IGES Commentary

Achieving the Goal of Contracting the Global Mean Temperature Increase to Less Than 2°C Is Possible: The Global Calculator’s Message

September 2016

Ambitious Goals Agreed in Paris Agreement

The world agreed on ambitious long-term climate change goals in the Paris Agreement adopted in December of last year. The agreement sets the targets of contracting the increase in the global mean temperature to “well below 2°C above pre-industrial levels, ”pursuing efforts“ to limit the temperature increase to 1.5°C above pre-industrial levels,” and also achieving “a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases,” in other words, net-zero greenhouse gas emissions, in the second half of this century.

However, even if the promises (voluntary targets) submitted voluntarily by each country were all realised, the 2°C target would still be a long way off. In order to achieve the 2°C target (not to mention the 1.5°C target), there is a limit to the amount of greenhouse gas emissions that can be permitted in the world as a whole. If the current level continues, it is estimated that the limit will be reached in 20–30 years. Therefore, it is urgently necessary for the world as a whole to drastically reduce emissions of greenhouse gases.

As well as medium-term targets (for 2030, for example), the Paris Agreement requires countries to formulate long-term low greenhouse gas emission development strategies. It is hoped that the major developed countries will play a leading role in this respect. On the occasion of the G7 Ise-Shima Summit, which was held in May of this year, the participants stated in the Leaders’ Declaration that “We commit to formulate and communicate mid-century long-term low greenhouse gas (GHG) emission development strategies well ahead of the 2020 deadline.” Governments must quickly set about formulating these long-term strategies.

In the process of formulating low-carbon long-term development strategies, it is important to have highly transparent and substantive discussions involving various interested parties and experts based on scientific evidence. As a foundation for these discussions, an objective tool enabling numerical assessments would be useful.

Launch of the Global Calculator

In order to achieve the 2°C target, the world needs to cut greenhouse gas emissions to around half of today’s levels by 2050. Also, in consideration of the responsibilities and important role of major developed countries, it is desirable for them to cut emissions by 80%– 90%. Is it physically possible to meet these targets and at the same time ensure that everyone on Earth has good living standards?

To answer this question, experts from 16 leading international organisations (including the International Energy Agency, World Resources Institute, Energy Research Institute of the Chinese National Development and Reform Commission, Potsdam Institute for Climate Impact Research, and UK Department of Energy and Climate Change) developed the Global Calculator, a model of the world’s energy, land, food, and climate systems to 2050.

The Global Calculator was built to model what lifestyle is possible for the world’s population and what amount of energy, resources, and land are required to satisfy it. The climate impacts of different pathways are also illustrated by linking the model to the latest Intergovernmental Panel on Climate Change (IPCC) climate science. The model has been tested with experts from more than 150 organisations around the world.

The unique point about the Global Calculator is that users can use the tool and test it for themselves. Users can view pathways to the 2°C goal proposed by other organisations, or they can formulate pathways themselves. Since the model depends on what kind of assumptions are set, the methodology and assumptions are all published so that users can verify them (see www.globalcalculator.org).

The Japanese version was translated by the Institute for Global Environmental Strategies (IGES) (translation supervised by the author) and is available on the IGES website.

Main Message of the Global Calculator

The Global Calculator tool shows that there are several different pathways to the 2°C target. The team generated four plausible pathways to achieve the 2°C target and maintain a sound lifestyle through sensitivity analysis on uncertainties about technology, fuels, and land use. The four plausible 2°C pathways show that:

(1) It is physically possible for all 10 billion people in the world to eat well, travel more, and live in more comfortable homes while at the same time reducing emissions to a level consistent with a 50% chance of under 2°C warming.

(2) To do so, it is necessary to transform the technologies and fuels we use. For example, the amount of CO2 emitted per unit of electricity globally needs to fall by at least 90% by 2050. Also, the proportion of households that heat their homes using electric or zero-carbon sources should rise from 5% today to 25%–50% globally by 2050.

(3) We also need to make smarter use of our limited land resources. In particular, we must protect and expand our forests globally by around 5%–15% by 2050, because forests act as a valuable carbon sink.

The common premises applied in all four pathways include (1) population and urbanisation are set at the central UN projections (level 2) and (2) no use of speculative greenhouse gas removal (GGR) technologies are considered, as these are unproven.

Important Points of the Global Calculator

The Global Calculator has around 40 levers for global greenhouse gas emissions, covering all choices affecting lifestyle, technology and fuel, land and food, and demographics. Users can choose levels 1 to 4 for each lever.

  1. Level 1: Minimum abatement effort
  2. Level 2: Ambitious but achievable abatement effort
  3. Level 3: Very ambitious but achievable abatement effort
  4. Level 4: Extraordinarily ambitious and extreme abatement effort

Most experts will tend to congregate in levels 2 and 3. Only a minority of experts will have the extreme view that level 4 is possible. Therefore, in order to avoid extremely ambitious or pessimistic scenarios, levels 1 and 4 are not selected.

In addition, since the Global Calculator has only limited geographical detail, it cannot give details of in which countries the technologies should be rolled out or who should pay for them. It also only models average consumption per person globally rather than according to country. So although the tool shows that global average diet, transport use, and household appliance use can rise to levels consistent with a good lifestyle by 2050, it does not specify how this consumption should be distributed by country (for example, whether the richest should reduce their consumption). These questions are beyond the scope of the Global Calculator.

Achievement of 2°C Target and Improvement of Living Standards Possible through Bold Action and Reform

Nevertheless, the Global Calculator does show clearly that it is physically possible to achieve both economic development and the climate change goals by 2050. The world has enough energy, land, and food resources for us all to live well. The technology, fuels, and land use methods already exist for us to meet our economic development goals while tackling climate change.

This transition, however, will require a massive effort across all sectors, and action must start urgently. The bold adoption of clean technologies across the electricity, buildings, transport, and manufacturing sectors and significant improvement in our land management practices are essential. To be on track for the 2°C target, it is necessary for us to continue technological and land management reforms throughout the rest of the century so that the world has zero net greenhouse gas emissions by 2100.

(This article was first published in Japanese in “Global Net”, July, 2016. With permission from the Global Environmental Forum, it has been translated into English and uploaded here.)

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