8 - 14 March 2001
Issue No.524
|
Al-Ahram Weekly On-line 8 - 14 March 2001 Issue No.524 |
||
| Published in Cairo by AL-AHRAM established in 1875 | Current issue | Previous issue | Site map | ||
Global warming dilemmas
In 1988, James Hansen, director of NASA's Goddard Institute of Space Studies, testified before the US Senate that, based on computer models and temperature measurements, he was "99 per cent sure the human caused greenhouse effect has been detected and is changing our climate now.
His statement was widely covered by the media and brought the term "global warming to the general public's attention for the first time.Two weeks ago, the Intercontinental Panel on Climate change (IPCC), grouping many hundreds of scientists from 99 countries, confirmed Hansen's forecast and warned that all countries of our planet, rich and poor, will be exposed in the decades to come to natural calamities including rising ocean levels, floods, melting polar ice caps, increased hurricane activities, severe droughts, famines, epidemics and other catastrophes on an unprecedented scale. According to the IPCC report, human activity accounts for the rise in global temperatures: Earth's average temperature rose by 0.6 degrees centigrade during the twentieth century and is expected to rise by 5.8 degrees centigrade in the twenty first.
Hansen and other proponents of the theory that humans are the cause of the dangerous change in the earth's climate point to the fact that since the Industrial Revolution in the mid-eighteenth century, the concentration of carbon dioxide in the Earth's atmosphere has increased by 31 per cent, reaching what is arguably its highest level in 20 million years. According to the IPCC report, snow cover decreased by 10 per cent since the late 1960s, while the twentieth century as a whole saw "a widespread retreat of mountain glaciers and "a rise in sea levels.
This latter development may result in the loss of small islands and tremendous displacement of people in other coastal areas (the Nile Delta and wide parts of t he Netherlands are threatened). Marine species will soon be endangered by changing ocean temperatures, resulting in a catastrophic breakdown in the food chain. One of the core long-term aspects of climate change is the loss of plant and animal species as well. Indeed, many land-dwelling animals will not be able to migrate fast enough to escape weather changes.Particularly critical are the changes now underway at the two poles. The Arctic ice has already lost 40 per cent of its volume in the last four decades. Instead of storing carbon dioxide in the frozen soil, the warming areas are now releasing carbon into the atmosphere. Permafrost has acted as a carbon sink locking away carbon and other greenhouse gases like methane for thousands of years. But there is now evidence that this is no longer the case. Higher temperatures are allowing bacteria is break down the previously frozen organic material. The permafrost in some areas is starting to give back its carbon. About 14 per cent of the carbon stores in the world's soils is estimated to be in the Arctic. This amounts to several hundred gigatonnes (emissions of all greenhouse gases produced by human activities are about six Gt annually). If carbon dioxide is released to one extent or other, this would add prodigiously to the warming that is already happening.
As to Antarctica, there is evidence that it is losing ice at a significant rate. What is vital to establish is whether or not the thinning is accelerating. Since 1992, the West Antarctic ice sheet has lost 31 cubic kilometres of ice. The loss is being caused by changes in the fast flowing Pine Island Glacier (PIG), the largest in West Antarctica. The PIG is two and a half kilometres thick and flows over bedrock over a kilometre and a half below sea level. Scientists speculate about whether a retreat of the West Antarctic glacier could accelerate ice flow from its interior, producing a rise in the sea level and possibly separating PIG from the bedrock underneath, thus leaving it afloat with dramatic consequences. The present theoretical understanding is not sufficient to accurately predict the future evolution of the PIG.
More generally, the information we now have is enough to confirm that human activity plays an undeniable role in global warming, but not enough to tell us how to avert the catastrophes this warming will provoke. Should we, for instance, spend billions of pounds on concrete flood defences, or should we acknowledge that some coastal regions are indefensible and should be abandoned? We are far from knowing enough to allow us to establish unequivocal strategies to face the danger.
What is still more disquieting is that a number of recent scientific discoveries are chipping away at the three cornerstones on which the global warming theory rests, namely, climate models, scientific analyses of past and present climate data and trends, and the assertion that increases in greenhouse gases drive up global temperatures.
In 1990, the IPCC predicted that if no further action were taken to curb greenhouse gas emissions, we could expect an increase in temperature of between 4.5 degrees and 6.0 degrees centigrade by 2050. In 1996, a new IPCC prediction was for an increase of 0.8 degrees to 3.5 degrees centigrade by 2100 -- less than half the warming in twice the time. As models improve, they show less and less warming and a reduced likelihood of harmful environmental events.
A study published in the 2 October 2, 1998, issue of Science showed that around 12,500 years ago global temperature rose by more than 20 degrees Fahrenheit in approximately 50 years -- ten times the catastrophic warming environmentalists claim humans are causing. The finding confirms that global climate can change dramatically in the absence of human influence.
Another study published by Science on 12 March, 1999, concluded that when the Earth shifts from ice ages to warm periods as it does every 100,000 years or so, temperature rise consistently precedes increased carbon dioxide levels by between 400 and a 1000 years. This finding is at odds with the global warming theory and the idea that increased levels of carbon dioxide force temperatures upward.
While scientists cannot afford to neglect evidence that global warming due to human activity will reach critical thresholds in the foreseeable future, they cannot ignore the growing body of evidence that human activity may not be entirely, or even mainly, to blame for global warming. Of course, economic considerations could be involved in either emphasising or dismissing the threats of global warming. Particularly significant in this respect are the differences between the great powers over what strategies should be applied. A protocol, agreed upon in Kyoto, Japan, in 1997, contains legally binding targets by which developed countries must reduce their combined emissions of key greenhouse gases, notably, carbon dioxide, methane and nitrous oxide, by at least 5 per cent by 2010, measured against the base year of 1990. But so far, no global agreement over how this protocol is to be implemented has been reached and the discrepancy between what things are and what they should be is widening dangerously.
At the end of the day, scientists are faced with a dilemma of epic proportions. On the one hand, there is no conclusive evidence that human activities are to blame for global warming; on the other, ignoring the effect human activity may be having in heating up the Earth's atmosphere could have disastrous consequences for the survival of the human species.
© Copyright Al-Ahram Weekly. All rights reserved
 |
|
|||||||||||||||||
| ARCHIVES Letter from the Editor Editorial Board Subscription Advertise! |
WEEKLY ONLINE: www.ahram.org.eg/weekly Updated every Saturday at 11.00 GMT, 2pm local time weeklyweb@ahram.org.eg |
 Al-Ahram Organisation |
Recommend this page