When the presidents of the two nations that are responsible for 40 percent of Earth's climate-changing greenhouse gases sit down to talk, big things can happen. In the case of Barack Obama and Hu Jintao on Monday and Tuesday, that meant flatly stating that emission reduction targets should be set at an international negotiation on climate change in Copenhagen this December, along with financial assistance figures to help poorer countries mitigate emissions and adapt to a changing climate. Oh, and the world should cut back on deforestation.

Adding those three puzzle pieces together could amount to solving half the globe's climate problem despite involving just four countries—besides the U.S. and China, count in Brazil and Indonesia, which could do plenty by cutting back on their rainforest clearing activities.

But during their summit this week, Jintao and Obama also laid out a comprehensive program to address the clean energy challenge facing both nations, which would go a long way toward reducing greenhouse gas emissions. To wit:

•    the opening of a joint clean energy research center (pdf) with $75 million in funding from China and the U.S. over the next five years. Goals? Energy efficiency, "clean coal" and clean vehicles, among others;

•    Electric vehicle demonstration projects (pdf) and the development of joint standards for the new technology;

•    Joint building efficiency standards, including inspector and auditor training;

•    Renewable energy development roadmaps for both countries, including grid modernization;

•    U.S. assessment of Chinese shale gas (pdf) potential as well as help with development of this lower carbon fuel;

•    22 U.S. companies to help develop clean energy projects in China, including alternative energy, a "smart" grid and greater energy efficiency, among others;

•    corporate and government cooperation on "21st Century Coal," such as developing carbon capture and storage at the so-called GreenGen plant and gasification of coal to help remove pollution before combustion, among other efforts.

Coal is clearly the linchpin of any efforts to address greenhouse gas emissions from the two countries: the U.S. gets half its power from the dirty black rock and China more than 80 percent. In fact, burning coal is the main reason the two countries lead the world in producing global warming pollution. And coal has now surpassed oil as the fossil fuel producing the most greenhouse gases (ending a 40-year run for petroleum), according to the Global Carbon Project, thanks largely to a rapid increase in its burning in China, India and other developing countries.

But as far as efforts to clean coal go, there is currently only one project in the world that both captures and stores the CO2 that would otherwise be emitted from a coal-fired power plant—Mountaineer Power Plant in West Virginia. And that demonstration project captures just 1.5 percent of that 1,3000 megawatt coal-fired power plant's emissions, or 0.00001 percent of global emissions of the greenhouse gas. China and the U.S. working together to solve climate change is exactly what the planet needs, yet it's clear there is a long way to go. In fact, European and environmentalist commentators have charged Obama with being "dishonest" or "fibbing" about climate change.

However, as an ancient (and possibly apocryphal) Chinese philosopher mused: "A journey of a thousand miles begins with a single step." Could this historic visit and agreement be that step for climate change?

Image: Official White House Photo by Pete Souza