Monthly Archives: March 2014

For the most recent report of the Intergovernmental Panel on Climate Change (IPCC), fifteen climate modelling groups from around the world were asked to provide simulation outputs from their state-of-the-art carbon cycle models. The objective of these experiments was to provide up-to-date estimates of what happens to anthropogenic CO2 emissions, how they will be apportioned between atmosphere, ocean and vegetation, how long they will stay in the atmosphere and what are the long-term climate change implications.

Researchers in the Palaeoenvironmental Change group were one of the contributing groups, providing results from more than 50 different experiments using the Earth system model GENIE. Strict protocols were defined for all of these experiments that every group had to adhere to. These protocols defined precisely how the experiments should be set up, an important element of all model inter-comparison projects as comparing the results of “identical” simulations from many different models helps to identify and quantify areas of uncertainty in our understanding.

Holden2. png

The results of these experiments were an important component of the IPCC AR5 report. They were also published as three separate scientific papers, examining separately the recent historical period, projections into the future and a specific study to quantify the atmospheric lifetime of anthropogenic CO2 emissions.  Predictions from twelve of the participating models are illustrated above, comparing simulated global warming with observations since preindustrial times. One significant conclusion of this inter-comparison project was that the uptake of CO2 by vegetation appeared to be underestimated by all contributing models. This conclusion was subsequently examined in some detail by the Palaeoenvironmental Change group, producing a study which helped to better quantify the strength of this important global sink.

Read more about the inter-comparison project in our scientific papers:

Eby, M. et al: Historical and idealized climate model experiments: an EMIC intercomparison, Climate of the Past, 9, 1111-1140, 2013.

Joos, F. et al.: Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis, Atmospheric Chemistry and Physics, 13, 2793–2825, 2013.

Zickfeld, K. et al., Long-term climate change commitment and reversibility: an EMIC intercomparison, J. Climate, Vol. 26, pp. 5782–5809, 2013.

Posted by Phil Holden

Summary        A two-day conference – Shale UK – was held in early March 2014 in London, and attended by over 250 delegates.  The conference, organised on behalf of the Geological Society by Global Event Partners, was designed ‘ present an authoritative state-of-the-art view of geoscience relevant to shale gas exploration, production and environmental management in the UK. It aims to bring together the leading experts in relevant areas of geology, from the UK, US and elsewhere, with decision-makers, potential investors, others in the hydrocarbons and energy supply chain, and other stakeholders with an interest in shale gas.’  The aims of the conference organisers were fully met in a comprehensive programme of 26 presentations and ensuing discussions, which ranged from fundamental aspects of the geology of organic-rich mudrocks to the impact of EU regulations on UK shale gas activity.  Aspects of the massive shale gas expansion in North America of the last seven years featured frequently in some presentations, whilst the similarities and differences between the North American and European/Asian situations were used to highlight how shale gas exploitation might, or might not, develop in the UK.

Introduction    Shale gas and oil are hydrocarbons that never escaped from their source rocks (organic-rich mudrocks), because the source rocks were insufficiently permeable for hydrocarbon migration.  Although relatively small amounts of shale gas have been produced for over 30 years, it is the development within the last decade of new techniques such as horizontal drilling and hydraulic fracturing that have given rise to the recent North American shale gas bonanza.  The rise in US shale gas production since 2007 is shown in Fig. 1, which breaks down gas production according to the major gas fields, whilst the contrasting prices of gas in the US, Europe and Japan are shown in Fig. 2.

COHEN shale gas fig 1

Figure 1

COHEN shale gas fig 2

Figure 2

Because organic-rich mudrocks are widespread and their distribution is not necessarily linked to regions that traditionally produce hydrocarbons, many other countries hope to emulate the North American shale gas experience and gain a source of cheap and plentiful energy.  However, some very specific features are associated with the recent expansion of shale gas production in North America such that similar shale gas expansion may not necessarily be possible elsewhere.  In particular, these features include:

-       A relatively low population density coupled with extensive suitable lithologies in sparsely populated regions.

-       Landowners who are willing to allow shale gas exploitation.

-       A substantial, highly motivated and experienced drilling industry.

-       An existing, extensive national gas pipeline.

-       Limited and expensive opportunities to export gas from the US at present.

Shale gas potential in the UK        The UK possesses thick successions of lithologies that are potentially suitable for shale gas exploitation.  The major challenges facing potential future exploitation were presented and discussed in detail, and include:

1.  The location of suitable gas-bearing lithologies: The UK’s shale gas potential is mostly based on the Carboniferous-age rocks of the Midlands and northern England, and the Jurassic rocks of southern England.  These successions underlie large centres of population.

2.  The relatively complex geological framework of the lithologies that varies on a small scale.

3.  The relatively short life span of wells; 3 years sees a fall of 85% in gas production.

4.  Legal and regulatory framework; a comprehensive regulatory framework already exists, although it is complex.  Permissions are required from the Local Authority, the Department of Energy and Climate Change, the Environment Agency and the Health and Safety Executive.

5.  Numerous environmental considerations include:

-       The high density of wells that is required for gas production.

-       The substantial infrastructure that is needed to produce and maintain the wells, using space and causing noise.

-       Possible microseismicity related to hydraulic fracturing (‘fracking’).

-       The production and handling of large volumes of well waters that are radioactive.

-       The potential contamination of aquifers and surface waters from well waters and drilling compounds.

-       The production of shale gas requires much more energy than conventional natural gas; it thus has a much greater carbon footprint.

PRG members and UK organic-rich mudrocks (‘shales’)    Three members of the Palaeoenvironmental Research Group have long-standing interests in the geochemistry, stratigraphy, sedimentology and palaeontology of organic-rich mudrocks of the UK and elsewhere.  Anthony Cohen, Angela Coe and David Kemp (recently joined by Marie-Laure Bagard) have developed new methods for extracting a range of geochemical and palaeoenvironmental information from important Mesozoic and Cenozoic organic-rich mudrock successions.  These methods have provided us with detailed information about the timing and extent of some key environmental changes in Earth history (including seawater oxygen levels, continental weathering rates, and associated changes in marine biota) set within accurately defined chronological frameworks.

Posted by Anthony Cohen

Experiments under controlled conditions have unambiguously demonstrated that photosynthesis is stimulated when atmospheric CO2 concentrations are increased. Although these studies help to quantify the strength of this CO2 fertilisation effect, extrapolating such estimates to the global scale is extremely difficult, especially since other nutrients such as nitrogen may be the locally limiting factor in nature. CO2 fertilisation is a very important process in the global carbon cycle as it acts as a negative feedback for anthropogenic COemissions. Increased atmospheric CO2 stimulates photosynthesis so that some fraction of these emissions is taken up from the atmosphere by vegetation.

Researchers in the Palaeoenvironmental Change group have derived a probabilistic estimate of the globally averaged strength of CO2 fertilisation that is independent of experimental evidence. Instead, we simply considered the changes in the global carbon budget since preindustrial times. Historical changes in atmospheric CO2 concentrations are very accurately known. Historical fossil fuel emissions are relatively well known. Emissions from deforestation can be quantified, albeit with significant uncertainty. These historical emissions are partitioned between the atmosphere, the ocean and the terrestrial biosphere. With careful attention to the considerable uncertainties (evaluated by performing many hundreds of simulations of the Earth system model GENIE), the strength of CO2 fertilisation can be treated as the unknown quantity that balances the carbon budget.

Holden Forest CO2 image

This figure summarizes the results of the calculation. Observed CO2 concentrations are plotted as the red line. The green line plots the modeled prediction of CO2 when no knowledge is assumed about the strength of CO2 fertilisation, besides some plausible range of possible strengths. The red line plots the CO2 that is simulated after the calibration, and brings the present day simulated CO2 much closer to observations. This calibrated model is likely to provide more reliable projections of future CO2 concentrations and climate change.

We estimate that the increase in gross primary productivity in response to a doubling of CO2 is very likely (90% confidence) to exceed 20%, with a most likely value of 40-60%. The most important caveat to this estimate is that GENIE does not represent all of the possible contributing mechanisms to the land sink. If these missing processes comprise a net sink, then our calibration of the strength of CO2 fertilisation represents an upper estimate.

Read more about the calibration of CO2 fertilization in our scientific paper: Holden PB, Edwards NR, Gerten D and Schaphoff S: A model-based constraint on CO2 fertilisation, Biogeosciences, 10, 339, 2013.

Posted by Philip Holden