1998

[Appenzeller et al. 1998a]
Relationship between Greenland climate and the rest of the Atlantic. Uses ice deposition rates in 5 ice cores and shows relationship between this variable and NAO.

Mapa de correlacions con precipitacion bon.
[Appenzeller et al. 1998b]
Relationship between Greenland climate and the rest of the Atlantic exploited. Uses [Appenzeller et al. 1998a] to reconstruct NAO index for the period 1675-1970. No dominant frequencies in wavelet spectrum. Stocasticity. Nice correlation maps between NAO and ice deposition. Aslo nice example of wavelet spectrum.
NAO reconstructions
[Briffa et al. 1998b]
Tree-ring widths and densities are related to spring and summer temperatures. 300 chronologies near the tree-line. In the 2nd half of the century wood density has progresively fallen. When examining residuals of comparison with temperature, there is a clear trend in those. Sensitivity to temperature on interanual scale remains but the long trend at the end of century not captured. The constant temperature-dependent biospheric CO2 uptake should be revised.
Tree-ring reconstructions, temperatures.
[Briffa et al. 1998a]
Record of Northern Hemisphere proxy summer temperatures from tree-ring densities. Compared with volcanic eruptions. Nice methods for lack of information in the past to control variance increments. Some extended cooling in last centures maybe related with concentrated eruptions.
Tree-ring reconstructions, temperatures.
[Cook et al. 1998]
Reconstruction of NAO 1700-1980 from 10 chronologies in Scandinavia an SE USA using a multi-linear model approach.
NAO reconstructions, tree-ring width.
[Cooper and Jones 1998]
ABSTRACT: A comparison is made between the effectiveness of the inversion of borehole temperature data (for the pur-pose of climate reconstruction) by the least-squares (L2) technique and the minimization of the absolute differ-ence between the observed and calculated data (L1) technique. The L1 technique is found to require approx-imately half the number of iterations to reach the prac-tically achievable minimum error compared to the L2 technique. The choice of which technique to use depends on the statistics of the difference between the observed and calculated data, and it can be advantageous to switch techniques during the inversion process. The inversion damping is also adjusted during the course of the inversion, based on the rate of change of the difference between the observed and calculated data. The aim is to get the best fit of the model to the data while minimising the model size, in the minimum number of iterations. Amethod of adjusting the damping to achieve this is suggested.
NAO reconstructions, tree-ring width.
[Esteban-Parra et al. 1998]
Studies annual and seasonal total precipitation ammounts at 40 sites. Use PCA and Mann-Kendall test. Compares with GCM output.
Iberian Precipitation. Trends.
[Esteban-Parra et al. 1998]
A Monte Carlo inverse method has been used on the temperature profiles measured down through the Greenland Ice Core Project (GRIP) borehole, at the summit of the Greenland Ice Sheet, and the Dye 3 borehole 865 kilometers farther south. The result is a 50,000-year-long temperature history at GRIP and a 7000-year history at Dye 3. The Last Glacial Maximum, the Climatic Optimum, the Medieval Warmth, the Little Ice Age, and a warm period at 1930 A.D. are resolved from the GRIP reconstruction with the amplitudes 23 kelvin, 12.5 kelvin, 11 kelvin, 1 kelvin, and 10.5 kelvin, respectively. The Dye 3 temper- ature is similar to the GRIP history but has an amplitude 1.5 times larger, indicating higher climatic variability there. The calculated terrestrial heat ßow density from the GRIP inversion is 51.3 milliwatts per square meter.
Iberian Precipitation. Trends.
[Etheridge et al. 1998]
Reference for CH4 along teh last millennium. Echog forcing
Methane reconstructions
[Ganopolski et al. 1998]
Abstract: Simulations with a synchronously coupled atmosphere ocean vegetation model show that changes in vegetation cover during the mid-Holocene, some 6000 years ago, modify and amplify the climate system response to an enhanced seasonal cycle of solar inso-lation in the Northern Hemisphere both directly (primarily through the changes in surface albedo) and indirectly (through changes in oceanic temperature, sea-ice cover, and oceanic circulation). The model results indicate strong synergistic effects of changes in vegetation cover, ocean temperature, and sea ice at boreal latitudes, but in the sub-tropics, the atmosphere vegetation feedback is most important. Moreover, a reduction of the thermohaline circulation in the Atlantic Ocean leads to a warming of the Southern Hemisphere.
Holocene Optimum, EMIC, Atmosphere, Ocean, Vegetation
[Goodess and Palutikof 1998]
Downscaling of daily SLP to rainfall in 6 sites in the Iberian Peninsula. Circulation-type classification transferred to precipitation. Then the model is applied to GCM outputs.
Downscaling. Iberian precipitation. GCM validation.
[Hegerl 1998]
Discussion on available mean temperature reconstrucions and importance for studies of climate change.
Paleoclimate, temperature reconstructions, gcms, natural variability.
[Heyen and Dippner 1998]
Assessment of relationship between salinity in the German Bight and slp and precipitation. Find that slp lag-modulates changes in salinity by several months.. The causal mechanism involves advection of precipitation. Advection of Atlantic water is of minor impact. Use cca approach.
Downscaling, cca, salinity, slp, precipitation.
[Huang and Pollack 1998]
Citation for borehole data base
Climate reconstruction, proxy data, borehole, surface temperature
[Jones et al. 1998]
Proxies limited to represent climate variations over a range of timescales. Coral and ice core poorer than treering and historical and instrumental. Description of diferent type of proxies. Spatial limitations of each proxy confined to certain regions. Timescale limitations: importance of standarization. Crossespectral analisys does not reveal presence of large scale patterns. Model and proxies agree from point of view of coherence. Recomendations for paleoclimatologists
Paleoclimate, tree-ring, ice-core, instrumental, temperature, reconstructions, proxies, models.
[Jones 1998]
Comparison of three NH temperature reconstructions. Need for more multi-proxy reconstructions.
Paleoclimate, reconstructions, multiproxy.
[Kerr 1998a]
Possible near global chain that loosely connects 3 oceans... the tropical Indian Ocean warms, then the tropical Pacific warms setting off the El Nino. 9 months after el Nino winds have leaped South America, they change the circulation of the tropical Atlantic to warm the ocean there and bring oceanic drought to the Sahel and the northeast Brazil. The Atlantic tropics connected to the Extratropics through the PADO, somehow associated to the NAO. The NAO is a regional version of the hemispheric AO which also affects the North Pacific. Here, the North Pacific Decadal Oscillation seems to connect with the tropics. The author states a chain of possibly connected oscillations that relate 3 ocean basins from tropics to northern latitudes and back.
Nao, ENSO, PADO.
[Kerr 1998b]
Danger of THC collapse through emissions of GHG. These produce freshwater accumulation in northern latitudes which can lead to THC collapse. There exist 24 Daansgaard-Oeschger events marked by $10^{circ}$ T swings that occurred in just a few years, the Younger Dryas being the last of them. The THC alterations have also happened during Heinrich events. IN the big events there seems to be connection with Antartica. GFDL computer simulations support this changes would occur under GHG scenarios.
THC, GHG.
[Mursula and Ulich 1998]
Revision of definitions of solar cycle length.New definition based on the median of the sunspot number.
Solar irradiance, solar cycle, climate change, solar forcing
[Kerr 1999]
The NAO as a regional version of the AO. Similar concept of zonal winds (annular patterns) in northern and southern Hemispheres. AO variability and predictability might be coming from the startosphere through external forcing, volcanos, etc.
THC, GHG.
[Kohl 1998]
Attenuation of signal with depth
Borehole inversions, topography effects
[Lewis and Wang 1998]
Influences of deforestation o local warming
Deforestation, induced warming
[Mann et al. 1998]
Use dendro, ice core, ice melt and long historical records to reconstruct annual temperature. Multiproxy calibration of SST EOFs throgh multivariate regression. Explains method. Provides reconstruction for period 1400-1995. Explores correlations with several external forcing and finds contribution of CO2 and explanations for some well known past episodes.
Paleoclimate, tree-ring, ice-core, instrumental, temperature, reconstructions, proxies, models.
[Oreskes 1998]
This paper argues that, even if model validation may reaveal useful information, it is not possible to demonstrate the predictive reliability of any model of a complex natural system in advance of its actual use.
Model validation
[Peterson et al. 1998a]
Description of quality control approaches and of methods used to create GHCN, a global dataset of monthly temperature data.
Quality control, outliers, monthly temperature.
[Peterson et al. 1998b]
Review paper on homogeneization adjustments.
Homogeneization
[Pollack et al. 1998]
318 borehole records allow analyses of underground temperature since 1500. Show warming of 20th century. Reconstruction from boreholes using inverse bayesian method. Cooling of 0.5 K in 20th century, of aprox 1K in last 500 yr. Different cooling amplitude relative to Mann et al is already appreciated.
Paleoclimate, global temperature, reconstructions, boreholes.
[Rajver et al. 1998]
Study of 9 boreholes from Slovenia. Use functional space inversion (fsi). Obtain warming of about 0.7 C in the last century compatible with observations. One borehole (Ljubljana) has 1965 m depth and shows last glaciation cooling of about 10 degrees compatible with polen reconstrucctions though much averaged due to thermal diffusion.
Paleoclimate, Mediterranean, inverse problem, Slovenia, temperature, thermal conductivity.
[Rodriguez-Puebla et al. 1998]
Analysis of annual prectipitation averages in 51 stations for the period 1949-1995. Rotated PCA and correlations of the time series with NAO, ENSO and everybody else... Spectral analysis of results to extract some fancy cycles.
Iberian precipitation. PCA. Homogeneization.
[Romero et al. 1998]
Development of daily rainfal data set for the period 1964-1993 with 410 stations from an original set of 3366 stations. Takes into account homogeneization. Description of statistics. Progressive desertification of wester Catalonia and central and western Andaluc&́#305;a.
Spanish Mediterranean daily precipitation. Homogenization.
[Salawitch 1998]
Coments on [Shindell et al. 1998].
Cooling the upper stratosphere would lead to higher concentrations of 03 due to T dependence of reactions but this might have been masked by O3 depletion through release of industrial CFCs. Changes in the circulation due to increase of CO2 would affect to the O3 maximum in the lower stratosphere. The more stable and colder polar vortex will acelerate depletion of O3 through chemical reactions. Increased concentrations of GHG lead to a lower latitudinal temperature gradient near the tropopause and a decrase in the poleward propagation of planetary waves. This leads to more stable polar vortices and also a feedback mechanism: cooling of Arctic (stratosphere) due to decreased absorption of solar radiation due to decrased O3.
Stratosphere, O3 depletion, GHG
[Shindell et al. 1998]
Tropical upper-tropospheric warming due to GHGs which leads to increase of latitudinal temperature gradient over 600 to 100 mbar which leads to enhanced lower stratosphere (300 to 10 mbar) zonal winds at 40-50 N. This alters the refraction of planetary waves limiting their ability to propagate into the stratosphere and warm it thus producing reduction in stratospheric warmings.
Radiative cooling by increase of GHG produces decrease of F in latitudes over 70 N in altitudes of 200 to 500 mb. Added to reduced frequency in stratospheric warmings, this produces a more stable and enhanced Arctic vortex and a greater loss of 03.
NAO, Ozone, stratosphere Interesting hypothesis. Plots of ozone losses.
[Sims and Quayle 1998]
The basking shark Cetorhinus maximus show planktivorous fish behavior with zooplanckton abundance. Fluctuations of the abundance of some planckton species depend on sst and thus are related to NAO.
NAO, ecology.
[Song 1998]
Reconstruction of the southern oscillation form historical hydrological indices from China using CCA.
Paleoclimate reconstructions, historical data, SOI.
[von Storch and Zwiers 1999]
Good book for referencing.
Statistics, climate.
[Taylor et al. 1998]
The position of the Gulf Stream is forecastable from the NAO index. This work shows better forecasts cab be obtained taking into account persistence and the NAO and SO indices lagged 2 years. The position of the Gulf stream shifts $0.2^{circ}$ 2 years after ENSO events. NAO explains about 60 $\%$ of variance while SO adds at least a further 9
Gulf Stream, sst, NAO, ENSO.
[Thompson and Wallace 1998]
Extends NAO concept to the whole Northern Hemisphere.AO is surface inprint of polar extratospheric vortex. Proposes that zonally asymmetric surface air temperature and mid-tropospheric circulation anomalies observed in association with the AO may be secondary baroclinic features induced by the land-sea contrasts.
NAO, AO, geopotential height anomalies, Northern Hemisphere, temperature, presure.
[Vettoretti et al. 1998]
Abstract: The authors describe a first paleoclimatological application of the Canadian Centre for Climate Modelling and Analysis atmospheric general circulation model (AGCM) to simulate the climate state 6000 calendar years before present (6 kyr BP). Climate reconstructions for this period are performed with both fixed SSTs and with the AGCM coupled to mixed layer ocean and thermodynamic sea ice modules. The most important difference between this epoch and the present involves the increased surface heating and cooling of the continental land masses in the Northern Hemisphere during summer and winter, respectively, which are a consequence of the modified orbital configuration. A comparison of a fixed SST experiment with a calculated SST experiment, incorporating a thermodynamic representation of oceanic response, is performed to assess the impact on the mid-Holocene climate. The results are also contrasted with those obtained on the basis of proxy climate recon-structions during this mid-Holocene optimum period. Of interest in this calculated SST experiment is the impact on the seasonal cycle of sea ice distribution due to the increased insolation at high latitudes during Northern Hemisphere summer. Also important is the fact that the mixed layer ocean in the simulation is found to further enhance the monsoon circulation beyond the enhancement found to occur due to the influence of modified orbital forcing alone. This increased response is found to be a consequence of the sensitivity of tropical SST to the amplification of the seasonal cycle due to the change in insolation forcing that was characteristic of the mid-Holocene period.
Paleoclimate, GCMs, Mid Holocene.
[Villalba et al. 1998]
Regional reconstruction of long term precipitation in subtropical south America. Find increases consisten with 2xCO2 integrations
Paleoclimate, tree-ring, precipitation, reconstructions.
[Wilby et al. 1998]
Comparison of statistical downscaling approaches: weather generators, vorticity based methods and neural network approaches.
Statistical downscaling, regional models.
[Woodhouse 1998]
Reference for International Tree-ring Data Bank, ITRDB.
Paleoclimate, tree-ring, proxies.
[Woodhouse and Overpeck 1998]
Analysis of frequencies and types of droughts in USA for the last 2000 years.
Droughts are one of the most devastating natural hazards faced by the United States today. Severe droughts of the twentieth century have had large impacts on economies, society, and the environment, especially in the Great Plains. However, the instrumental record of the last 100 years contains only a limited subset of drought realizations. One must turn to the paleoclimatic record to examine the full range of past drought variability, including the range of magnitude and duration, and thus gain the improved understanding needed for society to anticipate and plan for droughts of the future. Historical documents, tree rings, archaeological remains, lake sediment, and geomorphic data make it clear that the droughts of the twentieth century, including those of the 1930s and 1950s, were eclipsed several times by droughts earlier in the last 2000 years, and as recently as the late sixteenth century. In general, some droughts prior to 1600 appear to be characterized by longer duration (i.e., multidecadal) and greater spatial extent than those of the twentieth century. The authors assessment of the full range of past natural drought variability, deduced from a comprehensive review of the paleoclimatic literature, suggests that droughts more severe than those of the 1930s and 1950s are likely to occur in the future, a likelihood that might be exacerbated by greenhouse warming in the next century. Persistence conditions that lead to decadal-scale drought may be related to low-frequency variations, or base-state shifts, in both the Pacific and Atlantic Oceans, although more research is needed to understand the mechanisms of severe drought.
Paleoclimate, tree-ring, proxies.