2000

1. [Alexanderson et al. 2000]
   ABSTRACT: Within the WASA project (von Storch et al. 1998; Bull Am Meterol Soc 79(5):741 760) an extensive data set containing station pressure values was used to calculate geostrophic winds (Alexandersson et al. 1998; Global Atmos Ocean Syst 6:97 120). Geostrophic winds were analysed in terms of percentiles to give a measure of long-term variations in synoptic-scale storminess. In this paper an update to 1998 is presented. In the Scandinavia, Finland and Baltic Sea area the most recent years, especially the cold and calm year 1996, seem to have brought an end to the stormy period centred on 1990. In the more westerly British Isles, North Sea and Nor-wegian Sea area, storminess is still at high levels compared with the less intense period between 1930 and 1980. The long-term increasing trend in NW Europe storminess that started in the 1960s seems to have been broken.
   Pressure indices, atlantic storminess

2. [Bard et al. 2000]
   ABSTRACT: Based on a quantitative study of the common fluctuations of 14C and10Be production rates, we have derived a time series of the solar magnetic variability over the last 1200 years. This record is converted into irradiance variations by linear scaling based on previous studies of sun-like stars and of the sun s behavior over the last few centuries. The new solar irradiance record exhibits low values during the well-known solar minima centered at about 1900, 1810 ( Dalton) and 1690 AD (Maunder). Further back in time, a rather long period between 1450 and 1750 AD is characterized by low irradiance values. A shorter period is centered at about 1200 AD, with irradiance slightly higher or similar to present day values. It is tempting to correlate these periods with the so-called little ice age and medieval warm period , respectively. An accurate quantification of the climatic impact of this new irradiance record requires the use of coupled atmosphere ocean general circula-tion models (GCMs). Nevertheless, our record is already compatible with a global cooling of about 0.5 1°C during the little ice age , and with a general cooling trend during the past millenium followed by global warming during the 20th century ( Mann et al., 1999).
   Solar irradiance reconstructions, cosmogenic isotopes.

3. [Beltrami 2000]
   Uses 200 boreholes in eastern Canada to produce a GSTH inversion and estimation of ground flux. The mean ground heat flux at a single borehole location is of the order of $5 \ mWm^{-2}$
   Climate reconstructions, global warming evidence, borehole climatoloty, heat flux.

4. [Briffa 2000]
   Review of tree ring research. Present a reconstruction of NH annual temperature for the last 2000 years.
   Holocene temperature reconstructions, treerings.

5. [Brown 2000]
   Abstract: Historical and reconstructed snow cover data from stations in Canada, the United States, the former Soviet Union, and the People s Republic of China were used to reconstruct monthly snow cover extent (SCE) fluctuations over midlatitudinal (;408 608N) regions of North America (NA) and Eurasia back to the early 1900s using an areal snow index approach. The station distribution over NA allowed SCE to be reconstructed back to 1915 for 6 months (November April), along with estimates of monthly mean snow water equivalent (SWE) from gridded daily snow depth data. Over Eurasia, SCE was able to be reconstructed back to 1922, but major gaps in the station network limited the approach to 3 months (October, March, and April). The reconstruction provided evidence of a general twentieth century increase in NA SCE, with significant increases in winter (December February) SWE averaging 3.9$\%$ per decade. The results are consistent with an observed increasing trend in winter snow depth over Russia and provide further evidence for systematic increases in precipitation over NH midlatitudes. North American spring snow cover was characterized by rapid decreases during the 1980s and early 1990s with a significant long-term decrease in April SWE averaging 4.4$\%$ per decade. Eurasia was characterized by a significant reduction in April SCE over the 1922 97 period associated with a significant spring warming. The snow cover reduction was significant at the hemispheric scale with an estimated average NH SCE loss of 3.1 3 10 6 km 2 (100 yr)21 associated with significant warming of 1.268C (100 yr)21 over NH midlatitudinal land areas (408 608N). The computed temperature sensitivity of NH April SCE was 22.04 3 10 6 km 2 8C 21 . Since 1950, March SCE decreases have become more important than those in April with significant reductions over both continents averaging 8.5 3 10 6 km 2 (100 yr)21 . March was also observed to have experienced the largest warming during the November April snow season with significant post-1950 warming trends in both continents averaging 4.18C (100 yr)21 . The hemisphere-wide elevated March snow cover temperature response is consistent with the position of the snowline over continental grassland vegetation zones where snow cover is relatively shallow and the potential snow cover area albedo feedback is large.
   Snow cover,20th century, climate change

6. [Cavazos 2000]
   Application of SOMs and neural networks to predict precipitation in the Balkans. NAO effects discussion.
   Downscaling, neural networks, som

7. [Cook et al. 2000]
   Abstract We describe an improved tree-ring recon- struction of mean warm-season (November April) tem- peratures for Tasmania from Huon pine. This record extends back to 1600 BC and is based on a tree-ring chronology that was processed to retain as much low- frequency variance as possible. The resulting recon- struction explains 46.6 of the variance and veri®es signi®cantly when compared to withheld instrumental data. Cross-spectral analysis of actual and estimated temperatures over the 1886+-1991 common period indi- cates that most of the unexplained variance is at periods <12 years in length. At periods >12 years, the squared coherency ranges between 0.6±0.8, and the cross-spectral gain indicates that the amplitude of the reconstruction is a nearly unbiased estimate of the true temperature am- plitude. Therefore, this reconstruction should be espe- cially useful for studying multi-decadal temperature variability in the Tasmanian sector of the Southern Hemisphere over the past 3592 years. To this end, we examined the time evolution of low-frequency tempera- ture amplitude ¯uctuations and found evidence for a 35 amplitude reduction after AD 100 that persisted until about AD 1900. Since that time, the low-frequency temperature amplitude has systematically increased. We also show how this reconstruction is related to large-scale sea surface temperatures (SST) in the Indian Ocean and eastward to the dateline. Pointwise correlations between the Tasmanian record and SSTs reveal a relationship that extends across the southern Indian Ocean and towards the Arabian Sea. This pattern is largely determined by inter-decadal temperature variability, with correlations in this >10-year bandwidth commonly exceeding 0.6 over most of the southern Indian and southwestern Pa- ci®c sectors. A rotated empirical orthogonal function analysis reveals that the pattern of pointwise correlations found between the temperature reconstruction and SSTs is largely explained by the linear combination of three orthogonal modes of SST variability.
   Tasmanian tree ring composite

8. [Cox et al. 2000]
   The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate1. About half of the current emissions are being absorbed by the ocean and by land ecosystems2, but this absorption is sensitive to climate3,4 as well as to atmospheric carbon dioxide concentrations5, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change6. Here we present results from a fully coupled, three-dimensional carbon±climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a `business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5Gt Cyr-1 is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models2, resulting in a global-mean warming
   Carbon cycle feedbacks.

9. [Crowley 2000]
   External forcings for the last 1000 yrs. EBM response to forcing and comparison with reconstructions. Residuals show no trend when forcing substracted. Residuals substracting solar and volcanoes show 20th century trend. Results support anthropogenic climate changes now.
   External forcing, EBM, climate reconstructions, paleoclimate, multiproxy.

10. [Crowley and Lowery 2000]
    A frequent conclusion based on study of individual records from the so-called Medieval Warm Period ( 1000-1300 A.D.) is that the present warmth of the 20 th century is not unusual and therefore cannot be taken as an indication of forced climate change from greenhouse gas emissions. This conclusion is not supported by published composites of Northern Hemisphere climate change, but the conclusions of such syntheses are often either ignored or chal-lenged. In this paper, we revisit the controversy by incorporating additional time series not used in earlier hemispheric compilations. Another difference is that the present reconstruction uses records that are only 900 1000 years long, thereby, avoiding the potential problem of uncertainties introduced by using different numbers of records at different times. Despite clear evidence for Medieval warmth greater than present in some individual records, the new hemispheric composite supports the principal conclusion of earlier hemispheric reconstructions and, furthermore, indicates that maximum Medieval warmth was restricted to two-three 20 30 year intervals, with com-posite values during these times being only comparable to the mid-20 th century warm time interval. Failure to substantiate hemispheric warmth greater than the present consistently occurs in composites because there are significant offsets in timing of warmth in different regions; ignoring these offsets can lead to serious errors concerning inferences about the magnitude of Medieval warmth and its relevance to interpretation of late 20 th century warming.
    Medieval Warm Period MWP LIA, Northern Hemispheric temperatures, last millennium.

11. [Ganachaud and Wunsch 2000]
    Through its ability to transport large amounts of heat, fresh water and nutrients, the ocean is an essential regulator of climate1,2. The pathways and mechanisms of this transport and its stability are critical issues in understanding the present state of climate and the possibilities of future changes. Recently, global high-quality hydrographic data have been gathered in the World Ocean Circulation Experiment (WOCE), to obtain an accurate picture of the present circulation. Here we combine the new data from high-resolution trans-oceanic sections and current meters with climatological wind ®elds, biogeochemical balances and improved a priori error estimates in an inverse model, to improve estimates of the global circulation and heat fluxes. Our solution resolves globally vertical mixing across surfaces of equal density, with coeficients in the range... . Net deepwater production rates amount to ... in the North Atlantic Ocean and n the Southern Ocean. Our estimates provide a new reference state for future climate studies with rigorous estimates of the uncertainties.
    Paleo climate reconstructions, borehole data.

12. [Huang et al. 2000]
    Reconstruction of hemispheric and global temperatures from borehole data. Not much new since [Pollack et al. 1998]. Confirms that work. 616 instead of 358 boreholes allow for hemispheric and global inspection. Conclusions aligned with [Pollack et al. 1998]. Discussesspñroblemof discrepancy in trends with other reconstructions. Highlights potential of stablishing reference for model simullations.
    Paleo climate reconstructions, borehole data.

13. [Cullen et al. 2000]
    Review of several NAO reconstructions. Different reconstructions emphasize different features. Consensus reconstructions provide better results. Spectral properties assesment of several indices.
    NAO, climate reconstructions, paleoclimate, multiproxy.

14. [D'Odorico et al. 2000]
    Suggest use of neural networks to reconstruct climate from tree-ring
    Climate reconstructions, paleoclimate, tree-ring.

15. [González-Rouco et al. 2000]
    Downscaling of SLP to Iberian rainfal. Observations and scenarios.
    NAO. Climate models. Iberian rainfal. Wintertime. North Atlantic

16. [Latif et al. 2000]
    Ensemble of 4 integrations with observed 1951-94 monthly sst and sea ice. Concentrate on slp variability in winter (DJFM). Results are compared with reanalysis for the same period. Year to year variability is not reproduced. Low frequency is reasonably well simulated. Sistematic model errors and the fact that there exists only one observed realization may account for the deffects of reproducing the NAO index. CCA between NCEP and model simulations shows higher correlations that with point association (circulation indices). Model indicates dependency on sst and ice and thus predictability. Correlation maps of cca1 slp with model and obs sst are very similar. As in CCA model, patterns are shifted. Are sst predictable?
    NAO, winter predictability.

17. [Lean 2000]
    Reconstructions of spectral solar irradiance since 1600 AD. Time variability in the sun spectrum seems to be wavelength dependent. The reconstructions use contemporary observations to relate solar irradiance and solar activity and proxies of solar activity to extend these relationships historicall.
    Climate reconstructions, solar activity reconstructions, spectrum of solar irradiance, sun like stars.

18. [Levitus et al. 2000]
    ABSTRACT: We quantify the interannual-to-decadal variability of the heat content (mean temperature) of the world ocean from the surface through 3000-meter depth for the period 1948 to 1998. The heat content of the world ocean increased by ;2 3 10 23 joules between the mid-1950s and mid-1990s, representing a volume mean warming of 0.06¡C. This corresponds to a warming rate of 0.3 watt per meter squared (per unit area of EarthÕs surface). Substantial changes in heat content occurred in the 300- to 1000-meter layers of each ocean and in depths greater than 1000 meters of the North Atlantic. The global volume mean temperature increase for the 0- to 300-meter layer was 0.31¡C, corre- sponding to an increase in heat content for this layer of ;10 23 joules between the mid-1950s and mid-1990s. The Atlantic and Pacific Oceans have undergone a net warming since the 1950s and the Indian Ocean has warmed since the mid-1960s, although the warming is not monotonic.
    Climate change, oceans warming,AO

19. [Manrique and Fernández-Cancio 2000]
    Dendro reconstruction for the last millennium, Spain.
    Last millennium, dendro reconstruction.

20. [Meehl et al. 2000]
    ABSTRACT: Projections of statistical aspects of weather and climate extremes can be derived from climate models representing possible future climate states. Some of the recent models have reproduced results previously reported in the Intergov-ernmental Panel on Climate Change (IPCC) Second Assessment Report, such as a greater frequency of extreme warm days and lower frequency of extreme cold days associated with a warmer mean climate, a decrease in diurnal tempera-ture range associated with higher nighttime temperatures, increased precipitation intensity, midcontinent summer dry-ing, decreasing daily variability of surface temperature in winter, and increasing variability of northern midlatitude summer surface temperatures. This reconfirmation of previous results gives an increased confidence in the credibility of the models, though agreement among models does not guarantee those changes will occur. New results since the IPCC Second Assessment Report indicate a possible increase of extreme heat stress events in a warmer climate, an increase of cooling degree days and decrease in heating degree days, an increase of precipitation extremes such that there is a decrease in return periods for 20-yr extreme precipitation events, and more detailed analyses of possible changes in 20-yr return values for extreme maximum and minimum temperatures. Additionally, recent studies are now addressing interannual and synoptic time and space scale processes that affect weather and climate extremes, such as tropical cyclones, El Niño effects, and extratropical storms. However, current climate models are not yet in agreement with respect to possible fu-ture changes in such features.
    Climate change experiments, extreme events.

21. [Montavez et al. 2000]
    Monte Carlo model of nocturnal UHI in urban canyons.
    Monte Carlo techniques, urban heat island.

22. [Nakicenovic et al. 2000]
    Special Report on Emission Scenarios.
    Radiative emission scenarios, SRES.

23. [New et al. 2000]
    The authors describe the construction of a 0.58 lat long gridded dataset of monthly terrestrial surface climate for the period of 1901 96. The dataset comprises a suite of seven climate elements: precipitation, mean tem-perature, diurnal temperature range, wet-day frequency, vapor pressure, cloud cover, and ground frost frequency. The spatial coverage extends over all land areas, including oceanic islands but excluding Antarctica. Fields of monthly climate anomalies, relative to the 1961 90 mean, were interpolated from surface climate data. The anomaly grids were then combined with a 1961 90 mean monthly climatology (described in Part I) to arrive at grids of monthly climate over the 96-yr period. The primary variables precipitation, mean temperature, and diurnal temperature range were interpolated directly from station observations. The resulting time series are compared with other coarser-resolution datasets of similar temporal extent. The remaining climatic elements, termed secondary variables, were interpolated from merged datasets comprising station observations and, in regions where there were no station data, synthetic data estimated using predictive relationships with the primary variables. These predictive relationships are described and evaluated. It is argued that this new dataset represents an advance over other products because (i) it has higher spatial resolution than other datasets of similar temporal extent, (ii) it has longer temporal coverage than other products of similar spatial resolution, (iii) it encompasses a more extensive suite of surface climate variables than available elsewhere, and (iv) the construction method ensures that strict temporal fidelity is maintained. The dataset should be of particular relevance to a number of applications in applied climatology, including large-scale biogeo-chemical and hydrological modeling, climate change scenario construction, evaluation of regional climate models, and comparison with satellite products. The dataset is available from the Climatic Research Unit and is currently being updated to 1998.
    Precipitation data set

24. [Ogilvie et al. 2000]
    Discuss evidence from ducumentary data, ice core and marine sediment records for the period 800-1100 in the north Atlantic. All this evidence suggests that the climate for this period was favourable for the exploration and expanssion to Iceland, Greenland and Newfoundland. Seems that sea ice had retreated favouring traveling and temperatures were milder favouring fertile crops ...
    Paleoclimate, temperatures, North Atlantic, Greenland, North America, Viking.

25. [Pasquale et al. 2000]
    Borehole temperature inversions in nw Italy. Warmer period in the 18th century.
    Borehole temperature reconstructions, Italy.

26. [Pollack and Huang 2000]
    ABSTRACT: Temperature changes at the Earth s surface propagate downward into the subsurface and impart a thermal signature to the rocks. This signature can be measured in boreholes and then analyzed to reconstruct the surface temperature his-tory over the past several centuries. The ability to resolve surface temperature history from subsurface temperatures diminishes with time. Microclimatic effects associated with the topography and vegetation patterns at the site of a borehole, along with local anthropogenic perturbations associated with land use change, can obscure the regional climate change signal. Regional and global ensembles of boreholes reveal the broader patterns of temperature changes at the Earth s surface. The average surface tempera-ture of the continents has increased by about 1.0 K over the past 5 centuries; half of this increase has occurred in the twentieth century alone.
    Borehole temperature reconstructions.

27. [Rind 2000]
    Briefing over several previous papers. Description of temperature, energy and hidrological impacts in climate from the modification of latitudinal temperature gradients and/or global temperature. Discussion differenciates between changes in the ocean temperatures or externally induced through CO2 and/or solar forcing
    Latitudinal temperature gradientes. AOGCMs. Paleoclimate. Climate change.

28. [Rimi 2000]
    10 geothermal profiles from different climatic areas in Morocco. They support climate warming in spite of the meteorological record 1936-80 suggestinng cooling. Warming of 4 degrees in the arid regionns of ne Morocco
    Borehole reconstruction, Morocco.

29. [Robock et al. 2000]
    ABSTRACT: Soil moisture is an important variable in the climate system. Understanding and predicting variations of surface tem-perature, drought, and flood depend critically on knowledge of soil moisture variations, as do impacts of climate change and weather forecasting. An observational dataset of actual in situ measurements is crucial for climatological analysis, for model development and evaluation, and as ground truth for remote sensing. To that end, the Global Soil Moisture Data Bank, a Web site (http://climate.envsci.rutgers.edu/soil-moisture) dedicated to collection, dissemination, and analysis of soil moisture data from around the globe, is described. The data bank currently has soil moisture observations for over 600 stations from a large variety of global climates, including the former Soviet Union, China, Mongolia, India, and the United States. Most of the data are in situ gravimetric observations of soil moisture; all extend for at least 6 years and most for more than 15 years. Most of the stations have grass vegetation, and some are agricultural. The observations have been used to examine the temporal and spatial scales of soil moisture variations, to evaluate Atmospheric Model Intercomparison Project, Project for Intercomparison of Land-Surface Parameterization Schemes, and Global Soil Wet-ness Project simulations of soil moisture, for remote sensing of soil moisture, for designing new soil moisture observa-tional networks, and to examine soil moisture trends. For the top 1-m soil layers, the temporal scale of soil moisture variation at all midlatitude sites is 1.5 to 2 months and the spatial scale is about 500 km. Land surface models, in general, do not capture the observed soil moisture variations when forced with either model-generated or observed meteorology. In contrast to predictions of summer desiccation with increasing temperatures, for the stations with the longest records summer soil moisture in the top 1 m has increased while temperatures have risen. The increasing trend in precipitation more than compensated for the enhanced evaporation.
    Soil moisture

30. [Schmutz et al. 2000]
    Compares several NAO reconstructions. The existing NAO index reconstructions show an inconsistent picture both for interannual and decadal scale variability. [Luterbacher et al. 1999] is the most reliable reconstruction available to date. Linear combination of existing NAO indices das not lead to significant improvement of reconstruction skill. Authors suggest exploiting all available predictors in a new reconstruction. Studies 3 proxy and 2 instrumental indices. Proxy indices based on temperature (tree-ring) or precipitation (Appenzeller) show worse behavior than those obtained from early instrumental data. Results suggest nonstationarity in relationships. Implications for choice of verification period.
    NAO recosntructions. Paleoclimate.

31. [von Storch et al. 2000]
    About DATUN.
    NAO recosntructions. Paleoclimate. Upscaling, Nudging

32. [Stott et al. 2000]
    A comparison of observations with simulations of a coupled ocean-atmosphere general circulation model shows that both natural and anthropogenic factors have contributed significantly to 20th century temperature changes. The model successfully simulates global mean and large-scale land temperature variations, indicating that the climate response on these scales is strongly inßuenced by external factors. More than 80temperature variations are due to changes in external forcings. Anthropogenic global warm- ing under a standard emissions scenario is predicted to continue at a rate similar to that observed in recent decades.
    Warming, external forcing, anthropogenic warming, climate change, GCMs.

33. [Stephenson et al. 2000]
    Stochastic processes, arima, fractionally integrated, random walk ... can produce significant low frequency variability and trends. With this models less than $8 \%$ of variability of NAO is predicted. Comment about tied phases of low mean and variance.
    NAO variability, stochastic processes.

34. [von Storch and Stehr 2000]
    Perspective of climate change concern in history. Interesting.
    Climate change, policies, history.

35. [Thompson and Wallace 2000]
    The leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep, zonally symmetric or  annular   structures, with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude. The structure and dynamics of the Southern Hemisphere (SH) annular mode have been extensively documented, whereas the existence of a Northern Hemisphere (NH) mode, herein referred to as the Arctic Oscillation (AO), has only recently been recognized. Like the SH mode, the AO can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields. In this paper the structure and seasonality of the NH and SH modes are compared based on data from the National Centers for Environmental Prediction National Center for Atmospheric Research reanalysis and supplementary datasets. The structures of the NH and SH annular modes are shown to be remarkably similar, not only in the zonally averaged geopotential height and zonal wind fields, but in the mean meridional circulations as well. Both exist year-round in the troposphere, but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction: midwinter in the NH and late spring in the SH. During these  active seasons,   the annular modes modulate the strength of the Lagrangian mean circulation in the lower stratosphere, total column ozone and tropopause height over mid- and high latitudes, and the strength of the trade winds of their respective hemispheres. The NH mode also contains an embedded planetary wave signature with expressions in surface air temperature, precipitation, total column ozone, and tropopause height. It is argued that the horizontal temperature advection by the perturbed zonal-mean zonal wind field in the lower troposphere is instrumental in forcing this pattern. A companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades.
    AO, AAO

36. [Thompson et al. 2000]
    The authors exploit the remarkable similarity between recent climate trends and the structure of the  annular modes   in the month-to-month variability (as described in a companion paper) to partition the trends into components linearly congruent with and linearly independent of the annular modes. The index of the Northern Hemisphere (NH) annular mode, referred to as the Arctic Oscillation (AO), has exhibited a trend toward the high index polarity over the past few decades. The largest and most significant trends are observed during the  active season   for stratospheric planetary wave mean flow interaction, January  March (JFM), when fluctuations in the AO amplify with height into the lower stratosphere. For the periods of record considered, virtually all of the JFM geopotential height falls over the polar cap region and the strengthening of the subpolar westerlies from the surface to the lower stratosphere, ;50% of the JFM warming over the Eurasian continent, ;30% of the JFM warming over the NH as a whole, ;40% of the JFM stratospheric cooling over the polar cap region, and ;40% of the March total column ozone losses poleward of 408N are linearly congruent with month-to-month variations in the AO index. Summertime sea level pressure falls over the Arctic basin are suggestive of a year-round drift toward the positive polarity of the AO, but the evidence is less conclusive. Owing to the photochemical memory inherent in the ozone distribution, roughly half the ozone depletion during the NH summer months is linearly dependent on AO-related ozone losses incurred during the previous active season. Lower-tropospheric geopotential height falls over the Antarctic polar cap region are indicative of a drift toward the high index polarity of the Southern Hemisphere (SH) annular mode with no apparent seasonality. In contrast, the trend toward a cooling and strengthening of the SH stratospheric polar vortex peaks sharply during the stratosphere s relatively short active season centered in November. The most pronounced SH ozone losses have occurred in September October, one or two months prior to this active season. In both hemispheres, positive feedbacks involving ozone destruction, cooling, and a weakening of the wave-driven meridional circulation may be contributing to a delayed breakdown of the polar vortex and enhanced ozone losses during spring.
    AO, AAO

37. [Wahab and Hasanean 2000]
    Relationship between longwave radiation and planetary albedo at the surface and top of the atmosphere.
    Lonw wave, albedo, satellite

38. [Zheng et al. 2000]
    Based only on monthly mean data, an analysis of variance method is proposed for decomposing the interannual atmospheric variability in seasonal-mean time series into components related to weather noise and to slowly varying boundary forcing and low-frequency internal dynamics. The potential predictability is then defined as the fraction of the total interannual variance accounted for by the latter two components. A study using synthetic data showed that the method proposed here is comparable in performance to conventional methods requiring daily data. The technique was applied to gridded global data of monthly surface temperature, 500-hPa height, and 300- hPa wind in order to examine the geographical and seasonal dependencies of their potential predictability. For all the variables, the highest potential predictability tends to be found in the Tropics, where seasonal anomalies in the atmosphere are strongly coupled with the underlying sea surface temperature anomalies and the weather noise component is relatively weak. In contrast, the predictability is generally low over the extratropics. Surface temperature, however, exhibits relatively high predictability over the subtropical and midlatitude oceans, par-ticularly over the midlatitude North Pacific in winter, where the El NinÜo Southern Oscillation events exert strong influences through atmospheric teleconnection. These results appear physically reasonable and consistent with our current understanding based on previous observational and model-based analyses.
    Potential predictability, intraseasonal, interannual variance.

39. [Werner et al. 2000]
    Borehole and isotope temperatures in Greenland. Understanding differences with a model study.
    Climate change, paleo simulations, Greenland

40. [Zorita and González-Rouco 2000]
    Different AOGCMS simulate different response of the AO to GHG forcing. When the AO sighnal is filtered the resulting temperature change is in more agreement for the ECHAM and Hadley model
    AO, climate forcing, GHG, models.