We’re already at 1 C and CO2 just hit 410 ppm. What does 1.5 C or “turn it around now” — which scientists have been trying to tell us — entail?

May 4, 2017


Commentary and summary of a new paper for Science, by Brad Plumer on Vox.com

What would have to happen in each of the next three decades if we want to stay well below 2°C.  A group of European researchers try to do just that.  Get ready!

A simple (but daunting!) road map for staying below 2°C

They start with the big picture: To hit the Paris climate goals without geoengineering, the world has to do three broad (and incredibly ambitious) things:

1) Global CO2 emissions from energy and industry have to fall in half each decade. That is, in the 2020s, the world cuts emissions in half. Then we do it again in the 2030s. Then we do it again in the 2040s. They dub this a “carbon law.” Lead author Johan Rockström told me they were thinking of an analogy to Moore’s law for transistors; we’ll see why.

2) Net emissions from land use — i.e., from agriculture and deforestation — have to fall steadily to zero by 2050. This would need to happen even as the world population grows and we’re feeding ever more people.

3) Technologies to suck carbon dioxide out of the atmosphere have to start scaling up massively, until we’re artificially pulling 5 gigatons of CO2 per year out of the atmosphere by 2050 — nearly double what all the world’s trees and soils already do.

 (Rockstrom et al, 2017)

“It’s way more than adding solar or wind,” says Rockström. “It’s rapid decarbonization, plus a revolution in food production, plus a sustainability revolution, plus a massive engineering scale-up [for carbon removal].”

So, uh, how do we cut CO2 emissions in half, then half again, then half again? Here, the authors lay out a sample “roadmap” of what specific actions the world would have to take each decade, based on current research. This isn’t the only path for making big CO2 cuts, but it gives a sense of the sheer scale and speed required:

2017-2020: All countries would prepare for the herculean task ahead by laying vital policy groundwork. Examples:

  • Setting goals and communicating public policy objective of shift to 100% renewable.  This means communicating that electricity will become mostly solar and wind-powered electric and vehicles will become clean/non-emitting.  This is good news for city streets, intersections, and revitalizing public space, not to mention health!
  • Zeroing out investments in any new coal plants, even in countries like India and Indonesia.
  • All commit to evolution off of fossil fuels and elimination of carbon emissions by 2050.
  • By 2020, all cities, institutions, organizations and major corporations in the industrialized world should have decarbonization strategies in place.

2020-2030:  Cutting carbon emissions in half.  Ways to do this include:  Carbon prices in place at $50/ton and rising.  Aggressive energy efficiency programs ramp up. Coal power phase out occurring (phased out in rich countries in the 2020s and sharp declines everywhere else). Leading cities like Copenhagen are going totally fossil fuel free. Wealthy countries stop selling new combustion engine cars, with total phase out by 2030.  Transportation gets widely electrified.  Many short-haul flights replaced by rail.

In addition, spending on clean energy research increases by “an order of magnitude” this decade, with a sustained focus on developing new batteries, drastically reducing the cost of carbon capture and storage (CCS), and perfecting low-carbon processes for producing steel and concrete, plus improving smart grids, greener aircraft systems, and sustainable urbanization techniques.

Meanwhile, efforts to start pulling carbon dioxide out of the air start this decade. That means reforesting degraded land and deploying technologies such as direct-air capture or bioenergy with CCS to pull CO2 out of the atmosphere. By 2030, we’d need to be removing 100 to 500 megatons of CO2 each year and have a sense of how to scale up.

2030-2040: By this decade, hopefully, we’re reaping the fruits of major technological advances in clean energy. Leading countries like Denmark and Sweden should now have completely carbon-free grids and have electrified virtually all of their transport, heating, and industry. Cars with internal combustion engines “will have become rare on roads worldwide.” (Let that sink in.) Aircraft will be almost entirely powered by carbon-neutral fuels, say, biofuels or hydrogen. New building construction will be largely carbon-neutral, by using emissions-free methods for steel and concrete or through other techniques. And “radical new energy generation solutions will enter the market.”  Meanwhile, we’d need to be sucking about 1 to 2 gigatons of CO2 from the air each year, with a heavy R&D effort on expanding that further.

2040-2050: By the early 2040s, major European countries are close to carbon-neutral, and the rest of the world is moving toward that goal by the end of the decade. Electricity grids are nearly entirely carbon-free: “Natural gas still provides some back up energy, but CCS ensures its carbon footprint is limited. Modular nuclear reactors may contribute to the energy mix in some places.” Lower-income countries are still using some fossil fuels, and the world is still emitting a small bit of CO2 in 2050 (about one-eighth the amount of today), but work continues on eventually phasing that out.

Finally, by 2050, we’d need to be removing more than 5 gigatons of CO2 per year from the atmosphere. It’s possible this is simply impractical — if we tried to do that all by burning biomass for energy and sequestering the resulting carbon (a “negative emissions” process), we might well run into serious land constraints that hinder agriculture. If, in the 2020s, we realize this will be the case, then we’ll have to revamp the road map to cut CO2 emissions from energy and industry even faster.

The paper also notes that the precise details of any road map will be tentative — after all, the nature of unpredictable technological change means it’s difficult to say what the world will look like in 2030 or 2040 or 2050. So policymakers will need to meet regularly, take stock of where they are, and revise as needed.

This road map is staggering. That’s the point.


It’d be entirely understandable to look at this all and say, “That’s insane.” Phasing out sales of combustion engine vehicles by 2030? Carbon-neutral air travel within two decades? Cities going entirely fossil fuel–free in the next 13 years? Come on.

And fair enough. None of this is easy. It might well prove impossible. But this is roughly what staying well below 2°C entails — at least without large-scale geoengineering to filter out sunlight and cool the planet (a risky step). This is what world governments implicitly agreed to when they all signed on to the Paris accord.

“We wanted to show what meeting those Paris goals requires,” says Rockström. “Up until now, we felt that scientists haven’t been very effective in communicating what these carbon budgets actually mean in terms of concrete action.”

Rockström and his colleagues argue that future UN climate talks should strive to create a much more detailed decade-by-decade road map along the lines of their Science paper, in order to gain much more clarity on what needs to happen to stay below 2°C.

Rockström adds that the road map’s sheer difficulty doesn’t mean climate action is hopeless. “You could just as easily see this becoming a self-fulfilling prophecy,” he says. “Countries start taking these targets seriously and then begin pursuing the innovation needed to make this come true.” That’s what Moore’s law did for the semiconductor industry; the prediction that chip performance would double every 18 months helped guide firms in thinking what they needed to do to make that come true. A “carbon law,” Rockström argues, could do the same for countries and cities and companies.

Oliver Geden — a German climate policy analyst who wasn’t involved in the Science paper but who has criticized scientists and policymakers for obscuring what the 2°C target really requires — praised the broad approach here, though noted that some of the details were debatable.

“One thing I like is that this is not just another global calculation [on CO2 emissions] that doesn’t talk about actors or policies,” Geden told me by email. “I think this should be the way forward, translating [overarching climate goals] into ‘policy portfolios’ and then asking policymakers if they are going to do it or not.”

For example, the paper lays out a specific timeline for deploying technology to remove carbon dioxide from the atmosphere. Most modeling scenarios for staying below 2°C now envision massive CO2 removal efforts, but few policymakers have acknowledged this fact. Presenting them with a detailed proposed timeline could, hopefully, change that. If it turns out that scaling up bioenergy with CCS is logistically impossible (as it might be), then at least we’d come to terms with that sooner, rather than keeping it as an unspoken background assumption in broad climate plans.

Of course, it’s possible that if policymakers really grappled with what staying below 2°C entails, they might come away thinking it’s impractical or undesirable. They might decide to accept more global warming, say, 2.5°C or 3°C or more, and deal with the severe risks that result, from higher sea-level rise to droughts to crop failures. (I’ve written more on that here.)  But something has to force that conversation. If this 2°C climate goal is going to loom over every international climate meeting, every white paper and discussion, then the least people can do is take it seriously.

Further reading

— Here is a history of the 2°C global warming target — and what it would mean to miss it. And note that no country in the world is currently taking the goal seriously.

— This new paper by Jesse Jenkins and Samuel Thernstrom looks at the research around achieving deep decarbonization in the electricity sector. Note that while it might be physically possible to decarbonize the grid using only renewables, a number of studies suggest it’d be much more cost-effective to harness nuclear power or coal/gas with carbon capture and storage as well.

— The Science paper is also a good framework for thinking about Donald Trump. Trump, recall, wants to dismantle US climate policies and slash clean energy research. In the short term, that probably won’t hamper the incremental decline in US emissions already underway, as natural gas and renewables keep pushing out coal in the power sector. But Trump’s policies could easily hinder the push for deep decarbonization in the US — or at least delay it until well after 2020, making the 2°C goal all the harder.

— Over at Carbon Brief, Jocelyn Timperly dissects a new International Energy Agency report showing how we might stay on a 2°C pathway. It gets at the problem a little differently (and mainly focuses on short-term energy policies), but is basically compatible with the Science paper’s analysis.

By Stephen Leahy

UXBRIDGE, Canada, Mar 24 2017 (IPS)

The Carbon Law says human carbon dioxide (CO2) emissions must be reduced by half each decade starting in 2020. By following this “law” humanity can achieve net-zero CO2 emissions by mid-century to protect the global climate for current and future generations.

A “carbon law” is a new concept unveiled March 23 in the journal Science. It is part of a decarbonization roadmap that shows how the global economy can rapidly reduce carbon emissions, said co-author Owen Gaffney of the Stockholm Resilience Centre, one of international team of climate experts.

“Coal power plants under construction and proposed in India alone would account for roughly half of the remaining carbon budget.” –Steven Davis

To keep the global temperature rise to well below 2°C, emissions from burning fossil fuels (oil, gas and coal) must peak by 2020 at the latest and fall to around zero by 2050. This is what the world’s nations agreed to at the UN’s Paris Agreement in 2015. Global temperatures have already increased 1.1 degrees C.

“After the Paris agreement we began to work on a science-based roadmap to stay well below 2C,” Gaffney told IPS.

The “carbon law” is modelled on Moore’s Law, a prediction that computer processing power doubles every 24 months. Like Moore’s, the carbon law isn’t a scientific or legal law but a projection of what could happen. Gordon Moore’s 1965 prediction ended up becoming the tech industry’s biannual goal.

A “carbon law” approach ensures that the greatest efforts to reduce emissions happen sooner not later, which reduces the risk of blowing the remaining global carbon budget, Gaffney said.

This means global CO2 emissions must peak by 2020 and then be cut in half by 2030. Emissions in 2016 were 38 billion tonnes (Gt), about the same as the previous two years. If emissions peak at 40 Gt by 2020, they need to fall to 20 Gt by 2030 under the carbon law. And then halve again in 2040 and 2050.

“Global emissions have stalled the last three years, but it’s too soon to say if they have peaked due largely to China’s incredible efforts,” he said.


The Science paper, “A roadmap for rapid decarbonization”, notes that China’s coal use swung from a 3.7 percent increase in 2013 to a 3.7 percent decline in 2015. Although not noted in the paper, China’s wind energy capacity went from 400 megawatts (Mw) in 2004 to an astonishing 145,000 Mw in 2016.

“In the last decade, the share of renewables in the energy sector has doubled every 5.5 years. If doubling continues at this pace fossil fuels will exit the energy sector well before 2050,” says lead author Johan Rockström, director of the Stockholm Resilience Centre.

The authors pinpoint the end of coal in 2030-2035 and oil between 2040-2045 according to their “carbon law”. They propose that to remain on this trajectory, all sectors of the economy need decadal carbon roadmaps that follow this rule of thumb.

Elements of these roadmaps include doubling renewables in the energy sector every 5-7 years, ramping up technologies to remove carbon from the atmosphere, and rapidly reducing emissions from agriculture and deforestation.

The immediate must-do “no-brainer” actions to be completed by 2020 include the elimination of an estimated 600 billion dollars in annual subsidies to the fossil fuel industries and a moratorium on investments in coal. Decarbonization plans must be in place for all cities and major corporations in the industrialized world.

Rapidly growing economies in India, Indonesia and elsewhere should receive help to take a green path to prosperity. They cannot use coal as China did because CO2 emissions are cumulative and there is little room left in the global carbon budget, said Gaffney.

This is an extremely urgent issue. India is already on the brink of taking the dirty carbon path.

“Coal power plants under construction and proposed in India alone would account for roughly half of the remaining carbon budget,” said Steven Davis of the University of California, Irvine about his new study that will be published shortly.

Davis, who was not involved in the carbon law paper, agrees that rapid decarbonization to near-zero emissions is possible. Cost breakthroughs in electrolysis, batteries, carbon capture, alternative processes for cement and steel manufacture and more will be needed, he told IPS.

All of this will require “herculean efforts” from all sectors, including the political realm, where a cost on carbon must soon be in place. Failure to succeed opens the door to decades of climate catastrophe.

“Humanity must embark on a decisive transformation towards complete decarbonization. The ‘Carbon law’ is a powerful strategy and roadmap for ramping down emissions to zero,” said Nebojsa Nakicenovic of the International Institute for Applied Systems Analysis (IIASA) in Austria.