Last month the U.S. signed an ambitious but non-binding global climate change agreement which Secretary of State John Kerry and other international leaders negotiated under the auspices of the U.N. in Paris last December. The deal leans on the “best available science” as a guidepost for nations’ future greenhouse gas emissions reductions.
On April 22, Secretary of State John Kerry joined high-ranking representatives of 175 nations in signing onto a U.N. climate change agreement that he and other international leaders negotiated in Paris last December. President Obama, who has made addressing climate change on multiple fronts a legacy priority of his second term, called the agreement “a tribute to American leadership” and “a turning point for the world.”
The deal establishes a non-binding framework through which nations will commit to increasingly aspirational goals for reducing greenhouse gas (GHG) emissions, with an overarching goal of holding average global temperature “well below” a 2 degrees Celsius rise and preferably no more than a 1.5 degree rise. Nations’ emissions cuts will not be legally binding, but under the deal all 196 signatories have submitted pledges to reduce their emissions to specific targets. Signatory nations will revisit their emissions targets every five years to ensure they are making “ambitious” progress and are committing to reaching peak global GHG emissions “as soon as possible” with “rapid reductions thereafter in accordance with best available science.”
Paris Agreement draws upon climate science past and future
Over the past few decades, fundamental atmospheric science has brought attention to and helped define the problem of climate change. Science has continued to inform negotiations along the way, largely through the use of “emissions scenarios” developed by the U.N. Intergovernmental Panel on Climate Change (IPCC) in conjunction with the world’s leading atmospheric scientists. The emissions scenarios, based on the physical dynamics of the Earth system and the output of sophisticated general circulation models, project the sensitivity of average global temperatures to rising GHG emissions and also the likely risks of rising global temperature on human and natural systems.
The U.N. Framework Convention on Climate Change consensus goal, first adopted at a 2010 conference in Cancún, to hold the increase in average global temperature to no greater than 2 degrees Celsius is a political consensus deeply informed by science. Drawing on the best available science at the time, the parties to the conference agreed that any warming greater than 2 degrees would constitute “dangerous anthropogenic interference with the climate system.”
Altogether, current signatory nation pledges accompanying the Paris Agreement would hold the global temperature increase to about 3 degrees Celsius, falling short of the 2 degrees goal even if all nations meet their commitments. The Obama administration has pledged the U.S. will cut its GHG emissions to 28 percent below 2005 levels by 2025 and by 80 percent or more by 2050.
The preamble of the Paris Agreement calls out the shortfall with great concern:
[There is an] urgent need to address the significant gap between the aggregate effect of Parties’ mitigation pledges in terms of global annual emissions of greenhouse gases by 2020 and aggregate emission pathways consistent with holding the increase in the global average temperature to well below 2 degrees Celsius above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees.
At several points, the agreement calls on signatory nations to use the “best available science” when determining future emissions targets. Science will also play a key role in the monitoring and verification of greenhouse gas emissions reductions. The world’s space agencies are collaborating on a network of six to eight GHG-observing satellites – including NASA’s Orbiting Carbon Observatory-2 (OCO-2), launched in 2014, and OCO-3 in development – that could serve as an independent way to measure greenhouse gases. A 2010 National Academy of Sciences report titled “Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements” called for such a network to usher in a new era of precise measurement of GHG and to assist in effective climate diplomacy.
Notably, the Paris Agreement also invites the IPCC to provide “a special report in 2018 on the impacts of global warming of 1.5 degrees Celsius above pre-industrial levels and related global greenhouse gas emission pathways.”
Democratic leaders support agreement, while Republicans mostly oppose
In the U.S., leading Democrats have received the Paris Agreement favorably. “The signing of the Paris climate agreement represents a historic step in curbing the devastating effects of climate change,” Senate Majority Leader Harry Reid (D-NV) said on social media after Kerry signed the agreement. Likely 2016 Democratic presidential nominee and former Secretary of State Hillary Clinton, who personally negotiated on behalf of the U.S. at the 2009 U.N. climate change summit in Copenhagen, also called the agreement “a historic step forward.”
Republican leaders in Congress and running for president roundly attacked the agreement in the lead up to the Paris talks. Rep. Lamar Smith (R-TX), chairman of the House Science Committee, published an opinion editorial in the National Review on the day Kerry signed the agreement, calling into question “the president’s climate change agenda” and painting climate science as a weak basis for such an agreement:
This administration doesn’t care that many Americans believe climate change is exaggerated, that the scientific justification used for his regulations are flimsy, or that the models he uses to predict climate change impacts are often biased.
A number of scholars and members of Congress, such as Sen. Mike Lee (R-UT), are arguing further that under the Constitution the president must submit the agreement and the pledges for emissions reductions to the Senate for approval. The president and Secretary Kerry were careful to ensure that the agreement contained no legally binding language that would have required approval of a two-thirds majority of the Senate under the Constitution’s provision for Senate ratification of treaties. The result is a deal the president and the State Department say he can commit the U.S. to without the consent of the Senate.
Obama intends to ratify the agreement by executive action later this year. Nevertheless, the president risks the chance that without Senate ratification a future president could undo his executive action, effectively removing the U.S. as a party to the agreement.
“[It is] nothing more than a long-term planning document. The next president could simply tear it up,” said Senate Majority Leader Mitch McConnell (R-KY) on the Senate floor in December.
Sen. Jim Inhofe (R-OK), chairman of the Senate Environment and Public Works Committee, was swift to assert the Senate’s constitutional powers over any legally binding international matter:
This agreement is no more binding than any other ‘agreement’ from any [UN climate conference] over the last 21 years. Senate leadership has already been outspoken in its position that the United States is not legally bound to any agreement setting emissions targets or any financial commitment to it without approval by Congress.
Inhofe and a number of high profile congressional Republicans, including Smith and Sen. Ted Cruz (R-TX), continue to question the integrity of the science that underpins the understanding of climate change as a significant risk. Both have recently held hearings, Cruz in December and Smith in February, featuring a few researchers, such as John Christy, director of the Earth System Science Center at the University of Alabama in Huntsville, who have attempted to poke holes in the scientific consensus on climate change.
Obama, speaking at the Paris conference, made clear his confidence in the science and its clarion call to action:
This one trend, climate change, affects all trends. If we let the world keep warming as fast as it is and sea levels rising as fast as they are, and weather patterns keep shifting in more unexpected ways, then before long we are going to have to devote more and more and more of our economic and military resources not to growing opportunity for our people, but to adapting to the various consequences of a changing planet.