Earth Matters

Nimbus-4: A Satellite Pioneer For Ozone Research

April 9th, 2020 by Adam Voiland

When NASA launched the Nimbus-4 satellite 50 years ago, nobody knew the ozone layer over Antarctica was thinning. And nobody knew that chlorofluorocarbons (CFCs)—long-lived chemicals that had been used in refrigerators and aerosol sprays since the 1930s—were responsible.

But the mission included a sensor called the Backscatter Ultraviolet (BUV) experiment capable of measuring ozone nonetheless. “We simply wanted to measure the atmosphere. It was curiosity-driven research,” said Pawan Bhartia, an atmospheric scientist at NASA’s Goddard Space Flight Center in an interview about the discovery of the ozone hole.

Developed by a team led by NASA’s Donald Heath, BUV was the first space-based instrument to measure the total amount of ozone in the Earth’s atmosphere. “Don was really sweating the Nimbus-4 launch because his MUSE instrument on one of the previous Nimbus satellites ended up in the Pacific Ocean offshore from Vandenberg Air Force Base,” said Arlin Krueger, technical officer for the BUV science team. “That instrument was recovered from the ocean floor and sat on his filing cabinet for years as a reminder that risks are big part of the NASA experimenter’s life.”

Fortunately, the launch went smoothly. The BUV performed well and demonstrated a new way to measure total column ozone. This led to the Total Ozone Mapping Spectrometer (TOMS) on Nimbus-7. The ozone data it collected gave researchers baseline measurements that, in the mid-1980s, helped them recognize that a troubling hole in the ozone layer had opened up.

The global recognition of the destructive potential of CFCs soon led to the 1987 Montreal Protocol, a treaty phasing out the production of ozone-depleting chemicals. Since then, scientists have begun to see definitive proof of ozone recovery.

You can find the latest data and imagery of the status of the ozone hole on NASA’s Ozone Watch website. You can read more about the role that satellites played in the discovery of stratospheric ozone depletion here.

Kigali: A Huge Step Forward for Climate

October 27th, 2016 by Kathryn Hansen

View of the dais during the High-Level Segment Ministerial Round Table ‘Towards an Agreement on the HFC Amendment under the Montreal Protocol – Part 2: Ensuring Benefits for All.’ October 14, 2016 (day 6). Photo by IISD/ENB | Kiara Worth

The Antarctic ozone hole in 2016 was not exactly remarkable. But each year, we publish an annual update because, when strung together over time, the series shows the unparalleled success of the Montreal Protocol in stabilizing the atmosphere.

Now the scientists and negotiators behind the Protocol are taking on a new problem: the climate warming effects of chemicals that were supposed to be better for the ozone layer. NASA scientist Paul Newman attended the Montreal Protocol’s international meeting this October in Kigali, Rwanda, and he sat down with us to explain the new agreement, why it’s unique, and what it was like to participate in the meeting. Here are some of the main takeaways:

  • The Montreal Protocol is not just about ozone depleting substances; it’s also about their replacements.

“The Montreal Protocol is written so that we can control ozone-depleting substances and their replacements. Chlorofluorocarbons (CFCs) were initially replaced with hydrochlorofluorocarbons (HCFCs) and then hydrofluorocarbons (HFCs), making HFCs the so-called “grandchildren” of the Montreal Protocol.

HFCs very weakly affect the ozone layer. But the problem is that they are powerful greenhouse gases. One can of this keyboard cleaner [an aerosol can with HFC-134a] is equivalent to 1,360 cans of carbon dioxide. HCFs are much more powerful than carbon dioxide as a greenhouse gas, and that’s true of many HFCs, not just HFC-134a. And their use—particularly in refrigeration and air conditioning—has been going up fast.

It has been projected that by 2100, the effect of HFCs on temperature could be as high as 0.5 Kelvin (0.5 degrees Celsius, or 0.9 degrees Fahrenheit) if we did nothing. Because of the amendment, that number will be closer to 0.06 Kelvin (0.06 degrees Celsius, or 0.11 degrees Fahrenheit).

The point of the of Kigali amendment was to control these greenhouse gases because they are a replacement for CFCs. They are adding to the climate problem, so the world’s nations wanted to do something about it. The Montreal Protocol has evolved from strictly an ozone treaty, to an ozone and climate treaty.”

NASA scientist Paul Newman (right) on October 10, 2016 (day 2). Photo by IISD/ENB | Kiara Worth

  • The amendment looks into the future because the accumulation and removal of HFCs in the atmosphere takes a while.

“HFCs go through a series of steps before they can begin accumulating in the atmosphere. The first is production, in which factories make tanks of the gas (like a brewery making big vats of beer). The next step is consumption, when HFCs are added to things like refrigerators and air conditioners (to follow the beer analogy, that’s when the brewer puts the beer in a bottle or keg). Finally, HFCs are emitted when people use those things (pop the cork on the bottle or tap the keg).

The important point is that there is a time lag. Consumption of HFCs are projected to peak in the late 2020s, but emissions don’t peak until about 2035. Once in the atmosphere, HFCs last a long time before being destroyed by chemical reactions. For example, If I vent my can of 134a, 5 percent of it will still be in the atmosphere after 42 years. So they continue to accumulate and peak in the atmosphere by the mid 2050s.”

Delegates during the morning plenary on October 11, 2016 (day 3). Photo by IISD/ENB | Kiara Worth

  • Montreal Protocol meetings can be exhausting …

“Montreal Protocol meetings don’t have a schedule; they have an agenda. That means that we have a list of topics and we work until they are all addressed. For example, we worked all day Friday (October 14, 2016) but didn’t finish, so we reconvened Saturday at 1 a.m. and finished the amendment at 7 a.m. I was up for 27 straight hours, tired and hungry.”

… but uniquely effective.

“This agreement is a huge step forward because it is essentially the first real climate mitigation treaty that has bite to it. It has strict obligations for bringing down HFCs, and is forcing scientists and engineers to look for alternatives.

The Montreal Protocol is also technically the perfect mechanism for dealing with these issues. The technology people, economics people, science people, chemical manufacturers—they have all worked through the Montreal Protocol and are fully capable of dealing with refrigerants like HFCs and their alternatives.

The agreement wouldn’t go forward without a pretty good idea about what those replacements might be. Hydrofluoroolefins, for example, have a really tiny climate impact and only 10-day lifetimes and are already being used in some applications. The Montreal Protocol is pro-engineering, pro-technology, and very different than any other treaty. We can solve our environmental problems—that is the power of a technological society.”