A rough deadline for Tuesday saw only 33 out of 195 countries submit pledges for tackling greenhouse gases under UN climate talks scheduled to conclude just over eight months from now.
Analysts, though, said the commitments were generally encouraging, even if the UN's aim to curb warming to two degrees Celsius (3.6 degrees Fahrenheit) remained worryingly distant.
Among major carbon emitters, the United States, the European Union and Russia put their positions on the table as expected, along with Mexico, the first emerging country to do so.
But developing giants China, India and Brazil were absent for now, which could further complicate an already tortured process, these observers added.
"While there has been some progress in what governments are proposing for the post-2020 period, with several countries moving from 'inadequate' to 'medium,' proposals are still a long way from being 2 C compatible," said Bill Hare of Climate Analytics, a monitoring group.
"The delay (in submitting pledges) is going to be a problem," cautioned Celia Gautier of the French branch of Climate Action Network (CAN), an umbrella group of NGOs.
"The more time that countries take, the less keen they will be to comparing their pledges with those of other countries and improving what they've put on the table."
End-March had been set as a loose date for parties to the UN Framework Convention on Climate Change (UNFCCC) to put their proposed measures on the table.
Voluntary but open to scrutiny, these "intended nationally determined contributions" (INDCs) are deemed the core of a post-2020 pact, to be agreed in Paris by December 11, to peg global warming to 2C over pre-industrial levels.
Tuesday's deadline applied to countries "ready to do so" under an agreement in Lima last December, and several big players had already indicated they would make their announcements later.
Parties that had entered their commitments as of March 31 included the No. 2 emitter, the United States; the No. 3, the EU, which represents 28 nations; and Russia, ranked No. 5.
Indian Environment Minister Prakash Javadekar told AFP last week he would submit his country's pledge "in due course" before Paris, but did not give a specific date.
China, the world's No. 1 emitter, Australia and Japan are expected to make their submissions by June, the mid-point in the marathon negotiations this year.
The roster comprises these pledges:
- EUROPEAN UNION: The EU, one of the 196 UNFCCC parties, promised cuts in greenhouse-gas emissions of at least 40 percent by 2030 over a benchmark of 1990, under a binding target approved by its members last October.
- MEXICO: Emissions to peak in 2026 and then fall, plus reductions by 2030 of 22 percent in greenhouse and of 51 percent in heat-trapping "black carbon." The 2030 objectives are compared against "business as usual," meaning the tally for that year on the basis of current trends.
- NORWAY: Cuts in greenhouse gases of at least 40 percent by 2030 over 1990 levels.
- RUSSIA: Its INDC mentions a possible cut in greenhouse gases of 25-30 percent by 2030 over 1990 levels. The country would claim the maximum allowance for carbon-absorbing forests, and approving the pledge will depend on what "major emitters" promise.
- SWITZERLAND: Emissions reduction of 50 percent by 2030 compared to 1990.
- UNITED STATES: Under an initiative unveiled in November, a reduction of 26-28 percent in greenhouse gases by 2025 compared to 2005 levels.
Mafalda Duarte, manager of the Climate Investment Funds (CIF), an $8.3-billion (7.72 billion-euro) vehicle for developing and middle-income countries, said the submissions so far showed countries were "serious about reducing their carbon emissions and taking ambitious actions" on climate change.
A notoriously fractious process, the climate talks aim to seal a deal that eluded the ill-starred Copenhagen summit of 2009.
They pitch economic and national interests against the warnings of scientists, who say greenhouse gases must soon peak and then fall sharply.
One of the biggest hurdles is to agree whether the INDCs are comparable, fair and able to meet the 2 C goal.
UNFCCC chief Christiana Figueres said she was pleased that "many" of the tabled contributions "also speak to longer-term aims representative of progressively increasing ambition over time."
According to the UN's Intergovernmental Panel on Climate Change (IPCC), the global mean temperature could rise by up to 4.8 C this century alone, a recipe for worse drought, flood and rising seas.
A 2 C pathway requires annual greenhouse-gas cuts of 40-70 percent by 2050, compared to levels in 2010—and to zero or below by 2100.
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