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Andlinger Center News

October 18, 2016

By Sharon Adarlo

A global climate agreement was reached in Paris in late 2015. It will come into force on November 4, 2016 after 81 countries that generate more than half of the world’s greenhouse gas emissions have ratified it. The deal aims to have countries dramatically reduce greenhouse gas emissions and limit global warming to less than 2 degrees Celsius above pre-industrial levels, so as to keep as low as possible risks such as those associated with extreme weather patterns (e.g., droughts and storms), melting polar ice caps, and rising seas that would flood coastal cities and potentially erase small island nations, such as the Marshall Islands.

A few days ago in Rwanda, more than 170 countries agreed to a legally-binding deal to cut the use of chemical coolants (known as hydrofluorocarbons or HFCs) that are used in refrigerators and air conditioners. This move will impact the fight to combat global warming, according to many experts.

On a parallel effort, 20 countries pledged to double government investments in research and development for clean energy over the next five years in a broad effort called Mission Innovation. Countries that signed on include the United States, China, India, and Saudi Arabia. Simultaneously, Microsoft founder Bill Gates unveiled the Breakthrough Energy Coalition, an initiative backed by 28 prominent investors from around the world, including Princeton alumni Meg Whitman ’77, CEO of Hewlett-Packard, and Jeff Bezos ’86, founder and CEO of Amazon. The coalition will work with Mission Innovation countries to drive innovation from the laboratory to the marketplace by dramatically increasing investment in demonstrated transformational clean energy technologies to help speed up commercial deployment.

To examine the implications of the Paris climate agreement, the effort to halt climate change, and the growing interest in clean energy investment from public and private sources, we interviewed members of the Energy Systems Analysis Group at Princeton University’s Andlinger Center for Energy and the Environment. The research unit carries out technical and economic analyses of prospective technologies and strategies to help inform policy debates around major energy-related issues such as climate change, energy supply insecurity, air pollution, and rural energy access. The senior members of the group include Robert H. Williams, senior research scientist; Eric Larson, senior research engineer; and Thomas G. Kreutz, energy systems modeler.

The researchers also described several projects they are involved with that are aimed at catalyzing technological advances that would help the Paris agreement to succeed.

Why is the Paris climate agreement important?

Kreutz: The agreements forged in Paris change the nature of the dialogue. The new global narrative around climate change makes it much harder for climate skeptics because so many world leaders have openly acknowledged the gravity of the problem and agreed to take concrete actions to mitigate it.

Larson: This is a first step. It’s the world coming together saying they want to fix this problem. There are big challenges of course.

Williams: The most important accomplishment is that a promising process has been put into place that gives us a shot at addressing effectively the climate change challenge. It’s going to take a lot of hard work that will have to be sustained for decades to come. But I am guardedly optimistic.

What will the Paris agreement achieve?

Williams: If all countries are able to realize the voluntary commitments they made in Paris for reducing their own emissions, there is a reasonable chance of limiting global warming to less than 3 degrees Celsius by 2100—less than the expected warming of 3.6 to 4.0 degrees by then if the world were instead on a business-as-usual track. But the outcome could still mean far more warming than the Paris deal’s goal of limiting warming to less than 2 degrees—let alone the additional goal written into the agreement of 1.5 degrees. Furthermore, limiting global warming to less than 3 degrees is not assured, because country commitments are not binding.

But the agreement represents the first time that all 197 parties (196 countries plus the European Union), who signed the 1992 treaty, the United Nations Framework Convention on Climate Change, have agreed to take actions to reduce their greenhouse gas emissions, and the agreement puts into place a relatively transparent process for improving, over time, the long-term outlook. The hoped for improvement will come about in part via shared information as to what policies, strategies, and technologies work, and in part via cooperative and competitive pressures.

The Paris agreement contains mechanisms for ratcheting up ambitions over time. Beginning in 2020, and every five years afterwards, each country is to “prepare, communicate, and maintain successive nationally determined contributions that it intends to achieve.” Each “successive nationally determined contribution represent(s) a progression beyond the party’s then current nationally determined contribution and reflect(s) its highest possible ambition.”

Do you think the Paris agreement will work?

Larson: The world basically needs to get close to zero emissions of greenhouse gases by 2050 to limit warming to below 2 degrees Celsius. That’s 34 years from now. Is it possible? I think it’s technically feasible, but will require governments and the private sector to work together to decarbonize the energy system at a rate never before seen in human history. One way to think about the challenge is that there is a fixed remaining amount of carbon dioxide that can be added to the atmosphere this century if we don’t want to exceed a warming of 2 degrees – it’s about 1 trillion tonnes. At the current rate of emissions, the world will have spent this “carbon budget” by sometime in the 2040s. Reducing emissions as we go forward from today will extend the time until we expend the budget, but if we are unable to keep from exceeding the budget and still want to stay below 2 degrees warming, there would be the need to deploy technologies that remove CO2 from the atmosphere.

What kind of technologies are those?

Larson: There are several “negative emission” ideas. Two that have gotten much attention are:

  1. Growing biomass removes carbon dioxide from the atmosphere and converts it into stored energy. The biomass could be converted into useful energy, like electricity or fuels, and the byproduct carbon dioxide from these processes could be captured and stored in deep geological formations. This effectively permanently removes carbon from the atmosphere. It would be important that the biomass used in such systems is produced sustainably and without negative impacts on food production.
  2. Removing carbon dioxide directly from the air by chemical absorption or other means. This is sometimes called direct air capture. The captured carbon dioxide would then be stored permanently away from the atmosphere, e.g., in deep geological formations or by converting it into carbonate rocks.

The development and commercial deployment of these types of systems will take time. The most effective way to get this process moving is with policies that effectively put a price on greenhouse gas emissions. The price will eventually need to reach substantial levels to be able to economically justify negative emissions systems.

What do you think of the increased interest in clean energy from public and private investors, stemming from the Paris climate agreement?

Williams: It is much needed. Funding for clean energy research has been abysmally low relative to the need, in light of the climate-change challenge. The Mission Innovation commitment by 20 countries to increase that funding from $15 to $30 billion per year over five years is a laudable step towards turning this around. The Bill Gates initiative is a wonderful complement that can facilitate market launch for technologies identified as promising by Mission Innovation-supported research.

Larson:  Renewable energy investment is increasing rapidly—especially for wind and photovoltaic electricity. But if you look at the big picture in terms of contributions these sources make to the overall energy supply, it’s still 80 to 90 percent energy from fossil fuels in most countries, so the increased interest in clean energy investment triggered by the Paris agreement is very welcome and needed.

Kreutz:  It remains to be seen what role private investors will play in rolling out new, environmentally-friendly energy technologies, which are typically more costly than those currently in use. Strong public policies that send clear market signals will be required to induce business leaders to make the necessary investments in both capital and manpower. In the U.S, regulatory mechanisms instituted by the executive branch, which are threatened by a presidential election every four years, probably won’t provide the future certainty needed to stimulate significant action by the private sector. That will require the majority of U.S. citizens and Congress to follow the lead set in Paris.

How important is market launch for clean energy technologies?

Williams: As the innovative process evolves from laboratory experiments through development and demonstration and then on to market launch of new products, costs increase. First-of-a-kind energy systems can cost several times as much as these systems are expected to cost once they are well established in energy markets. Bringing down costs through experience (“learning by doing”) and continued technological innovation for “early-mover” projects is often referred to as “having to survive a trek through the valley of death,” represented by the negative cash flow to an enterprise during the process.

It is good that private investors like Bill Gates have agreed to focus on the market launch part of the innovative process. Hopefully the Breakthrough Energy Coalition will attract other private-sector investors to this multi-trillion-dollar challenge.

 What kind of technologies and systems are you examining that would help the Paris climate deal succeed?

Williams: Studies being done by the Energy Systems Analysis Group include the exploration of carbon capture and storage (CCS) for energy derived from fossil fuels and renewable biomass (plant matter), which can be provided in environmentally sound ways that don’t compete with food production. The UN Intergovernmental Panel on Climate Change’s Fifth Assessment Report in 2014 reached the judgments that it would be hard to limit the ill effects of climate change without CCS and perhaps impossible to limit global warming to less than 2 degrees Celsius without energy systems involving CCS for biomass that offer negative emissions. I have also has been exploring promising public policies for accelerating the market launch of low-emission technologies that appear likely to be economically viable once they are established in the market.

Larson: I was recently part of a project that designed and analyzed a process for converting biomass residues from sustainable forest harvesting into liquid fuels. Carbon dioxide captured during the fuel production process would be pumped underground into depleted gas shale formations – making the whole system carbon negative. The Andlinger Center has supported this project.*

Kreutz: I have been investigating novel technologies, such as molten-carbonate fuel cells and power cycles using high pressure carbon dioxide, both of which can help generate electricity from fossil fuels at high efficiency and low cost while simultaneously capturing carbon dioxide for secure storage underground instead of being emitted into the atmosphere. We’re also interested in analyzing the future decarbonization of the U.S. electric power sector, and how that process might be (dramatically) influenced by the unprecedented growth of intermittent renewable electricity generation in the U.S.


*For more information on this Andlinger Center-sponsored project, go to this link. Relevant publications related to this project include the following:

  1. Edwards RW, Celia MA, Bandilla KW, Doster F, Kanno CM, “A model to estimate carbon dioxide injectivity and storage capacity for geological sequestration in shale gas wells,” Environ Sci Technol 2015;49:9222–9.
  2. Hailey AK, Meerman, JC, Larson, ED, Loo Y-L, “Low-carbon ‘drop-in replacement’ transportation fuels from non-food biomass and natural gas,” Appl Energy 2016,

 The Andlinger Center Speaks is a Q/A series that features experts from the center addressing topical and timely energy and environmental issues.

For more information on the Andlinger Center for Energy and the Environment at Princeton University, contact Sharon Adarlo, communications specialist, at or (609) 258-9979.