Climate change has advanced so rapidly that work must start on unproven technologies now, admits US National Academy of Science

This article is more than 5 years old

This article is more than 5 years old

Climate change has advanced so rapidly that the time has come to look at options for a planetary-scale intervention, the National Academy of Science said on Tuesday.

The scientists were categorical that geoengineering should not be deployed now, and was too risky to ever be considered an alternative to cutting the greenhouse gas emissions that cause climate change.

But it was better to start research on such unproven technologies now – to learn more about their risks – than to be stampeded into climate-shifting experiments in an emergency, the scientists said.

With that, a once-fringe topic in climate science moved towards the mainstream – despite the repeated warnings from the committee that cutting carbon pollution remained the best hope for dealing with climate change.

“That scientists are even considering technological interventions should be a wake-up call that we need to do more now to reduce emissions, which is the most effective, least risky way to combat climate change,” Marcia McNutt, the committee chair and former director of the US Geological Survey, said.

Asked whether she foresaw a time when scientists would eventually turn to some of the proposals studied by the committee, she said: “Gosh, I hope not.”

The two-volume report, produced over 18 months by a team of 16 scientists, was far more guarded than a similar British exercise five years ago which called for an immediate injection of funds to begin research on climate-altering interventions.

The scientists were so sceptical about geo-engineering that they dispensed with the term, opting for “climate intervention”. Engineering implied a measure of control the technologies do not have, the scientists said.

But the twin US reports – Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration and Climate Intervention: Reflecting Sunlight to Cool the Earth – could boost research efforts at a limited scale.

The White House and committee leaders in Congress were briefed on the report’s findings this week.

Bill Gates, among others, argues the technology, which is still confined to computer models, has enormous potential and he has funded research at Harvard. The report said scientific research agencies should begin carrying out co-ordinated research.

But geo-engineering remains extremely risky and relying on a planetary hack – instead of cutting carbon dioxide emissions – is “irresponsible and irrational”, the report said.

The scientists looked at two broad planetary-scale technological fixes for climate change: sucking carbon dioxide emissions out of the atmosphere, or carbon dioxide removal, and increasing the amount of sunlight reflected away from the earth and back into space, or albedo modification.

Albedo modification, injecting sulphur dioxide to increase the amount of reflective particles in the atmosphere and increase the amount of sunlight reflected back into space, is seen as a far riskier proposition.

Tinkering with reflectivity would merely mask the symptoms of climate change, the report said. It would do nothing to reduce the greenhouse gas emissions that cause climate change.

The world would have to commit to continuing a course of albedo modification for centuries on end – or watch climate change come roaring back.

“It’s hard to unthrow that switch once you embark on an albedo modification approach. If you walk back from it, you stop masking the effects of climate change and you unleash the accumulated effects rather abruptly,” Waleed Abdalati, a former Nasa chief scientist who was on the panel, said.

More ominously, albedo modification could alter the climate in new and additional ways from which there would be no return. “It doesn’t go back, it goes different,” he said.

The results of such technologies are still far too unpredictable on a global scale, McNutt said. She also feared they could trigger conflicts. The results of such climate interventions will vary enormously around the globe, she said.

“Kansas may be happy with the answer, but Congo may not be happy at all because of changes in rainfall. It may be quite a bit worse for the Arctic, and it’s not going to address at all ocean acidification,” she said. “There are all sorts of reasons why one might not view albedo modified world as an improvement.”

The report also warned that offering the promise of a quick fix to climate change through planet hacking could discourage efforts to cut the greenhouse gas emissions that cause climate change.

“The message is that reducing carbon dioxide emissions is by far the preferable way of addressing the problem,” said Raymond Pierrehumbert, a University of Chicago climate scientist, who served on the committee writing the report. “Dimming the sun by increasing the earth’s reflectivity shouldn’t be viewed as a cheap substitute for reducing carbon dioxide emissions. It is a very poor and distant third, fourth, or even fifth choice. |It is way down on the list of things you want to do.”

But geoengineering has now landed on the list.

Climate change was advancing so rapidly a climate emergency – such as widespread crop failure – might propel governments into trying such large-scale interventions.

“The likelihood of eventually considering last-ditch efforts to address damage from climate change grows with every year of inaction on emissions control,” the report said.

If that was the case, it was far better to be prepared for the eventualities by carrying out research now.

The report gave a cautious go-ahead to technologies to suck carbon dioxide out of the air, finding them generally low-risk – although they were prohibitively expensive.

The report discounted the idea of seeding the ocean with iron filings to create plankton blooms that absorb carbon dioxide.

But it suggested carbon-sucking technologies could be considered as part of a portfolio of responses to fight climate change.

Carbon-sucking technologies, such as these ‘artificial forests’, could in future be considered to fight climate change - but reducing carbon dioxide emissions now is by far the preferable way of addressing the problem. Photograph: Guardian

It would involve capturing carbon dioxide from the atmosphere and pumping it underground at high pressure – similar to technology that is only now being tested at a small number of coal plants.

Sucking carbon dioxide out of the air is much more challenging than capturing it from a power plant – which is already prohibitively expensive, the report said. But it still had a place.

“I think there is a good case that eventually this might have to be part of the arsenal of weapons we use against climate change,” said Michael Oppenheimer, a climate scientist at Princeton University, who was not involved with the report.

Drawing a line between the two technologies – carbon dioxide removal and albedo modification – was seen as one of the important outcomes of Tuesday’s report.

The risks and potential benefits of the two are diametrically opposed, said Ken Caldeira, an atmospheric scientist at Carnegie Institution’s Department of Global Ecology and a geoengineering pioneer, who was on the committee.

“The primary concern about carbon dioxide removal is how much does it cost,” he said. “There are no sort of novel, global existential dilemmas that are raised. The main aim of the research is to make it more affordable, and to make sure it is environmentally acceptable.”

In the case of albedo reflection, however, the issue is risk. “A lot of those ideas are relatively cheap,” he said. “The question isn’t about direct cost. The question is, What bad stuff is going to happen?”

There are fears such interventions could lead to unintended consequences that are even worse than climate change – widespread crop failure and famine, clashes between countries over who controls the skies.

But Caldeira, who was on the committee, argued that it made sense to study those consequences now. “If there are real show stoppers and it is not going to work, it would be good to know that in advance and take it off the table, so people don’t do something rash in an emergency situation,” he said.

Spraying sulphur dioxide into the atmosphere could lower temperatures – at least according to computer models and real-life experiences following major volcanic eruptions.

But the cooling would be temporary and it would do nothing to right ocean chemistry, which was thrown off kilter by absorbing those emissions.

“My view of albedo modification is that it is like taking pain killers when you need surgery for cancer,” said Pierrehumbert. “It’s ignoring the problem. The problem is still growing though and it is going to come back and get you.”