With the end of his presidency in sight, President Bush is thinking about his legacy.

His chief of staff, Joshua Bolten, has reportedly given White House aides clocks set to show how many days and hours remain in this administration. He wants to push them to think about what can still be accomplished.

The Iraq war will define Bush's tenure. But there are a couple of issues on which the president could still improve history's verdict and rescue America's sinking global image. These include global warming and the fight against global hunger and disease. On both, Bush has made some moves in the right direction — then punted.

Last week, the president muffed a great opportunity to re-exert America's standing in the effort to confront global warming. On Monday, the United Nations convened a daylong meeting of 80 heads of state on climate change. Bush skipped the meeting and only attended the private dinner.

Instead, he convened his own "historic meeting" on climate change in Washington on Thursday and Friday. Historic it was, since for seven years administration officials have dismissed concerns about global warming. Having rejected the Kyoto Protocol on climate change, Bush never offered an alternative proposal.

By now, the scientific consensus on the need to curb greenhouse gas emissions has become so overwhelming that even this White House finally had to pay attention. State officials, such as California Gov. Arnold Schwarzenegger, had joined top U.S. energy executives in calling for government action. Everyone knows that U.S. action on curbing emissions is vital. Without it, developing powerhouses such as China and India will never take action.

Instead of providing U.S. leadership at the U.N. conference, Bush isolated U.S. officials further. At the White House gathering, Condoleezza Rice opposed any mandatory limits on emissions and told participants that any curbs should be voluntary, with every country setting its own limits.

This frustrated America's closest allies. John Ashton, a key adviser to the British foreign secretary, put it bluntly: "A voluntary approach to reducing greenhouse gases is hardly likely to be more effective than voluntary speed limits on the roads."

Bush could have spurred international momentum by putting forward a serious proposal. Instead, after raising some hope of a 180-degree turn on the issue, the president then squandered any boost for America's global standing. He convinced many that his only aim was to derail any international pact.

Similarly, Bush's handling of humanitarian foreign aid has failed to enhance his or America's image. This is an area that conservatives once disdained as the preserve of so-called squishy liberals. But Bush knows better. In a world where terrorism is the major threat, humanitarian aid and development funds for the Third World are essential to our security. This is now part of U.S. military doctrine.

In his speech last week to the U.N. General Assembly, Bush hardly mentioned Iraq but focused on the need to free people from hunger, disease, tyranny and violence. U.S. humanitarian aid — both government and private — has been rising. But U.S. aid contributions in per-capita terms still lag way, way behind most industrialized nations (even combining public and private aid). This makes Bush's rhetoric look lame.

Under Bush, the United States gets little credit for what it does give. I talked about this syndrome with the superstar rocker Bono, who was in Philadelphia last week to receive the prestigious Liberty Medal for helping to alleviate poverty in Africa.

"Now you (Americans) lead the world in the fight against HIV/AIDS," Bono said, "yet these are dangerous times for America. Brand USA has never been as vulnerable. The neon is fading on the windows, and in some quarters someone has thrown a petrol bomb through it."

Bono related a conversation he had a few months ago with Marine Gen. James Jones, who recently retired as supreme commander of NATO. Jones told him that stability in troubled areas now required both adequate development and security.

"He said, 'We have billions of technical equipment floating in the Mediterranean, but we are losing the war because (the Palestinian Islamist group) Hamas is building schools,'" Bono related.

"He also said, 'I'm a Marine, and I don't mind being fired at for the right reasons, but not for the wrong reasons.'" When Bono asked what was the wrong reason, Jones replied, "Being American." Jones felt the United States had good intentions, but these were not getting across.

A chilling reminder that, without strong presidential leadership — the type that shows the world our good intentions are matched with deeds — Brand USA will accumulate more tarnish. And George W. Bush's legacy will revolve squarely and solely around Iraq.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer. Reach her at trubin@phillynews.com.