What emission profiles aid remaining below two degrees of global warming?

In recent days multiple marches have taken place around the world, timed to coincide with the UN Climate Change summit in New York (23 September 2014). The many protestors have urged more action by governments to reduce greenhouse gas emissions.

CEH climate modeller Dr Chris Huntingford commented:

“There is still significant debate as to what constitutes safe levels of global warming. This almost certainly depends on the different impacts which can result from varying levels of warming. For example, meteorological changes affecting crop productivity detrimentally could be produced by a different level of climate change to that causing unwelcome sea-level rise. Yet despite this, the 2009 climate conference in Copenhagen pushed for the single threshold of no more than two degrees of global warming. There is a persuasive argument that this was a major achievement, as a single easy to understand temperature threshold will probably gain more traction in policymaker circles than debating a range of possible climatic futures.

The immediate question then became: “What emissions profiles can keep us below two degrees of global warming?” Working with colleagues from Met Office Hadley Centre, University of Oxford, Manchester Metropolitan University and the Committee on Climate Change, we carried out a study using a relatively simple coupled climate-carbon cycle model, but one capturing uncertainty based on differences between the fully complex climate models, as operated by various research centres across the world. The resultant paper provided “look-up” diagrams, where different emissions levels of years 2020 and 2050 can be related to the probability of remaining below two degrees. The paper also linked these 2020 and 2050 levels to both year of maximum emissions and required year-on-year emission cuts for the decades thereafter, in order to fulfil them.

The paper was published in 2012 in the journal Environmental Research Letters, but its message still stands. Namely that to have a reasonable chance of constraining warming to two degrees then emissions need to peak in the next few years, followed by year-on-year cuts of at least 3%.”

Chris Huntingford

UN Secretary General Ban Ki-Moon (front row, second from right) at the People's Climate
March in New York, held ahead of the Climate Summit he hosted at UN headquarters in
September 2014. Photo: UN / Mark Garten

Additional information

The paper can be read on the Environmental Research Letters website. It is "open access" allowing circulation of the document, and can be found here (doi: 10.1088/1748-9326/7/1/014039).

Chris Huntingford is a climate researcher at the UK Centre for Ecology & Hydrology, and also long-term visiting scientist at the Oxford University Centre for the Environment.

Information on the UN Climate Summit 2014

Integration and reflection - paperblog 8

This week we concentrate on recent papers with CEH scientists as the first author.

PhD student Philip Martin recently published a major paper summarising his research over the last few years. You can read more about "Carbon pools recover more quickly than plant biodiversity in tropical secondary forests" (published in Proceedings of the Royal Society B) on the CEH website and on Philip's blog.

Another PhD student, Christopher Malley, has a new paper out in Atmospheric Research which takes a detailed look at how well two of the UK's atmospheric monitoring 'supersites', including the site run by CEH at Auchencorth Moss in Scotland, represent the UK's background ozone conditions.

CEH is a Centre that carries out both ecological and hydrological science, sometimes together (the clue is in the name!). Our scientists produce many papers that seek to bring together varied data on water quantity, freshwater ecology, and water quality. In recent weeks, CEH scientists have published on estimating concentrations in rivers of different chemicals originating from sewage treatment plants (Keller et al., open access in Environmental Toxicology and Chemistry), and a new approach for predicting phosphorus concentrations in rivers (Greene et al., Journal of Hydrology).

Sometimes it is necessary to take a step back from day to day research to ponder some fundamental questions on how scientific knowledge can be used in wider society. Two examples have recently appeared. Alan Gray has a new paper in Transgenic Research examining whether applied ecology has failed the transgenic crops debate. Stefan Reis and colleagues from CEH, Universities and Health Institutes across the UK have put together a new analysis on how to integrate health and environmental impact analysis to address some of the new public health challenges.

Nitrogen science plays a big role in CEH activities. Laurence Jones and CEH colleagues have produced a new review of the evidence for nitrogen impacts on ecosystem services. Read it in the journal Ecosystem Services, where the paper is open access (full text freely available). Meanwhile, Mark Sutton is lead author on another new open access paper in Environmental Development looking at "Green Economy thinking" and relevance to control of nitrous oxide emissions.

Finally, Robert Mills, who completed a PhD at CEH's site in Bangor, North Wales, has just published a new paper on organic carbon turnover rates in natural and semi-natural topsoils. Working with Professor Ed Tipping, the study concludes with the interesting result that turnover is faster under trees than non-trees. Read more in the journal Biogeochemistry.

That's it. As ever, we welcome suggestions and comments on the material presented in the paperblog. Let us know what you think!

Barnaby Smith, Media Relations Manager

Additional information

If you'd like a fuller picture of new papers from CEH, just follow the CEH Paper Alerts Twitter feed, which lists CEH peer-reviewed papers newly published online. Full details of Centre for Ecology & Hydrology science publications, including those published in peer-reviewed science journals, are eventually catalogued on the NERC Open Research Archive (NORA).

Those of you who follow the scientific literature will know some journal websites require registration and some are subscription-only. CEH, as part of NERC, is working with publishers and funders to make more of our output open access, and we have indicated above where this is the case.

We also publish lots of our other outputs including biological records atlases and project reports. More details can be found in the publications section of the CEH website.

The Plynlimon catchments - an open air laboratory

The Plynlimon catchments in central Wales are the most important intensively studied long-term research basins in the UK. Managed by the Centre for Ecology & Hydrology (CEH), Plynlimon is among the key European and world sites in terms of catchment science - not just for the length of the records gathered (40 years and counting) but crucially because of the breadth of measurements, spanning hydrology and including water chemistry, groundwater studies, geomorphology, ecology and atmospheric science.

With the study now in its fifth decade, and inspired by a new paper* by Dr Mark Robinson, working with former colleagues John Rodda and John Sutcliffe, who played key roles in establishing Plynlimon, we take a look at the history behind the establishment of one of CEH's most significant scientific experiments, a long-term environmental monitoring project which has evolved and adapted to stay relevant to current problems and scientific needs.

Landscape view over the Plynlimon catchments in central Wales (photo: Simon Grant / CEH)

In the mid-20th century, against a backdrop of population growth, rising living standards and post-war industrial recovery, there was growing concern in the UK about increased demand for water and possible future water shortages. A severe drought in summer 1959 and dry winters in 1962/3 and 1963/4 underlined the belief in government circles that a national plan for water use was needed, as it seemed likely that demand would soon outstrip available resources.

There were concerns too about other factors potentially affecting water availability, not least the government's policy of encouraging widescale tree planting on reservoir catchments. The rapid growth characteristics of the conifer and the cheapness of the land resulted in conifer plantations on many upland regions of Britain throughout the first half of the 20th century. However, there were conflicting scientific views on the hydrological impact of forests, with some catchment studies, particularly in the USA, indicating that tree cover could reduce water yield relative to short vegetation.

Research in the late 1950s by Frank Law Senior, a water engineer in north-west England, tried to find out more about the water balance of woodlands under British conditions. His conclusions were controversial: that afforestation of the Stocks reservoir catchment area was substantially reducing runoff, with the additional evaporation representing a reduction in reservoir yield of over one third. At a time of anticipated increasing domestic and industrial water demands, the debate about water versus forestry was set for the decades ahead.

British hydrology and water industry were still rather fragmented in the decade after the Second World War, but these national pressures meant that more rational management of water resources was required. The particular need to understand the role of vegetation in the hydrological cycle led to the creation by the Department of Scientific and Industrial Research (DSIR) of a Committee on Hydrological Research in 1961. This committee soon proposed the establishment of a specialist unit to be responsible for applied research into surface water hydrology, including studies of the water balance of catchment areas in relation to land use.

The new Hydrological Research Unit was set up in the following year and attached to the existing Hydraulics Research Station at Wallingford in Oxfordshire. A steering group was appointed to guide its studies, with a range of potentially competing stakeholder representatives from the Forestry Commission, Nature Conservancy, Water Research Association, Met Office and Agricultural Research Council.

The Unit was asked to conduct a hydrological study of catchments with contrasting land cover, preferably grassland and coniferous forest, since that was seen as the land use distinction most likely to reveal differences in behaviour and was the most common source of land use concern.  The catchments would need to be on watertight geology, and it was felt that the difference in water used by the two vegetation types would be most clearly apparent in relatively dry climate.

Where exactly to base the experiment was not a straightforward decision. It proved difficult to identify pairs of almost identical catchments that differed only in their vegetation and had landowner agreement for access. Plynlimon was not even on the original eight potentially suitable paired catchments identified. The climate criterion was later relaxed to include ‘wet’ sites, and the adjoining headwater catchments of the Severn and the Wye rivers draining the slopes of Pumlumon Fawr, i.e. Plynlimon, were added to the list, and later judged to be the most promising of the possible sites. The headwaters of each catchment provide a land use contrast between the two major upland land uses: moorland (Wye) and plantation forest (Severn).

In addition to the ongoing scientific debate concerning forest evaporation, the organisational framework for UK environmental research was undergoing major change as part of a wider government reorganisation. In 1965 the HRU was transferred to the newly formed Natural Environment Research Council (NERC). The Unit’s remit was then expanded to encompass all aspects of the hydrological cycle including physical and applied studies, instrumentation and mathematical modelling.

The Plynlimon study officially started on 1 January 1967, with the NERC Annual Report foreseeing it as being an “outdoor laboratory of immense value to all sciences”. The delays in establishing a field site actually afforded the opportunity to develop expertise in cutting edge instruments and new technologies. There was pioneering work (widely adopted elsewhere) on neutron probes for soil water content measurement, as well as automatic weather stations capable of operating at remote locations, and new raingauge designs for windy sites.

Cefn Brywn crump weir on the River Wye, late 1960s

In recognition of the growing importance of hydrological research in Britain, NERC designated the HRU as a full component institute: on 1 April 1968 it became the Institute of Hydrology, which later became part of the Centre for Ecology & Hydrology. The Plynlimon study played a crucial role in proving beyond doubt the potentially serious reduction in water flows resulting from afforestation, leading to major changes in the management of water and land use by resource managers and policy makers.

Work continues at the Plynlimon catchments to this day. CEH conducts long-term measurements of weather, streamflow and chemical fluxes. We use this information to look for time trends, understand the processes operating, and investigate the impacts of land use on water resources, floods, drought flows, stream sediment and dissolved chemicals and acidification. 

Other Plynlimon research highlights

·        The original aim of the Plynlimon catchment experiment was to make measurements which could resolve the uncertainties concerning the water use of conifer forests. It not only helped to answer this question but subsequently developed into a long-term multi-disciplinary project.

·        Building upon the established catchment infrastructure, hydrochemical measurements commenced and now more than almost 30 years are available, together with the longer record of hydrological data.

·        The Plynlimon catchments have been one of the more successful catchment studies, advancing science and its findings have directly altered UK forestry environmental policy and informed UK government policy.

·        The Plynlimon study provided a considerable stimulus to the development of the science of hydrology in Britain. The research findings have been reported in more than 500 papers in refereed journals, and much of the Plynlimon record has been freely available to the international research community for decades, and is also accessible via the internet from the CEH Information Gateway.

  

Summarising the importance of the Plynlimon catchments, Dr Mark Robinson told us, “We owe a great debt to the farsightedness of the stakeholders and academics who recognised the need for, and supported the establishment of, the research catchments at Plynlimon. The catchments provided an important focus in British hydrology, promoting excellence in experimental hydrology and advancing our understanding of the physical processes controlling the hydrological cycle.”

Additional information

* The full paper reference is: Robinson, M., Rodda, J.C., and Sutcliffe, J.V. (2012), Long-term environmental monitoring in the UK: origins and achievements of the Plynlimon catchment study. Transactions of the Institute of British Geographers. doi: 10.1111/j.1475-5661.2012.00534.x 

View archive photos from Plynlimon on Flickr

CEH: Why monitor upland catchments? [PDF, 4.95mb]