The rationale for the Group of Eight, composed of leading industrialized nations, has been thinning for years. Not only has the group produced little of substance at its annual leaders' summit, but its members are unable to deliver on whatever pledges are produced. Moreover, the political heft of the eight has diminished as other countries have developed and demanded commensurate influence in global political deliberations. Their demand for more input into key institutions has meant that most G8 meetings include almost twice as many participants, as other key nations join the deliberations. But the size of the group, the ad hoc nature of the agenda and the lack of any real follow-through means the meeting is increasingly derided as a photo op, devoid of real substance.

The gap between the group's ambitions and its reality was on full display last week at the annual summit that convened in L'Aquila, Italy. The meeting backdrop may have been more revealing than intended: The summit host, Italian Prime Minister Silvio Berlusconi, decided to hold the get-together in a town devastated by an earthquake only weeks earlier to draw attention to the plight of the residents. So, world leaders occupied the remaining standing buildings while 25,000 people remained in the tents they call home. Mr. Berlusconi may have succeeded in getting the world's media to display the hardships borne by the people of L'Aquila, but it is unlikely that the attention will make their lives any easier.

Sadly, that is likely to be the assessment for the entire summit. One of the key agenda items at the summit was forging consensus on a formula to cut the greenhouse gas emissions that contribute to climate change. As always, real progress proved elusive. The G8 did make a long-term commitment to reduce carbon emissions by 80 percent by 2050, but they set no more immediate targets. But the developed countries continue to demand that their developing counterparts participate in any global regime to fight global warming, a position that is anathema to the developing world, whose leaders argue, not without some justification, that they should not have to pay to fix a problem they did not create. All participants agreed that global average temperatures should not rise over 2 degrees Celsius. But absent a truly global regime, there is little prospect for a genuine solution to the global warming problem.

Or take food security. Coming on the heels of reports that more than 1 billion people worldwide suffer chronic hunger, the need for sustained and systematic efforts to provide aid has never been higher. The G8 governments pledged $20 billion over three years for agricultural assistance to poorer countries. That was $5 billion more than was in the original draft communique, but it is not clear if that is new money or is part of the doubling of aid that was originally promised at the 2005 G8 meeting. Moreover, since the G8 provided $13 billion in assistance since January 2008, then this amount seems a bit small.

The best way for the G8 countries to aid poor and developing nations is to open markets to their goods. As expected, the leaders reconfirmed their "commitment to keep their markets open and free, and to reject protectionism of any kind." That is nice language, but close scrutiny shows that virtually every G8 member has implemented some measures that are trade restricting. Even more important is the need for all governments to push for the completion of the Doha Round of trade negotiations. Those talks were supposed to have been wrapped up in 2004. Instead, they have been stalled for years, despite repeated acknowledgments — by the G8 and other groups — that they are essential to sustaining the momentum for trade and spreading prosperity. Once again, rhetoric outpaces reality and the continued empty promises make the G8 look ineffectual.

If the G8's moment has passed, what will replace it? The obvious contender is the Group of 20, which includes all the G8 members and other economic powers, such as China, Brazil, India, and Saudi Arabia to name but four. Altogether, the group is responsible for 85 percent of global wealth, 80 percent of world trade, and two thirds of the world's population. The inclusion of the remaining 12 countries provides more than just heft, however: Their participation means that G20 decisions enjoy more international legitimacy than do those of the G8.

But if the size of the G20 makes it a more credible global leader, then it also makes consensus more difficult, especially given the diversity of its membership. G20 members cover the range of political and economic models, include both producers and consumers, debtors and creditors, developed and developing nations alike. Finding common ground has been difficult. In fact, the G20's record of delivering on its pledges is little better than that of the G8. That may provide some solace for G8 supporters, but it is not a compelling reason to keep the group going.