Is Planet Earth Under Threat?

GLOBAL WARMING has been described as the greatest threat facing humanity. What worries researchers, says the journal Science, “is the prospect that we’ve started a slow-moving but relentless avalanche of change.” Skeptics question this assertion. True, many agree that the earth is warming, but they are uncertain of both the causes and the consequences. Human activities may be a factor, they say, but not necessarily the primary one. Why the disagreement?

For one thing, the physical processes that underlie global climate systems are complex and not fully understood. In addition, interest groups tend to put their own spin on the scientific data, such as that used to show why temperatures are rising.

Temperature Rise​—Is It Real?

According to a recent report of the UN-sponsored Intergovernmental Panel on Climate Change (IPCC), global warming is “unequivocal,” or a fact; and “very likely,” mankind is largely to blame. Some who differ with this conclusion, especially in regard to the human factor, concede that cities may be heating up because they are growing in size. Moreover, concrete and steel readily absorb the sun’s heat and tend to cool down slowly at night. But urban readings, skeptics say, do not reflect the trend in rural areas and can distort global statistics.

On the other hand, Clifford, a village elder who lives on an island off the coast of Alaska, says he has seen changes with his own eyes. The people of his village travel across sea ice to the mainland to hunt caribou and moose. Rising temperatures, though, are making the traditional lifestyle impossible. “The currents have changed, ice conditions have changed, and the freeze-up of the Chukchi Sea has . . . changed,” says Clifford. The sea used to freeze up at the end of October, he explains, but now it does not freeze until late December.

In 2007, warming was also evident in the Northwest Passage, which was fully open for the first time in recorded history. “What we’ve seen this year fits the profile of lengthening melt seasons,” said a senior scientist for the National Snow and Ice Data Center in the United States.

The Greenhouse Effect​—Vital for Life

A reason given for such changes is an intensification of the greenhouse effect, natural phenomena vital for life on earth. When energy from the sun reaches the earth, about 70 percent is absorbed, heating air, land, and  sea. If it were not for this mechanism, the average surface temperature would be about zero degrees Fahrenheit (-18 degrees Celsius). Eventually, the absorbed heat is released back into space as infrared radiation, thus preventing the earth from overheating. But when pollutants change the composition of the atmosphere, less heat escapes. This can cause earth’s temperatures to rise.

Gases that contribute to the greenhouse effect include carbon dioxide, nitrous oxide, and methane, as well as water vapor. The atmospheric concentration of greenhouse gases has increased markedly over the past 250 years, since the start of the industrial revolution and the increased use of fossil fuels, such as coal and oil. Another greenhouse-enhancing factor seems to be the rising population of farm animals, whose digestive processes produce methane and nitrous oxide. Some researchers point to other causes of warming that they say occurred before humans could have influenced climate.

Just Another Fluctuation?

Skeptics of human-induced warming point out that earth’s temperature has undergone substantial fluctuations in the past. They point to the so-called ice ages, when the earth was supposedly much cooler than it is now; and in support of natural warming, they cite evidence that cold regions, such as Greenland, at one time supported vegetation that prefers warm areas. Of course, scientists concede that the further back they go, the more their certainty about climate diminishes.

What may have caused temperatures to vary significantly before human influence was a factor? Possible causes include sunspots and solar flares, which correlate with fluctuations in solar energy output.  Additionally, earth’s orbit moves in cycles that take many thousands of years and that affect our planet’s distance from the sun. There is also the influence of volcanic dust and changes in oceanic currents.

Climate Modeling

If earth’s temperature is rising​—no matter what the cause or causes—​how will it affect us and the environment? Precise predictions are hard to make. Nowadays, though, scientists have access to powerful computers, which they use to create digital simulations of the climate system. Incorporated into their models are the laws of physics, climate data, and natural phenomena that influence climate.

Simulations enable scientists to experiment with climate in ways that are otherwise impossible. For instance, they can “change” solar output to see how this affects polar ice, air and sea temperatures, evaporation rates, atmospheric pressure, cloud formation, wind, and rainfall. They can “create” volcanic eruptions and examine the effects of volcanic dust on weather. And they can examine the effects of human population growth, deforestation, land use, changes in the emission of greenhouse gases, and so on. Scientists hope that their models will progressively become more accurate and reliable.

How precise are present models? Much, of course, depends on the accuracy of the data and the amount of it fed into the machines. Hence, climate projections vary from the mild to the catastrophic. Even so, says Science, “surprises could spring from the [natural] climate system.” And some already have, such as the unusually rapid rate of Arctic melting, which has amazed many climatologists. Still, even if policymakers had only a rough idea of the consequences of present action or inaction, they could make decisions today that might reduce problems tomorrow.

With that possibility in mind, the IPCC examined six different sets of computer-simulated scenarios​—ranging from unrestricted greenhouse-gas production to business as usual to severe restraint—​each producing different climatic and environmental results. In the light of the predictions, analysts urge a variety of measures. These include mandatory limits on fossil-fuel emissions, penalties for offenders, more nuclear power generation, and the introduction of more environmentally friendly technologies.

Are the Models Reliable?

Present forecasting methods “oversimplify poorly understood climate processes” and “simply ignore others,” say critics. They also point to the inconsistencies in computed projections. One scientist who participated in the IPCC discussions said: “There are some  of us who remain so humbled by the task of measuring and understanding the extraordinarily complex climate system that we are skeptical of our ability to know what it is doing and why.” *

Some would argue, of course, that using an element of doubt as justification for doing nothing is gambling with the future. “How would we explain this to our children?” they say. Whether the climate models are accurate or not, we can be certain that the earth is in serious trouble. Its life-sustaining environment is being assaulted by pollution, deforestation, urbanization, and the extinction of species, to name just a few factors that no one can successfully dispute.

In view of what we know, can we expect mankind as a whole to make an about-face so as to spare our beautiful home​—and us too? What is more, if human activity is causing global warming, we may have only years, not centuries, to make the needed changes. At the very least, making such changes would mean promptly addressing the root causes of earth’s problems​—human greed, self-interest, ignorance, inept government, and apathy. Is such a prospect probable or just wishful thinking? If the latter, are we without hope? That question will be discussed in the next article.


^ par. 20 John R. Christy, director of the Earth System Science Center at the University of Alabama, Huntsville, U.S.A., as reported in The Wall Street Journal, November 1, 2007.

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To illustrate the challenges, how would you measure the temperature of a single, large room? Where, for example, would you put the thermometer? Heat rises, so air near the ceiling will likely be warmer than air lower down. The reading will also be affected if the thermometer is near a window, in direct sunlight, or in the shade. Color may also contribute to different readings, since dark surfaces absorb more heat.

One measurement, therefore, would likely be insufficient. You would have to take readings at several points and then calculate an average. And readings may change from day to day and from season to season. So to get a true average, you would have to take many readings over an extended period. Imagine how complicated it is, then, to measure the overall temperature of earth’s surface, atmosphere, and oceans! Yet, such statistics are essential to the accurate assessment of climate change.

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NASA photo

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Energy consumption worldwide is breaking record after record. Since the burning of oil and coal produces greenhouse gases, some governments are taking a closer look at nuclear power as a cleaner alternative. But it too presents challenges.

The International Herald Tribune reports that in France, one of the world’s most nuclear-reliant countries, up to 670 billion cubic feet [19 billion cubit meters] of water is required annually to cool reactors. In the heat wave of 2003, the hot water normally expelled from France’s reactors threatened to raise the temperature of rivers to environmentally damaging levels. Hence, some power stations had to shut down. This situation is expected to worsen if global temperatures rise.

“We’re going to have to solve the climate-change problem if we’re going to have nuclear power,” said nuclear engineer David Lochbaum of the Union of Concerned Scientists.

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The year 2007 saw a record number of weather-related disasters for which the United Nations Office for the Coordination of Humanitarian Affairs issued 14 emergency appeals​—4 more than the previous record, set in 2005. Listed here are just some of the disasters that occurred in 2007. Keep in mind, of course, that individual events do not necessarily indicate a long-term trend.

Britain: More than 350,000 people were affected by the worst flooding in over 60 years. England and Wales saw the wettest May to July since record-keeping began in 1766.

West Africa: Floods affected 800,000 people in 14 countries.

Lesotho: High temperatures and drought destroyed crops. Some 553,000 people may require food aid.

Sudan: Torrential rains left 150,000 people without shelter. At least 500,000 received aid.

Madagascar: Cyclones and heavy rains lashed the island, displacing 33,000 people and destroying the crops of 260,000.

North Korea: An estimated 960,000 were severely hit by widespread flooding, landslides, and mud slides.

Bangladesh: Flooding affected 8.5 million people and killed over 3,000, as well as 1.25 million farm animals. Nearly 1.5 million homes were either damaged or destroyed.

India: Floods affected 30 million people.

Pakistan: Cyclonic rains left 377,000 people displaced and hundreds dead.

Bolivia: More than 350,000 were affected by flooding, and 25,000 were displaced.

Mexico: Regional flooding left at least 500,000 homeless and affected more than a million.

Dominican Republic: Prolonged heavy rainfall caused floods and landslides, displacing 65,000.

United States: Fires across tinder-dry southern California forced 500,000 residents to flee their homes.

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Based on NASA/​Visible Earth imagery