Geoengineering – how could we detect its cooling effect?

Detecting sulphate aerosol geoengineering with different methods
Lo, Y. T. E. et al. Detecting sulphate aerosol geoengineering with different methods. Sci. Rep. 6, 39169; doi: 10.1038/srep39169 (2016).

Email: y.t.e.lo@pgr.reading.ac.uk

Sulphate aerosol injection (SAI) is one of the geoengineering proposals that aim to reduce future surface temperature rise in case ambitious carbon dioxide mitigation targets cannot be met.  Climate model simulations suggest that by injecting 5 teragrams (Tg) of sulphur dioxide gas (SO2) into the stratosphere every year, global surface cooling would be observed within a few years of implementation.  This injection rate is equivalent to 5 million tonnes of SOper year, or one Mount Pinatubo eruption every 4 years (large volcanic eruptions naturally inject SOinto the stratosphere; the Mount Pinatubo eruption in 1991 led to ~0.5 °C global surface cooling in the 2 years that followed (Self et al., 1993)).  However, temperature fluctuations occur naturally in the climate system too.  How could we detect the cooling signal of SAI amidst internal climate variability and temperature changes driven by other external forcings?

The answer to this is optimal fingerprinting (Allen and Stott, 2003), a technique which has been extensively used to detect and attribute climate warming to human activities.  Assuming a scenario (G4, Kravitz et al., 2011) in which 5 Tg yr-1 of SO2 is injected into the stratosphere on top of a mid-range warming scenario called RCP4.5 from 2020-2070, we first estimate the climate system’s internal variability and the temperature ‘fingerprints’ of the geoengineering aerosols and greenhouse gases separately, and then compare observations to these fingerprints using total least squares regression.  Since there are no real-world observations of geoengineering, we cross-compare simulations from different climate models in this research.  This gives us 44 comparisons in total, and the number of years that would be needed to robustly detect the cooling signal of SAI in global-mean near-surface air temperature is estimated for each of them.

Figure 1(a) shows the distribution of the estimated time horizon over which the SAI cooling signal would be detected at the 10% significance level in these 44 comparisons.  In 29 of them, the cooling signal would be detected during the first 10 years of SAI implementation.  This means we would not only be able to separate the cooling effect of SAI from the climate system’s internal variability and temperature changes driven by greenhouse gases, but we would also be able to achieve this early into SAI deployment.

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Figure 1: Distribution of the estimated detection horizons of the SAI fingerprint using (a) the conventional two-fingerprint detection method and (b) the new, non-stationary detection method.

The above results are tested by applying a variant of optimal fingerprinting to the same problem.  This new method assumes a non-stationary background climate that is mainly forced by greenhouse gases, and attempts to detect the cooling effect of SAI against the warming background using regression (Bürger and Cubasch, 2015).  Figure 1(b) shows the distribution of the detection horizons estimated by using the new method in the same 44 comparisons: 35 comparisons would require 10 years or fewer for the cooling signal to be robustly detected.  This shows a slight improvement from the results found with the conventional method, but the two distributions are very similar.

To conclude, we would be able to separate and thus, detect the cooling signal of sulphate aerosol geoengineering from internal climate variability and greenhouse gas driven warming in global-mean temperature within 10 years of SAI deployment in a future 5 Tg yr-1 SAI scenario.  This could be achieved with either the conventional optimal fingerprinting method or a new, non-stationary detection method, provided that the climate data are adequately filtered.  Research on the effects of different data filtering techniques on geoengineering detectability is not included in this blog post, please refer to the article cited at the top for more details.

This work has been funded by the University of Reading.  Support has also been provided by the UK Met Office.

Note: So how feasible is a 5 Tg yr-1 SO2 injection scenario?  Robock et al. (2009) estimated the cost of lofting 1 Tg yr-1 SO2 into the stratosphere with existing aircrafts to be several billion U.S. dollars per year. Scaling this to 5 Tg yr-1 is still not a lot compared to the gross world product. There are practical issues to be addressed even if existing aircrafts were to be used for SAI, but the deciding factor of whether to implement sulphate aerosol geoengineering or not would likely be its potential benefits and side effects, both on the climate system and the society. 

 

References

Self, Stephen, et al. “The atmospheric impact of the 1991 Mount Pinatubo eruption.” (1993).

Allen, M. R., and P. A. Stott. “Estimating signal amplitudes in optimal fingerprinting, Part I: Theory.” Climate Dynamics 21.5-6 (2003): 477-491.

Kravitz, Ben, et al. “The geoengineering model intercomparison project (GeoMIP).” Atmospheric Science Letters 12.2 (2011): 162-167.

Bürger, Gerd, and Ulrich Cubasch. “The detectability of climate engineering.” Journal of Geophysical Research: Atmospheres 120.22 (2015).

Robock, Alan, et al. “Benefits, risks, and costs of stratospheric geoengineering.” Geophysical Research Letters 36.19 (2009).

Discovering COP22

Email: j.f.talib@pgr.reading.ac.uk

Over the past two weeks 25,000 delegates have been gathering in Marrakech to discuss mitigation and adaptation for climate change. On the 4th November 2016 the Paris Agreement came into force and as a result discussions during the conference debated its implementation. The Walker Institute and the Department of Meteorology (University of Reading), with the support of the NERC SCENARIO doctoral training partnership and an UNFCCC partnership, supported two PhD students to be official UN observers at COP22, and enabled remote participation with students back at Reading University. To find out more about our work with COP22 continue reading this blog post and check out:

Today (18/11/16) the UK government are set to announce that the United Kingdom has ratified the Paris Agreement. Yesterday, Boris Johnson (UK foreign secretary) signed the Paris Agreement after no objections were raised by the House of Commons or House of Lords. The United Kingdom in accordance with the Intended Nationally Determined Contributions (INDCs) of the European Union, are set to reduce greenhouse gas emissions by 40% by 2030 relative to 1990 emission levels. Today also marks the end of the 22nd Conference of the Parties (COP) for the United Nations Framework Convention on Climate Change and here are some quick summary points that PhD students took away from observing the process in Marrakech:

1) The significance of the Paris Agreement.

“Now that we have Paris, we need to take action immediately”

Teresa Anderson, ActionAid UK.

The Paris Agreement marks a change in the intentions during the COP process. Due to the success and ratification of the Paris Agreement more discussions can be based on the adaptation and mitigation against climate change, rather than negotiating global targets on climate change prevention. The Paris Agreement states that a global response is needed to respond to the threat of climate change and that global temperature rise should be kept well below 2°C and that efforts should be pursued to limit the global temperature rise to 1.5°C. COP22 Marrakech, began by stating that this is the “COP of Action”, and therefore the focus seen during side events, negotiations, dignitary speeches and press conferences was on the need for action.

“Countries have strongly supported the [Paris] Agreement because they realize their own national interest is best secured by pursuing the common good. Now we have to translate words into effective policies and actions.”

Mr Ban Ki-Moon, Secretary General of the United Nations.

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2) A continued effort is needed to concentrate on the individual.

As SCENARIO PhD students we were challenged to understand the process that takes place during a UNFCCC conference. To do this we interviewed many conference delegates including policymakers, research organisations, industry experts, entrepreneurs, environmental consultants and funding sources to name a few. A common theme that ran through most of our interviews is that action is needed to prioritise the individual as well as thinking in terms of national- and community-level. To ensure the successful mitigation and adaptation to climate change, strategies need to come into place that protect the rights of the individual. This poses a global challenge, stretching from protecting the livelihoods of indigenous cultures and those impacted by sea level rise on low-lying islands, to supporting workers who rely on the non-renewable energy industry. In terms of climate research we need to ensure that we make our scientific conclusions accessible on an individual-level so that our work has a greater impact.

“a key goal for us is making climate change research accessible to the user community”

Clare Kapp, WMO Press Office Communications Leader.

3) Action is needed now, however the Paris Agreement only implies action post-2020.

Throughout our attendance in plenary meetings and side events there was an emphasis that whilst the Paris Agreement is an important stepping stone to combatting climate change, action is needed before 2020 for the Paris Agreement to be reached. Currently INDCs are proposed for between 2021-2030, however for the intended global temperature targets to be achieved it was argued that action is needed now. Although, pre-2020 action raises much contention, with the most popular argument against pre-2020 action being that more time and effort is needed for negotiations to ensure that a better understanding of national efforts to climate change mitigation is determined.

“We need to take action before 2020. Working for action post-2020 is not going to be enough. We need to start acting now.”

Honduras Party Representative.

“We need more time to work on the rule book for the Paris Agreement. Discussions on this should continue.”

Switzerland Party Representative.

4) There is a difference in opinion on whether 1.5°C can be reached.

For me the most interesting question we asked conference delegates was “do you think the target of 1.5°C can be reached?” This question brought a difference of opinion including some party members arguing that the change in our non-renewable energy dependence is far too great for the target to be achieved. Meanwhile, other political representatives and NGO delegates argued that accepting the target is unachievable before even trying makes negotiations and discussions less successful. There was also anticipation for the future IPCC report titled, Special Report on Global Warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways.

“Of course we want to fight for 1.5°C, why fight for 2°C? It just makes sense to fight for 1.5°C”

Martina Duncan, Party Representative for Grenada.

COP22 has been a fantastic opportunity for PhD students in our department to interact and understand the process that takes place during a UNFCCC conference. Whilst the past couple of weeks have been dominated by the results of the US election and the associated uncertainties, there has been an increasing global recognition of climate change and that action should be taken. In the next few years the challenge to mitigate and adapt towards climate change will be an increasing priority, and let us hope that these annual UNFCCC conferences are key stepping stones for climate change action.

“This is a problem people are recognising, and that it is time to change”

Jonathan Pershing, US Climate Envoy

Thank you all those who have supported our work at COP22 this year. Thank you to the Walker Institute, NERC SCENARIO doctoral training partnership and UNFCCC for this brilliant opportunity. Thank you to all those who have supported us with publicity including NERC, Royal Meteorological Society, members of staff and PhD students at the University of Reading and Lucy Wallace who has ensured the appropriate communication of our project. Plus a huge thanks to all delegates and staff at COP22 who volunteered their time to talk to us.

What will make the public and politicians take climate change seriously?

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Email: j.f.talib@pgr.reading.ac.uk

Imagine you’re creating a problem that we don’t understand. A problem where the majority of people just go, “meh, not important, I don’t really get it”.

What would it look like?

It would be complex, uncertain, something in the future and possibly an issue that was geographically distant.

Now those factors should you remind of climate change, and on 5th October 2016 the South-East Royal Meteorological Society local centre hosted a meeting where a panel of experts were presented with the question, “What will make the public and politicians take climate change seriously?”

The panel included professionals from a range of backgrounds including Professor Sir Brian Hoskins, leading expert in meteorology and climate, and first director of the Grantham Institute for Climate Change, Imperial College London. Dr Rachel McCloy a well-respected figure in behavioural science with experience in policy making in the former Department of Energy and Climate Change and the Treasury. Finally, Paul Simons a prominent journalist for the Times known for the depth of scientific understanding in his articles.

Images taken during the RMetS South East local centre meeting (06/10/16). Left image: Panelists (from left to right) including Dr Rachel McCloy, Sir Brian Hoskins and Paul Simons.

Sir Brian Hoskins opened the discussion with the challenge that we have a responsibility to “encourage” rather than “make” the public take climate change seriously, and recognised the progress in politics including targets announced in COP21, Paris and the UK Climate Change Act 2008. However, it was also recognised that climate change may not be prioritised high enough in political agendas, and the question was raised on whether governments take their environmental global responsibility seriously enough?

Discussion then moved onto personal actions each one of us can take to increase the public response. Repeating the “doom and gloom” message over climate change can become boring and repetitive, and we need to bring a positive message to tackling this global issue. We also need to recognise the responsibility of the individual in a global context and introduce small steps that can be taken to reduce our environmental impact.

One key message from Brian’s talk, and the meeting as whole, was that it’s currently hard for a member of the public to understand what climate change actually means to their daily lives. What impact will a 2°C global temperature rise actually cause? Researchers, the media and policymakers need to relate the science of global warming to our everyday lives, whether that’s through health, nutrition, the working environment, or air quality to name a few.

Our second speaker, Dr Rachel McCloy, introduced psychological behavioural frameworks that are introduced by climate change and how they impact the progression towards successful mitigation. For example, emotional reactions towards climate change can include dread and injustice, and this combined with typical adjectives used to describe the environmental changes including “natural” and “uncontrollable”, can lead to an increased likelihood of no effort being taken at all against climate change.

A component of Rachel’s talk I found particularly interesting was the impact of over-congratulating individuals and societies for taking “baby steps”. When we congratulate or applaud an action too much it reduces the likelihood of an even better action taking place. Therefore, as a society, we need to keep looking at the next step to mitigating against climate change. If we think about this in the present day, could we agree that we congratulated the agreements met in COP21 Paris too much, and as a result the likelihood of ratification and progress being made has been dropped. We as a community need to hold each other to account even when those “baby steps” have been made.

And finally, Paul, a leading science journalist for The Times, brought to the discussion how the media can be used to encourage climate change to be taken seriously. Everything in the media is a story and when a phenomena such climate change impacts health, water or even transportation it can gain a public interest. To increase the media’s attention to climate change, greater emphasis is needed on how environmental changes will impact our daily lives. Paul also reminded us that the public have begun to associate extreme weather events to climate change, whether proven to be a result of anthropogenic action or not. A recent example that comes to my mind is the recent European thunderstorms that occurred last summer. The media should be used to successfully “shape opinions” and it is up to us to grasp the opportunities that they have to offer.

After an intriguing set of three short talks to answer the question “What will make the public and politicians take climate change seriously?”, discussion was opened to the audience. Questions included: What is the importance of education to solving climate change? How much advocacy work should a climate scientist get involved in? The meeting as a whole stimulated a continued discussion on how climate change can be communicated effectively to “encourage” the public and politicians to take climate change seriously.

I would like to thank all three panellists for a set of thought-provoking and challenging talks. Thank you to the Royal Meteorological Society for supporting the local centre event, and to find out more about meetings taking place in your region check out https://www.rmets.org/events/forthcoming-meetings.

The impact of Climate Variability on the GB power system.

Email: h.bloomfield@pgr.reading.ac.uk

Bloomfield et al., 2016. Quantifying the increasing sensitivity of power systems to climate variability. View published paper.

Within the power system of Great Britain (GB), there is a rapidly increasing amount of generation from renewables, such as wind and solar power which are weather-dependent. An increased proportion of weather-dependent generation will require increased understanding of the impact of climate variability on the power system.

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Figure 1: Predicted installed capacity from the National Grid Gone Green Scenario. Source: National Grid Future Energy Scenarios (2015).

Current research on the impact of climate variability on the GB power system is ongoing by climate scientists and power system modellers. The focus of the climate research is on the weather-driven components of the power system, such as the impact of climate variability on wind power generation. These studies tend to include limited knowledge of the whole system impacts of climate variability. The research by power system modellers focuses on the accurate representation of the GB power system. A limited amount of weather data may be used in this type of study (usually 1-10 years) due to the complexity of the power system models.

The aim of this project is to bridge the gap between these two groups of research, by understanding the impact of climate variability on the whole GB power system.In this project, multi-decadal records from the MERRA reanalysis* are combined with a simple representation of the GB power system, of which the weather-dependent components are electricity demand and wind power production. Multiple scenarios are analysed for GB power systems, including 0GW, 15GW, 30GW, and 45GW of installed wind power capacity in the system.

This study characterises the impact of inter-annual climate variability on multiple aspects of the GB power system (including coal, gas and nuclear generation) using a load duration curve framework. A load duration curve can be thought of as a cumulative frequency distribution of power system load. Load can be either power system demand (i.e. the NO-WIND scenario) or demand minus wind power (ie. the LOW, MED and HIGH scenarios).

The introduction of additional wind-power capacity greatly increases the year-year variability in operating opportunity for conventional generators, this is particularly evident for baseload plant (i.e. nuclear power plants). The impact of inter-annual climate variations across the power system due to present-day level of wind-farm installation has approximately doubled the exposure of the GB power sector to inter-annual climate variability. This is shown in Figure 2 as the spread between the red and blue curves (from the LOW scenario) is double that of the black curves (the NO-WIND scenario).

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Figure 2: Load duration curves for the NO-WIND and LOW scenario in black and grey respectively. The two most extreme years from the LOW scenario are 1990 and 2010, plotted in red and blue respectively. Vertical dashed lines show the percentage of time that baseload-plant (91%) and peaking plant (7%) are required to operate

This work has shown that as the amount of installed wind power capacity on the power system is increased, the total amount of energy required from other generators (coal, gas, nuclear) is reduced. Wind therefore contributes to decarbonising the power system, however the reduction is particularly pronounced for plants which are operating as baseload rather than peaking plant (i.e. oil fired generation) where an increase in required production is seen.

This study adds to the literature which suggests that the power system modelling community should begin to take a more robust approach to its treatment of weather and climate data by incorporating a wider range of climate variability.

For more information contact the author for a copy of the paper with details of this work: Quantifying the increasing sensitivity of power system to climate variability (submitted to ERL).

* A reanalysis data set is a scientific method for developing a record of how weather and climate are changing over time. In it, observations are combined with a numerical model to generate a synthesised estimate of the state of the climate system.