Thursday, April 17, 2014

Mitigation of Climate Change – Part 3 of the new IPCC report

RealClimate, 17 April 2014

Guest post by Brigitte Knopf

Global emissions continue to rise further and this is in the first place due to economic growth and to a lesser extent to population growth. To achieve climate protection, fossil power generation without CCS has to be phased out almost entirely by the end of the century. The mitigation of climate change constitutes a major technological and institutional challenge. But: It does not cost the world to save the planet.

This is how the new report was summarized by Ottmar Edenhofer, Co-Chair of Working Group III of the IPCC, whose report was adopted on 12 April 2014 in Berlin after intense debates with governments. The report consists of 16 chapters with more than 2000 pages. It was written by 235 authors from 58 countries and reviewed externally by 900 experts. Most prominent in public is the 33-page Summary for Policymakers (SPM) that was approved by all 193 countries. At a first glance, the above summary does not sound spectacular but more like a truism that we've often heard over the years. But this report indeed has something new to offer.

The 2-degree limit

For the first time, a detailed analysis was performed of how the 2-degree limit can be kept, based on over 1200 future projections (scenarios) by a variety of different energy-economy computer models. The analysis is not just about the 2-degree guardrail in the strict sense but evaluates the entire space between 1.5 degrees Celsius, a limit demanded by small island states, and a 4-degree world. The scenarios show a variety of pathways, characterized by different costs, risks and co-benefits. The result is a table with about 60 entries that translates the requirements for limiting global warming to below 2-degrees into concrete numbers for cumulative emissions and emission reductions required by 2050 and 2100. This is accompanied by a detailed table showing the costs for these future pathways.

The IPCC represents the costs as consumption losses as compared to a hypothetical 'business-as-usual' case. The table does not only show the median of all scenarios, but also the spread among the models. It turns out that the costs appear to be moderate in the medium-term until 2030 and 2050, but in the long-term towards 2100, a large spread occurs and also high costs of up to 11% consumption losses in 2100 could be faced under specific circumstances. However, translated into reduction of growth rate, these numbers are actually quite low. Ambitious climate protection would cost only 0.06 percentage points of growth each year. This means that instead of a growth rate of about 2% per year, we would see a growth rate of 1.94% per year. Thus economic growth would merely continue at a slightly slower pace. However, and this is also said in the report, the distributional effects of climate policy between different countries can be very large. There will be countries that would have to bear much higher costs because they cannot use or sell any more of their coal and oil resources or have only limited potential to switch to renewable energy.

The technological challenge

Furthermore – and this is new and important compared to the last report of 2007 – the costs are not only shown for the case when all technologies are available, but also how the costs increase if, for example, we would dispense with nuclear power worldwide or if solar and wind energy remain more expensive than expected.

The results show that economically and technically it would still be possible to remain below the level of 2-degrees temperature increase, but it will require rapid and global action and some technologies would be key:

Many models could not achieve atmospheric concentration levels of about 450 ppm CO2eq by 2100, if additional mitigation is considerably delayed or under limited availability of key technologies, such as bioenergy, CCS, and their combination (BECCS).

Probably not everyone likes to hear that CCS is a very important technology for keeping to the 2-degree limit and the report itself cautions that CCS and BECCS are not yet available at a large scale and also involve some risks. But it is important to emphasize that the technological challenges are similar for less ambitious temperature limits.

The institutional challenge

Of course, climate change is not just a technological issue but is described in the report as a major institutional challenge:

Substantial reductions in emissions would require large changes in investment patterns

Over the next two decades, these investment patterns would have to change towards low-carbon technologies and higher energy efficiency improvements (see Figure 1). In addition, there is a need for dedicated policies to reduce emissions, such as the establishment of emissions trading systems, as already existent in Europe and in a handful of other countries.

Since AR4, there has been an increased focus on policies designed to integrate multiple objectives, increase co‐benefits and reduce adverse side‐effects.

The growing number of national and sub-national policies, such as at the level of cities, means that in 2012, 67% of global GHG emissions were subject to national legislation or strategies compared to  only 45% in 2007. Nevertheless, and that is clearly stated in the SPM, there is no trend reversal of emissions within sight – instead a global increase of emissions is observed.

Trends in emissions

A particularly interesting analysis, showing from which countries these emissions originate, was removed from the SPM due to the intervention of some governments, as it shows a regional breakdown of emissions that was not in the interest of every country (see media coverage here or here). These figures are still available in the underlying chapters and the Technical Summary (TS), as the government representatives may not intervene here and science can speak freely and unvarnished. One of these figures shows very clearly that in the last 10 years emissions in countries of upper middle income – including, for example, China and Brazil – have increased while emissions in high-income countries – including Germany – stagnate, see Figure 2. As income is the main driver of emissions in addition to the population growth, the regional emissions growth can only be understood by taking into account the development of the income of countries.

Historically, before 1970, emissions have mainly been emitted by industrialized countries. But with the regional shift of economic growth now emissions have shifted to countries with upper middle income, see Figure 2, while the industrialized countries have stabilized at a high level. The condensed message of Figure 2 does not look promising: all countries seem to follow the path of the industrialized countries, with no "leap-frogging" of fossil-based development directly to a world of renewables and energy efficiency being observed so far.

But the fact that today's emissions especially rise in countries like China is only one side of the coin. Part of the growth in CO2 emissions in the low and middle income countries is due to the production of consumption goods that are intended for export to the high-income countries (see Figure 3). Put in plain language: part of the growth of Chinese emissions is due to the fact that the smartphones used in Europe or the US are produced in China.

The philosophy of climate change

Besides all the technological details there has been a further innovation in this report, that is the chapter on "Social, economic and ethical concepts and methods". This chapter could be called the philosophy of climate change. It emphasizes that

Issues of equity, justice, and fairness arise with respect to mitigation and adaptation. […] Many areas of climate policy‐making involve value judgements and ethical considerations.

This implies that many of these issues cannot be answered solely by science, such as the question of a temperature level that avoids dangerous anthropogenic interference with the climate system or which technologies are being perceived as risky. It means that science can provide information about costs, risks and co-benefits of climate change but in the end it remains a social learning process and debate to find the pathway society wants to take.


The report contains many more details about renewable energies, sectoral strategies such as in the electricity and transport sector, and co-benefits of avoided climate change, such as improvements of air quality. The aim of Working Group III of the IPCC was, and the Co-Chair emphasized this several times, that scientists are mapmakers that will help policymakers to navigate through this difficult terrain in this highly political issue of climate change. And this without being policy prescriptive about which pathway should be taken or which is the "correct" one. This requirement has been fulfilled and the map is now available. It remains to be seen where the policymakers are heading in the future.

The report :

Climate Change 2014: Mitigation of Climate Change – IPCC Working Group III Contribution to AR5

Brigitte Knopf is head of the research group Energy Strategies Europe and Germany at the Potsdam Institute for Climate Impact Research (PIK) and one of the authors of the report of the IPCC Working Group III and is on Twitter as @BrigitteKnopf

This article was translated from the German original at RC's sister blog KlimaLounge.

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