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Sea level rise uncertainties: Why all eyes are on Antarctica



Donald Slater

A few years ago, an ice-sheet model grabbed attention when it projected much faster losses of Antarctic ice and, subsequently, faster sea level rise. Understanding how quickly Antarctica dumps ice into the ocean is the biggest issue in sea level science—the current range of possibilities is huge and includes remarkable rates of sea level rise that continue for centuries once started. And those sorts of possibilities have huge implications for societies around the globe.

The ice-sheet model that produced disturbing projections included new physical processes in its equations—they were obviously impactful, but their significance in the real world remains uncertain. Later research cast doubt on its most extreme scenarios, but the Antarctic crystal ball hasn’t gotten a lot clearer.

A pair of new studies published in Nature this week mark a new state of the art in ice modeling. Big questions about what we can expect are still there, and so planning for future sea level rise is still very much a matter of weighing risk under uncertainty.


The first study—led by Robert DeConto at the University of Massachusetts Amherst—describes the latest version of that worrisome Antarctic model we mentioned at the start. The model attempts to account for the spontaneous collapse of excessively tall cliffs of ice at the front of glaciers, as well as the pressure-driven expansion of deep cracks that fill with meltwater. The effect of these processes can be amplified in settings like the West Antarctic Ice Sheet, where significant areas of glacial ice sit on bedrock that drops in elevation as you move inland—ultimately dropping well below sea level. Once ice in this situation destabilizes, water can get under it, and it can retreat unstoppably until the bedrock slopes up again.

The model was fed several greenhouse gas-emissions scenarios relevant to recent international talks: futures in which warming is halted at 1.5°C, 2°C, and 3°C (which current pledges have us roughly on track for). The model was also fed a scenario in which unabated warming crosses 4°C before the end of this century. Interestingly, it also includes a series of scenarios where growing emissions halt and suddenly flip into active removal of atmospheric CO2 in 2030, 2040, or 2050, and so on.

Because of the uncertainty in some simulated processes, like ice-cliff instability and hydrofracturing, almost 200 configurations of the model were employed, each with knobs turned slightly differently. Each configuration was tossed if it couldn’t simulate a close match to several historical periods, leaving about 110 configurations to provide a range of results for each greenhouse gas-emissions scenario.

Overall, the revisions in the latest version have apparently led to simulations that produce slightly less extreme rates of ice loss, at least. The 3°C warming scenario jumps out as a transition point. With warming limited to 1.5 or 2°C, the rate of Antarctic ice loss is nearly linear this century. But in both of the higher warming scenarios, ice loss shifts into another gear around 2060 as significant portions of the ice sheet are destabilized. That remains true in scenarios where we follow the 3°C trajectory but aggressively remove CO2 from the atmosphere sometime after the 2060s. The amount of Antarctic ice loss seen by 2100 doubles despite those efforts.

Simulated scenarios, least warming at top, most warming at bottom. The red line (left axis) shows the rate of Antarctic contribution to sea level rise in millimeters per year. The blue shading (right axes) shows the total in meters.
Enlarge / Simulated scenarios, least warming at top, most warming at bottom. The red line (left axis) shows the rate of Antarctic contribution to sea level rise in millimeters per year. The blue shading (right axes) shows the total in meters.

In the 1.5 and 2°C scenarios, Antarctica contributes (on average) about 8 centimeters of sea level rise by 2100 and a bit more than 50 centimeters by 2200. In the 3°C scenario, it’s around 15 centimeters by 2100 and 80 centimeters by 2200.

In the highest emissions scenario, those numbers climb over 30 centimeters by 2100 and well over five meters by 2200.

Don’t emulate this behavior

The second study—led by Tamsin Edwards at King’s College London but involving a total of 84 authors—has a global focus. Because there are multiple groups building climate models of various kinds, there are frequent “intercomparison projects” in which everyone’s model runs the same set of simulations so that the results are directly comparable. This has been done for glacial-ice models in recent years.

Like a similar study we covered, this one uses an “emulation” technique that extracts the statistical characteristics of the model results so they can be analyzed in new ways without running new simulations. One reason for this is that the next IPCC report is being prepared with a new set of future greenhouse gas-emissions scenarios, while these ice-sheet models were run using the old scenarios. Emulation allows those results to be sort of scaled for the slight differences between the scenarios. It also allows for a consistent calculation of error bars—useful for a large compilation like this.

The average results of all these models show around 25 centimeters of global land-ice contribution to sea level rise by 2100 in the 3°C warming scenario—the one that current emissions pledges have us on track for. Limiting warming to 1.5°C instead, as countries have discussed in negotiations (but shown little ambition for), would reduce that contribution to around 13 centimeters by 2100.

(Keep in mind that land ice melt isn’t the only cause of sea level rise—the expansion of seawater as it warms is responsible for around half of sea level rise so far. The last IPCC report projected about 15-30 centimeters of sea level rise this century due to thermal expansion, depending on the warming scenario.)

If you’re scrolling up and struggling to marry these numbers to the first study, it’s because the average Antarctic contribution here is small—around 4 centimeters regardless of the scenario. And the model described above wasn’t used for this comparison project.

Avoiding the drunks

Recognizing this Antarctic uncertainty, this study creates an alternate set of scenarios using pessimistic assumptions for Antarctica. These “risk-averse projections” emphasize the worst-case simulations instead of the median. These scenarios shift the Antarctic contribution from around four centimeters to around 20 centimeters in 2100—more similar to our first study. In that case, the total global land ice contribution to sea level rise grows from 13-30 centimeters by 2100 to 30-48 centimeters.

The lower set of numbers is pretty similar to the projections in the 2013 IPCC report, while the second set of numbers is a bit higher. But it’s still progress. Whereas that report had to sort of wave its hands and say “it could be much worse,” the risk of higher sea level rise—if a large portion of Antarctic ice destabilizes, for example—has been better explored in the years since.

Still, future sea level rise is fundamentally uncertain. There’s a reason Richard Alley (an author on the first study) has described Antarctic glaciers as the “drunk drivers” of sea level rise—a low-probability but dangerous risk we work to manage on the roadways.

That means thinking about risk has to be at the center of the conversation about sea level rise. As the authors of the second study write, “Given this large range (between 13 centimetres [sea level rise] using the main projections under 1.5 degrees Celsius warming and 42 centimetres [sea level rise] using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.”

Nature, 2020. DOI: 10.1038/s41586-021-03427-0, 10.1038/s41586-021-03302-y (About DOIs).

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SpaceX to break the final frontier in reuse with national defense launch



Enlarge / The GPS III SV-05 vehicle is encapsulated in the Falcon 9 rocket’s payload fairing.

Lockheed Martin

A few years ago one of SpaceX’s earliest employees, Hans Koenigsmann, told me one of the company’s goals was to take the “magic” out of rocket launches. It’s just physics, he explained.

As its Falcon 9 rocket has become more reliable and flown more frequently—18 launches so far this year, and counting—it seems that SpaceX has succeeded in taking the magic out of launches. And while reliability should definitely be the goal, such regularity does distract from the spectacle of watching a rocket launch.

But there are still some special Falcon 9 missions, and that’s certainly the case with a launch expected to occur at 12:09 pm ET (16:09 UTC) on Thursday from Cape Canaveral Space Force Station in Florida. With the launch of a next-generation GPS III spacecraft, SpaceX will fly a national security mission for the first time on a reused booster.

Last year the Space Force and SpaceX agreed to contract modifications allowing for the launch of this GPS III mission (Space Vehicle-05) and another one (SV-06) on reused Falcon 9 first-stage rockets. The Space Force agreed to allow the GPS III satellites to be launched into a different orbital perigee, enabling a drone ship recovery attempt. The first stage set to launch Thursday previously flew the GPS III SV-04 last November. In return for this accommodation, SpaceX agreed to some additional spacecraft requirements for future missions and saved the US government $52 million.

This represents an important signal from the military that it is ready to embrace reused rockets for its most important missions and is something of a final frontier for SpaceX as it seeks to push forward the reuse of Falcon 9 first stages. NASA has already launched its highest-value missions, astronauts, on a reused first stage with the Crew-2 flight in April.

Thursday’s GPS mission is a high priority for the Space Force, too, as it seeks to modernize its navigation constellation. This new generation of global positioning satellites, built by Lockheed Martin, have three times greater accuracy and an anti-jamming capability that is eight times higher than earlier versions. The next five GPS satellites, vehicles 06 to 10, are in various states of readiness for launch. And Lockheed Martin has been contracted to build up to 22 additional vehicles.

Weather for Thursday’s 15-minute launch window looks reasonable, with only a 30 percent chance of unfavorable conditions. Upper-level winds may be a concern, however. The SpaceX webcast embedded below should begin about 15 minutes before the launch window opens.

Launch of GPS III SV-05 mission.

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After ruining 75M J&J doses, Emergent gets FDA clearance for 25M doses



Enlarge / The Emergent BioSolutions plant, a manufacturing partner for Johnson & Johnson’s COVID-19 vaccine, in Baltimore, Maryland, on April 9, 2021.

The US Food and Drug Administration is making progress in its efforts to sort out the fiasco at Emergent BioSolutions’ Baltimore facility, which, at this point, has ruined more than 75 million doses of COVID-19 vaccines stemming from what the regulator identified as significant quality control failures.

In March, news leaked that Emergent ruined 15 million doses of Johnson & Johnson’s vaccine as well as millions more doses of AstraZeneca’s vaccine. The spoilage happened when Emergent cross-contaminated batches of the two vaccines with ingredients from the other.

Last week, the FDA told Emergent to trash about 60 million more doses of Johnson & Johnson’s vaccine due to similar contamination concerns, The New York Times reported.

But at the same time, the agency cleared 10 million doses of Johnson & Johnson’s vaccine for use—with the catch that the doses must carry a warning saying that the FDA cannot guarantee Emergent followed good manufacturing practices while making them. And on Tuesday, the FDA cleared an additional 15 million doses of Johnson & Johnson’s vaccine, bringing the total number of acceptable doses to just 25 million, according to The Wall Street Journal.

Still, more than 100 million finished doses of Johnson & Johnson’s and AstaZeneca’s vaccines are still in limbo at the facility, awaiting FDA review. All of the doses at the facility were made prior to April 16, when the FDA shut down production after an investigation found sweeping and significant quality control failures and manufacturing violations.

Some lawmakers say the issues were clear before the investigation; Emergent has a long track record of such problems, as well as trouble fulfilling contracts.

Troubled past

Still, the manufacturer was contracted during the pandemic to produce both the Johnson & Johnson’s one-dose vaccine and AstraZeneca’s vaccine, which use similar adenovirus-based vaccine platforms. Emergent had also been awarded millions of dollars in federal grants to help respond to the pandemic swiftly, including $27-million monthly “reservation” payments to keep its facility at the ready to produce large amounts of vaccine under proper manufacturing standards and practices.

But the FDA’s nine-day inspection of the Baltimore facility, which began April 12, revealed that Emergent wasn’t putting that money to good use. FDA inspectors logged a long list of problems, including unsanitary conditions, paint peeling off of the walls and floors, black and brown residue on surfaces, improperly trained staff, and numerous opportunities for vaccine products to be contaminated. For instance, inspectors witnessed Emergent employees dragging unsealed, non-decontaminated bags of medical waste across different areas of the facility. In some cases, employees tossed unsealed bags of medical waste in an elevator.

Though Emergent had already scrapped the initial 15 million contaminated vaccine doses at the time, FDA inspectors concluded that “there is no assurance that other batches have not been subject to cross contamination,” the inspectors wrote.

The FDA shut down production April 16 and has been sorting through the premade doses ever since. For the most part, Emergent’s failures have not had a significant impact on vaccination efforts in the US. All of the doses of Johnson & Johnson vaccine administered in the US were made in the Netherlands. And demand for the one-shot vaccine has slipped amid slowed vaccination rates and concern over an extremely rare but life-threatening blood-clotting condition. In fact, US regulators recently extended the expiration data on millions of doses that have gone unused. AstraZeneca’s vaccine, meanwhile, is not yet authorized for use in the US.

However, Emergent’s failures have global effects—many of the doses have been earmarked to be donated to other countries in need of vaccine supplies. The contamination problem has held up the export of potentially usable doses.

In a statement Tuesday after the FDA cleared the additional 15 million doses, Emergent said:

We welcome the approval of an additional batch of J&J vaccine made at Emergent. We remain committed to addressing the FDA’s observations in order to resume production as soon as possible and look forward to continuing our work to end this pandemic.

Federal officials stripped Emergent of its control of the Baltimore facility back in April, putting Johnson & Johnson in charge and telling AstraZeneca to find another manufacturer. Federal lawmakers, meanwhile, opened a multipronged investigation into whether Emergent used ties to the Trump administration to improperly obtain lucrative government contracts.

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Cold-War-era missile launches three modern-day spy satellites



Enlarge / A Minotaur rocket launches the NROL-111 mission on Tuesday.

Trevor Mahlmann

For the first time in nearly eight years, a Minotaur 1 rocket launched into space Tuesday from NASA’s Wallops Flight Facility in Virginia. The rocket, which is derived from Cold-War-era surplus missiles, carried three classified satellites into orbit for the US National Reconnaissance Office.

This was the first launch of the four-stage Minotaur 1 rocket since a demonstration mission for the Air Force in 2013, which also orbited 23 CubeSats. Although the current mission was delayed for more than two hours by poor weather on Tuesday morning, it successfully launched at 9:35 am ET (13:35 UTC).

The Minotaur 1, which has the capacity to launch a little more than 500 kg into low Earth orbit, is a mix of decades-old technology and modern avionics. The vehicle’s first and second stages are taken from a repurposed Minuteman I missile, the first generation of land-based, solid-fuel intercontinental ballistic missiles. These missiles were in service from 1962 to 1965 before they were phased out in favor of the Minuteman II and Minuteman III missiles. The latter ICBMs are still in silos today.

To configure the Minotaur 1 rocket for satellite launches, engineers added two additional stages based on Orion solid rocket motors. These orbital rockets are now built and launched by Northrop Grumman. In addition to the Minotaur 1 vehicle, the company also supports the larger Minotaur C and Minotaur IV launch vehicles based on Peacekeeper missiles.

The small rockets are not cheap. This Minotaur I launch cost the Air Force $29.2 million when it procured the rocket for the National Reconnaissance Office in 2016. By contrast, Relativity Space, Firefly, and ABL Space are all developing rockets more capable than the Minotaur 1, with about 1 metric ton of lift capacity, at a fraction of its cost.

However, the Minotaur line of vehicles has a perfect record across 28 missions, having launched from Alaska, California, Florida, and Virginia with 100 percent success. The US military values this kind of reliability and the operational readiness of a solid-motor rocket.

Lt. Col. Ryan Rose, chief of the Space and Missile Systems Center Launch Enterprise’s Small Launch and Targets Division, said in a statement that she is looking forward to future launches from Northrop Grumman: “This success continues to reinforce that the Launch Enterprise has multiple paths to rapidly acquire agile launch services for small satellites and will continue to take advantage of the latest in small launch technologies.”

As for the top-secret payloads launched Tuesday, it’s a good bet they are spy satellites of some sort. The National Reconnaissance Office is charged with a “mission of providing critical information to every member of the Intelligence Community, two dozen domestic agencies, our nation’s military, lawmakers, and decision makers.” So they’re probably reading this article—from space.

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