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In 2015, lights on the Arc de Triomphe announced the signing of the Paris agreement to curb climate change. But the pact has produced mixed results.

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The Paris climate pact is 5 years old. Is it working?

When world leaders celebrated reaching a landmark climate change agreement in Paris in December 2015, the Eiffel Tower and Arc de Triomphe were illuminated with green floodlights and the message “Accord de Paris c’est fait!” (the Paris agreement is done!). Now, five tumultuous years later, a new slogan might be “travail en cours” (work in progress).

That will be the implicit message sent tomorrow when nations gather—virtually—to look back on what the Paris agreement has achieved in its first half-decade and, more importantly, to unveil new pledges to further cut planet-warming emissions. Although analysts say the pact has helped make progress toward its goal of preventing average global temperatures from increasing by 2°C above preindustrial levels, the effort is also shadowed by ample evidence that many countries aren’t living up to the promises they made in 2015. And even if nations had kept those promises, some researchers forecast that global temperatures would rise by 2.6°C by the end of the century, underlining the need for stronger action.

If a grade is awarded to the Paris pact “based on whether we have any prospect of meeting a 2°C target, from that point of view, it’s probably a D or an F,” says Michael Oppenheimer, a climate scientist and policy expert at Princeton University. But at the same time, he says, the pact has made a “real difference” by helping make climate change “a top concern of all countries.”

The Paris agreement is an unusual hybrid of soaring ambitions and few enforcement mechanisms. Every country in the world signed onto a promise to take steps to keep global temperature increases “well below” 2°C by 2100. Doing so would require weaning off fossil fuels for energy and transportation, halting the loss of forests, overhauling food production, and finding ways to suck greenhouse gases out of the atmosphere. Yet to meet the goal, countries were allowed to come up with their own goals and plans for how to accomplish them. Falling short comes with few concrete penalties.

Signs of progress

The idea was to create a dynamic structure that could evolve along with changes in national economies, technology, and political will, said Christiana Figueres, who headed the U.N. office that coordinated talks leading to the Paris accord. That flexibility, she noted, has recently allowed a number of nations to strengthen their initial pledges by promising to cut their net climate emissions to zero by 2050. The European Union, Canada, South Korea, Japan, South Africa, and the United Kingdom have all made that pledge. U.S. President-elect Joe Biden endorsed the target and has promised to make addressing climate change a centerpiece of his presidency. Meanwhile, China—the world’s single largest source of emissions—has said it will cut climate pollution faster than initially promised, aiming for carbon neutrality by 2060.

“We are constantly seeing the progress of the implementation of the Paris agreement,” Figueres said at a press conference held earlier this week in advance of Saturday’s summit, which was scheduled to be held in Glasgow, U.K., before the pandemic forced its cancellation. “Not as quickly as we want to, but it is definitely moving forward.”

There are also signs that the temperature spikes predicted for later this century are easing slightly. Before the 2015 Paris summit, global emissions were on course to push temperatures up by 3.5°C by 2100, according to estimates by the Climate Action Tracker, a nonprofit science consortium. Now, that trajectory has flattened to 2.9°C.

The shift is the result of a combination of technological, economic, and political changes, says Bill Hare, a physicist and CEO of Climate Analytics, a nonprofit that is part of the consortium. The cost of renewable energy technologies, such as solar power, has plummeted. Economic growth has slowed. Regulations, particularly in European countries, have begun to take a bite out of emissions. In Europe, emissions fell 23% below 1990 levels by 2018. On Friday, EU leaders agreed to a plan for a 55% reduction by 2030.

Setbacks emerge

Such promising moves, however, have been offset by less encouraging developments over the past 5 years. President Donald Trump, for example, withdrew the United States from the Paris deal with few penalties. (Biden plans to rejoin it.) And many U.S. states that rushed to launch a state-level version of the U.S. targets abandoned by Trump are also falling short, according to a new analysis by the Environmental Defense Fund (EDF). Even when accounting for the economic downturn caused by the COVID-19 pandemic, researchers found that states will likely cut emissions by just 18% below 2005 levels by 2025. In contrast, the United States under former President Barack Obama had promised cuts of between 26% and 28%.

“I think it’s easier to speak rhetorically about the importance of climate change than it is to do the hard work of putting in place the regulatory framework that actually ensure pollution declines,” says Pam Kiely, EDF’s senior director of regulatory strategy.

Meanwhile, Russia and Brazil, two other countries key to dealing with climate pollution, have largely thumbed their noses at the Paris agreement. In Brazil, under the government of President Jair Bolsonaro, deforestation has soared in the Amazon, releasing vast amounts of carbon that had been stored in trees and underground.

The challenging path ahead

Warming gases continue to collect in the atmosphere despite the Paris climate pact (top). Emissions are on track to decline (bottom), but deeper cuts are needed to hold warming below 2°C by 2100.

-20 -10 0 10 20 30 40 50 60 70 2000 2020 2040 2060 2080 2100 Historical Greenhouse gas emissions (gigatons of CO 2 /year) Atmospheric CO 2 (ppm) Year Year Ways to beat the heat Current policies2.7°C–3.1°C Current pledges2.6°C With ambitious net zero pledges2.1°C Path to 2°C goal Path to 1.5°C goal 340 350 360 370 380 390 400 410 420 430 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2020
GRAPHICS: (TOP TO BOTTOM) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION; CLIMATE ACTION TRACKER, ADAPTED BY V. ALTOUNIAN/SCIENCE

Such developments enabled global emissions of warming gases to continue climbing to a record high in 2019, according to a new U.N. report. This year, the pandemic has triggered a short-term drop in climate pollution as economies faltered and people avoided travel and worked from home. Emissions fell by about 7% this year compared with 2019, according to a new estimate by an international team of scientists in the journal Earth System Science Data. But emissions are expected to bounce back as economies revive.

What’s next?

The mix of contrasting trends has meant the progress enabled by the Paris agreement has been “very incremental,” Hare says. So, to stay below the 2°C warming threshold—or below the 1.5°C limit that vulnerable island nations say is needed to prevent rising seas from swallowing their communities—the countries gathering at Saturday’s summit will have to commit to stiffer emissions reductions. “What needs to happen in the next few years,” Hare says, “is something much more transformational.”

It’s not clear, however, that the political will exists. There are signs, for example, that many countries won’t be using the emissions reductions caused by the pandemic as an opportunity to give a boost to their climate ambitions. The world’s richest countries, the G-20, have earmarked $12 trillion to address the economic disruption caused by COVID-19, but just one-quarter of the donors are dedicating funds to efforts to reduce carbon emissions, according to a new report from the United Nations Environment Programme. “We’ve never had $10 [trillion] to $20 trillion, which will be spent in the next 24 months, ever before to reboot the world economy,” Andrew Steer, president of the World Resources Institute, said at a press conference this week. “If we invest that in yesterday’s economy we are basically committing a mortal sin for our grandchildren.”

Summitting nations will also face other financial challenges. Many leading developed nations had announced an initiative to double spending on clean energy R&D by this year, an increase of $10 billion per year. So far, however, the effort has raised spending just $4.9 billion. It’s also not clear whether the richest countries are making good on a previously promised $100 billion in annual public and private financing by this year for climate-related work such as renewable energy projects. (Spending had risen to $79 billion in 2018, the most recent year available, from a previous high of $62 billion in 2014, according to the Organisation for Economic Co-operation and Development.)

Meanwhile, the clock is ticking. At current rates, according to one project tracking carbon emissions, the world has 7 years before it has exhausted its budget of carbon to keep temperature increases below 1.5°C.