Global Climate: Burning Fossil-Fuels and the Human Response

by Chris Wilson ‘01

A few days ago, while basking in the warmth of winter, a friend asked me about Global Warming and what exactly the problems were with a rise in temperature. He seemed to have no problem with a 75 degree day in the middle of March and wanted to know what all the fuss is about. Since I am currently taking a class centered on climate change, I tried to answer his question by concisely summing up the evidence for global warming and the potential hazards of an increase in global temperature–surprisingly, I could not think of a decent response.

You see, I didn’t quite know how to respond to my friend’s forthright inquiry about the state of the Earth’s weather systems, because I really don’t have a clue what is happening or is going to happen. By studying the concepts of global climate, I have been introduced to a conundrum of interacting variables that appear impossible to decipher. So, after stammering out a few potential threats: sea-level change, drought, floods, loss of biomass, and heatstroke, I plunged back into science books and journals vowing to prepare myself for the next time someone posed a similar question (I am still looking for Klutz’s The Idiots Guide to: Global Warming--let me know if you have a copy). Unfortunately, further research revealed more questions and variables to puzzle over and a much more confounding dilemma than I had anticipated.

Initially, I hoped to find specific information which answered the questions of global climate variations and mankind’s influence upon climate systems. Yet, in digesting several different views, variables, data, satellite data, and proxy data, I only found that my discombobulation had lots of company. It seems nobody definitively knows, or can agree on, where long-run climate change is heading or what the effects will be on different ecosystems, or even whether increased CO₂ levels are responsible. Currently, the interrelation of feedbacks from all the possible variables adds too many chaotic complexities to provide a definitive answer, and models used to project climate are subject to a number of criticisms. Naturally, anthropogenic influence on climate change figures to be at the crux of the debate, and the dividing lines of opposing interest groups are sharply drawn. Policymakers are in a difficult situation. They have to weigh regulations that have a potentially harmful effect economically (Kyoto Protocol), against the possibility–given scientific error–of disastrous climate change. As a result, scientists confront the daunting task of separating the human effects on climate from the background noise caused by natural climate forcings.

The interaction of a seemingly infinite number of variables inflicts difficulties in distinguishing climate trends. Although we are well aware of rising temperatures and sea-level, pinpointing the causes of these fluctuations is arduous work. Factors such as El Nino, the orbital positions of the Earth, volcanic eruptions, topography, sunlight variations, respiration, and circulations of ocean currents all contribute to a system scientists are just beginning to understand. Variations in the Earth’s climate can often be explained by any number of these variables. However, the last two decades have yielded unprecedented increases in recorded temperatures. All sixteen of the warmest years since 1860 have occurred in the past two decades, the last being the warmest on record. According to the National Oceanic and Atmospheric Administrator, from December to February the United States experienced its warmest winter on record, breaking last year’s record. Can these warming trends and record-breaking heat waves be contributed to natural variations of the Earth’s systems, or are they related to anthropogenic actions which increase greenhouse gases?

Some researchers hope computer generated climate models provide understanding of the relationship of CO₂ and global climate. Scientists hope to generate accurate models by recreating climate variables that match actual temperature records. The Hadley Model, a popular model that contains influences of greenhouse gases and cooling effects of sulphate aerosols along with feedbacks such as albedo (a measurement of reflectivity) and many others, appears to recreate an accurate picture of the past. By incorporating regional cooling and warming, researches claim to have linked CO₂ concentrations to the model; the idea behind this addition is that different climate influences each operate under a recognizable pattern. If greenhouse gases altered climate they would have a specific pattern diagnostic of greenhouse gases. Scientists rely upon models, like those generated by the Hadley Centre, to predict future climates and provide vital evidence in the debate over anthropogenic contribution to global warming. The best models clearly indicate that human activities will affect climate if the current rate CO₂ emissions continue. In fact, the models have convinced many skeptical climatologists that greenhouse gases help cause global warming and can have a significant influence on future climate.

Models predict that climate will continue to increase over the next century. The IPCC has used models to anticipate an increase in global mean surface air temperature of anywhere from 1 degree Celsius to 3.5 degrees by the year 2100. A one degree change will occur if nations decide to curb carbon dioxide output and a 3.5 degree increase will occur if fossil-fuels remain the primary source of energy. These appear to be minimal increments of change; however, according to ice-core samples, the global mean surface air temperature for the coldest periods during ice-ages are estimated to have been merely 5 to 6 degrees colder than today. Clearly, even a change of a few degrees can have a dramatic effect on the Earth’s environment.

Critics claim that the models do not provide an accurate forecast of future climates. The American Petroleum Institute is quick to point out that models cannot reliably incorporate all factors that affect climate. Even model creators admit to possible uncertainties due to imperfect simulations of cloud cover, oceanic-atmosphere coupling, and the hydrological cycle. Currently, experts’ incomplete understanding of events like these raise serious questions about the accuracy of climate models. Furthermore, researchers can tinker with the results of models by changing the "flux" adjustments. Altering the input of the sun or effect of volcanic eruptions to "tune" model results is an example of "flux" adjustments. Ostensibly, with the right incentives, scientists could "fudge" model output. The freedom that "flux" adjustments provide modelers and the chance of misconstrued data damages the credibility of the model’s results. Although climate models have reproduced acknowledged climate trends, there still remains some ambiguity when linking global warming to greenhouse gases.

Perhaps the most daunting argument against scientists’ abilities to connect greenhouse gases with global warming involves the available sample data. Temperature records are only reliable since the late 1800's–an infinitesimal fraction of geologic time. In efforts to differentiate anthropological greenhouse effects from natural climate forcings, scientists must evaluate climate trends since long before human existence. By piecing together the Earth’s past warming and cooling periods we can distinguish the significance of human activities.

Studies of various proxy data, oxygen isotope ratios in ice-core samples and ocean carbonate sediment among them, reveal that the Earth’s climate has been anything but invariant. In fact the Earth alternates between two extreme temperature ranges: ice ages and interglacial periods. Durations of warming and cooling are nothing new to the Earth. Variations in the Earth’s orbit that influence solar radiation–Milankovitch cycles–explain the periodic glacier cycles. Currently, we are in an interglacial cycle that began around 10,000 years ago named the Holocene. Holocene climate has been a collection global-scale periods of warming and cooling. Through multiple proxy data (tree rings, coral, isotope ratios, and other paleoclimate data) reconstructions of climate suggest that temperature is the highest it has been in 1,000 years. During the 9^th century, North Atlantic colonization reveals a "Mediaeval Warming Period" that had warmer climate than today. Comparing our Holocene to the last interglacial period, 125,000 years ago, reveals that temperatures are cooler today than in a relatively similar environment. Clearly, paleoclimate data reveals that warm temperatures can occur from natural climate forcings. Our recent rise in temperature is not a unique phenomenon; can we close the book on this issue?

The fact that the Earth experiences periods of warming does not exactly let fossil fuel burning industries and biomass burners off the hook. Some scientists are still very confident that radiative forcing of greenhouse gases has accelerated a naturally occurring warming trend. The compound effect of such a situation could have serious effects upon our environment–both regionally and globally. If climate continues to increase, as it has in the past few decades, nobody can say whether mankind has the ability to reverse the outcome or adapt to it. To many, the correlation of increased levels of carbon dioxide in our atmosphere and climate increase cannot be ignored. In fact, it would be hard to convince most experts that carbon dioxide levels do not effect climate. However, doubt about the anthropogenic root of global warming cannot be eliminated.

Taking all of this into account, and returning to the question posed by my warm weathered friend, what is all the fuss about?

The final word about global warming is not yet in. Too many variables exist to make a greenhouse solution to global warming foolproof. Strong believers in global warming wonder whether time remains to come to a tried and true conclusion. Others hold that scientists must find answers before implementing any "cumbersome government rules" that may cause economic downturn.

Works Cited

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