For nearly two decades, world governments and international bodies have struggled to form a unified front in the fight against climate change. As parties assemble in Doha, Qatar, for a new round of climate talks next month, the world will likely be reminded of how distant that global compact remains.

In the absence of binding international rules, however, a patchwork of localized carbon markets, offset systems and cap-and-trade schemes have cropped up around the globe, from the state of California to the province of Quebec and far beyond.

Increasingly, these projects are reaching out to each other, adding weight to a movement that appears decreasingly fractured and increasingly interlinked, according to speakers and panelists at the Carbon Forum 2012 in Washington, D.C.

While those linked systems cannot fully stand in for a global climate agreement, they are currently the world's most effective tools for meeting global climate goals, the panelists said.

Localized efforts to regulate carbon, whether undertaken by governments, regional partnerships or private entities, "are a reaction to an international movement towards low carbon," said Christiana Figueres, executive secretary for the U.N. Framework Convention on Climate Change and the forum's opening speaker. "They are preparing for future regulation."

Around the world, many of the largest carbon markets are already forging partnerships. California, the world's ninth-largest economy and the home of its second-largest carbon trading system, is planning to hold a common credit auction with Quebec in early 2013. Australia and the European Union will have their respective carbon markets linked by 2018, and New Zealand may join the partnership via Australia.

In Japan, Tokyo has had a carbon trading system in place since 2010. Korea, Thailand and Vietnam all have programs set to come online in the next few years. And China and India, which together will account for the majority of the world's emissions growth over the next few decades, have both launched regional and citywide cap-and-trade pilot schemes.

The benefits of scaling up

As the world moves toward broader systems of carbon regulation, individual stakeholders are realizing the benefits, in terms of both cost and efficiency, of linking their respective schemes, Figueres said.

"Frankly, experience does show that larger markets are better than smaller markets" for tackling problems on the scale of greenhouse gas regulation, she added.

These markets have grown, in part, by drawing lessons from the success of systems that came before them -- the Regional Greenhouse Gas Initiative, a regional cap-and-trade initiative undertaken by nine northeastern U.S. states, is an oft-cited example -- and many have shown interest in transnational partnerships, panelists said.

"I've been to China; I've seen what they're doing. These projects are real," said Mary Nichols, chairwoman of the California Air Resources Board. Increasingly, she said, those provincial efforts are looking to broaden their base.

"Linkage is about learning how to have a successful market internationally," she added.

Ultimately, however, none of these systems will be able to provide the kind of stability an internationally binding agreement would bring, panelists said.

"You absolutely need climate policy because without overarching commitment, you don't have your main driver" for stakeholders to come on board, said Nichols. "If you don't put a stake in the ground, it's very difficult to muster the necessary resources."