Future historians will inevitably judge all 21st century presidents as failures if the world doesn’t stop catastrophic global warming.

If global warming exceeds 5°C (or even 3°C), then we will head inexorably toward an ice free planet with widespread desertification, sea levels rising 6 to 12 inches a decade for centuries, the oceans turning into a hot, acidic dead zone, and a billion or more environmental refugees; enduring such harsh misery, we will care little about Iraq, health care, an early 21st century recession, or the budget deficit.

Passing strong domestic climate legislation by itself cannot make Obama a successful president, let alone a great one, since we generate under one-quarter of world CO2 emissions and are an even smaller fraction of future growth. To be a great president, Obama must bring the entire world together onto a sustainable path.

Part 1 explained why Obama can’t get a global climate treaty ratified in the U.S. Senate. So what should Obama do instead? That is the subject of my new piece in Salon (click here):

Grist thanks its sponsors. Become one.

Since conservatives can ensure there is no U.S.-ratified treaty, Obama must pursue a different strategy, a high-leverage approach focusing on the world’s major emitters. Only two dozen countries account for about 85 percent of global emissions, and none of the remaining countries alone accounts for even 1 percent. Obama needs to move toward replacing the UNFCCC process with one that focuses on bilateral and multilateral negotiations with the major emitters, the most important of which is China. Together, our two countries account for nearly half of CO2 emissions from burning fossil fuels.

Talks with China over climate action will probably be the most difficult and most important negotiations in U.S. and world history. I have spoken to a number of experts on Chinese energy and climate policy, who say the leaders of the country understand the nature of the threat that climate change poses to them — including the loss of inland glaciers that provide water for the rivers on which hundreds of millions rely. They say that strong U.S. domestic action, coupled with strong U.S. international leadership, could move China to act. Others tell me China will not agree to emissions reductions anytime soon, since it sees itself as a developing nation with much higher priorities.

In fact, China is in a special category by itself. It has announced plans to spend more than half a trillion dollars on an economic stimulus and infrastructure plan. It is a hyper-developing country, with vast amounts of capital in key advanced technologies, including wind and solar.

At the same time, China has become the leader in carbon dioxide emissions. It is now at about 7 billion metric tons of CO2 a year, rising several percent a year. What would happen if it spent most of its stimulus money on clean energy and related infrastructure? Suppose it used some of it to build up an industry in concentrated solar thermal power and other clean technologies? Half a trillion dollars should be enough to keep Chinese emissions frozen for more than a decade, and possibly two decades, while dramatically reducing the projected air pollution. It could also ensure China’s leadership in the key clean-tech industries of the century.

Grist thanks its sponsors. Become one.

From a strictly economic point of view, China has the know-how and skilled labor to meet a 20-year cap on emissions, starting sometime in the next few years. China is already the world’s top manufacturer of both wind turbines and biogas fermenters. It is projected to become the top manufacturer of solar photovoltaics by 2010. And it has aggressively pursued leadership in electric drives for cars.

China is pursuing cleantech so aggressively that, were it not for the election of Obama, they would have been a lock to be the global leader in the clean energy production and export.

Last month, the Chinese premier opened a two-day climate conference in Beijing by calling on the rich nations to spend 1 percent of their GDP on clean-technology projects in the developing world. That would be more than $280 billion a year, with nearly half from the United States. Whether such action by the rich countries ever becomes politically feasible, one thing is certain: Americans won’t embrace giving much money to China, which already gets hundreds of billions of dollars from Americans each year, thanks to our large and growing trade deficit.

What’s more, I fear China has been building coal plants at such a rapid rate, two a week for many years, while knowing that those emissions and those plants are not sustainable, at least in part under the dubious assumption that the West will at some point pay to shut the plants down. After all, the West got suckered into giving China some $6 billion to destroy greenhouse gas refrigerants that probably cost Chinese companies $100 million to capture and destroy.

The entire Clean Development Mechanism should be scaled back sharply or eliminated (see “You can call a rip-offset a CDM project, but it’s still a rip-offset“). In any case, Americans are never going to pay a country as rich and successful as China to shut down its coal plants — certainly not in 10 years when China is even richer.

The health and well-being of future generations rests on the United States and China ending their mutual suicide pact. China won’t act until we do, and we won’t act if they don’t. President Obama can lead this nation in breaking half of that self-destructive cycle with a strong domestic climate bill. He has repeatedly laid out the targets: returning to 1990 emissions levels by 2020 and then reducing them another 80 percent by 2050. And that’s on top of a major energy bill and green recovery plan that will jump-start the transition to a clean energy economy.

But domestic legislation alone will not make Obama a successful president, let alone a great one. Future historians will inevitably judge all 21st-century presidents as failures if the world doesn’t stop catastrophic global warming. If Obama wants to be a great president, he will not merely have to put this country on a sustainable path; he will have to help bring China and the whole world onto that path too. And that is almost certainly the single hardest task he faces as president.

Obama said many times during the campaign that he would meet with our worst enemies in the name of world peace. Climate change is a far graver and for more preventable threat to the health and well-being of future generations of Americans than any current national security threat.

During the transition period, Obama should appoint a high-level envoy — paging Al Gore — to engage in direct shuttle diplomacy with China and other key emitters. He should meet with Chinese leaders himself in the first half of 2009. His presidency — and the fate of humanity — depend on it.

The Salon piece is here.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.