Draft of a proposal for a joint Earth Science/Atmospheric Science programme on the variability of climate

The following outlines the view of an ESTB group of the programme which RSG has asked ESTB and ASTB to explore. It is presented as a basis for discussion for an ESTB/ASTB working group.

1.	The Challenge

1.1.	One of the most important current preoccupations of the international scientific community and scientific policy makers in government and industry is the understanding of global climate; the coupling between human activity and climate change, the future of climate and the evaluation of its potential impacts and the development of national and intergovernmental policy.

1.2.	General circulation models of the atmosphere, partly coupled to ocean processes are key tools in the evaluation of potential climate futures. The most recent models have investigated the climate response to transient boundary conditions forced by historical changes in atmospheric chemistry, which have then been compared with the record of climate change over the last 100 years.

1.3.	The key challenge for science is to demonstrate that the climate system is sufficiently well understood and that scenarios for its future evolution are of such high probability that they demand a serious policy response by governments and industry.

1.4.	The key difficulty lies in the fact that climate has varied continuously and often rapidly during temperate periods similar to that of the present interglacial, such that it is difficult statistically to disentangle "natural" from anthropogenically driven changes, and that the mechanisms for such changes are poorly understood. To be confident that we understand present changes and can evaluate their future trajectory, requires that we understand more about the spectrum of climate changes, which the geological record shows can occur during temperate periods of earth history, and can simulate them computationally.

2.	The Opportunity

2.1.	The UK earth science community has played a major role in:

establishing the long term spectrum of climate change forced by "Milankovitch" insolation variations on timescales of 104-105 years due to changes in the earths orbit;

rapid climate changes on timescales of 102-103 years forced by ocean/ice sheet dynamics during the last glacial period.

2.2.	The UK atmospheric science community - analogous statement required.

2.3.	Atmospheric Science and Earth Science approach climatology from different standpoints. The former develops spatially integrated analyses of the present state or, occasionally, other time slices, but with little regard for transience. The latter recognises and reconstructs temporal variance of climate, but has a limited capacity to reconstruct change in the full spatial domain.

2.4.	The identification of natural geological archives which preserve records of change with an annual or decadal resolution now permits us to explore the spectrum of sub-Milankovitch climate change with a rigour not previously possible, to investigate the mechanisms of such change and to test more fully than presently possible the capacity of computer models to simulate transience.

2.5.	Sites and methods which would provide important archives of change have been established through recent UK initiatives such as TIGGER, LOIS and NEAPACC and through ODP. A broader context which secures international collaboration is provided by UK involvement in PAGES, IMAGES, CLIVAR, PMIP and WDC-A.

3.	The Programme

3.1.	The magnitude of possible climate change during the next 100 years is potentially much greater than the range of global climate change during the last 100 years as captured by the instrumental record. For advice based upon General Circulation Model (GCM) studies to have a sound scientific basis requires that they are tested for their capacity to simulate as wide a range of climates as possible, and certainly as wide a range as could occur over the next 100 years. If they are not, models will extrapolate their theory well beyond their data, a cardinal feature of poor science.

3.2.	The Earth Science component of the programme will be concerned to reconstruct climate variance during temperate periods of recent Earth history, and in particular to document rapid and extreme climatic excursions. (Note, for example, increasing evidence from spectral analyses of high resolution records, of well defined periodicities of change during the present interglacial; and the strong contrast between the high climatic variance of the last interglacial, which was also warmer than the present, and the relative stability of the present interglacial.) It will concentrate on producing high resolution records, and contemporary and correlatable records from different environments and geographical areas (eg contrasts between NE Atlantic Sea Surface Temperatures and continental European records of palaeotemperature), in which leads and lags and relative magnitudes of change in time dependent sequences can be identified. Key observation points will be derived from: blanket peats; speleothems; tree rings; glacier variations; ice cores; shelf, slope and deep ocean sediments. Annually laminated sediments will be a key target. Appropriate tephras events will be used as event markers.

3.3.	The Atmospheric Science component of the programme will concerned with.....(Modesty forbids us to prescribe this section, it properly being a subject for discussion with our atmospheric science colleagues, however, we suggest that exploration of the changes in model parameter/boundary conditions required to simulate observed temporal and spatial patterns of change could be the way to formulate the approach).

4.	The UK Community

4.1.	The UK palaeoclimate community is large, diverse and amongst the worlds strongest. The directors of IGBP and PAGES are UK scientists.

4.2.	Analogous statement about modelling community.

4.3.	The integration of geology and modelling in a programme linking the strong UK paleoclimate and climatology communities will enhance even further the strength of the science base in this area and gives the opportunity to make a major impact on the international scientific and policy agenda.

4.4.	Such a programme would also provide a framework within which ecological and other resource impacts could be evaluated and should be linked to activity funded by ESCRC in the policy impacts of global change. It would also link with the global change policy imperatives in the emergent EU 5th framework programme.