VICE News is closely tracking global environmental change. Check out the Tipping Point blog here.
In a document submitted to the United Nations on Tuesday, the Obama administration committed the United States to lowering greenhouse gas emissions by nearly 30 percent in the next 10 years.
The plan, known as an Intended Nationally Determined Contribution (INDC), formalizes a commitment made by Obama in November as part of a joint US-China pledge to reduce greenhouse gas emissions. The US pledge calls for a 26-28 percent emissions cut below 2005 levels by 2025 and requires the pace of emissions reductions to double after 2020.
"Putting this out there early is a critical signal to other countries that have been sitting on the sidelines wondering whether the United States is serious about climate change," Jake Schmidt, director of the International Program at the Natural Resources Defense Council, told VICE News. "It's started to sink in more that things are different in the US than they have been in the last 15 years on climate policy."
In December, the 196 member countries of the United Nations Framework Convention on Climate Change (UNFCCC) will meet in Paris to develop an international agreement on climate action after 2020. That agreement aims to keep warming to within 2 degrees Celsius (3.4 degrees Fahrenheit) above preindustrial temperatures, a limit that most scientists agree could help the world avoid the most catastrophic effects of climate change.
Global temperatures have already risen nearly 1 degree Celsius (1.8 degrees Fahrenheit), according to the United Nations Intergovernmental Panel on Climate Change, and because of the inertia of the Earth's climate system nearly another degree Celsius of warming is likely to occur even if global emissions are drastically cut in the next several years.
And that has some concerned that the level of commitment from the United States, as well as other leading emitters, remains inadequate to hold off dangerous levels of warming.
"While it does get us a step closer on the pathway to 2 degrees, it clearly does not represent the level of ambition that we need," Heather Kaplan, climate change manager for Oxfam America, told VICE News. "We need the United States government to continue to take a leadership role in providing climate finance to the most vulnerable."
Meena Raman of the Third World Network said: "This is a proposal for more drought, more devastated fish stocks, and more wars over water. The US proposal is an ingredient in a recipe for disaster."
In November, the United States pledged $3 billion over the next four years to the UNFCCC's Green Climate Fund, which distributes financing for adaptation measures, like defending coast lines against rising seas, and clean energy projects in developing countries, which have contributed little to global warming but are often the most susceptible to its impacts.
Five other plans have been submitted to the UN since February: the European Union (EU), Mexico, Norway, Switzerland, and Russia, which also submitted its plan today. They cover about 65 percent of greenhouse emissions from the industrialized world, according to the UNFCCC.
The EU committed to reducing emissions 40 percent compared to 1990 levels by 2030. That's an additional 20 percent over its 2020 goal. Russia, which in 2011 was the fourth largest emitter in the world, reiterated its commitment to reducing emissions between 70 and 75 percent below 1990 levels by 2020.
Mexico is the first developing country to submit a plan to the UN, committing to a peak in emissions by 2026 and a 22 percent reduction in greenhouse gases compared to a projected "business as usual" scenario by the year 2030. With investments from other countries, that reduction could increase to 36 percent.
"Importantly, many of these contributions also speak to longer term aims representative of progressively increasing ambition over time," Christiana Figueres, UNFCCC executive secretary, said in a statement. "Over the coming months, we expect many more nations to come forward to make their submissions public. The pace at which these contributions are coming forward bodes well for Paris and beyond."
China's INDC is expected to require the country to peak its emissions by 2030, following the agreement it made with the United States.
Senator Jim Inhofe, a Republican from Oklahoma who chairs the Senate Environment and Public Works Committee, vowed to shoot down Obama's pledge.
"As the Obama administration continues to pursue a radical agenda on global warming, it's clear Americans are beginning to question if the cost of billions of dollars to our economy and tens of thousands of lost job opportunities is really worth it for potentially no gain," Inhofe said in a statement.
Yet, Inhofe — and Congress — may never get to vote on a UN climate agreement. Whatever emerges from the Paris talks is unlikely to take the form of an international treaty, which would require Congressional approval. Instead it's likely to be built around voluntary pledges backed by each nations' head of state.
"At some point, going forward into the future, we are going to need to find ways to have Congress act," David Waskow, international climate director at the World Resources Institute, told VICE News. "But our analysis shows that there is a suite of things using existing authority that can be done to achieve the target set out."
Follow Laura Dattaro on Twitter: @ldattaro