Wedging the Gap

A bottom-up approach to the global climate challenge

Weather records are piling up in the US and worldwide, and the seasonal state of the Arctic sea ice melt is the worst we’ve seen so far. And in the meantime, greenhouse gas emissions are still rising, where they should now start to go down to keep average global warming below 2 degrees C (3.6 degrees F), the goal that was internationally agreed on.

“Business-as-usual” emissions would grow by another 12% to reach 56 billion tonnes of CO2-equivalent by 2020. To remain on track for 2 degrees C, we would need them to be 12 billion tonnes lower: this difference is known as the ‘emissions gap’.

At the global Earth Summit in Rio de Janeiro, exactly 20 years ago, countries agreed on a Framework Convention on Climate Change. In spite of the tremendous effort by the UNFCCC Secretariat, negotiations to really start reducing global emissions are going through a difficult stretch. Attention is shifting to a treaty that takes effect from 2020, and the country commitments for the period 2012-2020 would close half of the gap, at the very best.

Reducing emissions is feasible
In any approach, real measures will have to bring about the emission reduction. There is ample realistic potential to reduce emissions to close the emissions gap, and at least a third of that is in energy efficiency. Many measures have environmental and economical benefits, much beyond greenhouse gas emission reduction only.

Solar PV technology is developing at an incredible pace, bringing down cost, and ramping up application by over 50% per year. It is now within reach to bring global solar PV capacity to 1.6 Terawatt (1.6 million Megawatts) by 2020, which will reduce emissions by 1.4 billion tonnes of CO2 per year. Other technologies like LED-lighting, electric vehicles, and their batteries are developing quickly as well.

Front running companies, cities, and individual citizens are taking climate action on their own, demonstrating that the potential and the benefits are real.

Wedging the Gap
In the UNFCCC negotiations, countries should agree on measures, then make sure that emitters in their countries comply with the agreed reduction. The negotiations have increasingly turned into “I will only accept limitations on my economy if I’m absolutely sure you will do the same for yours”, obscuring the fact that many emission reduction measures have multiple benefits. As it became apparent in recent years that such a top-down approach alone would not work, a bottom-up approach was suggested, but so far, no concrete proposals for this on a global scale have been put forward.

Wedging the Gap is a bottom-up approach, building on all the rapid developments in technology and implementation and on the great initiatives in many places to bridge the global emissions gap. It consists of amplifying the actions of frontrunners in 21 types of activity by applying them on a large scale, under the leadership of organizations already active in the field.

Bringing together all these initiatives in a grand scheme with a major collective impact will serve as a catalyst for individual action. We have selected the 21 ‘wedges’ by applying the following criteria:


Ongoing activity, starting from which major scaling up before 2020 is possible


Significant additional benefits next to reduction of greenhouse gas emissions


There are organisations that can lead a global initiative


The initiative has the potential to reach an emission reduction in the order of 0.5 billion tonnes of CO2-equivalent by 2020

Examples: Companies, wind energy and cities
Worldwide, over 30 leading companies have entered into Climate Savers agreements with WWF, reducing their emissions significantly below business-as-usual. In doing so, many of them found out it’s easier than thought, brings lower cost and less exposure to energy price risks, and helps build their reputation. Together, these companies reduced their CO2-emissions by over 100 million tonnes over the past 12 years. A recent analysis by Ecofys has shown that taking this approach to major corporations in the 16 business sectors where the program is active could reduce global emissions by 0.5-1.0 billion tonnes of CO2 per year by 2020. Many other companies are making similar pledges already; a perfect starting point for a ‘Companies wedge’!

Wind energy has made big strides over the past decades. By the end of last year, 238 GW of installed capacity already provided 2-3% of the world’s electricity. GWEC, the Global Wind Energy Council, has published an ‘advanced scenario’, showing that wind power capacity could grow to 1,070 GW (a TeraWatt) by 2020. Doing so would reduce dependence on fossil fuels, improve air quality, and provide an additional emission reduction of 1.2 billion tonnes of CO2 by 2020, compared to the reference scenario.

Many cities have ambitious climate programs, combining the creation of new cleantech jobs with improvements in housing and infrastructure, lower energy cost, and better air quality. Organizations like C40 and ICLEI are leaders in these efforts. If the 40 megacities in C40, or an equivalent sample of other cities, reduce their emissions to 20% below business-as-usual by 2020, this would already result in an emission reduction of 0.7 billion tonnes of CO2-equivalent.

Emissions reduction from the wedges adds up to 10 billion tonnes!
All wedges are shown in the figure on the left. Of course, there will be some overlap: companies and cities may use wind turbines as part of their emission reduction programmes. Taking that into account, we estimate the total emission reduction of the first 19 wedges to be 10 billion tonnes of CO2­-equivalent per year, achievable by 2020! Adding up the climate benefits of 2 wedges addressing classic air pollutants, including efficient cookstoves in rural areas, would bring us very close to what is needed to keep the world on track for an average global warming of 2 degrees C.

A paper on our approach has been published online by Nature Climate Change:
K. Blok, N. Höhne, K. van der Leun, and N. Harrison
Bridging the greenhouse-gas emissions gap

2 reactions on 'Wedging the Gap'

  • Jessee McBroom 05-07-2012 at 13:58 I loke this wedging the gap approach. I too have had my doubts that Tnternational Actions would actually result in an rffective campaign to resolve the Climate Change issue. I believe also wind is a good place to start; but all other zero emmissions power production systems should be pursued with vigor and due respect to the environment as well. Solar Geothermal Hydro Wave and Tidal Flow systems as well as other benign electrical production systems and zero emmissions transportation systems should be persued as vigorously as Wind.
  • Kees van der Leun 05-07-2012 at 21:12 Thank you for your comments, Jessee. Many of the technologies that you mention are also represented in one or more of the 21 wedges!

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