Over a period of decades, the great failure of American foreign policy has been the absence of an effective energy policy.

From Richard Nixon to Barack Obama, American presidents have committed themselves to reducing our dependence on foreign oil to little avail.

As we witness the ongoing devastation of the BP oil spill in the Gulf of Mexico, now is the time to refocus our energies on the threat posed by our dependence on fossil fuels. For the sake of our national security, our economy and our nation’s future, the U.S. must reinvigorate our efforts to move to cleaner, more sustainable sources of energy.

In the short term, our dependence on fossil fuels results in sending billions of dollars to countries that are not always friendly to the United States. Our oil spending sometimes puts us in the position of funding both sides of conflicts and complicates our fight against terrorism. The volatility of global fuel prices further increases our economic vulnerability and makes it more difficult to compete with the rest of the world.

Our consumption of fossil fuels not only leaves us dependent on unsavory governments and unstable regions, but it also contributes to climate change and consequent rises in sea levels, more severe weather events, longer droughts in some areas, worsening floods in others and changes in disease patterns.

As the then-chair of the National Intelligence Council told Congress last year: “Climate change and climate change policies could affect … domestic stability in a number of key states, the opening of new sea lanes and access to raw materials, and the global economy more broadly – with significant geopolitical consequences.”

Climate change, in and of itself, is a national security threat.

Drilling for oil alone will not solve this problem. Neither will being more efficient in the use of energy. Both steps are necessary but not sufficient. Despite comprising less than 5 percent of the world’s population, the United States uses 25 percent of the world’s oil, while controlling only 3 percent of known reserves. This is not sustainable.

It is time for America to seize the opportunity to usher in a clean energy future. Energy is the largest industry, by revenue, in the world, and clean energy technology is poised to be the next breakout technology sector. The government estimates the global market potential for clean energy technologies at more than $180 billion each year. That represents real money, good jobs and a sustainable basis for economic recovery.

Indiana stands to do especially well in the emerging clean energy economy. We are well positioned, with a combination of manufacturing experience, agricultural know-how and a ready supply of renewable resources, such as biomass and wind. As of 2007, Indiana already had more than 1,200 clean-energy businesses employing more than 17,000 people. And recent studies suggest that Indiana could see 45,000 new jobs if comprehensive climate and energy legislation is signed into law.

But we should be realistic about the prominent role oil will play in our economy for years to come. Disentangling ourselves from oil-producing autocracies and unfriendly governments is not a realistic short-term goal.

We must aim to safely increase our energy supply, reduce our energy demand through improved energy-efficiency and step up our investment in alternative fuels.

Americans are up to the challenge. We need our leaders to put in place a framework that will help move the United States away from fossil fuels and toward a clean energy future.

This could be our gift to future generations of Americans: a more secure, more prosperous, more sustainable nation.