MY VIEW
We must take the necessary steps to slow global warming
by Sarah Oktay
If you believe some form of global warming exists either as human-induced or as natural planetary weather cycles or unexplainable phenomena, with the potential impacts on Nantucket in mind, what are your thoughts on its validity, how it is caused or not caused, and what should be done to neutralize or even reverse it? The National Academy of Sciences, The American Geophysical Union, The American Meteorological Society, and the Intergovernmental Panel on Climate Change (IPCC) have all issued statements affirming that climate change is underway, the impacts are significant and humans have influenced recent climate changes. According to the IPCC in its Third Assessment Report (2001): "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities." This statement is backed by over 2,500 scientists from 100 countries and supported by hundreds of peer-reviewed articles.

Combustion of fossil fuels, burning of forests and land-use changes have contributed to a 34-percent increase in atmospheric carbon dioxide (CO2) and a 150-percent increase in methane (CH4), both greenhouse gases (GHG) that warm the planet. Current atmospheric CO2 concentrations, at 380 parts per million, are the highest they have been, in 400,000 years. A warming trend of about 1°F has been recorded since the late 19th century. Warming has occurred in both the northern and southern hemispheres and over the oceans. Confirmation of global warming is further substantiated by melting glaciers, decreased snow cover in the northern hemisphere, thawing of permafrost, lengthening of the growing season in middle and high latitudes; a poleward and upward shift of plant and animal ranges, a startling change in ocean wide currents from melting northern latitude ice; and earlier flowering of trees, emergence of insects and egg-laying in birds. Fortunately, the biosphere and oceans have absorbed nearly half of the anthropogenic CO2 in recent decades. Without these "sinks" of CO2, atmospheric concentrations would be even higher and so would the expected temperature increases.

Figuring out to what extent humans are responsible for the global warming trend is not easy because many factors, both natural and human, affect our planet's temperature. When climate scientists look at the entire last century, however, they are unable to explain the significant temperature increases solely from natural planetary and meteorological variations due to the cycles of the earth's orbit and distance from the sun. Only after humaninduced inputs are inserted into these models do the model results and the recorded temperature changes match up. This is particularly true of the pronounced warming that has occurred since 1970.

Scientists predict that continued global warming on the order of 2.5° to 10.4°F over the next 100 years will result in a rise in sea level of 0.3-0.5 meters and greater threats to human health as mosquitoes and other disease-carrying insects spread diseases over larger geographical regions. Worldwide, significant agricultural disruption will occur due to dramatic fluctuations in precipitation, and significant property and human losses could occur from the inundation of low-lying areas such as Bangladesh and the Mississippi River delta, as we have seen over the past few years.

The impacts to Nantucket include more property damage and erosion during storms, higher costs for consumer goods, changes in migration patterns for birds and butterflies, a potential propensity for more powerful storms and a loss of land in lowlying areas such as Coatue and Madaket. Fortunately, although most scientists believe that is it impossible to reverse global warming trends, we can slow down anthropogenic contributions and use technology to adapt to some of the changing conditions.

Governments can reduce greenhouse gas emissions by increasing energy efficiency standards, encouraging the use of renewable energy sources, eliminating subsidies that support the use of coal and oil by making them artificially cheap, and protecting and restoring forests, which serve as important storehouses of carbon. We have the technology to significantly increase fuel efficiency in our vehicles; what we need is the political will. It is disgraceful that in the past 25 years, the average gas mileage for vehicles in the U.S. has only increased by 0.5 gallons!

Individuals can reduce their use of fossil fuels (and often save money) by driving less and by buying fuel-efficient cars, and through the use of energy saving appliances and greater home insulation. As energy costs rise, more people may be willing to use energy-saving devices. Many people find the web site http://www.carbonfootprint.com/ useful in determining their "carbon footprint" which allows them to "trade off" some of their carbon usage with deliberate attempts to reduce their energy load on the environment. For Nantucketers, shopping intelligently and considering the fuel cost of shipping items to the island is a great way to save energy and reduce greenhouse gases.

Businesses can increase efficiency and save substantial sums by doing the same things on a larger scale. Many large corporations have already reported substantial savings after they instituted measures to reduce GHG emissions.

One success story is the global reduction in the use of chloroflurocarbons (CFCs) as accelerants and coolants. Some CFCs act as trace gases, which have a much greater impact on atmospheric warming than does CO2. Most scientists believe that the Kyoto Treaty needs to be modified to emphasize reductions of trace gases such as methane and nitrous oxide in addition to CO2.

In conclusion, most scientists agree that at least a portion of the observed increase in both atmospheric and oceanic temperature is attributable to human inputs. Questions remain on the amount of natural contributions and the ability of the earth's feedback systems to ameliorate the buildup on carbon in the atmosphere. We need to aggressively implement readily available technologies for improving building energy efficiency, harnessing alternative and clean power options and increasing vehicle gas mileage. Each step we take as individuals and nations can significantly reduce this problem.

- Sarah Oktay, who has a Ph.D in chemical

oceanography, is the managing director for the University of Massachusetts Boston Nantucket Field

Station/Grace Grossman Environmental Center.