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Beyond Paris, Part 3: Overshooting Dangerous Warming Likely, But For How Long?

Matthew Stepp's picture
Center for Clean Energy Innovation

Matthew Stepp is the Executive Director for the Center for Clean Energy Innovation specializing in climate change and clean energy policy. His research interests include clean energy technology...

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  • Jun 11, 2014

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global warming and risks and safety

By Matthew Stepp and Amanda Kibbe, Center for Clean Energy Innovation

In 2012, Jesse Jenkins and Matthew Stepp took stock of the global climate policy challenge in an online series titled The Future of Global Climate Policy. Since then the Intergovernmental Panel on Climate Change (IPCC) completed its Fifth Assessment and many countries are taking stock of their existing—and some argue, failed—climate policies. Looking to the future, the latest round of international climate negotiations is set to close in Paris at the end of 2015, potentially offering the end of one era of global climate policymaking and the start of something new. With an eye on the long-term impacts of the 2015 negotiations, Amanda Kibbe and Matthew Stepp take an updated look in a five-part series on the state of the climate challenge. For Part 1, click here. For Part 2, click here.

Solving climate change is an extremely difficult—even monumental—challenge to address. Carbon emissions come from burning fossil fuels and are deeply embedded in the global economy. Turning on the lights, driving vehicles, powering industry, and living a prosperous life all emit carbon. As a result, cutting global carbon emissions is not a simple task and with each passing year the number of pathways to mitigating climate change dwindles. In fact, the scientific community indicates that mitigating climate change is still possible, but will most likely result in exceeding “dangerous” levels of carbon emissions in the short and mid-term followed by historically unprecedented decarbonization rates and the use of carbon removal technologies.

The IPCC goes into detail on whether and how the world can solve global climate change in part three of their Fifth Assessment report on mitigation. Scientists have built sophisticated, and increasingly complex, computer models of the global climate system, which are used to predict what the future climate might look like depending on how fast, slow, deep, or shallow the world cuts carbon emissions. The IPCC reports on over 900 different carbon reduction scenarios, which it uses to estimate how much carbon reduction is needed to keep global average temperatures within 2°C warmer than pre-industrial levels, the globally accepted, but arbitrarily set limit for what society deems “dangerous climate change.”

In Part 2 of this series, we summarized why the status quo is unacceptable moving forward. To keep temperatures from exceeding 2°C warming, the IPCC estimates that CO2 concentrations should not exceed 450 ppm by 2100. Currently, global emissions are hovering around 400 ppm and are rising fast—carbon emissions have risen faster from 2000 to 2010 than in the previous three decades. Between 1970 and 2010, emissions from fossil fuel combustion were responsible for about 78 percent of this increase (the remaining largely from land-use change). And under the status quo, emissions will continue to rise, and by 2100, temperatures will increase 3.7°C to 4.8°C warmer compared to pre-industrial levels.

Keeping concentrations below 450 ppm by the end of the century requires substantial cuts in carbon emissions. According to the IPCC, global CO2 emissions must decline 90 percent between 2040 and 2070, and should be near or below zero by 2100. Any delay in reducing emissions in the short-term reduces our ability to keep temperatures below 2°C, and requires adapting to a fundamentally different planet than what humans are accustomed to.

No doubt, this resolution is daunting, particularly because the two main drivers of fossil fuel consumption—population and wealth growth—are increasing as well. Global population nearly doubled since 1970 (3.7 billion to 6.9 billion) and is forecasted to increase by up to 28 percent by 2040. Global wealth—defined as GDP per capita—is forecasted to increase by roughly 127 percent by 2040. The challenge becomes even more difficult if the world aggressively addresses global energy poverty and provides access to the 1 billion or more that have none or little access to energy at all.

These trends will have significant impacts on energy demand and, therefore, carbon emissions if the world continues to use fossil fuels. Power and transportation sector CO2 emissions are expected to double by 2050 compared to 2010 levels. Buildings and industrial sector CO2 emissions are expected to increase between 50-150 percent during the same period.

According to the IPCC’s carbon reduction models, keeping global emissions to 450 ppm even with global population and wealth growth is possible, but it’s going to be very difficult. The majority of reduction scenarios produced in the IPCC report cannot realize the short-term carbon emission reductions needed to stabilize around 450 ppm. Instead most model simulations forecast “overshoot,” where global carbon concentrations exceed 450 ppm (often up to 530-580 ppm), but by the end of the century fall back to around 450 ppm after a low-carbon global energy transformation and the deployment of “carbon dioxide removal” technologies. In all scenarios that stabilize global concentrations at around 450 ppm, deep carbon cuts of 40 to 70 percent compared to 2010 are needed by 2050. And if the world waits until after 2030 to start cutting global emissions, the rate of reductions after 2030 must double to roughly 6 percent per year, a rate of decarbonization never seen before in recent human history.

It’s particularly important to put an even finer point on the scale of this challenge compared to current efforts. Stabilizing carbon emissions around 450 ppm requires large scale changes to global and national energy systems in the coming decades. This includes tripling or quadrupling renewable, nuclear, and carbon capture technology by 2050 compared to 2010 levels. Reducing emissions through energy demand, such as energy efficiency, plays a role, but is not sufficient by itself. And the modest voluntary carbon reduction pledges made by countries during international climate negotiations are completely incompatible with any scenario for stabilizing emissions at 450 ppm.

It’s clear that 2°C warming limits set by the climate community has a high likelihood of being surpassed and it’s no longer whether we can avert 450 ppm, but whether we can limit how long we exceed those levels. The majority of focus by the international climate community has rightfully been on mitigation and clean energy technologies. But the most viable pathways to addressing climate change now also include the development of scalable carbon removal technologies and advancing global adaptation efforts as quickly as possible.

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Engineer- Poet's picture
Engineer- Poet on Jun 11, 2014

Arguably we are already past the point of danger.  Both Greenland and Antarctic glacier flows are accelerating and we have signs from the latter that the trend is unstable and will not cease until large areas have been drained of ice.  Bill McKibben is almost certainly right, we need to aim for 350 ppm.

David Newell's picture
David Newell on Jun 11, 2014

“Solving climate change is an extremely difficult—even monumental—challenge to address. “

Yes, it is.  And, as Engineer Poet says, 

“Arguably we are already past the point of danger.”


Given the apparent truth of the two above statements,  it is clear that a method of Direct Air Capture of CO2 MUST be found.

The contents of www.EarthThrive.Net demonstrate a methodology to effect D A C.


I would be glad to debate this in any public forum whatsoever, (Support for the contents referenced..) 

but most “news aggregators”  would rather ignore me, (for instance, Jim Pierobon)

and most scholoarly on-line PooBahs

would rather bicker about the accuracy of “MODELS”

than imagine and think about how we can get out of this MESS..


I see the names of the Esteemed Advisory Panel,

to the right of this screen I’m typing on:

and I wonder why  they (jointly or severally) 

would not see fit to actually put this irritating idea, (www.EarthThrive.Net

and the guy who keeps talking about it AS IF it would WORK (this writer),

completely out if it’s/his misery by pointing out

WHY it would NOT work..


Is this “challenge” enough, or  ~~ is fiddling while Rome burns~~

the best use of your combined “wisdom”.

We are all in this together.





Engineer- Poet's picture
Engineer- Poet on Jun 11, 2014

You can find papers regarding the sequestration of carbon by the accelerated weathering of olivines.  Some authors suggest incorporating crushed olivine into soil, where the CO2 content is enriched by respiration by plant roots.  Others suggest shallow shoreline areas, where the minerals will be exposed to carbon-laden seawater and worked by wave action.

The crushing of minerals for carbon sequestration appears to be an ideal task for intermittent renewable energy supplies.  You don’t care much when it gets done, just as long as you have X amount per year.

Bas Gresnigt's picture
Bas Gresnigt on Jun 12, 2014

You cannot expect major investments to reduce CO2 without broad public support.

However the belief in global warming seems to decrease as shown by Kelly Klima here.
So it is not strange the new EU climate targets are less strict.

So little will happen unless:
– IPCC improves its credibility;
The not predicted recent cooling down period didn’t help.
– climate education to the public is improved.

Robert Bernal's picture
Robert Bernal on Jun 12, 2014

The simple fact that the oceans are already slightly more acidic, and that we are observing the ice caps melting faster, and the obvious rise in CO2 ppm should be education enough.

Efficiency is already the most worked on (half) solution because it’s the cheapest. Now, the world needs unimaginable amounts of clean energy to the tune of:

At least 10,000 modular molten salt reactors (or better meltdown proof, spent fuel “eating” reactor), or,

500,000 square miles of solar with about 48 hours of storage (and more powerlines, international agreements for the solar “have nots”, etc), or

Millions of square miles of wind tubines (total area that can also be used for farming, etc), or,

Mandatory CCS and thousands of miles of pipes built just for that cause.

Everything else such as biofuels, wave and tidal does not have the potential to power the world. Hydropower, though not capable of powering the entire world has far more potential than biofuels.

Therefore, we need to incorporate ALL of the above (if sustainable). We also need to electrify or switch the vehicle fleet to clean liquid fuels and fuelcells (no matter what).

The technical issues are easy compared to the fight against money.

We need advanced robotics capable of simultaneously producing, installing and recycling (old) solar panels, batteries, wind turbine parts, (and other RE parts), dealing with (lots of) nuclear HLW (not spent fuel which must be reprocessed/recycled), and which must help with the gigantuan task of properly isolating half a trillion tons of excess CO2 from the biosphere at a cost that will not crush civilization.


Bas Gresnigt's picture
Bas Gresnigt on Jun 12, 2014

“…crushing of minerals for carbon sequestration appears to be an ideal task for intermittent
Seems a good idea!
Can be added to other similar ideas, such as power-to-fuel conversion.

So wind & solar capacity can be raised, each towards >200% of the average electricity consumption.
So for Germany (av. consumption ~50GW): 
For solar from 37GW now towards ~200GW
For wind from 34GW now towards ~100GW.
For solar that 200GW target implies that ~15% of all roofs have to be covered with PV-panels. A major operation. But reachable.

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