Climate scientists continue to unravel the mystery of why the planet was so hot last year and how that record heat has kept up through this year.

Why it matters: The lack of a complete explanation could mean that the climate is behaving in new and unexpected ways, due largely to human-caused emissions of greenhouse gases.

• If so, then a faster warmup — with potentially devastating consequences — could happen sooner than climate projections have shown.

The big picture: Two new studies provide insights about factors that may have helped boost the planet's temperatures during the last two years, above what would normally be expected during a strong El Niño episode in the equatorial tropical Pacific Ocean.

• A study published Nov. 28 in the journal Earth Systems Dynamics examined the effects of a switch to reduced sulfur fuel sources for container ships that went into effect in January 2020.
• The fuel shift was made to reduce air pollution. But in doing so, it cut down on emissions of tiny particles known as sulfate aerosols.
• These particles can reflect incoming solar radiation and help cool the planet.

Climate scientists are asking whether this fuel change, which the International Maritime Organization mandated, has influenced the climate to the extent that it largely explains the past two years' anomalous warming.

Zoom in: The study, by two Cornell University researchers, found that the marine shipping emissions shifts made 2023's record global heat significantly more likely than what would have occurred without it.

Yes, but: The researchers' estimates of the shipping contribution to warming came out on the higher end of what the scientific literature shows on this topic.

The intrigue: Another new study, published in Science on Dec. 5, investigates a decline in low-cloud cover in the northern mid-latitudes and tropics, which could also be causing increased warming rates.

• Reducing low clouds can trap more heat in Earth's atmosphere. Clouds' net warming effects depend on their altitude and composition.
• Depending on the driving forces behind the cloud trends, the study's findings are a potential warning sign since they could imply faster warming rates would continue, if not accelerate, in the coming years.
• However, scientists who didn't participate in the study told Axios the mechanism behind the reduction in low cloud cover needs to be more fully studied.

The bottom line: "I think it's still an open question whether we've broken the climate or not (by which I mean the climate has shifted into a new regime). We probably won't know the answer to that for a few years," Texas A&M climate scientist Andrew Dessler, who did not participate in either new study, told Axios.

If you want evidence that gas is a winner in the AI-driven data center frenzy, Chevron CEO Mike Wirth's new comments are a good place to start.

Why it matters: Wirth disclosed Friday that Chevron is exploring new gas plants to directly power data centers.

📢 Driving the news: "A lot of it may be what's called behind the meter, so it would not be through the grid and through a utility," he said at an Atlantic Council event.

• "We're doing some work right now with a number of different people that's not quite ready for prime time," Wirth said.
• They're "looking at possible solutions to build large scale power generation that would not go into the rate base."

🏀 State of play: He noted hyperscalers need reliable power and argued small modular reactors that big tech players are exploring are likely a decade away.

• "I think what we're likely to see is gas turbine generation is going to be a big part of the solution set," he said.

🏎️ Catch up quick: Data center developers are seeking power sources — including gas.

• Entergy is building over 2 gigawatts to support Meta's big planned Louisiana data center and "our growing customer base," the utility said. The units could have some hydrogen co-firing.
• Energy Transfer on Friday cited data center growth as one reason it's moving ahead with a $2.7 billion gas pipeline project in Texas.

🔭 What we're watching: Details on Chevron's plans. The company did not elaborate.

🤝 BP and Japanese energy giant JERA formed an offshore wind JV with combined investment capped at $5.8 billion by the end of 2030.

• Why it matters: The deal underscores BP's increasingly selective approach to renewables.
• State of play: It merges JERA's existing assets and the companies' combined development pipelines and leases, totaling a potential 13 gigawatts.
• The big picture: "This will be a very strong vehicle to grow into an electrifying world, while maintaining a capital light model for our shareholders," BP CEO Murray Auchincloss said in a statement.

🚪Bloomberg reports that Goldman Sachs is quitting the UN-convened Net Zero Banking Alliance.

• Why it matters: The move comes as "increasingly complex regulations and US political attacks lead some of the financial industry's biggest firms to rethink such affiliations," their piece notes.

⚖️ The Supreme Court will hear arguments tomorrow in a case that could limit National Environmental Policy Act reviews beyond a project's "proximate effects."

• State of play: Utah counties and Uinta Basin Railway are challenging an appellate court rejection of a freight system to carry oil to a larger network and refineries.
• Why it matters: "The case could impact the extent to which GHG emissions are assessed, whether as cumulative effects or as indirect effects of an action," said Michael Burger, executive director of Columbia's Sabin Center for Climate Change Law, via email when the court first agreed to hear the case in June.

🛢️Anyone tracking the fallout of OPEC+ delaying production hikes will have plenty to chew on this week.

• What we're watching: The International Energy Agency's oil market analysis drops Thursday. OPEC's latest monthly supply and demand report arrives Wednesday, while U.S. Energy Information Administration's new look-ahead comes tomorrow.

That's the share of global oil tankers estimated to belong to the "shadow fleet" — the aging, hard-to-track ships that Russia uses to evade Western restrictions.

The figure — via S&P Global — is part of a new Atlantic Council deep dive into the fleet and many ideas for deterring it.