The scientific community has understood that burning fossil fuels could cause global temperatures to rise for nearly two centuries, but it wasn't until the 1990s that efforts were made to address this phenomenon.

This post examines key milestones in carbon emission mitigation efforts since the first international effort to create a treaty to stabilize greenhouse gas emissions at the United Nations Earth Summit in 1992. The Clean Energy Transition Institute created this graphic to depict key efforts over the past 26 years, with a narrative to accompany each entry.

1992: Global action on climate got underway in 1992 with the United Nations Framework Convention on Climate Change in Rio de Janeiro, the first UN convention with the founding objective to stabilize GHG emissions. Since 1995, there have been yearly Conferences of the Parties or (COPs) to assess progress.

The same year, Joseph J. Romm and Amory B. Lovins made the case that the US needed to reprioritize energy to address global security in a post-cold war world (see Fueling a Competitive Economy, Foreign Policy, 1992/Winter). While there is much that is outdated in this article looking back now in 2018, it is deeply distressing to think how different the world would be if the United States had embraced Lovins and Romm’s recommendations from 1992. (See also Losing Earth: The Decade We Almost Stopped Climate Change, The New York Times, July 31, 2018).

Romm and Lovins trace the history of fossil fuel extraction from the 1950s to the 1990s; discuss resource efficiency and fossil fuel subsidies. They observe that, “. . .pursuing energy supplies led the nation astray. Energy security is better defined as the nation’s ability to sustain adequate, reliable energy services in ways that maximize economic competitiveness and minimize environmental degradation.”

The authors note that after the 1973 oil shocks, the country’s initially moved away from the consumption and imports of oil into investment in energy efficiency and renewable energy, which “worked spectacularly” but these were rolled back with the Reagan administration. Their prescription: adopt a market-oriented energy policy, demilitarize economic policy, practice sustainable environmental policy, and integrate all three of these courses.

1997: The Kyoto Protocol was the first international agreement to mandate country reductions in greenhouse gas emissions. Finalized in 1997, it went into effect in 2005 by which time global emissions had risen substantially. The United States refused to ratify the treaty and developing countries such as China and India were not subject to the mandated emissions.

2004: Robert Socolow and Stephen Pacala, economists with the Princeton University Carbon Mitigation Institute developed the wedge stabilization models in 2004, which have become a standard tool for breaking down carbon emission reduction targets.

This image from 2004 shows what was needed at the time to mitigate global emissions with the x axis for the years starting in 1950 and going to the beginning of the 22nd Century, and the y axis for the amount of carbon emitted per year in billions of tons.

The top line of the triangle shows the current path or “ramp” of unchecked emissions, also referred to as “business as usual” or “BAU.” The known historical emissions are plotted from 1950 until 2004 and then projected out to 2050. The target of attaining an 80 percent reduction of 1990 levels by 2050 was set coming out of the Kyoto Protocol in 1997, hence the wedges are designed to attain reductions by that year.

The goal was to determine how to stop the upward trajectory of emissions starting in 2004, the “flat path” and achieve the same emission levels in 50 years (2054) with eight different wedges, or sets of strategies, and thereby avoid the increased emissions scenario. Then in 2054 the goal would be to bring emissions back down to levels present in the mid-1900’s.

Below is an example of a carbon wedge analysis created in 2014 for Washington Governor Jay Inslee’s Carbon Emissions Reduction Taskforce published in a November 2014 report. The graphic depicts historical greenhouse gas emissions, business-as-usual projection, and expected reductions from existing and potential policies, relative to the emissions targets.

For an in-depth discussion of this methodology in practice and to see how carbon wedge analyses are used to drive decision-making on climate change strategies, please see Creating Strategies for Emission Reduction.

2005-06: The Regional Greenhouse Gas Initiative (RGGI) is the first mandatory market-based program in the United States to reduce greenhouse gas emissions. RGGI started in 2005 with the initial signing of a memorandum of understanding among seven northeastern states and administered its first auction of CO₂ emissions in 2008. RGGI requires fossil fuel power plants with capacity greater than 25 megawatts to obtain an allowance for each ton of CO₂ emitted each year.

Today nine states are committed to RGGI: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont to cap and reduce CO₂ emissions from the power sector. The states have set a goal of reducing emissions an additional 30 percent by 2030. By 2020, the cap-and-trade program is expected to help the states reduce annual power-sector CO₂ emissions 45% below 2005 levels. For analyses of RGGI’s success, please see: The Regional Greenhouse Gas Initiative is a Model for the Nation and The Regional Greenhouse Gas Initiative is boosting state economies.

The California Global Warming Solutions Act of 2006 (Assembly Bill 32 or AB32) was a first-in-the-nation comprehensive, long-term approach to addressing climate change by requiring a sharp reduction in greenhouse gases. This watershed legislation required the largest state in the union to reduce emissions to 1990 levels by 2020, a 15% reduction below emissions expected under business as usual. For analyses of how California is fairing with implementing AB32 please see California Hitting Clean Energy Targets and California is set to hit its green-energy goals a decade early.

2007: Per-Anders Enkvist, Tomas Naucler, and Jerker Rosnader offered another important tool along the way for thinking about the impact of greenhouse gas emissions their article “A cost curve for greenhouse gas reduction” published in the McKinsey Quarterly in 2007. The article offered “policy makers, if they choose to act, an understanding of the significance and cost of each possible method of reducing emissions and of the relative importance of different regions and sectors.”

The authors plotted the cost curves of different approaches to help business leaders understand the impact of different potential regulations, now commonly referred to as the McKinsey Cost Abatement Curve.

2014-15: A wide variety of decarbonization models and studies were undertaken and released in 2014 and 2015. For an in-depth treatment of the major studies, please read the Clean Energy Transition Institute’s Analysis of Selective 2010-2018 Economy-Wide Decarbonization Studies.

2015-16: The Paris Agreement achieved at the Conference of Parties 21 in December 2015 aimed to strengthen the global response to the threat of climate change by keeping a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to propose efforts to limit the temperature increase even further to 1.5 degrees Celsius.

Parties that signed on to the Paris Agreement agreed to achieve net-zero global emissions in the second half of the 21st century and committed to submitting near-term targets called “nationally determined contributions” or NDCs, as well as to develop mid-century, long-term low greenhouse gas emission development strategies.

In the waning days of the Obama Administration and just before Donald Trump was elected President, the United States Mid-Century Strategy for Deep Decarbonization (MCS) was released (November 4, 2016). The MCS categorized U.S. decarbonization efforts into three areas:

• Low carbon energy system: Cutting energy waste; decarbonize electricity; deploy clean electricity, and low-carbon fuels in transportation, buildings, and industrial sectors  
• Sequestering carbon: Forests, soils (“land sinks”) + CO₂ removal carbon beneficial bioenergy with carbon capture and storage (BECCS)  
• Reducing non-CO₂ emissions: Methane, nitrous oxide, fluorinated gases

While the Trump Administration is not interested in adhering to the MCS roadmap and solutions proposed, thousands of climate policy advocates and clean energy advocates throughout the United States are working hard to ensure that progress toward these commitments is achieved nonetheless. Please see the Clean Energy Transition Institute’s Case Statement for a Northwest Deep Decarbonization Pathways Study.

In 2016, Drawdown was released and became a New York Times Bestseller. Project Drawdown gathered a broad coalition of researchers, scientists, graduate students, PhDs, post-doctorates, policy makers, businesses leaders, and activists to present the best available information on the financial, social, and environmental impacts of various climate solutions over the next 30 years. Below is a snapshot of the top 10 of 100 solutions to reverse global warming. Note that energy is only three of the top 10.

Project Drawdown open-sourced its table of solutions so anyone can download them and organize them for their purposes.  See the graphic below for the top 15 city-related solutions that I created using the Drawdown data. Project Drawdown also updates the solutions table as new data become available.

For a clever treatment of the Drawdown results, see this Periodic Table of Climate Solutions by Ryanjenningsnz.

2017: More recently, an excellent paper, A roadmap for rapid decarbonization, published in Science on March 24, 2017 by Johan Rockström, Owen Gaffney, Joeri Rogelj, Malte Meinshausen, Nebojsa Nakicenovic, and Hans Joachim Schellnhuber of the Stockholm Resilience Centre contributed greatly to the discussion and starkly paint how challenging global decarbonization is.

The authors assert that there was a 50% chance of limiting global warming to no more than 1.5 degrees Celsius and a 66% chance of limiting to 2 degrees Celsius, and in either case, global CO₂ emissions had to peak no later than 2020.

The authors framed the “decarbonization challenge in terms of a global decadal roadmap based on a simple heuristic—a “carbon law—of halving gross anthropogenic carbon-dioxide emissions every decade,” as the graphic below shows. Scalable carbon removal technologies as well as carbon sinks from bioenergy are also key to achieving the required level of decarbonization.

Additional Resources

For further information regarding this subject, see the Clean Energy Transition Institute's presentations on Low-Carbon Pathways for the Northwest; Low-Carbon Pathways: Transportation; Low-Carbon Pathways: Electricity; Low-Carbon Pathways Overview. For readings and studies, please consult Selected Decarbonization Reading List, which is the reading list for Western Washington University Institute for Energy Studies class taught winter quarter, 2018; Key Decarbonization References; and Transportation Decarbonization References.