By Bernie Sanders - Burlington Free PressFor the last few doubters who may be holding out for more science on global warming, the answer came recently when a U.N.-funded international panel of experts on climate change released a report concluding with near certainty that human activities -- primarily the burning of fossil fuels -- are the cause of global warming. This report represents consensus among scientists around the world that global warming is real and, if not addressed, will have horrendous consequences for our planet. Eleven of the past 12 years are the warmest on record globally, and 2006 has just been logged as the hottest year for the U.S. The effects of global warming will be felt through more extreme weather events such as floods, heat waves, intense hurricanes and widespread droughts that put increased pressure on already stressed water and food supplies. We will also see new threats to human health, including more outbreaks of infectious diseases such as West Nile virus and malaria. The certainty of rising sea levels and flooded coastlines are now well known. We must never submit to hopelessness in the face of this bad news. Quite the contrary! Our response must be to act boldly and to act NOW. That is why, consistent with Vermont's long-standing concern about the environment, I sought seats on both the Environment and Energy committees. And that is why, within my first days as a U.S. senator, I introduced the most comprehensive set of policies yet proposed to combat global warming: the Global Warming Pollution Reduction Act, S.309. The act calls for the United States to reduce global warming pollutants to 1990 levels by 2020 and requires an 80 percent reduction -- compared to 1990 levels -- by 2050. This will be accomplished by using a combination of mandatory reduction targets for pollutants and incentives that will help develop clean alternative energies. Vermont's former Sen. Jim Jeffords was the original author of this bill last year, and I am proud to have my name on it now. Last year the bill was dead on arrival because Sen. James Inhofe -- then chairman of the Environment Committee -- believes that global warming is a "hoax." Thankfully, this year we have a new Congress with a very different outlook. Sen. Barbara Boxer, the new chair of the Environment Committee, Sen. Leahy and nine other senators have co-sponsored this bill. Since November I have met with dozens of Vermont farmers, entrepreneurs, advocate groups and business owners who are overflowing with ideas on energy conservation and renewable energy generation. Like me, they know that our state can become a leader in the nation by breaking our dependency on fossil fuels and moving toward energy efficiency and sustainable energy. Vermonters also know that in the process, we can not only reverse global warming, but create thousands of good-paying jobs in our state. Through innovative programs in Vermont we have already replaced tens of thousands of incandescent light bulbs with compact fluorescent bulbs, but we have the opportunity to change hundreds of thousands more, saving millions of dollars in energy costs and many tons of greenhouse gas emissions. Energy savings must continue to be delivered to our lowest-income neighbors through strong, federally funded weatherization programs. And we need to encourage the growth of wind, solar, hydropower, hydrogen, geo-thermal and other renewable energy sources through a wide variety of incentives. As we break our dependency on Mideast oil, we also need to support renewable bio-fuels as a new cash crop for our farmers. At the national level, increased fuel-efficiency standards would force car companies to produce vehicles that get much better mileage. Additionally, good, reliable public transit should be available to many more of our citizens. Global warming is a huge threat to the health and well-being of hundreds of millions of people on our planet. Now is the time for all of us -- the government, the business community and ordinary citizens -- to stand together to reverse that trend. My strong hope is that, in that monumental struggle, Vermont will be a national leader. Sen. Bernie Sanders, I-Vt., is a member of the Committee on Environment and Public Works and the Committee on Energy and Natural Resources.