Expert Commentary

How to mitigate climate change: Key facts from the U.N.’s 2014 report

2014 study by the U.N. Intergovernmental Panel on Climate Change on ways that nations, states and municipalities can act to limit or reverse trends in CO2 emissions.

(Unsplash/public domain)

The March 2014 report from the U.N.’s Intergovernmental Panel on Climate Change (IPCC), “Climate Change 2014: Impacts, Adaptation, and Vulnerability,” was unequivocal: Human-induced climate change is happening and the effects are already evident — shrinking ice caps, droughts and flooding, storms and extinctions. If greenhouse-gas emission levels continue to rise, the IPCC stated, future changes are likely to be even more extreme, with millions of people displaced by rising sea levels and global food supplies under threat.

Around the world, progress and inaction are present in what seems like equal measure. In 2013, renewables contributed 44% of the new electrical-generation capacity that year, with wind power providing the lion’s share. Yet the fastest-growing fuel is the dirtiest, coal. As the International Energy Agency states, “Coal use has never stopped increasing and the forecasts indicate that, unless a dramatic policy action occurs, this trend will continue in the future.” Natural gas is often thought of as a “bridge fuel” to a low-carbon future, but compared to solar and wind it’s still high carbon, and its extraction can lead to significant releases of methane, a potent greenhouse gas. A nuclear power plant produces fewer emissions over its lifetime than one powered by coal or natural gas, but the Fukushima disaster once again highlighted the substantial risks inherent to the technology.

To point the way forward, in April 2014 the IPCC released “Climate Change 2014: Mitigation of Climate Change,” which lays out ways to limit or reverse harmful trends in greenhouse-gas emissions. The need for international cooperation and especially a price on carbon are central to the report, but it also highlights the importance of direct actions at every level. Many of the suggestions are “actionable” by state and local authorities, businesses and individuals.

The graph below shows the proportion of greenhouse gases emitted by the various sectors of the global economy. Indirect emissions, shown on the right, are those that result from the generation of electricity and heat; direct emissions by sector are shown on the left.

 Greenhouse-gas emissions by economic sector (IPCC)

The report looks at each sector, outlining the potential for reducing greenhouse-gas emissions through greater efficiency, reduced use or other means.

Energy generation:

  • Reducing carbon emissions from electrical generation is one of the most cost‐effective ways to blunt climate change: “Decarbonization happens more rapidly in electricity generation than in the industry, buildings and transport sectors. In the majority of low‐stabilization scenarios, the share of low‐carbon electricity supply increases from the current share of approximately 30% to more than 80% by 2050.”
  • The U.S. Environmental Protection Agency’s proposed power plant rules, to be published in June 2014, are anticipated to accelerate the shift to natural gas and provide sufficient incentives to encourage the deployment of industrial-scale carbon capture and storage for coal-fired plants.
  • Despite political uncertainty, wind and other renewables have continued to grow rapidly and per-kilowatt prices are falling to near-parity with fossil fuels. States play a central role in the growth of renewables, wind and solar in particular, and a wide range of incentives are in place that can be leveraged.
  • Over the next 20 years, annual investments in renewables, nuclear and electricity generation with carbon capture and storage are projected to rise by $147 billion, while those for fossil-fuel electrical generation capacity will decline by about $30 billion. (While the relative changes are significant, note that the average annual investment in energy systems is $1.2 trillion.)

Industry and municipalities

  • In 2010, industrial uses accounted for 28% of global energy consumption and produced 13 gigatons of CO2. While emissions are projected to increase between 50% and 150% by 2050, the sector’s energy intensity could be reduced by 25% from the current level through the wide-scale adoption of currently available technologies.
  • The primary barriers to increased industrial efficiency are the initial investment costs and lack of information. “Information programs are a prevalent approach for promoting energy efficiency, followed by economic instruments, regulatory approaches and voluntary actions.”
  • Businesses of all sizes can reduce emissions through small changes such as the use of more-efficient motors and eliminating air and steam leaks. When new facilities are built, sharing of infrastructure and utilization of waste heat would cut energy losses substantially.
  • Municipal solid waste and wastewater contributed the equivalent of 1.5 gigatons of CO2 in 2010. Because only 20% of municipal solid waste is recycled on average, “waste-treatment technologies and recovering energy to reduce demand for fossil fuels can result in significant direct emission reductions from waste disposal.”


  • Transportation greenhouse-gas emissions can be “decoupled” from economic growth with a combination of mitigation efforts and non‐climate policies at federal, state and local government levels. “These strategies can help reduce travel demand, incentivise freight businesses to reduce the carbon intensity of their logistical systems and induce modal shifts.”
  • By 2050, new mass-transit infrastructure and urban redevelopment has the potential to cut final energy demand 40% below the baseline, an improvement over that reported in the IPCC’s Fourth Assessment Report on Climate Change. “Projected energy efficiency and vehicle performance improvements range from 30% to 50% in 2030 relative to 2010 depending on transport mode and vehicle type.” In particular, bus rapid transit has relatively low infrastructure costs and can be implemented relatively quickly.
  • “Integrated urban planning, transit‐oriented development, more compact urban form that supports bicycling and walking, can all lead to modal shifts as can, in the longer term, urban redevelopment and investments in new infrastructure such as high‐speed rail systems that reduce short‐haul air travel demand.” These changes have the potential to cut transport GHG emissions by 20% to 50% in 2050 compared to baseline.


  • In 2010 the building sector was responsible for about 32% of final energy use and 8.8 gigatons of direct and indirect CO2 emissions. In baseline scenarios, by mid‐century the sector’s energy demand is projected to approximately double and its CO2 emissions to increase by 50% to 150%.
  • Green-building standards are among the most cost‐effective ways to reduce emissions. “In some developed countries they have contributed to a stabilization of, or reduction in, total energy demand for buildings. Substantially strengthening these codes, adopting them in further jurisdictions, and extending them to more building and appliance types, will be a key factor in reaching ambitious climate goals.”
  • Retrofits of existing buildings can reduce energy use by 50% to 90%. “Recent large improvements in performance and costs make very low energy construction and retrofits economically attractive, sometimes even at net negative costs,” and can even help roll back global warming.

Infrastructure, spatial planning

  • As the world’s population has grown, it has rapidly urbanized, but often in low-density sprawl that damages ecosystems and leads to even higher greenhouse-gas emissions: “Accounting for trends in declining population densities, and continued economic and population growth, urban land cover is projected to expand by 56% to 310% between 2000 and 2030.” The nearly six-fold difference between the extremes shows the range of potential outcomes, and highlights the importance of action.
  • The majority of future urban growth is expected in smaller cities in developing countries. “Effective mitigation strategies involve packages of mutually reinforcing policies, including co‐locating high residential with high employment densities, achieving high diversity and integration of land uses, increasing accessibility and investing in public transport and other demand management measures.”
  • Infrastructure, spatial planning and energy consumption are closely interlinked; the greatest risk is our “locking in” to infrastructure and settlement patterns that require high levels of energy consumption, and thus greenhouse-gas emissions. Once such assets are built, future emissions are much more difficult to prevent or offset. An example in the United States is Minneapolis’s proposed $1.7 billion Zoo Interchange, which is focused strictly on automotive travel and has a planned 75-year lifespan.

Agriculture, forestry and other land uses

  • The land uses account for the equivalent of 10 to 12 gigatons of CO2 per year, approximately 25% of anthropogenic emissions. These primarily result from deforestation, agriculture and livestock. With a reduction in deforestation, increasing restoration of forests and the widespread adoption of sustainable cropland and grazing management techniques, it is possible that this sector could become a net CO2 sink before 2100.
  • “The most cost‐effective mitigation options in forestry are afforestation, sustainable forest management and reducing deforestation, with large differences in their relative importance across regions. In agriculture, the most cost‐effective mitigation options are cropland management, grazing land management, and restoration of organic soils.”

Demand reduction:

  • Cutting energy demand through conservation is crucial not only because it reduces consumption, but also because it increases long-term flexibility: “Near‐term reductions in energy demand are an important element of cost‐effective mitigation strategies, provide more flexibility for reducing carbon intensity in the energy supply sector, hedge against related supply‐side risks, avoid lock‐in to carbon‐intensive infrastructures.”
  • Because demand happens at the individual level, emissions can be substantially lowered through changes in consumption patterns. These include driving less, switching to higher efficiency cars, using mass transit, buying longer‐lasting products and reducing food waste. “A number of options including monetary and non‐monetary incentives as well as information measures may facilitate behavioral changes,” the authors note.

Many of the above approaches also have “co-benefits,” as the IPCC report calls them: “These mitigation scenarios show improvements in terms of the sufficiency of resources to meet national energy demand as well as the resilience of energy supply, resulting in energy systems that are less vulnerable to price volatility and supply disruptions.” Other advantages include reduced ecosystem impacts and pollution, improved human health through the increase in cycling and walking, and even increased worker productivity and employment gains that result from building-related mitigation options. When monetized, these and other co-benefits can exceed energy cost savings and potentially even climate benefits.

Related: In the United States, because many of the suggested actions take place at the regional and municipal levels, coordination is essential, particularly when working with state authorities. Urban-rural tensions have a long history, but recently larger cities have had significant trouble moving their agenda forward — for example, New York Mayor Bloomberg’s attempt to get congestion pricing “died in a closed conference room” at the New York State Legislature. A 2013 study published in the American Political Science Review, “No Strength in Numbers: The Failure of Big-City Bills in American State Legislatures, 1880–2000,” looked at 120 years’ worth of “district bills” in 13 state assemblies to see why many big cities had so little clout. Overall, the study found that cities with the largest delegations had the highest failure rates for district bills. “The larger the delegations are, the more likely they are to be internally divided, and the less likely their bills are to pass.”


Keywords: greenhouse gases, climate change, global warming, adaptation, cars, mass transit, sprawl, carbon sequestration, carbon capture, coal, fossil fuels

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