"Unease is no excuse for inaction."

These were President Obama's words at the United Nations in his most significant speech on climate change since taking office, setting the tone for a bold vision that will hold the U.S.-- and the world-- accountable for its actions on one of the great challenges of our generation. President Obama clearly signaled that the previous eight years of excuses, denials and delays on climate change are no longer acceptable.

"This is a new day. It is a new era. And I am proud to say that the United States has done more to promote clean energy and reduce carbon pollution in the last eight months than at any other time in our history."

From his first days in office, the president has indicated that he is prepared to take a strong leadership role on climate-- both internationally and domestically. In this speech, the president delivered on both fronts.

Reminding us of the work that the administration has already done and the economic promise of a clean energy future, he remarked:

"We're making our government's largest ever investment in renewable energy . . . Across America, entrepreneurs are constructing wind turbines and solar panels and batteries for hybrid cars with the help of loan guarantees and tax credits -- projects that are creating new jobs and new industries."

With high profile meetings at the UN in New York and at the G20 meetings in Pittsburgh, this is an opportunity to demonstrate that the U.S. is ready to take on a leading role in securing an international climate agreement later this year:

"Because no one nation can meet this challenge alone, the United States has also engaged more allies and partners in finding a solution than ever before."

At home, there are new developments, as well. President Obama reminded the world of the historic vote in the House of Representatives and of the need for the Senate to move forward with a comprehensive clean energy and climate bill. And he indicated that he will continue to engage with Congress as the process unfolds.

"Most importantly, the House of Representatives passed an energy and climate bill in June that would finally make clean energy the profitable kind of energy for American businesses and dramatically reduce greenhouse gas emissions. One committee has already acted on this bill in the Senate and I look forward to engaging with others as we move forward."

In the Senate, Senator Boxer and other leaders are preparing to unveil new legislation on clean energy and climate that will provide a framework for the Senate to move forward this year. The EPA has also signaled that it is ready to act to reduce carbon pollution through strong actions, such as the new fuel standards for cars and trucks that were proposed last week.

This week, climate change will be front and center in the media and public's eye. I hope that our leaders in Congress are watching. We need them to be bold and to rise above partisan and petty bickering to engage with this vital issue. We need to ensure that America shows true leadership on this global issue by limiting our carbon pollution and helping to unleash a worldwide transition to clean energy sources. By taking these steps, we can strengthen our economy and our security.

As President Obama said,

"If we can resolve to work tirelessly in common effort, then we will achieve our common purpose: a world that is safer, cleaner, and healthier than the one we found; and a future that is worthy of our children."