The Group of Eight summit involves leaders from Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.
Around 5,000 protesters will maintain pressure on the leaders by marching within shouting distance of the resort to demand action, not words.
The meeting is hosted by British Prime Minister Tony Blair, who has invited United Nations Secretary General Kofi Annan to come along, as well as the leaders of key nations including Brazil, China, India, South Africa and Mexico, among others.
The leaders are also expected to discuss the Arab-Israeli conflict, the war on terrorism, the spread of weapons of mass destruction and rising oil prices.
Mr Blair has admitted it will be “very difficult” to strike a deal on the global warming problem as the US has repeated its refusal to sign the Kyoto Protocol , insisting that technological developments by 2040 will solve the issue.
The debate is over how much scientific proof there is for the causes of global warming, as well as whether to follow Kyoto targets for cutting carbon emissions blamed for climate change.
However British targets for cutting African poverty appear more hopeful.
UK finance minister Gordon Brown in January developed a three-pronged bid to help poor nations by writing off their debt, doubling development aid and removing protectionist barriers in rich nations.
The G8 last month adopted the first aim of the Marshall Plan, deciding to immediately write off US$40 billion worth of debt owed by 18 mainly African nations,
The second aim, which seeks to raise total annual development aid from $50b to $100b by 2015, is on the agenda for this week’s meeting.
African leaders, who met earlier this week, have taken a common list of demands to Gleneagles, calling for more debt relief and a permanent Africa seat on the UN Security Council.
John Kirkton of the G8 Research Group at the University of Toronto said Gleneagles may be the most successful summit yet, since the group’s first meeting in Rambouillet, France in 1975, then known as G6.
Speaking to AFP, he said there may be a move to draw down export subsidies that make it virtually impossible for Africa’s farmers to sell their produce overseas, a key demand of the anti-poverty lobby.
He said despite the US’ rejection of the Kyoto Protocol, the summit could see rising economic powers China and India become part of a fresh initiative to curb greenhouse gases.
“Gleneagles is destined to say: we’re all in this together, but we all have to act,” he said.