On June 1, when President Trump announced that the U.S. would pull out of the 2015 Paris Climate Agreement, Los Angeles Mayor Eric Garcetti announced (see here and here) that his city and 60 others have another plan.

Los Angeles with San Gabriel Mountains in the background. Credit: Todd Jones (Flickr) (CC BY 2.0)

“The President’s denial of global warming is getting a cold reception from America’s cities,” he said in the prepared statement. “As 61 Mayors representing 36 million Americans, we will adopt, honor, and uphold the commitments to the goals enshrined in the Paris Agreement.”

Garcetti was referring to the Mayors National Climate Action Agenda, a coalition of city leaders from around the nation who say cities can play a leading role in the global effort to cut emissions.

The mayors group is one of several that have responded to Trump’s withdrawal from the Paris Agreement with a re-commitment to addressing climate challenges. For years, cities and states have banded together to see how they can make progress on cutting greenhouse gas emissions – not only in coordination with federal initiatives but also independent of them.

The declarations of solidarity with the Paris Agreement sound great to those upset by President Trump’s stark White House Rose Garden. But actually achieving the goal the U.S. and all but two of the world’s countries (Nicaragua and Syria) had agreed to in Paris – 26 percent below 2005 emissions by 2025 – will be tough. The clock is running.

Cities nevertheless can make a tremendous dent in worldwide emissions. They consume more than two-thirds of the world’s energy, and they account for 70 percent of global emissions, according to the C40 Cities Climate Leadership Group, which connects 80 cities around the world to promote urban actions to reduce greenhouse gas emissions.

”L.A., Click To Tweet

Committing to the Paris Agreement goals is a worthy goal for countless U.S. cities and states, business, universities, and other entities beyond the federal government. It sets a target, and it keeps people and organizations moving forward, and voicing their commitment can help generate momentum. But it’s important to fully understand the challenge, to quantify it, and to take stock of where we are today on the road to meeting those lofty and ambitious goals.

A quick look at one city, Los Angeles, and one state, California, offers insights into the actual scale of the challenge.

L.A., the ‘City of Angels’

In 2015, Garcetti released his city’s latest plan to cut greenhouse gas emissions – 45 percent by 2025, 60 percent by 2035, and 80 percent by 2050 – all against a 1990 baseline of 36.2 million metric tons of CO2 equivalent, or MMTCO2e. (The word “equivalent” refers to the concentration of carbon dioxide that would cause the same amount of atmospheric warming as a given type and concentration of greenhouse gas, such as methane or nitrous oxide.)

Los Angeles, with a population of about 4 million, has made extraordinary progress since 1990. By 2013, greenhouse gas emissions had fallen to 29 MMTCO2e, according to the Los Angeles Climate Action Report, released at the end of 2015. That’s a drop of nearly 20 percent over a period when the city grew from a population of 3.4 million to 4 million. One persistent challenge pops out of the city’s own report: carbon emissions from transportation grew as a percentage of the total, from 30 percent in 1990 to 34 percent in 2013. Further progress overall clearly will require an expansion in public transportation, more electric cars, and other efforts to get more gas-powered cars and trucks off the road.

Garcetti’s goal of cutting emissions to 80 percent from 1990 levels, meanwhile, is hard to imagine. Annual greenhouse gas emissions would have to fall to 7.24 MMTCO2e by mid-century.

It’s also worth recognizing the obvious: The city of Los Angeles isn’t an island; it’s part of a greater metropolitan area that’s home to more than 10 million people. Los Angeles County, which includes 15 cities from Lancaster in the north to Long Beach in the south, and from Santa Monica in the west to Pomona in the east, has a long way to go. A report released in April by researchers at UCLA gave the county a “C” grade in energy use and air quality. The report noted the region’s “failure to reduce fuel use, increasing commute times and some of the worst smog in the nation,” the Los Angeles Times reported on April 27.

The ‘Golden State’

California, with the most ambitious goals in the country to reduce emissions, has led the nation in expanding renewable energy and electric car sales, and it has vocal political leadership committed to a low-carbon future. But look at the numbers, and the enormity of the task ahead comes into focus.

In 2005, greenhouse gas emissions statewide totaled 482 million metric tons of CO2 equivalent (MMTCO2e). Of that total, 423 million tons was actually CO2.

Greenhouse gas emissions for 2015 – the latest year for which data is available – totaled 440.4 MMTCO2e. That’s an 8.6 percent drop from 2005 levels.

Those reductions come during a period when the state’s population has grown to 39 million – although growth over the past decade has slowed. The 8.6 percent drop in emissions is impressive, but it’s far from the 26 percent drop needed by 2025 to meet the Paris Agreement target for the U.S.

California’s own latest targets, championed by the governor and set by the state legislature over the past decade, call for emissions to fall 40 percent below 1990 levels by 2030, and 80 percent below 1990 levels by 2050. Here’s what those goals mean, in hard numbers:

1990 GHG emissions: 431 MMTCO2e
40 percent below 1990 levels by 2030: 258 MMTCO2e
80 percent below 1990 levels by 2050: 86.2 MMTCO2e

Keep in mind: by 2050 the state’s population is projected to grow to 50 million people.

Energizing cities toward action

The Mayors National Climate Action Agenda, which Garcetti co-founded, is one of several initiatives by alliances of cities around the world: the Compact of Mayors and the C40 Cities Climate Leadership Group are among others.

On June 5, former New York City Mayor and philanthropist Mike Bloomberg announced (see here and here) a new effort by more than 1,200 U.S. mayors, governors, state attorneys general, business executives, investors, and college and university administrators to independently strive toward the Paris Agreement goals. “American society remains committed to achieving the emission reductions we pledged to make in Paris in 2015,” said Bloomberg, who serves as the United Nations Secretary-General’s Special Envoy for Cities and Climate Change, in a prepared statement.

Bloomberg’s group submitted a declaration titled “We Are Still In” to UN Secretary General Antonio Guterres and the UN Framework Convention on Climate Change (UNFCCC). The declaration states that President Trump’s withdraw from the Paris accord is “out of step with what is happening in the United States.”

Local and state governments and businesses have been primarily responsible for reductions in carbon emissions in recent years, and “actions by each group will multiply and accelerate in the years ahead, no matter what policies Washington may adopt.”

In cities, urban density can provide opportunities for less carbon-intensive living. Making public transportation powered by renewable energy and easier to use is obviously one solution. So is making cities more conducive to walking and bicycling. Office towers, apartment complexes, civic buildings, and other structures can be made more energy efficient.

Cities in general have a strong motivation to act. More than 90 percent of all urban areas are on the coasts and vulnerable to flooding as seas rise and storm surges become more destructive, according to the C40 Cities group. Remember Sandy and Katrina? But cities can also be islands of extreme heat, and a recent study concluded that global warming combined with localized urban heating could raise average temperatures in some of the world’s cities more than 14 degrees Fahrenheit by 2100.

Beyond lowering carbon emissions, Los Angeles also has been studying how to combat the urban heat island effect in a variety of ways, according to a recent Los Angeles Times report. Garcetti wants to lower average temperatures in the city by three degrees Fahrenheit over the next 20 years. It’s an effort to limit what L.A. experienced last summer, when it endured five straight day-time high temperatures of more than 100 degrees. That kind of heat was consistent with 2016 globally – the warmest year on record for the planet. The summer of 2016 could be a mild prelude to what’s in store for Los Angeles: By 2050, the city could see 22 days per year exceeding 95 degrees, computer models suggest.

Faced with that kind of forecast, the city is looking to replace city streets and sidewalks with materials that reflect more sunlight during the day and, as a result, stay cooler at night. In one test, the city found that these “cool pavements” were 11 degrees cooler than conventional pavement during peak afternoon temperatures. “Cool roofs” also could help lower city surface temperatures.

Climate conditions from one part of the city to the next can vary dramatically – with some neighborhoods cooled by sea breezes and others oppressed by heat trapped by the surrounding geography.

One surprising finding the city made was that xeriscaping, immensely popular across Southern California since the recent drought, actually makes surface temperatures warmer. Because drought-tolerant landscaping needs less water, there’s less water in the soil, and as a result less evapotranspiration. In other words, less water evaporates out of the ground, taking heat with it. At night, when heat rises from the ground, water in the soil helps with that heat transfer; dry soil inhibits it. “That means drought-tolerant landscaping could reduce the nighttime temperature by about 5.4 degrees,” said the Los Angeles Times report.

As cities tackle the climate change challenge, lowering carbon emissions definitely will be only one goal. Another will involve making cities cooler and more livable places.

Bruce Lieberman

Bruce Lieberman, a long-time journalist, has covered climate change science, policy, and politics for nearly two decades. A newspaper reporter for 20 years, Bruce worked for The San Diego Union-Tribune...