Climatic Research Unit : Research

Research Areas

Research areas – the 1990s

This information was compiled in the 1990s and represents a valuable archive of CRU research activity during that period. For current research see


Research in CRU covers a wide range of topics. This is a list of the main research areas in the 1990s, together with some projects within them.

The list of people against any subject does not imply seniority, but rather the order in which they should be approached for further information.



People: Keith Briffa, Phil Jones, Tim Osborn
Projects: ADVANCE-10K
Further details: "Trees as indicators of climate change"


Present-day climate

People: Mark New

Construction of observed climatologies

Gridded monthly climate datasets are required for a wide range of climate analyses, ranging from climate change detection and climate model evaluation to climate change impact assessment. The extensive monthly station normals and timeseries data collected by the Climatic Research Unit have been used to construct gridded climatologies on a number of different resolutions and for different world regions. These include:

  • Global (land)
    • 5° lat/long mean temperature, 1856-1997 time series
    • 5° lat/long precipitation, 1900-1996 time series
    • 2.5° lat by 3.75° long. precipitation, 1900-1996 time series
    • 0.5° lat/long, 1961-90 mean monthly climatology for 10 variables
    • 0.5° lat/long, 1900-1995 time series for 5 variables
  • UK
    • 10km and 10 minute 1961-90 mean monthly climatology

People: Mike Hulme, Mark New, Phil Jones, Julie Jones, Elaine Barrow
Projects: NERC Carbon Project


Observed climate change

Numerous factors are thought to change the Earth's average temperature, factors acting on a variety of timescales from orbital changes on the longest to the explosive volcanic eruptions on the interannual. Assessing the importance of the various factors requires measurements of past changes in climate. Evidence comes principally from measurements during the observational period (approximately 1850 to the present) and earlier palæoclimatic data.

Mediterranean desertification

See MEDALUS under Downscaling of scenarios to local scales

Drought in the Sahel

Sahel research in CRU aims to further our understanding of the mechanisms which initiate and sustain drought in the region. This involves analysis of rainfall variability as observed over the twentieth century and as modelled in long-term climate simulations. The impact of atmospheric dust on the climate of northern Africa, particularly the Sahel, is also being investigated.

People: Nick Brooks, Mike Hulme
Projects: Ph.D. (Nick Brooks)

Instrumental climate change

The instrumental period is generally accepted to begin in the mid-nineteenth century, when sufficient sites became available to look at observed changes on the global scale. On this scale near-surface air temperatures have risen by about 0.6°C, much of the warming occurring in two phases between 1920 and 1940 and since 1975 (see figure). Spatially this temperature increase has occurred in most regions (especially Siberia and northwestern North America), although cooling has prevailed over the northwestern Atlantic. Precipitation changes show even more complex patterns with regions of increasing and decreasing annual precipitation amounts. The largest decreases are evident in Sahelian regions of Africa with increases in northwestern Europe and parts of northern Siberia.

Instrumental records in Europe extend back into the 18th and in some cases 17th century. A 215 year (1780-1995) gridded pressure dataset has been constructed from these records and will be used to analyze changes in circulation patterns over Europe and the Eastern North Atlantic between pre- and post-industrial periods.

These instrumental data bases are being used in a study of the natural and anthropogenic causes of recent climate change using empirical and modelling techniques.

People: Phil Jones, Mike Hulme, Mick Kelly, Trevor Davies, Vicky Slonosky
Projects: Causes of 20th century climate change, ADVICE
Papers: Estimating Global Changes in Precipitation


Natural climate variability

El Niño Southern Oscillation (ENSO)

The El Niño Southern Oscillation (ENSO) is one of the most important causes of large-scale climate variability known and is associated with disrupted climate patterns around the world. ENSO is a large-scale natural fluctuation of the global climate system, a result of interactions between the ocean and the atmosphere. There are two components to ENSO. El Niño refers to the oceanic component which is manifest as a marked warming of the waters of the central and eastern Pacific. The term Southern Oscillation refers to a see-saw effect in atmospheric pressure between the eastern and western Pacific. There are two phases of ENSO. The best known is El Niño, meaning the boy or Christ child. The less well known phase is called La Niña - the girl - which displays opposite characteristics to an El Niño. ENSO is quasi-cyclic in nature and an event normally occurs every three to six years and lasts on average up to about 18 months. ENSO events have impacts on climate throughout much of the world with the strongest influence felt in the tropics and subtropics. In particular rainfall patterns are widely effected by El Niño. Some regions, for example parts of South America, southern Africa, and Australasia, experience low rainfall or droughts. Other areas, for example eastern Africa, have heavier that average rainfall. Seasonal forecasts are available for some of the probable impacts. Research is being undertaken to assess variations on shorter timescales as well as how these forecasts are utilised by the agricultural sector.

People: Louise Bohn
Data: SOI

North Atlantic Oscillation (NAO)

The North Atlantic Oscillation (NAO) is one of the major modes of variability of the Northern Hemisphere atmosphere: a see-saw in atmospheric mass between the Azores High and the Iceland Low. It is driven, in part at least, by variations in North Atlantic storms and has hemispheric-wide influences. Particularly strong impacts are felt in the European sector, including the United Kingdom. These impacts come about because the NAO, besides being related to the distribution of Atlantic storms, also represents the strength of the westerly flow and so affects the size of Atlantic waves, European temperature and precipitation, and the ocean circulation (including controls on icebergs, zooplankton and fisheries). The NAO has its strongest effects in winter, and is of particular interest recently because an increase in the winter NAO index has occurred between the 1960s and 1990s (the largest low-frequency change in a 170-year record), coinciding with a strong warming of the Northern Hemisphere land masses relative to the oceans. Since this pattern of warming is similar to that expected when either the NAO increases or greenhouse gas concentrations increase, important questions are raised. Is the observed warming simply due to a natural fluctuation of the climate system, or is the greenhouse effect the cause? Or perhaps the greenhouse effect is manifesting itself by amplifying the natural modes of the climate system? How unusual are the recent changes in the state of the North Atlantic Oscillation and the recent winter warming of the Northern Hemisphere?

People: Tim Osborn, Phil Jones, Keith Briffa
Projects: The NAO in a climate model
Data: NAO, NAO update


Climate change detection and attribution

"Climate Change Detection" is the process of demonstrating that an observed change in climate is highly unusual in a statistical sense, but does not provide a reason for the change. "Attribution" is the process of establishing cause and effect, i.e. that changes in anthropogenic emissions are required in order to explain satisfactorily the observed change in climate. Unambiguous attribution is feasible only in the sense of demonstrating that the observed change is consistent or inconsistent with the climate responses to a given set of external forcing mechanisms.

Statements regarding the detection and attribution of an anthropogenic effect on climate are inherently probabilistic in nature. They do not have simple "yes-or-no" answers. The Second Assessment report of the IPCC in 1996 concluded that the balance of evidence suggests a discernable human influence on global climate. A probability range for successful attribution of the detected changes to human effects will be more difficult to define.

People: Phil Jones, Tim Mitchell


Climate variability and the "missing carbon" sink

The objective is to assess the theoretical effect of climate variability on timescales of up to 100 years on carbon fluxes derived from a dynamically coupled global vegetation soil respiration model (with Ian Woodward at the University of Sheffield). A high-resolution terrestrial gridded climate database is being developed as model input. Empirical evidence for changing tree-growth in wide regions of the Northern hemisphere is being used to aid validation of the model.

Projects: Missing Carbon
See also: Dendroclimatology, Construction of observed climatologies
People: Mark New, Trevor Davies, Phil Jones, Keith Briffa, Mike Hulme


Simulated future climate

The Climatic Research Unit is involved in various aspects of research into the simulation of future climate and climate change. Although we do not perform climate change experiments using global climate models, we evaluate the results of many climate modelling centres, especially the Hadley Centre. This evaluation involves comparison of simulated climate and climate variability against observations at global, regional and local scales. We also undertake research into the most effective ways of constructing climate change scenarios based on model results and using model results in conjunction with observed climate data. This involves us developing and using simple climate models, weather generators and statistical and dynamical downscaling methods.

People: Mike Hulme, David Viner

Construction of climate change scenarios

The Climatic Research Unit has been at the forefront of climate change scenario construction for nearly two decades. Our current work in this area makes use of our extensive global observational datasets, a simple climate model (MAGICC), and the large archive of results from GCM climate change experiments held by the Unit (e.g. the Hadley Centre model results managed by the LINK project). We have also been asked by the IPCC to co-host the IPCC Data Distribution Centre which is responsible for preparing and distributing climate change scenarios and related data for the Third Assessment Report of the IPCC due to be published in 2001.

People: Mike Hulme, David Viner, Elaine Barrow, Sarah Raper

Downscaling of scenarios to local scales

MEDALUS (Mediterranean Desertification and Land Use) is an international EC-funded research project to investigate the effects of desertification in Mediterranean Europe. Changes in climate and in the social and economic structures of the region have important implications for water resources, vegetation cover, erosion rates and agriculture. These implications can be studied through hydrological models. The role of CRU is to construct scenarios of future climate changes, for input to these catchment-based models. This requires downscaling to a very fine spatial and temporal scale. Ten years of daily rainfall, maximum and minimum temperatures have been generated for the decades 1970-79, 2030-39 and 2090-99 and for multiple sites in two catchments: the Agri in southern Italy and the Guadalentin in south-east Spain.

People: Jean Palutikof, Clare Goodess, Maureen Agnew, Sarah Watkins, Phil Jones, Declan Conway

Evaluating climate models

The Climatic Research Unit has a contract with the DETR to work on climate model evaluation, especially with respect to the Hadley Centre models. The contract extends over a two year period from 1 June 1997 to 31 March 1999. The primary purpose of the contract is to facilitate and provide an independent evaluation of Hadley Centre climate model performance in relation to international efforts to model the climate system, to detect human-induced climate change and to predict future climate change.

People: Mike Hulme, Tim Osborn, Tim Mitchell
Projects: Climate Model Validiation

Climate change and sea level with simple climate models

Computationally efficient simple climate models for the projection of anthropogenic climate change have been developed and further improvements are being made. The main outputs are global mean temperature and sea level changes from pre-industrial times to a few centuries into the future. A set of linked models enables the consistent calculation of results from prescribed green-house-gas and aerosol emissions, through atmospheric concentrations, radiative forcing , global mean temperature, thermal expansion of the oceans and land ice melt. Development of the upwelling-diffusion energy balance climate model is based on on-going detailed comparisons with A/OGCMs. This work together with changes in the volume of glaciers and ice-sheets is being carried out as part of an EC project "Climate Change and Sea Level" co-ordinated at CRU.

People: Sarah Raper, Olga Brown, Tim Osborn, Tom Wigley
: Climate Change and Sea Level


Impacts of climate variability and change

Climate affects both social and natural systems through the occurrence of weather extremes, through interannual climate variability and through longer-term climate change. The Climatic Research Unit researches into aspects of all three of these scales of climate impact, with projects ranging from the UK to Europe, Africa and Vietnam. A better understanding of the ways in which climate extremes and variability have affected society and environment in the past is a pre-requisite for attempting to understand how serious the range of impacts associated with future climate change are likely to be. The results of analyses such as these therefore feed directly into the design of climate change response policies, whether these be mitigation or adaptation.

Impacts of weather extremes on UK and Europe

A recent study for the DETR examined the impacts (particularly economic and social) of the hot summer of 1995 in the UK, and compared these with the impacts sustained in previous extreme summers such as 1976. In 1995, the mean July and August Central England temperature anomaly was +3°C, exceeding the previous record of +2.5°C set in 1983. Some common themes emerged in the study. First, both negative and positive impacts were incurred. Clear positive impacts (to the general public) were found for energy and health, and clear negative impacts for agriculture, water supply and buildings insurance (claims for subsidence). Second, changes in sensitivity to climate extremes have occurred over time. Some are caused inadvertently through technical innovation or a shift in the source of raw materials. But some are a result of deliberate adaptation, and this was seen particularly in the transport, water and insurance sectors. Third, it appears that for most areas of human activity the greatest impacts are sustained from anomalous winter weather. In the transport and construction sectors, for example, activity is severely disrupted by severe winter weather, but the impact of very hot summer weather is by comparison relatively small.

This study is now being extended through Europe as part of an EC-funded project Weather Impacts on Social and Economic Systems (WISE). The impacts of a recent hot summer, warm winter and a wind storm on the economies, societies and natural environments of four European countries (the UK, the Netherlands, Italy and Germany) are to be studied primarily through quantitative analysis of published statistics. Transnational impacts will be examined through case studies of perturbations in international tourism and the flows of agricultural produce in response to climate extremes. Perceptions of the impacts of climate variability, both among the general public and among policy makers and management, will be examined by questionnaire and interview. At the close of the project, a workshop will be held with participants from public, private and non-governmental environmental organizations to discuss the wider implications of the results.

The study of the 1995 hot summer suggested that it might be possible to create a set of indicators of climate change specific to the British Isles, and which could be up-dated on a year-by-year basis. This work is currently being undertaken by CRU in partnership with CEH and funded by DETR. CEH is responsible for indicators related to the natural environment, such as the arrival dates and spread of migrant species, whereas CRU is responsible for economic indicators as diverse as the productive area of vineyards, domestic gas sales and activity in the Scottish skiing industry.

People: Jean Palutikof, Maureen Agnew, David Lister
Projects: WISE

Climate change and Africa

Analysis of African climate variability using instrumental datasets, together with the specification of future climate change scenarios for Africa based on climate modelling. These scenarios have been used in collaborative impacts assessments for the Nile Basin, the Southern African Development Community (see WWF report), and for an African-wide overview of climate change impacts. Work is also progressing on how climate information is best used to improve short and medium term strategic planning in certain sectors and regions.

People: Mike Hulme, Declan Conway, Nick Brooks, Louise Bohn, Mick Kelly
Projects: Nick Brooks' PhD, Louise Bohn's MPhil

Climate and development

Support for the developing country response to the global warming problem is essential if the international community is to respond effectively to the threat of climate change. The Climatic Research Unit is actively contributing to this process through:

  • information provision — the production of the quarterly bulletin Tiempo and related Tiempo Climate Cyberlibrary and various briefing documents;
  • training — the Climate Change MSc, short courses, studentships and visiting fellowships; and
  • collaborative research — for example, a study of vulnerability to climate hazards in Vietnam with the Center for Environment Research Education and Development and various other institutes in Hanoi.

The Climatic Research Unit has a long-term agreement with the International Institute for Environment and Development (London, UK) regarding support for developing countries and arious aspects of the climate and development programme, such as the production of Tiempo, are undertaken in collaboration with IIED.

People: Mick Kelly, Mike Hulme
Projects: Climate Change MSc, Tiempo Climate Cyberlibrary, Global Warming and Vietnam

Vulnerability to climate change in East Africa

The project "Responding to global change: Vulnerability and management of local agro-ecosystems" is undertaken at CRU in collaboration with the African Centre for Technology Studies, Nairobi, Kenya.

Measures need to be identified which meet the aims of the three major international conventions - the UN Framework Convention on Climate Change, the Convention on Biological Diversity and the Convention to Combat Desertification – and which at the same time address local needs. The impact of drought on local populations, and loss of biological diversity and productivity of the land, are common concerns of the three conventions. The project examines household knowledge as a factor in capacity to respond and vulnerability. Comparative analysis of Mbitini, Kenya, and Pare, Tanzania will enable identification of causal relationships, and reasons for variations between the two sites in household knowledge of uses of indigenous plants and trees and capacity to respond to drought.

The project will lead to understanding of the processes leading to decreased vulnerability to environmental change, and an approach for integrating various environmental goals in development policies. The research will result in recommendations for national action in Africa that facilitates implementation of environmental conventions at the local level in such a way as to strengthen means to ensure local level living standards at the same time as environmental concerns of all three conventions are addressed.

People: Siri Eriksen
Projects: "Responding to global change: Vulnerability and management of local agro-ecosystems"


Application of climate information

Climate change over very long timescales

The major aim of the climate studies is to provide information about the nature and succession of future climate states in the British Isles on timescales of the order of the next 100,000 years. Research on these timescales is being carried out in three major areas:

  1. modelling studies using the zonally-averaged climate model developed at the University of Louvain-la-Neuve, Belgium;
  2. quantitative climate reconstructions based on pollen cores from West Cumbria; and,
  3. review-based studies.

A list of publications arising from this research is available.

The work is supported by UK Nirex Ltd as part of the Nirex Science Programme. This involves research into options for the long-term management of radioactive waste in the U.K.

People: Clare Goodess, Jean Palutikof, Paul Burgess, Sarah Watkins

Wind climatology

POWER is an EC-funded project to Predict the Offshore Wind Energy Resource, involving collaborators from the UK, the Netherlands and Denmark. There is mounting pressure to limit the burning of fossil fuels and increase the contribution of renewable energy resources. Although wind energy has substantial potential in western Europe, this is limited on land by visual and noise considerations. The potential resource at sea is known to be large, but is poorly studied. This project aims to generate an atlas of offshore wind speeds for the seas surrounding the countries of the European Union, and looking in detail at time-dependent variations on daily, seasonal, annual and decadal scales.

People: Jean Palutikof, Tom Holt
Projects: POWER

Links between atmospheric circulations and transport/deposition of air pollution

The role of climate change/variability, especially circulation patterns (weather types, circulation indices, trajectories) is determined in the variability and trends of ambient concentrations and aqueous concentrations in the UK and Europe. Over periods of years to decades, circulation changes are often the dominant factor, notwithstanding changes in emission rates. Some research involves direct measurements (e.g lake bed cores, and cloud/precipitation samples in the heavily-polluted regions of the Czech Republic). Other research uses GCM results to assess the consequences for acidic deposition across Europe of possible future climate change.

People: Trevor Davies, Julie Jones, Steve Dorling

Surface ozone

Much of the variability in surface ozone concentrations is linked to climate variability, but trends over decades may be partly influenced by climate change. Links between surface ozone trends and climate are examined, including observations from the Montsouris Observatory in Paris where data are available from the turn of the century. These observations have generated considerable interest because of the information they give on long-term trends.

People: Trevor Davies, Evi Schuepbach


Atmospheric sciences and hydrology

Stratosphere-troposphere exchange

Ozone is a tropospheric greenhouse gas and is a pollutant of some importance. Tropospheric concentrations are dependent on complex processes which include cross-tropopause exchange, in-situ photochemical production, transport and destruction, and cross-tropopause exchange. A number of cases of pronounced ozone episodes at the surface (both low and high elevation sites) have been linked to stratosphere-troposphere exchange using a variety of indicators such as potential vorticity, specific humidity and back-trajectories. One intrusion has been observed and studied as far south as Greece. Other episodes in the Swiss Alps have been successfully modelled using a mesoscale model nested in a limited area model (in collaboration with ETH Zurich).

People: Trevor Davies, Evi Schuepbach, Tasos Kentarchos

Acidic episodes in surface water

Transient decreases in acid neutralising capacity in surface waters are practically ubiquitous. There are only few occasions when they are directly related to contemporaneous acidic deposition. They are initiated by precipitation events and by snowmelt, the distributions of which are both controlled by climate. The precise character of the episodes depends on complex flowpaths, and these are influenced by antecedent conditions (largely governed by climate). Studies include observation, and developing models to predict the severity and the contributions (base cation dilution, acidic anion increase, etc.) to the decline in acid neutralising capacity.

People: Trevor Davies


Last updated: August 2007