No. The debate is over. There is international consensus that most of the warming observed over the last 50 years is attributable to human activities. (Intergovernmental Panel on Climate Change, 2001; Arctic Climate Impact Assessment, 2004, p.2) Since the publication of those reports, scientists have collected even stronger evidence from ice cores, ocean sediment cores and increasingly sophisticated computer modeling. Even Exxon now admits that the burning of fossil fuels contributes to global warming.

The issue with global warming isnÌt just that the average temperature will rise a few degrees; climate change is evident in many other ways. Disruption of our climate can lead to a number of effects, including:

• increased severity of tropical storms like Katrina
• more frequent droughts, such as those currently affecting the Southwestern US
• rain falling in big events during the winter instead of throughout the growing season
• rising sea level
• disruption of climate-regulating ocean currents
• insect infestations like the spruce bud worms that are killing millions of trees in Alaska and Canada
• loss of biodiversity
• spread of disease

Yes. We have the knowledge and technology we need to help us reduce our emissions of greenhouse gases, but we must act aggressively and act now. The long atmospheric residence time of greenhouse gases and the thermal inertia of the oceans mean that even if we stopped all emissions today, the climate would continue to warm for a few hundred years. This is not a reason to give up -- it is a call to action to avoid the potentially devastating effects of global warming.

The polar regions are important for several reasons. First of all, they are the canaries in the coal mine; effects of global warming are seen first and most dramatically near the poles. Second, warming at the poles directly effects the climate of the rest of the world. Melting ice increases freshwater output from Arctic rivers, slowing ocean circulation and raising the sea level. The retreat of reflective snow and ice cover exposes more area of dark-colored land and water to solar radiation; this additional absorbed heat further warms the oceans and earth. The Arctic permafrost itself may contain the most dire effects of all. As it melts, it releases trapped carbon and methane greenhouse gases. Arctic soils hold one-third of the earthÌs soil carbon. If this were released, it would dwarf human-caused emissions.