While much of the discussion and advocacy at the United Nations climate summit Wednesday focused on a goal of full decarbonization by 2050, the idea ran into stiff opposition from some countries—including developing countries that can’t yet see a pathway to eliminating all fossil fuels by mid-century without imperiling their economic development.

The conflict played out in debates over the method of differentiating carbon reduction targets and responsibilities between developed and developing countries, and on the process for reviewing and verifying countries’ adherence to the carbon reduction commitments they filed with the UN climate secretariat in the months leading up to the Paris conference. At last year’s climate summit in Lima, Peru, negotiators agreed that developing countries would pursue carbon reductions “in light of national circumstances,” implying a continuum of responses to the climate crisis in which each country does what it can.

This year, negotiators are weighing language that applies the requirement for carbon reductions to “countries that are in a position to do so”—a phrase that implies some form of third-party verification—or “countries that are willing to do so,” language that allows more flexibility.

As the negotiations played out, a December 2 analysis in MarketWatch asked one of the key questions surrounding the Paris negotiations: “Will the chosen path to 2030 provide the basis for ending greenhouse-gas emissions later in the century?”

Countries are debating whether a 25%, 30%, or 40% carbon reduction by that year will give them enough momentum to reach full decarbonization. “But the most important issue is whether countries will achieve their 2030 targets in a way that helps them get to zero emissions by 2070 (full decarbonization),” write authors Jeffrey Sachs of Columbia University’s Earth Institute, Guido Schmidt-Traub of the U.N. Sustainable Development Solutions Network, and Jim Williams of the Deep Decarbonization Pathways Project. (The 43-member Climate Vulnerable Forum and the international Climate Action Network are calling for full decarbonization by 2050.)

If countries “merely pursue measures aimed at reducing emissions in the short term, they risk locking their economies into high levels of emissions after 2030,” the MarketWatch article states. “Deep decarbonization requires not natural gas and fuel-efficient vehicles, but zero-carbon electricity and electric vehicles charged on the zero-carbon electricity grid. This more profound transformation, unlike the low-hanging fruit eyed today by many politicians, offers the only path to climate safety.”