Global Warming

There are lots of evidences that the Earth's surface is warmer today than it was a century ago. As for why this is so, research by thousands of scientists strongly suggests that the cause is the largely uncontrolled and still increasing release of anthropogenic (human-caused) greenhouse gases. Yet there remain a few scientists who oppose these conclusions, claiming that either the evidence for significant global warming is unreliable or that, granting the problem, the sources are natural cycles over which we have little or no control.

The conclusions held by leaders in a variety of fields can't help but have a profound impact on social, political, and economic policy. Thus each side has expended considerable effort to convince the public, and through it the political establishment, of the validity of its stance. But because neither has been entirely successful, particularly in the United States, policies have been inconsistent and changeable, subject to partisan wrangling, corporate lobbying, and a general inadequacy of resolve.

The importance of the issue was most forcefully brought to the public's attention with Hurricane Katrina and Hurricane Rita. Their unusual severity, being among the strongest ever recorded in the Gulf of Mexico, reminded a number of network newscasters of recent scientific reports predicting an increase in hurricane severity.

WHAT IS THE EVIDENCE THAT SIGNIFICANT GLOBAL WARMING IS OCCURRING?

If the summarized results of thousands of scientific studies that appear in the Report of the Intergovernmental Panel on Climate Control-Climate Change 2001, The Scientific Study are valid, the answer is unambiguously that significant global warming is occurring.

Climate scientists define global warming as the measured increase in the mean Earth surface temperature over a specified time interval. The most reliable data are properly averaged over land and ocean surfaces, statistically weighted according to the density of measurements within each equal-area element.

So, according to the IPCC 2001 report, the Earth's surface has warmed by approximately 0.6 degrees Centigrade over the twentieth century.The warming hasn't been uniform over the globe, however. In general it has been greater over the land than the oceans and, probably for that reason, greater over the northern hemisphere than the southern. There is also some speculation that the greater industrial activity, hence greater greenhouse gas emission, in the northern hemisphere may have contributed.

Of particular concern is the rapid temperature rise over the last quarter of the twentieth century. The curve of increasing surface temperature in the twentieth century shows a definite increase in the first part of the century, then an extended plateau over the years 1940 to 1975, and finally the rapid increase.

If the weight of evidence suggests a problem is both real and likely to become more serious with time, most reasonable people would say that doing nothing is the height of folly. Therefore, notwithstanding the aforementioned uncertainties, there remains the fact that an enormous body of well-calibrated observations supports the unambiguous rise in global surface temperature.

HOW SERIOUS ARE THE CONSEQUENCES OF GLOBAL WARMING?

It remains necessary to ask if the likely harmful effects of global warming sufficiently outweigh the probable benefits of policies that might have harmful economic consequences. Furthermore, we need to ask about the likely positive effects of global warming? Might the news be good rather than bad?

There is some truth in this latter idea. Moderate global warming will enhance the agricultural productivity over parts of the globe. Climate models haven't advanced to the point of yielding accurate predictions of the detailed effects on all regional climates, but all of the more sophisticated models, in agreement with observations, predict that warming is greatest at the higher northern latitudes. Thus, for example, it seems probable that large areas of Russia and Canada could become more productive as the Earth's surface warms, though this could be offset by insufficient regional rainfall, currently difficult to predict.

But are these benefits likely to significantly offset the known harmful effects of global warming? Let's review the negative consequences.

Perhaps most disturbing is sea-level rise. Water expands with increasing temperature, causing the sea level to rise accordingly. Many of the world's glaciers are also retreating and very few are growing. If greater warming should induce significant melting of the West Antarctic Ice Sheet (anchored in the ocean below sea level) or, worse, a significant part of the Greenland Ice Cap, the rise in sea level could exceed twenty feet or more. The effect on major coastal cities, if warming continues, is likely to become significant by the end of the twenty-first century and will be disastrous or even catastrophic if the warming exceeds moderate increases of a few degrees Fahrenheit.

Many other damaging effects of global warming are known with near certainty. Warming increases the incidence of pathogens responsible for many human and animal diseases. Warming induces changes in weather patterns And warming means that a smaller fraction of the Earth's surface will be covered by snow and ice, which reflect sunlight more effectively than other land and sea surfaces. This increased absorption of sunlight sets in motion an unstable process that further enhances global warming.

IS HUMAN ACTIVITY THE CHIEF CAUSE OF GLOBAL WARMING TODAY?

It is often noted by critics of the current consensus that many natural processes might contribute to global warming and that one or more of them may be the dominant driver or drivers. It is therefore necessary to look at this claim and see if it holds up.

The lack of a convincing argument based on solid research for any hypotheses leads us to ask what we humans are doing that may be causing global warming. This leads naturally into an examination of anthropogenic greenhouse gases. Unlike the more speculative discussion of possible causes reviewed above, a very strong case can be made that carbon dioxide, in particular, is probably a significant driver, and could well be the dominant driver, of the current rapid rise in global mean surface temperatures.

There is no disagreement over the occurrence of the greenhouse effect to which carbon dioxide contributes. The question becomes how much greenhouse effect is good for us. Carbon dioxide is a well-studied gas that readily absorbs Earth's infrared radiation and reradiates part of it back to the Earth, thus causing warming.

The most effective driver of global warming reported in the IPCC 2001 report identify carbon dioxide as the strongest contributor. To summarize, the extensively studied and well-known greenhouse effects of carbon dioxide are so strong that, combined with its persistence in our atmosphere, we can reasonably conclude that the increasing atmospheric concentration of carbon dioxide from human activity is very likely the dominant driver of global warming, and the warming effects will probably become worse with time for several decades, even after the emission rate has subsided.

There are other greenhouse gases that contribute to global warming. Methane is the most important of these, but nitrous oxides also contribute and their concentration is rapidly increasing. All these gases are well mixed and will remain in the atmosphere for many decades. Aerosols also play an important role in global warming, and the effect of most of them, especially the sulphates, is generally toward cooling, as we have learned from the effect of large volcanic eruptions

TOWARD A SOLUTION

Given all this, what can be done? Unfortunately, at this moment, there seem to be no technologically workable schemes for removing enough carbon dioxide from the atmosphere to make a measurable difference.

There are, after all, things that can be done. Reopening a serious international dialogue, and not just saying a few good words, would be a useful if inadequate start. Not every problem must be solved before the weight of evidence becomes so compelling that certain initial steps become almost mandatory. We already know how to make more fuel-efficient automobiles, yet no national policy has surfaced to accomplish this. The scientific and engineering communities are the ones best suited to identify the scientific research that is still needed and the technical projects that show the greatest promise. These issues should be decided by them and not the politicians. Once solutions look promising, as a few already do, industry will be all too ready to jump in, for at that stage there is money to be made. And only a fool would underestimate human ingenuity when given a proper incentive, or the strength of American industry once the boiler is lit under it.

The important thing is to get started doing some of these things in earnest, and not for us to stick our head in the sand doing business as usual until the water comes in over our eyelids. If we wait long enough, it will.

Source : Internet