On Tuesday, Make Sunsets announced it had completed three balloon launches near Reno, Nevada, each of which contained less than 10 grams of sulfur dioxide, which is the most commonly sited aerosol particle discussed in conversations about solar geoengineering. Two of the balloons launched also had location trackers, and one had a camera, too.
The idea of solar geoengineering has been around for decades and generally refers to spraying aerosol particles into the upper atmosphere in order to reflect the sun’s rays away from earth and back to space, cooling the earth and temporarily mitigating the effects of climate change.
Essentially, solar geoengineering is mimicking what happens when a volcano erupts, and it’s known to work. When Mount Pinatubo in the Philippines released thousands of tons of sulfur dioxide into the stratosphere in the 1991 eruption, the global temperature of the earth was lowered on average by about 1 degree Fahrenheit, according to the U.S. Geological Survey.
Solar geoengineering is not a solution to climate change, and nobody who studies it rigorously suggests it should be. It’s a temporary stopgap measure.
In addition, while releasing sulfur dioxide particles will cool the earth quickly and relatively inexpensively, it’s also dangerous. Injecting sulfur dioxide into the atmosphere could damage the ozone layer, cause respiratory illness and create acid rain.
But as the effects of climate change become more obvious, people are beginning to take the idea more seriously.
The White House is coordinating a five-year research plan into solar geoengineering, the quadrennial U.N.-backed Montreal Protocol assessment report included an entire chapter addressing stratospheric aerosol injection (more colloquially called solar geoengineering), and Dustin Moskovitz, a co-founder of Facebook, is funding solar geoengineering research via his philanthropic organization, Open Philanthropy.
While momentum is building, there isn’t any international governance rules about how to study and potentially regulate the idea.
Luke Iseman, a serial inventor and the former director of hardware at Y Combinator, launched Make Sunsets in October in an effort to push that envelope. San Mateo-headquartered venture capital firm BoostVC invested $500,000 in the startup and Iseman brought in a co-founder, Andrew Song.
The launches in Nevada earlier in February occurred at the Rancho San Rafael Regional Park in Reno, , where an annual hot-air balloon festival takes place, Iseman told CNBC.
They chose Nevada “because it’s in the U.S., we’re very confident we know and followed all applicable rules, know the terrain well from past adventures, and, we didn’t want to interfere with a friend’s efforts to get a marine cloud brightening project permitted in California,” Iseman told CNBC.
The Nevada launch was previously detailed by Time reporters, who were there. It was a shoe-string MacGyver-ed event orchestrated out of a hotel room, with a grill and weather balloon equipment. But, as evidenced by the images embedded below, shared with CNBC by Make Sunsets, the balloons lifted off.
Make Sunsets team is filling sulfur dioxide in a bag preparing for launch.
Photo courtesy Make Sunsets
Make Sunsets team is weighing the bag filled with sulfur dioxide gas in a bag preparing for launch.
Photo courtesy Make Sunsets
Make Sunsets is filling the balloon with helium here.
Photo courtesy Make Sunsets
Here, founder Luke Iseman is preparing to release the weather balloon filled with sulfur dioxide and helium into the atmosphere. Make Sunsets says this is the first deployment of SAI, or stratospheric aerosol injection, another and more specific name for solar geoengineering.
Photo courtesy Make Sunsets
Luke Iseman, the founder of Make Sunsets, is about to launch a weather balloon filled with sulfur dioxide and helium into the air in Nevada.
Photo courtesy Make Sunsets
Make Sunsets launching a weather balloon filled with sulfur dioxide and helium into the air in Nevada.
Photo courtesy Make Sunsets
A view from the Make Sunsets balloon launched in Nevada.
Photo courtesy Make Sunsets
A view from the Make Sunsets balloon launched in Nevada.
Photo courtesy Make Sunsets
Iseman has both idealistic and practical goals.
“Most importantly: We need to cool earth to save millions of lives, hundreds of thousands of species, and buy the time we need to decarbonize,” Iseman told CNBC.
To make the business sustainable, Make Sunsets is selling cooling credits, which gives companies and individuals a way to offset the effects of their carbon emissions. But the startup has yet to deliver.
“We have 2,790 cooling credits ordered by 58 paying customers that we haven’t yet delivered,” Iseman told CNBC. “On one hand, we’re working hard on a controversial project to cool earth. On the other, we’re a startup with the same basic challenge as any other: get customers to pay more for what we’re selling than it costs to make it.”
Make Sunsets said it made the FAA aware that it was releasing a balloon.
The FAA provided the following statement: “The FAA has comprehensive regulations for safely operating unmanned free balloons. Among other things, the regulations require the balloon to be equipped so it can be tracked by radar, and the operator to notify the FAA prior to and at the time of launch, monitor and record the balloon’s course, make position reports to the FAA as requested, and notify the FAA when the balloon begins its descent and its expected trajectory.”
Correction: A previous version of this story misstated what the balloons contained. All three of them had sulfur dioxide.
Every weekday, the CNBC Investing Club with Jim Cramer holds a “Morning Meeting” livestream at 10:20 a.m. ET. Here’s a recap of Tuesday’s key moments. 1. Stocks were mixed on Tuesday, with the S & P 500 and Dow Jones Industrial Average up and the Nasdaq Composite down slightly, with Big Tech names under pressure. Nvidia shares fell more than 6% after The Information reported that Meta may use Google’s tensor processing units (TPUs) in its data centers starting in 2027. Broadcom , which helps Google design its TPUs, jumped 11% Monday on the news. Jim Cramer said the pullback in Nvidia is a buying opportunity. “If you don’t have any Nvidia, it’s time to buy,” he said. He added investors are also “getting an opportunity to buy Meta” on the possibility the company could save money on chips and see its stock bounce. 2. This “discouraging day” for tech investors shows the value of having a diversified portfolio, Jim said. That’s why the Club favors defensive names like Procter & Gamble . With a new CEO taking over in January, Jim expects changes ahead. “You can’t have a new CEO come in and not have some change from what’s going on,” he said, noting that underperforming units will likely be cut. Procter has been a disappointment lately, but our thesis is that money will move out of high-flying tech stocks and into more profitable, economically resistant companies. That’s why we added to our position on Tuesday. Elsewhere, home improvement retailer Home Depot is down nearly 12% year to date. We used that weakness to add to our position last week. When interest rates fall, the stock will rise. 3. Shares of Nike are up 3% after Dick’s Sporting Goods announced plans to close a slew of Foot Locker locations during its third-quarter earnings on Tuesday. Dick’s acquired Foot Locker in May. “Nike is a buy, off of Dick’s problems,” Jim said. Ed Stack, executive chairman of Dick’s Sporting Goods, told “Squawk on the Street” that the retailer’s relationship with Nike is improving. “They’re moving in the right direction,” he said, citing strong performance from Nike’s running line. “If you take a look at what they did with their running construct, what they did with Pegasus, what they did with Vomero, what they did with Structure, this running concept has done extremely well on the Dick’s side, and where it’s been put into Foot Locker stores, it’s done really well there too.” 4. Stocks covered in Tuesday’s rapid fire at the end of the video were: Best Buy , Agilent Tech , and Abercrombie . (Jim Cramer’s Charitable Trust is long NVDA, META, AVGO, PG, HD, NKE. See here for a full list of the stocks.) As a subscriber to the CNBC Investing Club with Jim Cramer, you will receive a trade alert before Jim makes a trade. Jim waits 45 minutes after sending a trade alert before buying or selling a stock in his charitable trust’s portfolio. If Jim has talked about a stock on CNBC TV, he waits 72 hours after issuing the trade alert before executing the trade. THE ABOVE INVESTING CLUB INFORMATION IS SUBJECT TO OUR TERMS AND CONDITIONS AND PRIVACY POLICY , TOGETHER WITH OUR DISCLAIMER . NO FIDUCIARY OBLIGATION OR DUTY EXISTS, OR IS CREATED, BY VIRTUE OF YOUR RECEIPT OF ANY INFORMATION PROVIDED IN CONNECTION WITH THE INVESTING CLUB. NO SPECIFIC OUTCOME OR PROFIT IS GUARANTEED.
Elon Musk attends the U.S.-Saudi Investment Forum in Washington, D.C., U.S., November 19, 2025.
Evelyn Hockstein | Reuters
Elon Musk’s artificial intelligence startup xAI is expected to close a $15 billion round at a $230 billion pre-money valuation next month, sources familiar with the matter told CNBC’s David Faber.
The deadline for allocation is the end of day on Tuesday, with the round expected to close on Dec. 19, the sources said.
This confirms earlier CNBC reporting that the company was raising $15 billion. The Tesla CEO later called the report on the round “False” in a post on the social media platform X.
At the time, sources told CNBC that xAI would use a large portion of the money for funding graphics processing units responsible for powering large language models.
CNBC had previously reported in September that the startup was looking to raise $10 billion at a $200 billion valuation.
The funding round is yet another sign of the insatiable demand for AI tools. Companies, including OpenAI and Anthropic, have raised billions and reached sky-high valuations as investors pour more money into companies building foundational AI models.
Musk’s xAI is responsible for creating the Grok chatbot that has come under fire for disseminating hate speech, including antisemitic content. The company recently debuted Grokipedia, an AI-powered competitor to Wikipedia.
In March, Musk announced the merger of xAI with X in a deal valuing the social media platform at $33 billion.
TSMC on Tuesday filed a lawsuit against a former senior vice president it accused of leaking “confidential information” to Intel.
Wei-Jen Lo joined Intel after 21 years at TSMC, having left in July, the Taiwanese chip maker said in a statement, announcing the lawsuit.
The lawsuit is based on Lo’s employment contract and non-compete agreement with TSMC, and regulations such as the Trade Secrets Act, the statement said.
“There is a high probability that Lo uses, leaks, discloses, delivers, or transfers TSMC’s trade secrets and confidential information to Intel,” it said.
TSMC’s share price fell on Tuesday and was last seen over 3% lower.
Intel did not immediately respond to CNBC’s request for comment.
It follows earlier reports by local media and later by Reuters, which stated Lo may have taken TSMC’s technology data to Intel. Taiwan’s High Prosecutors opened an investigation into the allegations.
Intel CEO Lip-Bu Tan told Bloomberg News last week that his “company respects intellectual property rights” and denied any wrongdoing.
The U.S. firm’s stock price moved 1.5% lower in mid-morning trade.