When climate negotiators meet in Bangkok this week for the latest session of the UN Framework Convention on Climate Change (UNFCCC), they will (hopefully) begin substantive discussions under new terms better reflecting how much the world has changed since the Convention’s adoption in 1992.

Of particular relevance is the dramatic shift in the distribution of global carbon dioxide (CO₂) emissions over the past two decades, as highlighted in the Netherlands Environmental Assessment Agency’s 2012 Trends in global CO₂ emissions. A telling statistic: In 1990, industrialized countries that negotiated targets under the Kyoto Protocol (including the U.S.) accounted for 68 percent of global CO₂ emissions; in 2011, the authors estimate, this share was 41 percent.  Developing countries now account for well over half of annual global emissions – with China and India generating a full third.

Add to this that the U.S. never ratified the Kyoto Protocol, and that starting in 2013 even fewer countries will be covered by it, and the need for a new, more balanced, multilateral agreement becomes stark. These trends are neither unknown nor surprising. They follow broader shifts in global production, consumption, and economic growth. Until last year, however, they were not well reflected within the UNFCCC process. The year-end conference in Durban, South Africa, launched a new round of negotiations called Durban Platform on Enhanced Action aiming for an agreement in 2015 to apply in 2020.

In contrast to the 1995 Berlin Mandate launching the Kyoto Protocol negotiations, which explicitly excluded developing countries from new commitments, the Durban Platform calls for a legal outcome ”applicable to all Parties.” This more inclusive approach is timely and necessary. The Trends report notes that to limit average global temperature increase to 2 degrees Celsius, cumulative CO₂ emissions from 2000 to 2050 must not exceed 1000 billion to 1500 billion metric tons. In just over a decade, we have emitted 370 billion to 470 billion metric tons, and emissions continue to increase.

Following a May meeting at which it took a week for the chairpersons and agenda of the Ad-hoc Working Group on the Durban Platform to be decided, delegates must now roll up their sleeves and tackle issues of substance. Over the next three years, they will hopefully arrive at an agreement that is effective and durable.  The difficulty of anticipating how the world might evolve and the importance of accounting for inevitable evolution are important lessons of the Convention’s past two decades.

Countries’ individual circumstances vary significantly of course, and they have different and evolving responsibilities and capacities to undertake action, as reflected in the UNFCCC’s principles. The Trends report also shows how differently countries compare depending on whether one looks at total emissions, per capita emissions, or emissions per unit of economic output. It is easy to allocate blame for both historic and future emissions; looking at the data reminds us of our collective responsibility, and our shared interest in all countries – particularly the top 25 emitters – taking meaningful mitigation action.

In a proverb attributed to Lao Tzu that is frequently (and understandably) quoted within the UNFCCC negotiations, the Bangkok meeting represents the substantive “single step” in the “journey of a thousand miles” the Durban Platform negotiations represent.