Headline: IPCC includes geoengineering in summary for policymakers – what does this mean?

On 27th September, the Intergovernmental Panel on Climate Change (IPCC) has published the summary for policymakers (SPM) of its working group I (WG I) report, and for the first time, the topic of “geoengineering” is included in such a summary. As the IPCC is a scientific body under the auspices of the United Nations (UN) and its assessment reports provide a baseline for the UN climate negotiations, this is of considerable importance in the global discussions around climate change.

Geoengineering, also known as “climate engineering”, is an umbrella term for a set of hypothetical techniques. It has been suggested that these techniques could be capable of reversing some effects of climate change, yet no technique can compensate perfectly for all climatic and non-climatic changes that occur due to elevated levels of greenhouse gas concentrations in the atmosphere. Thus, no technique is capable of providing an effective substitute for mitigation and adaptation. Furthermore, the techniques are associated with a number of uncertainties and risks, contributing to their controversial nature.

What, then, is the significance of the IPCC including climate engineering in its fifth assessment report (AR5)? Several members of the IASS research microcosm on climate engineering are co-authors of the IPCC working group III (WGIII) report. Below we provide answers to key questions that arise in this context and outline our reasons for carrying out research on climate engineering at the IASS.

1. What is climate engineering and why does the IPCC include it in its fifth assessment report?

Climate engineering is a set of largely hypothetical techniques that aim to reverse some of the effects of climate change. These techniques are generally grouped into two broad categories:

  • Carbon dioxide removal (CDR) methods attempt to absorb and store carbon from the atmosphere;
  • Solar radiation management (SRM) methods aim to reduce temperatures by reflecting sunlight away from the Earth’s surface. They do not address the problem of rising greenhouse gas concentrations, which would lead to other effects such as ocean acidification and changes in terrestrial ecosystems due to the CO2-rich air, and are thus an imperfect and inherently risky approach to moderating global climate change.

An example of a CDR technique is ocean iron fertilization, which involves the addition of iron to ocean waters as a nutrient to fertilize regions where the phytoplankton (algae) growth is limited due to lack of this nutrient. These organisms take up CO2 from the atmosphere when they grow, and when they die, a fraction of the plankton biomass sinks to the deep ocean, bringing along the atmospheric carbon they took up. The effectiveness of this technique and its possible unintended side effects are highly uncertain given the early state of research.

An example of an SRM approach is the injection of sulfate particles into the stratosphere at about 20 km altitude. These particles reflect sunlight and cool the planet, a process that happens occasionally following large volcanic eruptions. As with other techniques however, more research is required in order to better understand the details of the anticipated impacts, as well as possible unintended side effects of carrying out such an activity on a global scale.

The IPCC has taken up this issue in AR5 in large part because discussions about climate engineering and the number of research projects on various aspects of climate engineering have increased considerably in the seven years since the last IPCC report was published, and it is the IPCC’s purpose to review and summarize research published in scientific journals. However, this should not be taken as an indication that the IPCC in any way advocates climate engineering as a substitute or complimentary approach to mitigation or adaptation.

2. What would happen to the climate if climate engineering techniques ever were to be implemented in the future?

Since climate engineering is not one idea, but many different ideas lumped together, the answer to this depends on what technology (or technologies) would be implemented. What is clear is that, while climate engineering may help to alleviate some of the effects of climate change in some regions, no climate engineering technique that has been proposed so far would be capable of returning the planet to its preindustrial climate state. Even if the global average temperature were reduced to its previous level, there would be regions that would still be warmer than before, and other regions that would even be cooler than before. Rainfall amounts would also change in ways that differ substantially from region to region.

There would also be unintended effects. For example, ocean iron fertilization would modify ocean ecosystems, with potentially far-reaching effects; the number and variety of ocean species in modified regions would likely change, and other species may migrate to take advantage of the shifting patterns of prey species. The plankton blooms themselves may cause more direct problems; for instance, when these plankton blooms die out, the oxygen in the water column could be depleted by the bacteria that break down the dead plankton, and various gases are expected to be produced in significant amounts, especially nitrous oxide, a strong greenhouse gas. Sulfate aerosol injection might also have unintended effects, including effects on the appearance of the sky, as well as changes in stratospheric chemistry, in particular a reduction of stratospheric ozone amounts, thus increasing the amount of harmful UV radiation reaching the Earth’s surface.

3. Are the climatic impacts of climate engineering the only thing we need to worry about?

Although the WG I report of the IPCC is focused on the physical science basis, it is important to note that climate engineering would not only affect the climate. Research and development of climate engineering techniques takes place in a complex social, political, economic, and cultural context, which is more appropriate for the WG II and III reports to discuss. For example, even the thought that there may be some “quick fix” available in the future, regardless of how realistic or unrealistic that is, could decrease the incentive to reduce greenhouse gas emissions. And since some states might be in favor of a climate engineering intervention while others might oppose this, climate engineering could lead to international tensions over its research, development and use. This makes the issue of governance – even the governance of research on climate engineering – both very important and very complex. Furthermore, if SRM techniques were implemented and greenhouse gas concentrations were not reduced, then an obligation would be placed on future generations to continue the SRM intervention – otherwise, as indicated by the IPCC WG I report, “If SRM were terminated for any reason, there is high confidence that global surface temperatures would rise very rapidly to values consistent with the greenhouse gas forcing.” Finally, amidst such questions as interregional and intergenerational justice, the issue of climate engineering is good cause for us to reflect on our overall relationship with the planet as humanity in the “Anthropocene”, the geological epoch in which humans make their mark as a planetary forcing agent.

4. What’s next for climate engineering?

It is widely acknowledged that mitigation must remain the priority for the international community; it is too early to say with confidence how, if at all, any form of climate engineering would help address the various challenges of climate change. Thus, as indicated by the IPCC WG I report, the uncertainties in the physical basis of CDR and SRM suggest that considerable research is still needed on these aspects. Another very important next step will be to better understand options for developing effective governance for climate engineering, first particularly for field testing, due to the many social concerns noted above.

5. What is the approach of the IASS to climate engineering research?

At the IASS, we are critically evaluating climate engineering technologies from many different points of view to explore the effects, uncertainties and risks of the various ideas. We are not developing climate engineering technologies; instead, researchers at the IASS are tackling key questions such as:

  • What would the consequences of SRM climate engineering be for the global climate and the atmosphere at large, as well as other aspects of global change, such as ocean acidification, biodiversity and the ozone layer?
  • Is climate engineering an ethically defensible response to climate change?
  • How is climate engineering perceived by various social groups, for example by residents of small island states, or by religious and spiritual communities?
  • What forms of governance are appropriate for climate engineering?
  • What international treaties and norms apply to climate engineering?

Researchers working on the issue of climate engineering at the IASS come from a wide range of backgrounds, from a number of different disciplines, and hold various perspectives on the issue. Bringing together researchers in this way helps us understand the implications of climate engineering in a broader perspective, and helps us to more effectively engage political and societal leaders and the public in the emerging debate on this topic.

Further Information

At the IASS the following people contribute to the IPCC working group III:

Photo: ©IPCC WGI AR5