Last year was the second warmest since regular records began 120 years ago, according to the National Climatic Data Center, and scientists predict 2002 may be the warmest year yet. Global warming is here, and an international panel of scientists has determined that humans are in large part responsible.

Burning coal to generate electricity in power plants, driving cars, and heating our homes with oil are examples of activities that release carbon dioxide and other pollutants into the air. Many of these pollutants remain in our atmosphere for decades or even centuries, creating a blanket that surrounds the Earth, trapping heat and raising temperatures on the ground.

But the changes brought by global warming don’t just mean warmer temperatures. The projected shift in worldwide temperature could bring major disruptions, from coastal flooding to changes in crop production, which affect us all. Simple steps now, along with planning and adaptation strategies, can help minimize the damage without sacrificing our economy or our quality of life.

The crucial step is to reduce global warming pollution immediately. Some of the largest corporations are already doing so voluntarily. The federal government should require these reductions and develop incentives to reduce pollution from big and small businesses as well as individuals. The Bush administration also needs to restore the United States to its leadership role in the international effort to control global warming.

Here’s a glimpse at what the nation could look like in 100 years if we don’t take prudent steps now to reverse the warming trend:

It is likely that many areas will be much hotter than today. In Des Moines, Iowa, according to some models, the number of days a year with temperatures over 90 degrees could nearly double, rising from the current average of 30 days to more than 50 days – that’s nearly two months of 90-degree-plus weather. Houston could go from a handful of days above 100 degrees to more than a month.

Because warm temperatures increase smog, global warming could mean worse urban air pollution. Smog contributes to respiratory ailments like asthma and is responsible for thousands of hospital visits every year.

Steamy temperatures also could cause tropical diseases like dengue fever to move northward in the United States. Widely reported incidences of West Nile virus here could be a harbinger of more to come.

Melting glaciers and expanding oceans could cause flooding to become common in many areas. The nation’s capital, for example, built on former swampland bordering the Potomac River, is already susceptible to flooding.

In places like North Carolina and Florida, heavy downpours like those associated with 1999’s Hurricane Floyd could increase the threat of death and property damage and contaminate beaches already threatened by rising water.

On the West Coast, the climate may become increasingly variable, with more severe storms alternating with more severe droughts. An increase in El Nino-type conditions, already more common, could add to the severity of winter storms. More severe storms and a rising ocean could decimate many California beaches and harm marine animals such as sea lions. More frequent droughts and hotter temperatures also could increase the risk of wildfires.

Without proper policies to reduce pollution, the heartland will also feel the effects of climate change. A warmer climate could mean a longer growing season, but such a change would also bring massive shifts in crop production, with the growing region for the Midwest’s current staple crops shifting northward. The changes also could mean increased flooding along major rivers like the Mississippi and a greater threat of pests and diseases.

Given the severity of the potential damages predicted by scientists, it makes sense to take prudent action now to reduce the risks. Protecting the nation from global warming doesn’t have to mean our economy will suffer, as some politicians have claimed.

Leading companies are already proving they can reduce global warming pollution and still make a profit. A small expenditure now in the form of smart policies and sound planning will help us avoid paying a higher price later.

Janine Bloomfield is a senior scientist for Environmental Defense, a national nonprofit organization.