The Green Climate Fund, a green bank aimed at supporting developing countries' climate actions, has received a pledge of 10.2 billion U.S. dollars. By June 3, however, only 59 percent of the total pledged money was really delivered. No promised money was transferred from Canada, Italy and the United States yet.

"We urgently need a roadmap to the pledged 100 billion U.S. dollars. These (G7) countries still have plenty of opportunity between now and Paris to step up to the plate," said Anoop Poonia from Climate Action Network South Asia.

Finance and allocation of carbon emission reduction responsibilities are two of the key issues in the ongoing tough climate negotiations under a United Nations framework towards a new global climate deal set to be reached at the end of 2015 in Paris.

Developed countries request developing countries to take a similar binding responsibility of absolutely reducing carbon emissions as they themselves were obliged by their historical responsibility and strong capability to, whereas developing countries insist that a principle of "common but differentiated responsibility" must be respected in the new agreement and, due to their limited capability and needs to develop economy and phase out poverty, they could only make contributions to address climate change in various ways depending on the financial and technology support they received from developed countries.

Analysts said the G7 countries themselves were not making enough efforts to phase out fossil fuels and cut emissions.

"G7 leaders have indicated that fossil fuels are on their way out. However you would not know it by looking at the national emissions reduction pledges they have put on the table for the crucial climate conference in Paris," said Oxfam's spokesman Jorn Kalinski, "They must now live up to their own rhetoric and kick their dirty coal habit."

In its Intended Nationally Determined Contributions (INDC), or climate actions it was willing to take under the new climate deal after 2020, officially submitted to the UN, Canada pledged to cut its greenhouse gas emissions by 30 percent below 2005 levels by 2030.

The pledge was criticized by environmental groups which pointed out that the target was just equivalent to 14 percent below 1990 levels, a more commonly used base year for calculation of emissions reduction.

A similarly weak pledge was planned to be submitted by Japan, whose Prime Minister Shinzo Abe announced earlier this month that his country was willing to reduce carbon emissions to 26 percent below 2013 levels by 2030. When compared with the 1990 levels, the target means Japan would only cut its emission by 18 percent by 2030.

According to Intergovernmental Panel on Climate Change, a scientific body of the UN, developed countries must reduce their emissions by 25-40 percent below 1990 levels by 2020 in order to limit global warming to 2 degrees Celsius above pre-industrial levels.

The European Union, which had already reduced its carbon emissions by 19 percent from 1990 levels in 2013, insisted during the ongoing UN climate talks in Bonn Germany that it was only willing to to further reduce its emissions to 20 percent below 1990 levels by 2020.

"We know that there will be a lot of words at this summit...That's fine as long as there's real action behind it. We are looking for more than 'hot air'. We are looking for real action from this summit," said Adrian Lovett, Europe Executive Director of international campaign group "One" which floated huge balloons depicting G7 leaders on Sunday when the summit started.

"'Hot air' can mean empty promises...when it's all talks, and no action," he said.