Increased worldwide reductions of greenhouse gas emissions and swifter transitions to clean energy are essential to limit average global temperature rise to 2°C and avoid significant climate destabilization. So concludes the third and final Working Group paper (WGIII) of the Fifth Assessment Report from the world’s foremost authority on climate change, the Intergovernmental Panel on Climate Change (IPCC). The WGIII report, published this week, focuses on climate change mitigation, which is defined as “human intervention to reduce the sources or enhance the sinks of greenhouse gases.” According to German economist and co-chairman of IPCC, Ottmar Edenhofer, “If we lose another decade, it becomes extremely costly to achieve climate stabilization.” There are several key take-aways from WGIII AR.

  • We need to do much more than we do now to reduce greenhouse gas emissions (GHGs). Although 67% of countries, states, and cities have adopted climate change mitigation plans, up from 45% in 2007, we have not seen a correlated deviation in global emissions. Substantial reductions in emissions require actions such as a 20% decline in investment in electrical power plants that use fossil fuels and a 100% increase in investment in low-carbon energy, with a 39% reduction from 2010 levels by 2030, a mid-century reduction of 72% from 2010 levels, and a complete elimination of GHGs by 2100. Our ability to limit average global temperature rise to 2°C (3.6°F) – the target agreed to by world leaders – is tied to these kinds of significant and immediate actions.
     
  • The longer-term benefits of taking greater action now significantly outweigh the costs and options we will have if we delay. Waiting or making less effective infrastructure choices now will require more extreme and costly measures later. Some choices that delay the costs of mitigation may make needed changes impossible to bear at a later date, and may force us to rely on more risky technology such as geoengineering.
     
  • All countries as affected by the emissions of other countries because GHGs mix and are long lasting in the atmosphere. Effective preservation of the global commons will require unparalleled cooperation, collaboration, and action. More work needs to be done to understand how to promote and achieve such efforts.
     
  • Cooperation, collaboration, and action will need to come from a wide range of communities, not just from governments, and will need to occur at the local, national, and international levels. Efforts by individuals, businesses, NGOs, and trading groups are all going to be needed to solve climate change problems because there are so many variable and interconnected issues that drive emissions.

WGIII states that “[D]eep cuts in emissions will require a diverse portfolio of policies, institutions, and technologies as well as changes in human behaviour and consumption patterns (high evidence; high agreement).” The report also points to a number of significant forces that drive emissions, such as population, the structure of the economy, income distribution, consumption patterns, investment decisions, technology, energy resources, and changes in land-use. Each of these areas presents opportunities to have a positive impact on reducing GHG emissions and protecting the global commons. Each creates opportunities for each of us to cooperate, collaborate, and take action.

The complexity of predicting and solving climate change issues is also brought home in WGIII:

“[P]olicies to mitigate emissions are extremely complex and arise in the context of many different forms of uncertainty. While there has been much public attention to uncertainties in the underlying science of climate change—a topic addressed in detail in IPCC’s Working Group I and II reports—profound uncertainties arise in the socioeconomic factors addressed here in Working Group III. Those uncertainties include the development and deployment of technologies, prices for major primary energy sources, average rates of economic growth and the distribution of benefits and costs within societies, emission patterns, and a wide array of institutional factors such as whether and how countries cooperate effectively at the international level. In general, these uncertainties and complexities multiply those already identified in climate science by Working Groups I and II. The pervasive complexities and uncertainties suggest that there is a need to emphasize policy strategies that are robust over many criteria, adaptive to new information, and able to respond to unexpected events.”

One of the many interesting aspects of WRIII is its discussion of human capacity for risk management and human motivation to act, and how these might affect the almost 1200 scenarios of socioeconomic development analyzed in writing the report. The connections drawn between climate change policy and solving other social objectives can be important factors in determining support for a mitigation strategy. The report highlights, for example, efforts to balance and recognize synergies between protection of the environment with other goals such as eradication of poverty, social justice, and economic growth. Greater “consideration and quantification of ‘co‐benefits’ and ‘adverse side‐effects’ of mitigating climate change, i.e., effects that a policy or measure aimed at one objective might have on other objectives” is a central theme in the sections of the report that focus on mitigation strategies in particular industries.

The overarching message of WRIII is that eliminating the human causes of climate change is a global issue that will require broad-based and significantly increased efforts by all, and a great deal of flexibility as uncertainties at the edge of our scientific knowledge and capabilities evolve into unfolding realities.