Kennedy: If We Spend $50 Trillion, How Much Will It Lower World Temperatures? (February 15, 2023)

On February 15, 2023, the Senate Budget Committee, chaired by Sen. Sheldon Whitehouse of Rhode Island, held a hearing titled “Climate-Related Economic Risks and Their Costs to the Federal Budget and Global Economy” [1]. Three economists testified: Mark Carney, former governor of the Bank of England and the Bank of Canada, appearing remotely; Robert Litterman, a founding partner of Kepos Capital, former head of risk management at Goldman Sachs and chair of a climate-risk subcommittee for the Commodity Futures Trading Commission; and Douglas Holtz-Eakin, president of the American Action Forum, which describes itself as “a 21st century center-right policy institute,” and director of the Congressional Budget Office from 2003 to 2005 [1][2]. Sen. John Kennedy of Louisiana used his time to press the witnesses on one question: what would cutting U.S. emissions to net zero actually buy? This video shows that exchange. All quotes below are from the official hearing record, Senate Hearing 118-008 [1].

Key Moments

”You’re going to look at $50 trillion”

Kennedy first asked how long the two economists had studied climate change. “Let’s say 15” years, said Litterman; “About 25,” said Holtz-Eakin. Then: “Dr. Litterman, how much will it cost to make the United States of America carbon neutral by 2050?” “I don’t know, sir,” Litterman said. “So, you’re advocating we do these things, but you don’t know the ultimate cost?” “Yes, absolutely. I certainly don’t know the ultimate cost and it’s very uncertain. It depends on innovations.”

Kennedy put the same question to Holtz-Eakin, counting public and private spending. “You’re going to look at $50 trillion,” Holtz-Eakin answered. Kennedy started to say that Holtz-Eakin was advocating that spending, then corrected himself. “If you’re going to do something, do something smart. That’s what I advocated,” Holtz-Eakin said.

”How much will that lower world temperatures?”

“If we spend $50 trillion to make the United States of America carbon neutral by 2050, how much will that lower world temperatures?” Kennedy asked. “I can’t speculate what China and India and the rest of the world has done,” Holtz-Eakin said. Had anyone in the Biden administration said how much? “No.” Does anybody know? “No one can know for sure.”

Litterman gave a similar answer: “Senator, that depends on the rest of the world. We have to work with the rest of the world. We’re in this together.” Kennedy narrowed the question: what if Europe and most Western democracies cooperate, “but India and China don’t”? “If China and India do not help?” Litterman asked. “Yes.” “I don’t know.”

President Xi and the Tooth Fairy

Kennedy asked whether Chinese leader Xi Jinping would “ever do anything that is inconsistent with China’s best interests in the name of global climate change.” Litterman replied, “I understand that China has a federal carbon tax,” and said he believed Xi “understands that we have to work together to address this global problem.” Kennedy closed with three more questions. “Do you believe in the Tooth Fairy?” “No, sir.” “Do you believe in the Easter Bunny?” “No, sir.” “Do you believe that Jimmy Hoffa died of natural causes?” “No, sir.” “Okay. Thank you, Mr. Chairman.”

The Answer the Witnesses Would Not Give

Neither witness offered a number, but climate science provides a rough way to estimate one. The U.N.’s Intergovernmental Panel on Climate Change found in 2021 that warming rises in a “near-linear” relationship with cumulative carbon dioxide emissions: “Each 1000 GtCO2 of cumulative CO2 emissions is assessed to likely cause a 0.27°C to 0.63°C increase in global surface temperature with a best estimate of 0.45°C” [3]. U.S. energy-related emissions were about 4.9 billion metric tons in 2025, according to the Energy Information Administration [4].

As a rough illustration, suppose U.S. energy emissions fell steadily from that level to zero by 2050, instead of staying flat. The avoided emissions would add up to about 61 billion tons by 2050 and about 306 billion tons by 2100. At the IPCC’s best estimate, that is roughly 0.03°C less warming by 2050 and about 0.14°C less by 2100, within a likely range of about 0.08°C to 0.19°C. The illustration counts carbon dioxide from energy only, and the answer would change if U.S. action led other countries to cut faster or pushed emissions abroad. That is why both witnesses said the result depends on what other countries do.

The Record

“You’re going to look at $50 trillion.” Holtz-Eakin, a former director of the Congressional Budget Office, gave the figure at the hearing as his estimate of total public and private spending to make the country carbon neutral by 2050 [1][2].
“No one can know for sure.” The IPCC math above puts the answer for a U.S. path to zero, on its own, at roughly a tenth of a degree Celsius of avoided warming this century: about 0.14°C by 2100 at the best estimate [3][4].
“China has a federal carbon tax.” Not quite. China’s national carbon price comes from an emissions trading system, a market in which companies trade emission allowances. It began trading on July 16, 2021, starting with more than 2,200 power-sector companies responsible for about 40 percent of China’s carbon dioxide emissions [5][6].

What Happened Next

U.S. emissions: EIA data show U.S. energy-related emissions falling from 4,945 million metric tons in 2022 to 4,789 million in 2024, then rising to 4,904 million in 2025 [4].
U.S. policy: On January 20, 2025, his first day back in office, President Trump ordered the U.S. ambassador to the United Nations to submit formal notice of the United States’ withdrawal from the Paris climate agreement [7].
Mark Carney: The former central banker who testified remotely became Canada’s prime minister on March 14, 2025. That day, he said a formal order to dismantle Canada’s consumer carbon tax would follow that afternoon [8].