Last September, The Guardian ran the following headline: “New York City accelerates emissions efforts in face of daunting sea level rise.” The story described a city trying to combat climate change and its impacts, a laudable goal. Given the global mechanics of Earth’s atmosphere, though, the headline articulates a profound non-sequitur. It has become popular to champion sub-national governments—cities in particular—as critical contributors in the global effort to limit carbon emissions, because of their capacity to innovate and relatively strong immunity to partisanship. But individual cities face a stronger motivation to adapt to climate change’s near-term effects—examples from The Guardian story include finding ways to live with sea level rise and warmer, stormier weather—than they do to try to help mitigate climate change that may affect them in the longer run. In the politically important shorter run, virtually all the benefits of emission-mitigation by New York City will occur outside city limits, while nearly all the benefits of its adaptation measures will be felt within the five boroughs.
More generally, if local sea level rise is the problem in a given city, then reducing that city’s emissions is an ineffective policy mechanism for dealing with it. Budgets being limited, the city might be better off building barrier walls and drainage systems. On the other hand, if global emissions reduction is the goal, then cities are an inefficient policy platform for achieving it. Consequently, national policy that relies on subnational governments will likely fail to meet national pledges to global mitigation goals, because those goals will be displaced by increasingly urgent local adaptation needs. This is not a call for first-world cities to save themselves by abandoning mitigation for adaptation; rather, the conflicting pressures on local governments show that collective solutions based on national (and potentially global) policies are needed to adequately limit global emissions. Efforts by cities and other subnational governments will not be enough.
Think global, act global. In December 2015 in Paris, 195 Parties to the United Nations Framework Convention on Climate Change (UNFCCC) agreed to a mechanism of voluntary pledges to limit global temperature rise in this century to 2 degrees Celsius above pre-industrial levels (with an ambition to limit the rise to 1.5 degrees Celsius).
The Paris Agreement was a watershed moment for participation by cities in global climate change policy. Organizations like the C40 Cities Climate Leadership Group, ICLEI-Local Governments for Sustainability, and the Global Covenant of Mayors for Climate & Energy all tout their role in creating and implementing the historic agreement. ICLEI estimates that 50 percent of the national pledges made in the Paris Agreement “focus on action at the local or subnational level.” These efforts were lauded in the press: The Economist wrote that “Local policies can combat emissions where international ones fall short” and The Atlantic’s CityLab ran the headline, “Why Cities Are Key to Success at the Paris Climate Talks.”
But there is a two-part problem with this celebration. First, the Paris pledges are insufficient. The latest research suggests that both the pledges and the implementation of the Paris Agreement fall far short of the 2 degree Celsius goal. A recent paper in Nature by Jeffery Greenblatt and Max Wei shows that the United States would fall short of its Paris pledge for 2025 even if the Obama Administration’s climate policies were fully implemented. The latest analysis by Carbon Action Tracker, a consortium of three research organizations, estimates that if all Paris pledges were fully implemented, the global temperature would still rise 2.8 degrees Celsius over pre-industrial levels by 2100. A roundup by the World Resources Institute of various estimates projects end-of-century warming in the range of 2.7 to 3.7 degrees Celsius under full implementation of the Paris pledges.
Savvy observers of the Paris Agreement point out that it was only meant to be the beginning of a virtuous cycle of increasingly ambitious pledges over time. But the insufficiency of current pledges and the uncertainty of future ones raise a second problem. Climate change impacts are already being felt in places around the world. A 2015 report by the UNFCCC clarifying the risks of exceeding the 2 degree Celsius “guard rail” was blunt:
“Significant opportunities for adaptation exist in a world 2 degrees Celsius warmer, although under all of the assessed scenarios some residual risk from adverse impacts remains. There are limited prospects for risk reduction through adaptation in a world 4 degrees Celsius warmer, and impacts would significantly increase in all regions. With that amount of warming, limits to adaptation would be reached in relation to aspects such as urban water supply systems, heat-sensitive people, agricultural productivity and food security, means of implementation, and the preservation of cultural identity.”
Urban conundrums. Cities everywhere have limited resources when it comes to money, ideas, and attention spans. On the margins, cities will make decisions that yield the highest returns on local efforts for the benefit of local interests. For city leaders to do otherwise risks losing the kind of sustained political support needed to make significant change. Nothing that New York City does to mitigate local carbon emissions will limit the impacts of climate change that it already faces: sea-level rise, storm surges, heavy rains and flooding, excessive heat, and so on. It’s a mistake to think that any city or region will volunteer resources to help reduce local emissions when it needs those same resources for climate change adaptation.
So what should cities do, given the limits of local decision-making in meeting global goals?
First, it is critical that local governments understand and advocate for the local net benefits of emissions reductions. Such information can help sustain local commitment to efforts over time. This is different than simply adopting an emissions-reduction goal because it aligns with national or international pledges. Many US cities and states have pledged to reduce greenhouse gas emissions by 80 percent by the year 2050. But cities need to assess the local costs and benefits across a range of local climate policies.
Second, when local governments shift their attention to adaptation, they should consider the impact on efforts to reduce emissions, and where possible, choose investments that can generate benefits for both global mitigation and local adaptation. Certain adaptation strategies, like increased use of air conditioning and diesel back-up generators, can actually harm mitigation efforts. But some strategies, like improved building insulation, watershed management, and restoring wetlands can boost both adaptation and mitigation simultaneously. There are times when identifying and pursuing an integrated approach leads to clear benefits at both the city and global scale.
Meanwhile, national governments and international organizations need to recognize and address the fact that cities can’t solve climate change by themselves. We will need national and global policies—like caps or taxes on carbon dioxide emissions, and trade agreements—that go beyond what cities and states are capable of doing out of enlightened self-interest. Research has long showed the limits of local government in pursuing policy goals such as income redistribution. It is difficult for municipal leaders to sustain policies in which local costs exceed local benefits. And as climate impacts on local areas intensify over the coming years, city and regional governments are likely to see spending marginal dollars on adaptation as more urgent than mitigating future impacts. Only national and international policies seem capable of meeting the mitigation challenge.
To be sure, if enough subnational governments around the world team up, as many have tried to do as part of the Under2 Coalition, they may be able to significantly influence, implement, and enforce the global regime on carbon emissions. And of course, a handful of subnational governments, such as California, are large enough to exert greater powers than all but a few nations. But whether large or in coalition, subnational governments have limited sovereignty in most parts of the world. In the United States, the potential for the national government to preempt city and state policies related to energy, the environment, and climate change casts a troubling shadow.
The recent US presidential election appears to have stopped Washington’s progress on mitigating climate change and made relations among governments more adversarial. The mayors of many US cities have quickly gone from being partners in policy change with the Obama White House to bulwarks against policy change from the Trump White House. In the absence of US national leadership on climate change mitigation, cities do have an important role to play. Nevertheless, relying on cities and states to lead the way in the absence of strong national policies poses grave risks, because local policies will be shaped by local interests—almost certainly failing to meet the collective action challenge of global climate change.
This column is by Mark Alan Hughes, Cornelia Colijn, and Oscar Serpell. Hughes is a Professor of Practice at the University of Pennsylvania and founding director of the Kleinman Center for Energy Policy, where Colijn is deputy director and Oscar Serpell is a research associate. You can follow the group on Twitter @kleinmanenergy.
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