Net zero carbon goal is achievable and necessary say Potsdam, Stanford, and Australian researchers

February 26, 2016

Scientists and policy experts say the time has come to phase out carbon emissions entirely; Shell, Exxon and BP still find it unrealistic for the business model they continue to hang onto, but the time is coming…

The most striking recent development to emerge from UN climate negotiations is the growing consensus that within a generation the whole world will have to stop spewing carbon dioxide into the air from energy use.

This means that within the lifetimes of today’s toddlers we would entirely eliminate CO2 emissions, unless they are offset by subtractions. (Carbon dioxide could be subtracted naturally, for example, by growing more trees.)

In shorthand, the new goal is “net zero”—and the sooner the better. Climate hawks say it should be met as early as 2050. Others see a few more decades of wiggle room, but they too emphasize the need for rapid action.

Two degrees Celsius of warming is the widely accepted target, but some say the goal should be 1.5 degrees. At present, the world seems to be aimed at 4 degrees of warming, at least.

Ahead of COP-21 70 leading climate experts (click here) from around the world met in a “structured expert dialogue” from 2013 to 2015 to review the adequacy of the 2°C target.  They simplified their key conclusions into 10 core messages. Among them:

  • Message 1: “Parties to the Convention agreed on an upper limit for global warming of 2°C, and science has provided a wealth of information to support the use of that goal.” Incorporating concerns about ocean acidification and sea level rise, “only reinforces the basic finding emerging from the analysis of the temperature limit, namely that we need to take urgent and strong action to reduce GHG emissions” (emphasis in original).
  • Message 2 (again, original emphasis): “Limiting global warming to below 2°C necessitates a radical transition (deep decarbonization now and going forward), not merely a fine tuning of current trends.”
  • Message 4: “Significant climate impacts are already occurring at the current level of global warming” (which is about 0.85°C) and so additional “warming will only increase the risk of severe, pervasive and irreversible impacts. Therefore, the ‘guardrail’ concept, which implies a warming limit that guarantees full protection from dangerous anthropogenic interference, no longer works.
  • Message 5: “The 2°C limit should be seen as a defence line … that needs to be stringently defended, while less warming would be preferable.”
  • Message 6 (from the 2014 IPCC mitigation report): “Limiting global warming to below 2 °C is still feasible and will bring about many co-benefits, but poses substantial technological, economic and institutional challenges.”

To have a “likely” chance (a 66 percent probability) means that deeper, earlier reductions will be necessary that what’s needed for a mere 50-50 chance of success. To have a 95 percent chance at success, cuts would have to be radically deeper and astonishingly fast.

Last fall, China pledged to “increase the share of non-fossil fuels in primary energy consumption to around 20% by 2030.” That “will require Chinato deploy an additional 800-1,000 gigawatts of nuclear, wind, solar, and other zero emission generation capacity by 2030 — more than all the coal-fired power plants that exist in China today and close to total current electricity generation capacity in the United States.”

Over the next 15 years, the Chinese will build enough clean electricity to power America. So how exactly is it “nonsense” to think the U.S., EU, or even India could not do the same over, say, twice as much time? Answer: It isn’t.

  • Here’s Message 8 from the world’s leading climate experts: “The world is not on track to achieve the long-term global goal, but successful mitigation policies are known and must be scaled up urgently.

A new briefing note from Climate Analytics at the Potsdam Institute describes the timetables in great detail.  For a 66 percent likelihood of avoiding 2 degrees of warming at the end of this century, global greenhouse gas emissions by 2050 would have to be 40-70 percent below 2010 levels; CO2 emissions alone from energy and industry would have to drop 35-80 percent. Overall emissions of all greenhouse gases would need to reach zero some time between 2080 and 2100, but energy and industry emissions of CO2 would have to reach zero sooner, by 2060 to 2075.

Research led by a multi-university consortium including Stanford’s Mark Jacobson has produced 100% wind, water, and solar plans tailored to each of 139 countries’ and 50 US states’ resources and weather, along 15-30 minute intervals over a sample 6 year span of sunlight, wind, and other weather for each, documenting how available renewables can be combined in a complementary mix, without the batteries now becoming economically accessible. (See

in 2010, a previously reticent Lonnie Thompson explained why previously reticent climatologists had begun speaking out: “Virtually all of us are now convinced that global warming poses a clear and present danger to civilization.” It’s why, when Joe Romm launched Climate Progress nine years ago he created a category called “uncharacteristically blunt scientists.”  The time has come to move in the direction of zero emissions, and as rapidly as possible.

Idea Takes Hold

The net-zero goal emerged last year out of the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC). The panel detailed more thoroughly than ever the concept of a global carbon budget—the amount of cumulative emissions that scientists say cannot be exceeded if the world is to keep global warming within safe limits.

Scientists and energy policy experts translated that work into an ambition of breathtaking simplicity: to phase out carbon emissions entirely.

At talks in Lima in Peru, the idea took hold more strongly than ever, and in a treaty-drafting session in Geneva this month, it was widely embraced.

“The text mentions net-zero, near zero, climate neutrality or full decarbonization 15 times,” wrote Simon Evans in an excellent treatment of the subject at Carbon Brief. “Some include deadlines for reaching net zero, others do not.”

Net-zero advocates say getting there by 2050 would be none too soon.

That extraordinarily ambitious timeframe is what a group of prominent business leaders, who call themselves the B Team, recommended on Feb. 5. Among their leaders are Paul Polman, the chief executive of Unilever, and Richard Branson, the founder of Virgin Atlantic.  They say the goal is reasonable, and spreading.  Two of the world’s leading electric vehicle (EV) producers say that they will soon deliver 200+ mile range EVs at a game-changing price of $30,000 or less — including tax incentives.  And Honda says that two-thirds of the company’s offerings will be plug in vehicles by 2030.

“Momentum is already growing in finance, business and political circles for a net zero goal,” wrote Catholic leader Mary Robinson, a former president of Ireland who is the UN Secretary General’s special envoy on climate change.

“But we need more. Adopting the net zero goal is not something to be put off until later,” she went on in the foreword to a report published by called “The Business Case for Adopting the Long-Term Goal for Net Zero Emissions.”

The Naysayers

The big oil and gas companies such as Shell, Exxon and BP call it an unrealistic idea. So do some big petro-states like Saudi Arabia.  The 2050 timeline is “not really practical,” said David Hone, the climate change adviser for Shell.  “The Paris agreement should certainly be geared around an end-goal of net-zero emissions, but the realistic, albeit still aggressive, time span for this is 80+ years, not 35 years,” he wrote on his blog.

Hone said he does understand the imperative.  “There is no doubt that to quickly and decisively solve the climate issue and have a better than even chance of keeping the surface temperature rise below 2 degrees C that we need to do this,” he wrote, “but that doesn’t mean we can.”  Certainly the momentum under current policies is still taking the world in the wrong direction, despite pledges to act by many major polluting countries.  BP, in its annual forecast this week, said that it expects emissions of carbon dioxide to rise another 25 percent by the year 2035. That would certainly make it all but impossible to reach zero by 2050, and probably less than likely to get there by the end of the century—unless something changes.

Technically Possible

One particularly powerful change, the big oil companies often say, would be the worldwide use of carbon pricing schemes, either through taxes or cap-and-trade regimes.  In any event, there are credible reviews that show that it is technically possible for society to choose realistic pathways to deep decarbonization—even to eliminate emissions from fossil fuels altogether.

A newly updated study called “Pathways to Deep Decarbonization in the United States” conducted by economic consultants and two U.S. national labs using standard energy and economy models found that “it is technically feasible to achieve an 80 percent greenhouse gas reduction below 1990 levels by 2050 in the United States, and that multiple alternative pathways exist to achieve these reductions using existing commercial or near-commercial technologies.”

The cost, it said, “does not appear prohibitive.” But it would “constitute an ambitious transformation of the energy system.”  The report is part of a comprehensive effort organized by the Sustainable Development Solutions Network and the Institute for Sustainable Development and International Relations, which last year brought together experts from around the world to advise the UN on deep decarbonization pathways.

Elsewhere, there’s even a new on-line calculator you can use to try out various pathways toward decarbonization, answering the question posed by its sponsors: “Is it physically possible to meet our climate targets and ensure everyone has good living standards by 2050?” (Spoiler alert: the sponsors themselves generated four “plausible pathways” to a 2-degree-warmer world.)  Economists and numerous social science researchers have shown that shifting investment from fossil fuels to alternatives will prove economically rewarding, not punitive, especially when the benefits from reducing health impacts from pollution are taken into account.

“Many still seem to be talking and acting as if change is too difficult and costly and as if delay is not a problem,” wrote Nicholas Stern, a preeminent climate and development scholar, in a December 2014 policy paper. “Yet we can now see that the transition to a low-carbon economy can be highly attractive, embodying strong and high quality growth, driven by strong investment and innovation.”

Whatever the uncertainties, the scientific consensus is clearly warning against business as usual. A new summary of mainstream thinking by Australia’s National Academy of Science hits all the highlights. The current rate of emissions is leading to temperatures not seen on the earth for millions of years, and the risks of that are high. At the current rate of emissions, the 2-degree limit would be violated within just a few more decades. What’s needed long term are reductions of 5.5 percent to 8 percent per year.

Short of geoengineering, which has risks and costs all its own, just about “the only way to stop human-induced climate change is to reduce greenhouse gas emissions to net-zero levels,” the Australian academy said. The longer this takes to achieve, and the more greenhouse gases that are emitted in the meantime, the larger the scale of future climate change.


The International Energy Association’ s 2011 World Energy Outlook [WEO] release said that if internationally co-ordinated action is not taken by 2017, all permissible emissions in the 450 ppm ccenario would come from the (fossil fuel) infrastructure developed by that point, such that all new infrastructure from then until 2035 would need to be zero-carbon, unless emitting infrastructure is retired before the end of its economic lifetime to make headroom for new investment.  This is not impossible.  For example, coal plants in China are running at around 50% capacity currently, but it is unpalatable to investors and considered a waste of money/investment by govts.

Yes, shutting down existing fossil fuel infrastructure is much more costly than not building it in the first place. It is politically difficult (see U.S. coal plants), but it also happens all the time (see U.S. and China coal plants).  People can use the political difficulty of averting catastrophe as a reason to express hopelessness if they think that is productive, but don’t try to pin this on climate scientists or climate advisors.  There’s an old saying “it’s better to light a candle than curse the darkness” that is based on a Chinese proverb, “Don’t curse the darkness – light a candle.”  But it turns out there is a third option. You can curse the candle lighters, maybe because you have your eyes closed. And that’s the really awful truth.