(Bloomberg) -- The US just enacted its biggest-ever climate law with massive investments in clean energy that will help significantly slash greenhouse gas emissions. 

But euphoria over the achievement is dimmed by a sobering reality: Talks between Beijing and Washington on the issue have collapsed -- and now diplomats for the world’s two biggest climate polluters are sparring on Twitter, underscoring the tensions threatening global efforts to curb rising temperatures.

The online spat began when Nicholas Burns, the US ambassador to China, took a victory lap on Twitter. 

“The US is acting on climate change,” he boasted. “The recent bill passed by Congress is the largest climate investment in our history and could lead to a roughly 40% reduction in US emissions by 2030.”

Burns ended with a parting shot, insisting that China should follow the US lead and “reconsider its suspension of climate cooperation with the US.”

That drew a rebuke from China’s Foreign Ministry, with a spokesperson tweeting: “Good to hear. But what matters is: Can the US deliver?”

Cooperation between the US and China -- which together account for more than 40% of global greenhouse gas emissions -- is crucial to the international effort to fight climate change. The online skirmish lays bare longstanding climate tensions between the two nations, with Beijing frustrated about Washington’s history of setting aggressive climate goals -- and demanding the same from other countries -- then falling short on meeting them. Under former President Donald Trump, the US walked away from the Paris Agreement. Under both Trump and President Joe Biden, the country has fallen short of its promise to deliver billions in climate funding for developing and vulnerable nations.

The new law -- in combination with a measure enacted in July that devotes $52 billion to domestic semiconductor manufacturing -- marks a sea change in the US approach to clean energy investment. Both measures also threaten China’s dominance of clean-energy technology, from solar panels to batteries. The Inflation Reduction Act, for instance, bars electric vehicle tax credits for cars whose batteries were sourced from China by 2024.

Yet the investments unleashed by the new US law alone won’t be enough to meet the nation’s pledge under the Paris Agreement to slash greenhouse gas emissions at least 50% from 2005 levels by the end of the decade. Independent analysis by the Rhodium Group puts the likely trajectory under the law at 32% to 42% by 2030. 

Supporters say the $374 billion in direct climate and clean-energy spending under the measure promises to unlock billions more in private investment, while triggering heartier action by corporations and local governments to tackle greenhouse gas emissions.  

Still, when both public and private investments are considered, China has been the biggest spender on accelerating the energy transition, according to data compiled by Bloomberg NEF. China spent $297.5 billion last year on the energy transition, while EU member states devoted $155.7 billion and the US $119.7 billion, according to BNEF.

Read More: US Lags China on Climate Spending Even With $374 Billion Package

Yet China also has plans for 169 new and expanded coal projects, deepening the country’s reliance on the fossil fuel at a time when climate change demands a pivot toward lower-emitting power sources.

US-China talks on climate -- invigorated in 2021 by the countries’ top climate envoys, John Kerry and Xie Zhenhua -- had already diminished this year. But they went into a tailspin the moment US House Speaker Nancy Pelosi’s arrived in Taiwan, enraging Beijing. In response, China’s foreign ministry announced it was suspending talks with the US on an array of topics, including crime, illegal immigration and climate. China claims sovereignty over the self-governing island.

US leaders decried the move, with US Secretary of State Antony Blinken calling it “irresponsible” earlier this month. “We should not hold hostage cooperation on matters of global concern because of differences between our two countries,” Blinken said.

The breakdown in talks has alarmed climate activists, who say multilateral action is critical to address the global threat. If the world’s top two greenhouse gas emitters aren’t talking, that diminishes the chance for united, global progress, which was already in jeopardy because of Russia’s invasion of Ukraine and an energy crisis in Europe.

Initially, the US law stoked some calls for China to move faster to reduce its coal consumption. The Twitter exchange, however, shows that “they don’t think the US has caught up with them yet, so they’re not particularly acknowledging any pressure there,” said Alden Meyer, a senior associate with research group E3G.

The US and China had, for a time, found ways to work together climate, despite tensions on other issues, including trade and human rights. For instance, at last November’s UN climate summit, the two countries unveiled a wide-ranging agreement to advance clean energy, combat deforestation and tackle methane emissions. And collaboration between the US and China was critical to developing the 2015 Paris accord itself.

The Twitter exchange underscores how much other issues have now intruded on climate diplomacy. On Tuesday, even as Biden was signing the Inflation Reduction Act into law and climate activists were cheering American progress, China was highlighting the US shortcomings. 

In a tweet, China’s Foreign Ministry said the US should lift sanctions on Chinese solar exports and follow through with its pledge to deliver billions in climate finance. 

©2022 Bloomberg L.P.