Professor of Chemistry Ian Rosenstein began his presentation by discussing where our planet gets its heat from in the first place -- that is, the sun's radiation. When the Earth recieves visible light, UV rays and infared radiation from the sun, some of it is absorbed by the atmosphere or the Earth itself, but much of it is radiated back towards space. The greenhouse effect is what traps the heat of infared radiation in the atmosphere, and is necessary for life on Earth. Rosenstein explained that without the greenhouse effect, the Earth's mean temperature would be around -18 degrees C (0 degrees F), too cold for life to exist on the planet. The gases in the atmosphere which create the greenhouse effect include carbon dioxide, methane, nitrous oxide, ozone and chloroflourocarbons. Most of these gases exist naturally in the atmosphere, but human activity, particularly since the industrial revolution, adds large quantities of extra greenhouse gas into the air. For example, Rosenstein said, fossil fuel production and combustion cause an imbalance in the environment's natural carbon cycle, emitting an approximate 3.3 gigatons of extra carbon into the atmosphere every year. The increase in greenhouse gases in the atmosphere are the probable cause of recent global warming.
Professor of Geology Eugene Domack elaborated on the factors that affect global climate and its fluctuations. Both the sun's natural variability in radiation and large volcanic events can cause temporary changes in the Earth's climate. Humans have only been keeping scientific records of climate variation since the mid 19th century, which Domack pointed out is around the same time we started to change it. There are methods to reconstruct temperature records from much earlier, however, such as tree rings and glaciers. Domack showed data from this sort of analysis showing that the global mean temperature of the planet has been steadily increasing. This increase exceeds any natural variability seen elsewhere in history, a distinct "hockey stick pattern" spiking upward since the 1850s. Domack said that natural forcing factors do not create the sort of drastic climate change that has occurred because of the increase of greenhouse gases. The geological consequences of a continued increase in global temperature include the melting of glaciers, particularly those in the Antarctic, which contain enough water to raise the sea level 200 feet. A change of that sort would inundate many coastal cities and cover small islands. Domack has studied the effect of climate change on the Antarctic ice sheet in his expeditions there, where he saw ice shelves that were beginning to collapse from too many warm summers without adequate time for refreezing in between.
Such drastic changes in climate will obviously create consequences for life on Earth, as Professor of Biology Bill Pfitsch explained. The effect of climate change on the biosphere will be as complex as the Earth's biological systems and communities, he said. A main effect that can be anticipated is a decrease in biodiversity, as warming climate destroys habitats that animals and plants have evolved specially to live in. This is particularly true for trees and other plant species, since they are less able to quickly move as their environment changes. According to a study published in the January 2004 issue of the journal Nature, current climate change patterns would cause anywhere from 15% to 37% of the Earth's species to be committed to extinction by the year 2050, due simply to reduced habitat range. Even for species that do not die out, their life cycle and seasonal activities will be forced to adapt to new climate, or they will be forced to change their habitat. Pfitsch said that there will most likely be a poleward shift to many species' ranges, as well as a shift towards higher elevations.
Professor of Government Peter Cannavo ended the discussion by talking about the ethical and political rammifications of climate change. As a scientific layperson, he said, it seems to him that the scientific community is fairly united in saying that there is a problem with global warming. The question then, according to Cannavo is, "Ought we to prevent this?," and more specifically, "Ought we take political action to prevent this?" To Cannavo, the answer is yes, if only because of the many negative impacts human society will sustain due to climate change, let alone humanity's moral obligation towards the natural world. The negative effects on humans will also be disproportionally born by the poor and by underdeveloped countries, to the extent that climate change could lead to political instability. Cannavo said that issues such as climate change overwhelm our political decision making processes because of their long-term time scale and complexity. All sides in the debate over how to respond to climate change cite the avoidance of risk as a major factor in their opinions -- those against taking action mention the economic risks, while those in favor of action emphasize risks to the natural environment. Currently, the only well developed international plan of action is the 1997 Kyoto Protocol, which was rejected by the Bush administration as well as the governments of other large developed nations. Cannavo recommended that the US and other nations get back on track with the Kyoto Treaty, saying that though it isn't perfect in many ways, it remains the "only game in town" when it comes to preventing the dire consequences of climate change.
The event was sponsored by the Arthur Levitt Public Affairs Center's 2003-2004 series, "The environment: public policy and social responsibility," as well as the Environmental Studies program.