cool climate change (Clarkson, North, and Schmandt).
Since no one can create another Earth (let alone one that behaves exactly like ours) and perform atmosphere-altering experiments on it, we are left with the alternative of theorizing based on observations. In other words, the only way we can purport to know anything about what might be changing in our climate is by playing with data, such as records of temperature, borehole measurements, etc., and seeing what scenarios the data will agree with.
Most of the body of global warming theory is based on computerized climate models called global circulation models or GCMs, for they are almost the only tools global warming researchers have. GCMs are difficult to make as making them properly involves a deep-rooted understanding of the way the atmosphere works and how its actions are interconnected with other planetary bodies, such as the oceans or the terrestrial biosphere. But our understanding of the inner workings of the atmosphere and the ways it relates to other planetary bodies is not very good. Renowned NASA climate modeler James Hansen, the man whose summer 1988 congressional testimony kicked off the climate change debate, states in the Proceedings of the National Academy of Sciences: “The forcings [outside factors] that drive long-term climate change are not known with an accuracy sufficient to define future climate changes.” One of the fundamental illustrations of chaos, the butterfly effect, displays the interconnectedness of the atmosphere system when it states that a butterfly fluttering through the air in China could cause rain in New York the following spring.
GCMs are made by formulating mathematical descriptions of the interrelationships between the atmosphere/ocean/biosphere/cryosphere system and conducting numerical experiments. They certainly are unable to form a mathematical description based on the kind of interconnections, or feedbacks, that the butterfly effect would suggest. Indeed, Michael Schlesinger, modeler at the University of Illinois, Urbana-Champaign, tells us that “in the climate system, there are 14 orders of magnitude, from the planetary scale–which is 40 million meters–down to the scale of one of the little aerosol particles on which water vapor can change phase to a liquid [cloud particle]–which is a fraction of a millionth of a millimeter.” Of these 14 orders of magnitude, only the two largest (the planetary scale and the scale of weather disturbances) can currently be included in models. Schlesinger notes that, to include the third order of magnitude (the scale of thunderstorms, at about 50 km resolution) a computer a thousand times faster would be necessary, “a teraflops machine that maybe we’ll have in 5 years.” Including all orders of magnitude would require 1036-1037 times more computing power (Kerr – Greenhouse Forecasting).
Because GCMs are so hard to make, often they account for the same processes differently; two models may have two different mathematical descriptions of what effect clouds have on warming, for example. Processes with a resolution smaller than a few hundred kilometers cannot be represented directly in the models, but instead must be parameterized, or expressed in terms of the larger scale motions, since the models do not have the resolution necessary to properly represent the actions of important weather systems such as tropical and extratropical cyclones. To offset this downfall, a few parameterizations (such as horizontal eddy viscosity, large-scale precipitation cumulus convection, gravity wave drag, etc.) are calibrated. Added to these parameterizations are adjustments commonly referred to as flux corrections, and they are an important “fudge factor” for the GCMs. These factors keep the models from floating off into nowhere. As Kerr (Model) stated, “Climate modelers have been ‘cheating’ for so long it’s almost become respectable.” Through these parameterizations, GCMs attempt to represent certain climate features reasonably well, but it is possible that they may be getting the right numbers but have the wrong underlying reason for them. As a result, such models’ ability to simulate climate change properly would be negatively impacted.
Lately, a model has been designed and tested at the National Center for Atmospheric Research to eliminate the flux corrections. This model better incorporates the effects of ocean eddies, not by shrinking the scale, but by parameterization, passing the effects of these invisible eddies onto larger model scales using a more realistic means of mixing hear through the ocean that any earlier model did. This model doesn’t drift off into chaos even after 300 years of running. This model gives a 2oC rise in temperature due to a CO2 doubling. (Some of the more popular GCMs assume that the concentration of CO2 will double in 70 years or quadruple in 140 years and use the assumption to try to predict what the climate will be like in decades or even centuries based on that doubling or quadrupling.) This figure is on the low side of estimates and puts the model’s sensitivity to greenhouse gases near the low end of current model estimates (Kerr – Model).
GCMs are very sensitive to the representations of the effects of clouds and oceans, as their effects are complex and not understood well. While some GCMs are being specially made to simulate water behavior in clouds, limited vertical resolution (i.e., they don’t go up far enough) and coarse horizontal resolution (i.e., the cloud activity of large areas of the Earth is averaged together and this average is used for the entire area) prevent even these models from accurately covering thin clouds and some cloud formation processes. Most early simulations were run with fixed cloud distributions based on observed cloud cover data, but these fixed levels didn’t allow any feedback between cloud distributions and changing atmospheric/oceanic temperatures and motions. Problems in cloud feedback are seen as the Achilles heel of GCMs. Likewise, ocean representations were initially crude; in some early models, a swamp (stagnant, heat-absorbing, heat and water vapor-releasing body of water) was used as the oceanic model. Later models had a 50 meter thick slab of ocean that allowed summertime heat storage and wintertime heat release. While not including ocean currents (caused by the movement of heat to colder areas of ocean), these models attempted to represent seasonal responses to temperature in the upper ocean, but the lack of currents resulted in tropical oceans being too hot and polar regions too cold. Even today’s most sophisticated, computationally-intense climate models are still just numerically experimental approximations of the exceedingly complex atmosphere/ocean/biosphere/cryosphere system. And yet, these GCMs are the basis of global warming theory, if for no other reason than the near-impossibility of conducting physical experiments at the global level (Cotton & Pielke).
The main means of testing these mathematical models of the climate involves taking climate data from previous years, running the programs, and seeing if the computer results are close to the actual present climatic data. The problem there is that the data are not exactly accurate. When the predicted global warming ranges from .5oC to 4oC, data accuracy is important, to say the least. Satellite data (view some) is called insubstantial by some researchers for the short length of its records, but Phil Jones states that the shortness even of global-scale surface temperature records (about 100 years) aids the uncertainty in the field. Interestingly enough, current surface temperature measurements have shown a .5oC warming over the past century, but satellite measurements for the past fifteen years (satellite data has only been available for nineteen years) shows a slight downward trend. Satellite trends in temperature vary smoothly, while in some surface data, one region will appear to be warming while those regions around it appear to cool. According to Dr. Roy Spencer, a NASA scientist, “We see major excursions [from the trend] due to volcanic eruptions like [Mount] Pinatubo and ocean current phenomena like El Niño, but overall the trend is about 0.05 degrees Celsius per decade cooling” (Horack and Spencer). Earlier this year, it was realized that the satellite data needed correction for orbital decay, or “downward drift,” in the satellites that cause erroneous cooling to show in the data. However, even after a careful readjustment the trend is still 0.01oC per decade of cooling, while weather balloons show -0.02 and -0.07oC per decade in Britain and America respectively, and British surface data show a warming of 0.15oC per decade. The Intergovernmental Panel on Climate Change (IPCC) climate model predictions estimate surface warming to be 0.18oC per decade and warming in the deep layer measured by satellites and weather balloons to be about 30% faster, or +0.23oC per decade. None of the satellites or weather balloons show values anywhere near this, not even when the adjusted satellite record is updated through July 1998 to show a trend of +0.04oC per decade, which is still only 1/6 of the IPCC-predicted rate (Spencer).
Even while the satellites may need adjustments in their data for changes in orbit, this data is still more accurate than surface data. Satellites do not have anything in their surroundings to skew the data. On the other hand, many sources of error exist here on Earth. Things as seemingly minuscule as variation in the color and type of paint used for the instrument shelters can skew data slightly, for different types and colors of paint absorb small but differing amounts of solar radiation. As another example, the urban heat island effect is known to make cities warmer at night and milder during the day. The growth of urban areas during this century has resulted in a 0.4oC bias in the US climate record, making the amount of warming appear larger than it was (Cotton and Pielke). Thomas Karl, climatologist at the National Oceanic and Atmospheric Administration (NOAA), demonstrated in a 1989 paper that, if surface temperatures are corrected for the urban heat island effect, the years around 1940 emerge as the warmest, with readings since then showing a downward trend (Crandall). If this bias exists in the global climate data set, its use to represent a wider geographic record for climate change studies will be misleading.
Another largely-ignored factor affecting temperature data is solar variation, or periodic changes in the brightness of the sun based on sunspots and the like. Some climate modelers say that the Sun only varies with an 11-year cycle, and this period is too fast for the climate system to respond to. Hoyt points out that explosive volcanic eruptions have a one to two year long radiative forcing which does appear to affect climate, and so solar variance should have a substantial impact on climate. James Hansen, the famed NASA modeler, put it this way: “Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especally changes of atmospheric aerosols, clouds, and other land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from GHGs alone” (NASA’s). Current research by Daniel Cayan and Warren White of the Scripps Institution of Oceanography gives evidence that “the waxing and waning of the sun” may be behind current climate change. They studied North Pacific sea surface temperatures for the past 50 years and noticed that their pattern looked remarkably like that of satellite records of solar irradiance (Kerr – New). Based on this, it would seem logical to include these effects in GCMs, but few researchers do.
Moreover, any calculated warming would be reduced by this cooling effect of volcanoes. Even though we cannot predict the occurrence of a volcanic eruption, we have sufficient statistical information about past eruptions to estimate their average cooling effect; yet this is one of several factors not specifically considered by the IPCC (Singer – Scientific) and many other models.
If these models are wrong in their assumptions about climate, then everything that is thought to be known because of them is wrong. If, however, their assumptions are right, but essential factors or effects within the global system are being omitted from study, then GCMs thought to be wrong may actually need only an enlightened tweaking. Unfortunately, enlightenment is difficult to come by in this field. Many, many things are still unknown.
Effects of Global Warming on Our Everyday Lives
Another area where uncertainty rears its head is in the realm of the “real life” effects of global warming. The possible effects of global warming have been played out in the media: hurricanes, plagues, a great increase in sea level, etc. Some scientists refute these claims. But, again, since the climate models can tell us little with much certainty, we can not know for certain if a global warming would have these effects or not.
Some researchers, such as those involved with the IPCC, claim that global warming will lead to an increase in violent storms such as hurricanes and typhoons. But, as S. Fred Singer points out (Scientific), warming should actually lead to a reduction in these storms as the equator-to-pole temperature differences diminish, for it is this atmospheric temperature heterogeneity that drives storms and makes them strong.
Record-breaking temperatures are given by others as a consequence of global warming. But they actually are the consequence of having records to break; on an average day, 2 million square miles (the equivalent of an area 1400 miles by 1400 miles) of the Earth are experiencing weather which breaks 100-year-old records. Indeed, the probability of breaking a weather record is equal to 1/n, where n is the number of years for which records exist (Hoyt).
Some, such as virologist Robert Shope, do say that warming could cause the mosquito carrying dengue fever and yellow fever to migrate northward, causing epidemics in North America. Cholera (which is known to live in sea-borne plankton), he says, could become epidemic in America as changes in marine ecology favor the growth and transmission of the pathogen. Rita Colwell, Paul Epstein, and Timothy Ford, another group of researchers, went a step further and blamed an El Niño warming of the Pacific at least partially for a 1991 Latin American cholera epidemic affecting 500,000 and killing almost 5,000. But cholera is known to spread from humans to other humans through food, water, and feces; this is why cholera epidemics appear when public health and sanitation break down. CDC medical epidemiologist Fred Angulo stated that “We had a powder keg ready to explode, an entire continent in which the sanitation and public water supplies and everything was primed for transmission of this organism once it was introduced,” possibly by ships emptying bilge water near fishing areas. He adds that cholera has been introduced into the US several times in the past few years; it didn’t spread “because we have a public health and sanitation infrastructure that prevents it.”
As for the mosquito-borne diseases, epidemiologist Mark L. Wilson of the University of Michigan-Ann Arbor says that the predictions suffer from many levels of uncertainty. No one disputes that weather patterns have an impact: “There’s reason to believe that if it’s an extremely rainy spring, summer mosquito populations will increase,” but he and his colleagues point out that no one knows just how patterns of temperature and rainfall will change in a warmer world, or how these changes will affect the biology of diseases. Paul Epstein has attributed Latin American dengue epidemics in 1994 and 1995 to El Niño and global warming, but experts on dengue at the Pan American Health Organization and the Centers for Disease Control and Prevention say these epidemics resulted from a breakdown in programs to eradicate the specific species of mosquito responsible and its subsequent return. The epidemics once caused by mosquitoes in the US have vanished due to mosquito control, eradication programs, piped-water systems, and lifestyle changes (we have good housing, air conditioning, and television to keep us inside, and screens to keep the mosquitoes outside). They note as an example 1995’s Mexican dengue pandemic that stopped at the Rio Grande, with over 2000 confirmed cases in Reynosa, Mexico, but only 7 across the river in Texas. And so it is a bit early to say, as the IPCC did, that “climate change is likely to have wide-ranging and mostly adverse impacts on human health, with significant loss of life” (Taubes).
It is interesting that there does appear to be an increase in sea level along the coastlines. According to Robert T. Watson, IPCC chairman, “We’ll see sea level rise that could displace tens of millions of people…and whole islands…could be significantly inundated. The shorelines of America could be severely attacked.” But Dr. David Aubrey, oceanographer and senior scientist with the Woods Hole Oceanographic Institute in Massachusetts, states that “I have seen no convincing evidence that recent sea level rises are caused by human effects or global warming” (Hoyt). And even global warming proponents’ estimates have been steadily falling; initially, it was projected by the EPA that an atmospheric CO2 doubling would cause 80-120 inches of rise, but by 1990 the estimate was a quarter of that. In 1996, a UN science advisory panel, predicted a rise of only 15-22 inches by 2100. Even these smaller estimates are quite uncertain, for sea level changes are terribly difficult to measure. Historical data are based on tide gauges, which are mainly from Northern Europe and North America. Long-term trends can be found only after the data is adjusted for waves, storm surges, and tidal variations (Singer – Sky). In addition, the land itself may be rising or falling. The Mid-Atlantic US coast, for example, is falling as a bulge formed by Ice Age glaciers slowly settles, according to the Detroit News in 1996 (Hoyt). The global sea level record as reconstructed and adjusted shows an interesting trend: levels have been rising at about 7 inches per century for several centuries over which much fluctuation of global climate has occurred. It is now believed that slow tectonic changes have caused the steady rise, not the melting glaciers some global warming theorists propose. Incidentally, the World Glacier Monitoring Service in Zurich determined that between 1926 and 1960, when the planet was supposedly cooler than today, 70% of US and European glaciers retreated. Since 1980, however, 55% of those same glaciers have advanced (Carlisle). This would not support the theory that global warming is happening now, it is melting glaciers, and that water is causing a rise in sea level. While global warming may cause mountainous glaciers to melt and a thermal expansion of water, accelerating the natural rise, it also may cause more water to evaporate from the surface of warmer oceans, leading to greater rainfall and a thickening of polar icecaps. Data from the period of warming from 1900-1940 shows a sea level drop, while the subsequent cooler period showed a rise in sea level (Singer – Sky).
Other areas of life global warming has an effect upon are those affected by attempts to stop global warming. Some people (Clark, Kerr – Greenhouse Report) suggest that small changes, such as using high-efficiency compact fluorescent lights, using self-powered or public transportation more often, etc., could make a big impact on the global warming problem (assuming it exists). This would go along with the idea expressed by some scientists that the only actions that should be taken until there is more certainty are those that would (or should) be taken anyway . But will people do these things if they don’t have to? Some other scientists are more pessimistic.
Greater measures are suggested by these people. As Cotton and Pielke state in Human Impacts on Weather and Climate, “Clearly, reductions in CO2 emissions in these countries [the US, China, and the former Soviet Union] will have a significant impact on global CO2 emissions and reduce the chance that human activity will have a significant impact on weather and climate.” In working with such an uncertain issue, one can only weigh one’s risks, look at the costs and benefits of all alternatives, and take one’s most competent guess at what the best course of action is. In the face of all this uncertainty, I would propose a sort of Climatologists’ Wager (a variation of Pascal’s Wager to this issue). Let’s assume for a moment that there is a global warming occurring. If this is anthropogenic global warming and it will have a negative impact on climate and life, then we must take action. If this is not anthropogenic global warming and warming will have a negative effect on climate and life, nothing can be done. If there is no anthropogenic global warming and the warming will not have a negative effect on climate and life, nothing need be done. Likewise, if humans have caused the global warming but it will not have a negative impact on climate and life, no action is necessary.
But there is one other dimension to choosing what to do: assuming that anthropogenic global warming is occurring and it will negatively impact climate and life, one must weigh the costs and benefits of maintaining that risk against the costs and benefits of action. Let us take the Kyoto Protocol as an example. President Clinton signed it on November 12, 1998, but he is waiting to give it to the Senate. This agreement, if ratified by the Senate, would force the US to cut GHG emissions (mostly of CO2) to 7% below the 1990 levels within the next 10 to 14 years. The costs of this mandatory decrease in emissions are substantial. Compliance would cost the US $3.3 trillion from 2001 to 2020, or $30,000 per household. Gas prices are expected to increase by 65 cents a gallon or more. Residents of Michigan are expected to have to pay 77.3% more for home heating oil, 73.5% more for natural gas, and 64.2% more for electricity. Industries and businesses will suffer. It is thought that some of the hardest hit sectors will include energy-intensive manufacturing (such as automobiles, cement, iron, steel, chemicals, aluminum, etc.), transportation, telecommunications, paper and allied products, petroleum refining, and utilities. Wages and salaries would fall, while food, housing, and medical costs rose. The state of Michigan would lose 96,500 jobs (49,800 in manufacturing), $9.3 billion in output, and $3.4 billion in tax revenues, decreasing the ability of the state to provide even more greatly needed social services. It is expected that the jobless rate would reach 5.5% and 1.1 million US jobs would be lost (Novak, Littmann).
This would be a grim picture if these changes were known to be necessary for survival. But a far grimmer picture is one of going through all this economic hardship for an unproven theory, and then potentially discovering that these costly changes really had a negligible effect upon climate and life as a whole. There is no scientific understanding of what GHG level is “dangerous.” How can we, then, regulate what the level should be, not knowing if the danger is above or below the standard we would set? For that matter, how can the 1992 Global Climate Treaty say that its purpose is to “achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” (Singer – Scientific)? It also seems a bit funny that only a fast-growing, prosperous society would best be able to afford the extra technology to make itself cleaner, healthier, and safer, but this treaty would certainly not have that effect upon the US economy. In not sanctioning developing countries, Kyoto almost encourages industry to move from the reasonably efficient and well-regulated developed countries to the developing countries, which have few (if any) regulations on pollution. S. Fred Singer has an interesting thought in “Dangers From the Global Climate Treaty”: “This [the Kyoto Protocol] has been rightly labeled a transfer of money from the poor in the rich countries to the rich in the poor countries.” Meanwhile, climate scientists who support the anthropogenic global warming theory say that it is unlikely that the Kyoto Protocol will even temporarily slow the accumulation of GHGs in the atmosphere. Jerry Mahlman, director of the Geophysical Fluid Dynamics Laboratory at Princeton, states that “it might take another 30 Kyotos over the next century” to cut global warming down to size (Malakoff).
Fact and Fiction:
FICTION: Even if the Earth is warming, we can’t be sure how much, if any, of the warming is caused by human activities.
FACT: There is international scientific consensus that most of the warming over the last 50 years is due to human activities, not natural causes. Over millions of years, animals and plants lived, died and were compressed to form huge deposits of oil, gas and coal. In little more than 300 years, however, we have burned a large amount of this storehouse of carbon to supply energy.
Today, the by-products of fossil fuel use – billions of tons of carbon (in the form of carbon dioxide), methane, and other greenhouse gases – form a blanket around the Earth, trapping heat from the sun, unnaturally raising temperatures on the ground, and steadily changing our climate.
The impacts associated with this deceptively small change in temperature are evident in all corners of the globe. There is heavier rainfall in some areas, and droughts in others. Glaciers are melting, Spring is arriving earlier, oceans are warming, and coral reefs are dying.
FICTION: The Intergovernmental Panel on Climate Change predicts an increase in the global average temperature of only 1.4°C to 5.8°C over the coming century.
This small change, less than the current daily temperature range for most major cities, is hardly cause for concern.
FACT: Global average temperature is calculated from temperature readings around the Earth. While temperature does vary considerably at a daily level in any one place, global average temperature is remarkably constant. According to analyses of ice cores, tree rings, pollen and other “climate proxies,” the average temperature of the Northern Hemisphere had varied up or down by only a few tenths of a degree Celsius between 1000 AD and about 1900, when a rapid warming began.
A global average temperature change ranging from 1.4°C to 5.8°C would translate into climate-related impacts that are much larger and faster than any that have occurred during the 10 000-year history of civilization.
From scientific analyses of past ages, we know that even small global average temperature changes can lead to large climate shifts. For example, the average global temperature difference between the end of the last ice age (when much of the Northern Hemisphere was buried under thousands of feet of ice) and today’s interglacial climate is only about 5°C .
FICTION: Warming cannot be due to greenhouse gases, since changes in temperature and changes in greenhouse gas emissions over the past century did not occur simultaneously.
FACT: The slow heating of the oceans creates a significant time lag between when carbon dioxide and other greenhouse gases are emitted into the atmosphere and when changes in temperature occur.
This is one of the main reasons why we don’t see changes in temperature at the same time as changes in greenhouse gas emissions. You can see the same process occur in miniature when you heat up a pot of water on the stove: there is a time lag between the time you turn on the flame and when the water starts to boil.
In addition, there are many other factors that affect year-to-year variation in the Earth’s temperature. For example, volcanic eruptions, El Niсo, and small changes in the output of the sun can all affect the global climate on a yearly basis.
Therefore, you would not expect the build-up of greenhouse gases to exactly match trends in global climate. Still, scientific evidence points clearly to anthropogenic (or human-made) greenhouse gases as the main culprit for climate change.
FICTION: Carbon dioxide is removed from the atmosphere fairly quickly, so if global warming turns out to be a problem, we can wait to take action to reduce greenhouse gas emissions until after we start to see the impacts of warming.
FACT: Carbon dioxide, a gas created by the burning of fossil fuels (like gasoline and coal), is the most important human-made greenhouse gas.
Carbon dioxide from fossil fuel use is produced in huge quantities and can persist in our atmosphere for as long as 200 years.
This means that if emissions of carbon dioxide were halted today, it would take centuries for the amount of carbon dioxide now in the atmosphere to come down to what it was in pre-industrial times. Thus we need to act now if we want to avoid the increasingly dangerous consequences of climate change in the future.
FICTION: Human activities contribute only a small fraction of carbon dioxide emissions, an amount too small to have a significant effect on climate, particularly since the oceans absorb most of the extra carbon dioxide emissions.
FACT: Before human activities began to dramatically increase carbon dioxide levels in the atmosphere, the amount of carbon dioxide emitted from natural sources closely matched the amount that was stored or absorbed through natural processes.
For example, as forests grow, they absorb carbon dioxide from the atmosphere through photosynthesis; this carbon is then sequestered in wood, leaves, roots and soil. Some carbon is later released back to the atmosphere when leaves, roots and wood die and decay.
Carbon dioxide also cycles through the ocean Plankton living at the ocean’s surface absorb carbon dioxide through photosynthesis. The plankton and animals that eat the plankton then die and fall to the bottom of the ocean. As they decay, carbon dioxide is released into the water and returns to the surface via ocean currents. As a result of these natural cycles, the amount of carbon dioxide in the air had changed very little for 10,000 years. But that balance has been upset by man.
Since the Industrial Revolution, the burning of fossil fuels such as coal and oil has put about twice as much carbon dioxide into the atmosphere than is naturally removed by the oceans and forests. This has resulted in carbon dioxide levels building up in the atmosphere.
Today, carbon dioxide levels are 30% higher than pre-industrial levels, higher than they have been in the last 420,000 years and are probably at the highest levels in the past 20 million years. Studies of the Earth’s climate history have shown that even small, natural changes in carbon dioxide levels were generally accompanied by significant shifts in the global average temperature.
We have already experienced a 1°F increase in global temperature in the past century, and we can expect significant warming in the next century if we fail to act to decrease greenhouse gas emissions.
FICTION: The Earth has warmed rapidly in the past without dire consequences, so society and ecosystems can adapt readily to any foreseeable warming.
FACT: The Earth experienced rapid warming in some places at the end of the last glacial period, but for the last 10,000 years our global climate has been relatively stable. During this period, as agriculture and civilization developed, the world’s population has grown tremendously. Now, many heavily populated areas, such as urban centers in low-lying coastal zones, are highly vulnerable to climate shifts.
In addition, many ecosystems and species that are already threatened by existing pressures (such as pollution, habitat conversion and degradation) may be further pressured to the point of extinction by a changing climate.
FICTION: The buildup of carbon dioxide will lead to a “greening” of the Earth because plants can utilize the extra carbon dioxide to speed their growth.
FACT: Carbon dioxide has been shown to act as a fertilizer for some plant species under some conditions. In addition, a longer growing season (due to warmer temperatures) could increase productivity in some regions.
However, there is also evidence that plants can acclimatize to higher carbon dioxide levels – that means plants may grow faster for only a short time before returning to previous levels of growth.
Another problem is that many of the studies in which plant growth increased due to carbon dioxide fertilization were done in greenhouses where other nutrients, which plants need to survive, were adequately supplied.
In nature, plant nutrients like nitrogen as well as water are often in short supply. Thus, even if plants have extra carbon dioxide available, their growth might be limited by a lack of water and nutrients. Finally, climate change itself could lead to decreased plant growth in many areas because of increased drought, flooding and heat waves.
Whatever benefit carbon dioxide fertilization may bring, it is unlikely to be anywhere near enough to counteract the adverse impacts of a rapidly changing climate.
FICTION: If Earth has warmed since pre-industrial times, it is because the intensity of the sun has increased.
FACT: The sun’s intensity does vary. In the late 1970’s, sophisticated technology was developed that can directly measure the sun’s intensity. Measurements from these instruments show that in the past 20 years the sun’s variations have been very small.
Indirect measures of changes in sun’s intensity since the beginning of the industrial revolution in 1750 show that variations in the sun’s intensity do not account for all the warming that occurred in the 20th century and that the majority of the warming was caused by an increase in human-made greenhouse gas emissions.
FICTION: It is hard enough to predict the weather a few days in advance. How can we have any confidence in projections of climate a hundred years from now?
FACT: Climate and weather are different. Weather refers to temperatures, precipitation and storms on a given day at a particular place. Climate reflects a long-term average, sometimes over a very large area, such as a continent or even the entire Earth.
Averages over large areas and periods of time are easier to estimate than the specific characteristics of weather.
For example, although it is notoriously difficult to predict if it will rain or the exact temperature of any particular day at a specific location, we can predict with relative certainty that on average, in the Northeastern United States, it will be colder in December than in July.
In addition, climate models are now sophisticated enough to be able to recreate past climates, including climate change over the last hundred years. This adds to our confidence that projections of future climates are accurate.
Finally, when we report climate projections, we use a range of results from climate models that represent the boundaries of our projections (what’s the least global average temperature could change to what’s the most global average temperature could change) and our degree of certainty of the projections.
FICTION: The science of global climate change cannot tell us the amount by which man-made emissions of greenhouse gases should be reduced in order to slow global warming.
FACT: The U.N. Framework Convention on Climate Change states that emissions of greenhouse gases should be reduced to avoid “dangerous interference with the climate system.” Scientists have subsequently attempted to define what constitutes “dangerous interference.”
One study (O’Neill and Oppenheimer, 2002) supplies three criteria that could be used:
1) risk to threatened ecosystems such as coral reefs
2) large-scale disruptions caused by changes in the climate system, such as sea-level rise caused by the break-up of the Antarctic Ice Sheet and
3) large-scale disruptions of the climate system itself, such as the shutdown of the thermohaline circulation of the Atlantic Ocean (the Gulf stream), which would result in a severe drop in temperature to Europe.
This study projects that if C02 concentrations are capped at 450 parts per million (ppm), major disruptions to climate systems may be avoided, although some damage (such as that to coral reefs) may be unavoidable.
Current estimates of atmospheric CO2 concentrations likely to be reached without aggressive action to limit greenhouse gas emissions are far higher – from 550 ppm to as much as 1000 ppm in the next hundred years.
FICTION: Because of the uncertainty of climate models, it is extremely difficult to predict exactly what regional impacts will result from global climate change.
FACT: According to the IPCC, certain climate trends are highly likely to occur if greenhouse gas emissions continue at their current rate or increase: sea level will rise; droughts will increase in some areas, flooding in others; temperatures will rise, leading to heat waves becoming more common and glaciers likely to melt at a more rapid rate.
Regional impacts are very likely to occur, but exactly when and what they will be is harder to predict.
This is because:
1) regional climate models are more computer intensive than global climate models – they take longer to run and are more difficult to calibrate, and
2) many non-climate factors contribute to impacts at regional levels. For example, the risk of mosquito-borne illnesses like Dengue fever and malaria may rise due to increased temperatures, but the actual likelihood of infection will depend greatly on the effectiveness of public health measures in place.
A Better World Climate: How Do We Get There From Here?
As has been stated previously, there are a great many unanswered questions about global warming. We wonder whether or not there really is an anthropogenic global warming or the threat of one because we don’t have the perfect climate model to tell us so. And we don’t have this model because we don’t understand what is going on; we don’t understand how the atmospheric system interacts with the oceans, the terrestrial biosphere, the cryosphere, or any of its other contributing factors. Therefore, the research that should be first and foremost in our minds is that to better understand the rich interrelationships between these bodies as well as the various features of each that may not be well understood. The effect of clouds, for example, on warming and vice versa are not understood very well. Do they simply cool by reflecting heat back to space, or is their role more complex than that? What effect does each shape and size of cloud have? What outside factors have an effect upon cloud formation? And, most importantly, how can we best relate these effects into GCMs?
Likewise, aerosols are in need of study. Do they simply cause cooling by reflecting solar radiation back out into space, or, as one researcher stated, is that effect canceled out by heating through reflection of terrestrial radiation back to earth and give their real cooling effect by fortifying clouds with water droplets, giving them a higher albedo?
Are variations in solar radiation and sunspot cycles behind part or all of the perceived global warming? Could there be changes in the sun’s energy output that would cause warming such as some have observed?
How does the tropical ocean interact with global atmospheric circulation, given that tropical cyclones (hurricanes) form there? Are there any special processes at work there that would affect the global warming theory? Likewise, how do the atmosphere, the ocean, and sea ice interact at high latitudes?
What, exactly, is the terrestrial biosphere’s place in the carbon cycle? How much CO2 does different types of vegetation, soil, or rock absorb? If CO2 is shown to be a substantial problem, would there be any way to make parts of the terrestrial biosphere take on more CO2? What effect would that have on the various ecosystems involved?
And on and on the potential questions go. As can be seen above, there are a lot of different directions global warming research can go in and is going in. All of these would be helpful in trying to better determine the climatic direction we as a planet are headed in. But there is one other dimension to this attempt to better understand global warming: the modeling. Currently, even the most sophisticated and encompassing of the GCMs is incredibly crude and oversimplified compared to the actual atmospheric system and its feedbacks. And so, given new findings in research related to above topics and others, we must continue to update the models. We must keep working on the models, improving them, until flux corrections or “fudge factors,” as they are called, are unnecessary to make them properly predict today’s conditions. As computer technologies continually become smaller and faster and more capable of complex systems, we must keep shrinking the scale of the models and bringing in more variables to account for or better, more detailed understanding of the existing variables. To have a perfect model, every variable, every ocean eddy and sulfate particle would have to be accounted for. While this is improbable as a state of modeling, we can continue to try to better explain what is going on and how things are connected and interrelated by bringing bigger and better understandings of atmospheric intricacies to the modeling table.
Unfortunately for these global climate change researchers, the computer industry is not moving nearly fast enough for this research. In many ways, climatologists are waiting on the computer industry to build more powerful supercomputers so they can make more complex models to take advantage of that computing power. And yet, there is at least a small advantage to waiting: many valuable studies being conducted with innovative, legitimate methods simply haven’t been collecting data long enough to be as useful as possible. Satellite data is a good example of this. If we wait, the data will be better.
And so, we can see that the science behind global warming is far from settled. Much is not known and conflicting theories abound, as they often do in scientific forums. New ideas and new studies keep the science of global climate change going, keep it second guessing itself, keep it looking for newer, better ways to explain what’s going on. In the end, global climate change may be a way for science to prove it can work well even under the most uncertain of circumstances.
Introduction to Global Warming: