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A brief overview is given of the major contributions of dendroclimatology to current knowledge and understanding of climate variability and change. Particular attention is given to: (1) greatly enhanced information on the spectrum of climate variability, especially on interannual, decadal, and multidecadal timescales; (2) the history of regional to hemispheric temperatures over recent centuries; (3) the probable causes of the variability seen in tree-ring and other records over the past millennium; (4) attempts to determine the quantity `climate sensitivity΄ of the Earth΄s climate system; and (5) reconstructions of the behavior of circulation features and of regional climates, notably drought. Emphasis is given to the importance of regional, continental, and broader-scale networks, as well as to a wide array of technical advances, in making these achievements possible. Then an impressive array of applications is discussed, ranging from ecology and hydrology to anthropology and archaeology. Finally, attention is given to the prospects for dendroclimatology, and in particular to suggestions for making best use of its strengths and for overcoming its weaknesses. [ABSTRACT FROM AUTHOR]

Vegetation reconstruction from north-western Portugal estuarine cores reflects millennial- to centennial-scale climate variability during the Last -Glacial–Interglacial Transition (LGIT) in the Douro basin. These vegetation cover changes match perfectly the climatic pattern detected in the North Atlantic region and in Greenland. Changes between high and weak forested phases in the Douro basin are associated with warm and cold episodes, respectively. The first warm episode, the Bölling, occurring within the LGIT, follows the Oldest Dryas episode (terrestrial equivalent of the marine Heinrich 1 event) and was characterised by the expansion of pine, oak and birch. Subsequently, a rapid climate reversal was revealed by the contraction of that arboreal association and increase of herbaceous taxa probably reflecting the centennial-scale Older Dryas episode (one of the well-known Intra Bölling-Allerød cold events). The Allerød event, representing the subsequent warming phase, was characterised by the expansion of alder -followed by pine. Afterwards, an abrupt cooling occurred, evidenced by the replacement of temperate trees (pine and oak) by herbaceous plants (compositae and grasses), reflecting the Younger Dryas cold event. Finally, the end of the LGIT was characterised by a maximal expansion of temperate and humid forest (birch, oak, pine, ashes, alder), as likely being the result of the climate improvement that characterises the present-day interglacial, the Holocene. [ABSTRACT FROM AUTHOR]

Climate Services for Development in Africa (ClimDevAfrica) Programme is a joint initiative of the African Union Commission (AUC), the United Nations Economic Commission for Africa (UNECA) and the African Development Bank (AfDB), to the inception of which the author has contributed since 2005. The programme has been mandated at regional meetings of African Heads of State and Government, as well as by Africa's Ministers of Finance, Planning, Economic Development, and Environment and it responds to the urgent challenge that climate variability and change pose to the achievement of Africa's sustainable development objectives. Although the programme encompasses all sectoral activities influenced by climate (agriculture, health, water management, etc.), energy should be one of the sectors with potentially high-impact demonstration projects. Weather and climate conditions are in fact critical for both energy supply and demand, including aspects such as production and transmission. The energy sector could therefore provide benchmarks for other sectors. The flow of information and climate risk knowledge across sectors should be facilitated by the holistic approach taken in the ClimDevAfrica programme. In this chapter, most of the emphasis is on the main aspects of the ClimDevAfrica programme as a whole, without specific links to the energy sector but the reader is encouraged to reflect on potential energy projects that could be developed under the upcoming ClimDevAfrica programme. This chapter gives some indications on the necessary partnership initiation to support a multi sectoral and multi stakeholder development programme needed to cope with climate variability and change. Some pilot activities for ClimDevAfrica, have started and one of them is highlighted in Appendix A. [ABSTRACT FROM AUTHOR]

In this chapter, we assess the relationship between climate variability and hurricane hazard in the U.S. using data mining techniques. Regression trees are developed to investigate the relationship between seventeen climate variables (with their quarterly and annual averages) on the yearly cumulative destructive potential of U.S. land-falling hurricanes. The U.S. coast is divided into three separate sections: the Atlantic Coast excluding Florida, Florida, and the Gulf Coast excluding Florida. Each region is analysed separately as well as the aggregate of all the regions in an effort to better understand the factors that drive the frequency and intensity of hurricanes making landfall in the U.S. The results indicate that a large number of climate variables contribute to the observed historical variations in hurricane activity. This insight is validated by demonstrating that the models outperform previously published models that are based on only two climate variables. The results show that geographic partitioning is essential in both understanding the pattern of past hurricane activity and forecasting future hurricane hazard. The analysis of variable importance shows that temperature-related variables are useful for explaining hurricane activity, even though their importance differs between regions. [ABSTRACT FROM AUTHOR]

A core from the western end of the subtropical gyre (ODP Leg 172 Site 1060, 31°45N, 74°24W, 3400m water depth) in close proximity with the Gulf Stream was studied at high resolution to clarify the surface hydrology changes involved during the last interglacial, their relations and impact over deep circulation as well as continental climate as recorded by pollen. The occurrence of high-frequency cold events at subtropical latitudes is also examined. For the time span from 134 to 108 kyr, eight distinct periods can be recognised on the basis of planktonic foraminifera assemblages. These faunal changes are related mainly to changes in the summer stratification tracing the Gulf Stream current influence and late winter mixing controlling the formation of the subtropical mode water. In addition, our results indicate that during the deglaciation, the sea level rise first during 4 kyr, while sea-surface temperatures stay cold. Only at 128 kyr do the two vary in phase sharply and rapidly; after that date the Gulf Stream increases its influence and reaches a maximum on the core site after 125 kyr. Therefore, the onset of the warm current seems to predate by 2 kyr the onset of the Eemian on land as recorded off Portugal. During the interval 122-116, the sea-surface temperatures are maximum in winter but start to decrease in summer. Superimposed on this cooling trend, we found several high-frequency cooling events better marked in winter (around 2°C). For most of these, cooling peaks of lithic concentration (90-150 μm) probably representing periodic ice rafting to the core site were found. We found that the repeated pacing of these events is about 1400 years. [ABSTRACT FROM AUTHOR]

Existing observations of ocean temperature, sea level and transport within the Indonesian seas and south-east Indian Ocean are reviewed and compared with a simulation. The dynamical mechanisms by which the Indonesian Throughflow (ITF) interacts with the surrounding oceans in the model and real oceans are discussed. The focus is on the variability on timescales ranging from the intraseasonal (<3 months) to the interannual (a few years). A lagged multiple regression technique is applied to anomalies of sea level from a mean seasonal cycle for observed and modeled fields. The results reveal that the region comprises the intersection of two ocean wave guides where sea level and upper ocean temperature anomalies can be largely understood in terms of Kelvin and Rossby waves generated by remote zonal winds along the Indian and Pacific equators, with local wind forcing appearing to play a minor role in generating interannual variability. Variations in zonal Pacific equatorial winds force a response along the Arafura/Australian shelf break through Pacific equatorial Rossby waves exciting coastally trapped waves off the western tip of Irian Jaya, which propagate westward into the Banda Sea and poleward along the Australian west coast. Equatorial Kelvin waves excited by Indian Ocean winds propagate eastward and scatter into coastal waves along the Sumatra—Java—Lesser Sunda coasts to penetrate the western internal seas of Indonesia. While the model captures the variability generated by the equatorial Indian Ocean winds, its pathway eastward into the Indonesian region is prevented by a dynamically "wide" Lombok Strait, which carries too much of the main throughflow and allows too little wave energy to pass directly into the Banda Sea. The model response to El Nino-southern oscillation (ENSO) wind changes is too weak as expressed by its sea-level response in the western Pacific. The subsequent transmission of this ENSO signal into the ITF region and along the west coast of Australia is also much weaker in the model than observed. Generally, the model/data comparisons suggest that too little energy gets scattered into the model coastal wave guide. An assessment of whether this difference is a model resolution or model dissipation issue (and they are related) needs further work. [ABSTRACT FROM AUTHOR]