President Joe Biden celebrated Earth Day 2021 with a bang: He pledged to reduce US greenhouse gas emissions by more than 50 percent below 2005 levels by 2030.

Under the 2015 Paris Agreement, almost every country on Earth pledged to try to hold the increase in average global temperature to 1.5 degrees Celsius (or 2.7 degrees F)—the threshold scientists have established for staving off the worst effects of climate change. Biden’s ambitious pledge represents the United States' promise to do its part to meet that goal. 

The big question now is what will it take for the United States to fulfill Biden’s promise? 

Short answer: To meet Biden’s goal, the United States would need to embark on a rapid and thorough transformation of our economic and energy systems that would affect just about every aspect of American life.  

Several recent analyses have come to the conclusion that such a sweeping transformation is possible with current technologies. The analyses show that the United States has multiple pathways to achieve a 50 percent reduction in greenhouse gas emissions by 2030. They also show that achieving much more than that would be hard. No matter which path we take, there is only so much that is politically and technologically feasible in nine years. 

All of this is to say that the window for meeting such a target is closing fast—the longer we wait, the further real progress on climate action moves out of reach. Every little bit helps.

“It’s an excellent target in that it fulfills two important dimensions,” said Nathan Hultman, who helped develop the first US emissions-reduction target as a member of the Council on Environmental Quality for the Obama White House. “It’s highly ambitious. It challenges us to start working immediately to implement climate policies across all parts of our economy. At the same time, it’s achievable. It’s going to be a challenge, but it’s a challenge that with determination, effort, and a lot of planning, can be achieved.”

In two recent studies, Hultman, now director of the Center for Global Sustainability at the University of Maryland, modeled the plausible pathways to achieving at least a 50 percent reduction by 2030. Here’s what it would take to get there:

Electricity Generation  

Emissions reductions from the electricity sector could account for more than half of Biden’s goal. By 2030, half of the country’s electricity would need to come from renewable sources such as wind, solar, or hydropower—and that’s more than four times today’s levels. Virtually all of the country’s remaining coal plants would need to shut down unless they incorporate technology that captures carbon dioxide instead of releasing it into the atmosphere. And starting in 2025, nearly all new natural gas plants would need to capture their emissions and bury them underground. 

Biden has backed a proposal for a clean energy standard that would require utilities to get 80 percent of their electricity from emissions-free sources by 2030—a milestone on the way to achieving his campaign promise to make the nation’s power sector “carbon-pollution-free” by 2035. Recent research shows this is technologically feasible—and it wouldn’t raise costs or compromise reliability. 

But Republicans in Congress are showing no signs of supporting Biden’s climate agenda. Their support might not matter. Leah Stokes, an expert on energy and environmental politics at the University of California, Santa Barbara, wrote earlier this year in Vox that Democrats could pass a clean energy standard through budget reconciliation. 

“Cleaning up our electricity system is crucial to meeting Biden’s pledge,” Stokes wrote in an email to Sierra. “If Congress were to pass a clean electricity standard, this would get us more than halfway to that emissions cut.”

Transportation

The tailpipes of American cars and trucks produce more greenhouse gas emissions than any other economic sector in the United States. This takeover has been spurred, in part, by the rapid expansion of wind and solar and the retirement of more than half of the country’s coal plants since 2005—and by Americans’ seemingly insatiable desire for SUVs and large pickup trucks. Reducing emissions from transportation is, therefore, crucial to meeting Biden’s goal.  

To meet Biden’s target, roughly two-thirds of the new cars sold at dealerships would need to be powered by electricity, not gasoline. That’s up from 2 percent today. A recent IHS Markit report illustrated the long road we face to achieve transportation electrification. It projected that just a quarter of new car sales will be fully electric by 2030.

How, then, to make up the difference between current market projections and the president’s goal? The administration has a couple of tools at its disposal. 

Biden has already signed an executive order directing federal agencies to buy zero-emission vehicles, and his new infrastructure and clean energy plan would allocate $174 billion to advance the transition to electric cars and help states and cities install a network of 500,000 vehicle-charging stations by 2030. At the same time, companies such as Amazon and FedEx are replacing their fleets with electric delivery vehicles. General Motors has pledged to completely phase out the internal combustion engine by 2035.

“There’s a lot of momentum,” Hultman said. “But it’s going to take a while for the country’s overall fleet to reflect the number of electric vehicles available on the market because Americans tend to keep their cars for around eight years.”

Buildings

In 2019, buildings in the United States emitted the greenhouse gas equivalent of 577 million metric tons of carbon dioxide. Gas appliances such as furnaces and stoves are partially to blame. Each year, the infrastructure that funnels gas to buildings and homes leaks enough methane (a greenhouse gas 86 times more potent than carbon dioxide) to match the emissions of all vehicles in the country. To meet Biden’s goal, all new buildings would need to be heated by electricity rather than natural gas.

“We used to talk about gas as a bridge fuel,” Hultman said. “We’re getting to the end of that bridge. To reach the 2030 goal, we need to halt and start to reverse the rapid expansion of gas that has happened in the last couple of decades.”

In the last few years, a dozen states—and more than 50 municipalities in California alone—have passed climate action plans or building codes that encourage or mandate the electrification of new buildings. But politicians in other states—including Texas, Arizona, and Louisiana—have pushed back, passing laws that preemptively ban cities from passing so-called gas bans. Climate-action advocates say a federal clean energy standard could include a provision calling for 100 percent building electrification that would supersede state laws.

Oil and Gas Overhaul 

To avoid climate catastrophe, sometime this century the world’s oil and gas corporations and petro-states will have to move past selling fossil fuels. In the short term—meaning, between now and 2030—oil and gas producers must at the very least slash emissions of methane by 60 percent to achieve the Biden goal. 

For starters, this would mean reinstating and strengthening an Obama-era rule that required companies to detect and repair methane leaks at new drilling sites and was rolled back by Donald Trump last summer. There’s already some progress on this front. On April 28, the Senate voted to reverse Trump’s rollback and reinstate the federal limit on methane leaks from oil and gas wells.

Reforestation 

An old-fashioned technology known as trees are one of the best ways to draw down the excess carbon in the atmosphere. And that means that preserving existing forests while reforesting degraded lands is a key strategy to meeting Biden’s ambitions.  

The nation’s forests would need to expand so that they pull 20 percent more carbon dioxide out of the air than they do today. According to a recent study of national forests published in the Proceedings of the National Academy of Sciences, this would mean reforesting at least 81 million acres. Biden has pledged $10 billion to create a New Deal–style Civilian Climate Corps that would put Americans to work restoring the nation’s public lands. 

It’s a beautiful vision, but there’s a hitch. Without a significant investment in nurseries, there won’t be enough tree seedlings to keep up with replanting efforts. A study published in the journal Frontiers in Forests and Global Change found nurseries would have to increase the number of seedlings they grow to at least 5 billion per year—more than three times current levels—to meet Biden’s goal.

Hultman said that it’s important to remember that 2030 is just a waypoint on the path toward 2050, which Biden has set as the deadline for economy-wide net-zero emissions. “While the power and transportation sectors deliver the highest absolute quantity of potential reductions, we can’t focus on power and transportation alone,” Hultman said. “If we’re going to get to 2050, we need to invest in all of these sectors simultaneously.”