Some gases in the atmosphere, such as carbon dioxide, methane, nitrous oxide, and ozone, absorb energy radiating from the sunlight-warmed surface of the Earth. By preventing this energy from escaping into space, the "greenhouse effect" keeps the Earth warm and hospitable to the life teeming around us. However, human activity is rapidly raising the concentration of greenhouse gases in the atmosphere.
The Intergovernmental Panel on Climate Change, in its fourth assessment of the science and effects of climate change, identified unequivocal evidence that our planet - land, sea, and air - is warming. The Panel concluded, "Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations."
The warming of the Earth is changing its climate. Some areas of the Earth will start getting more rain, and others less. Most places, including New England, will be hotter, though some will be colder. The timing of the seasons, as evidenced, for example, by the first flowers in spring or the first winter ice on ponds, will shift. These and other changes will affect:
Human health, through extreme weather, air pollution, drinking water shortages, and changes in disease patterns;
Local economies, especially in coastal communities, where increased sea levels and flooding and more violent storms will disrupt homes, businesses, infrastructure, and ecosystems;
Water resources, through changes in rainfall, floods, and droughts;
Ecosystems, their biodiversity, and by extension, their vast range of benefits to human societies;
Agriculture, through changes in precipitation, temperature, and disease and pest prevalence.
As greenhouse gases enter the atmosphere in greater amounts, the rate of climate change is predicted to accelerate. Because we all cause greenhouse gas emissions by heating, cooling, and lighting buildings, traveling to work, school, and vacation, changing the use of land, and disposing of waste, it might seem that the problem is impossible to solve. But it is time to change our thinking, to contribute to the solution, to take actions that reduce greenhouse gas emissions and mitigate climate change.