Long-term Temperature Trends Research Articles

Temperature and precipitation variations in Norway 1900-1994 and their links to atmospheric circulation

The main aim of the present study was to identify to what degree decadal scale variability and long-term trends in temperature and precipitation in Norway can be attributed to variations in the dominating atmospheric circulation patterns. Empirical models were developed and tested on monthly series of temperature and precipitation in different regions in Norway. The monthly mean sea level pressure (SLP) field over the northern North Atlantic and northern Europe was used as a predictor. Principal components (PCs) deduced from this field were used as a basis for stepwise multiple regression analysis. The downscaling models were developed using 1925–1969 as a training period, while 1900–1924 and 1970–1994 were used as validation periods. Model testing revealed that the temperature variability during 1970–1994 in most cases was better simulated than the variability during 1900–1924. The models reproduced most of the observed trends and decadal scale variability from 1940 to present. They also reproduced the precipitation trends in western Norway before 1940. However, the temperature increase observed over all the country in 1900–1940 was not reproduced. Nor was the increased winter precipitation in southeastern Norway during the same period. It is concluded that the temperature and precipitation changes observed in Norway during the last 40 years can mainly be attributed to variations in the SLP field. Variations in the precipitation conditions in the eastern parts of the country, and in temperature all over the country, during 1900–1940 are probably connected to changes in external forcings and/or atmosphere–ocean interactions. Copyright © 2000 Royal Meteorological Society

Trends in the characteristics of the annual and semiannual variations observed in the radio wave absorption in the lower ionosphere

Abstract. The continuous increase in concentration of greenhouse gases in the atmosphere is expected to cool higher levels of the atmosphere. There is some direct and indirect experimental evidence of long-term trends in temperature and other parameters in the mesosphere and lower thermosphere (MLT). Here we look for long-term trends in the annual and semiannual variations of the radio wave absorption in the lower ionosphere, which corresponds to the MLT region heights. Data from central and southeastern Europe are used. A consistent tendency to a positive trend in the amplitude of the semiannual wave appears to be observed. The reality of a similar tendency in the amplitude of the annual wave is questionable in the sense that the trend in the amplitude of the annual wave is probably induced by the trend in the yearly average values of absorption. The phases of both the annual and semiannual waves display a forward tendency, i.e. shift to an earlier time in the year. A tentative interpretation of these results in terms of changes of the seasonal variation of temperature and wind at MLT heights does not contradict the trends observed in those parameters.Key words. Ionosphere (ionosphere – atmosphere interactions; mid-latitude ionosphere) · Meteorology and atmospheric dynamics (middle atmosphere dynamics)

A Rare Long Record of Deep Soil Temperatures Defines Temporal Temperature Changes and an Urban Heat Island

A long-term set of deep soil temperature data collected over a 64-year period beginning in 1889 in a rural Illinois area provide a rare opportunity to assess the natural shifts in temperatures in a pristine environment without any urban or instrument bias. Temperatures from 1901 to 1951 increased 0.4 °C, and this was 0.2 °C less than nearby values from two high quality surface temperature data sets that supposedly are without any influence of urban heat islands, shifts in station locations or instrumentation, or other changes with time. Comparison of the soil values with surface air temperatures from a nearby weather station in a growing university community revealed a heat island effect of 0.6 °C. This value is larger than the adjustment based on population that has been recommended to eliminate the urban bias in long-term temperature trends in the U.S. Collectively, the results suggest that additional efforts may be needed to eliminate the urban influence on air temperatures, beyond techniques that simply use population as the basis. Population is only an approximation of urban factors affecting surface temperatures, and the heat island influences inherent in the values from weather stations in smaller communities which have been used as control, or data assumed to be unaffected by their urban environment in the adjustment procedures, have not been adequately accounted for.

A multicentury stable isotope record from a New Caledonia coral: Interannual and decadal sea surface temperature variability in the southwest Pacific since 1657 A.D

A 335 year stable isotope record from a New Caledonia coral (22°S, 166°E) helps fill a large gap in historical climate reconstructions. Although the long‐term coral δ18O‐based sea surface temperature (SST) trend is one of warming, there are notable decadal fluctuations, especially in the early 18th and early 19th centuries. Mean annual SSTs between 1658 and 1900 are estimated to be ∼0.3°C lower than the 20th century average, with interdecadal excursions of 0.5°–0.8°C. Time series analyses of the coral isotope record reveals significant concentrations of variance in the El Niño band; an inderdecadal spectral peak is present, but its robustness requires additional statistical evaluation. A secular but irregular decrease in coral δ13C values begins in the mid‐1800s and may reflect the anthropogenic perturbation of the carbon reservoir. These and other results indicate that the New Caledonia coral isotope record is a valuable source of information on southwest Pacific climate history.

Long-term trends in precipitation and temperature in the Norwegian Arctic: can they be explained by changes in atmospheric circulation patterns?

Observations from the Norwegian Arctic show positive trends in annual mean temperatures from 1912 to the 1930s and from the 1960s to 1996. Between these periods there was a negative trend, and there is no statistically significant trend in the record as a whole. The present temperature is approximately the same as in the 1920s, and lower than during the 1930s and 1950s. Spring is the only season which shows a statistically significant warming from 1912 to 1996. Annual precipitation, on the other hand, has increased in the Norwegian Arctic. At Spitsbergen the measurements show a statistically significant increase in annual and in spring, summer and autumn precipitation. Monthly values of mean sea level pressure of 4 grid points were used to develop models for monthly mean temperature and monthly precipitation at Spitsbergen. During the period 1912 to 1993 the temperature model accounts for 30 to 45% of the variance in the seasonal mean temperatures. The correlation between observed and modelled values is at a minimum in the summer and at a maximum in the autumn. The precipitation model accounts for 15 to 35% of the variance in seasonal precipitation sums. The correlation between observed and modelled values is lowest in winter, when the problems with drifting and blowing snow are greatest. Even though the observed and modelled seasonal values in most cases are better correlated for temperature than for precipitation, the precipitation model accounts for more of the decadal scale variability and long-term trends. The precipitation model reproduces the observed positive precipitation trends on both a seasonal and annual basis. Concerning decadal scale variability, most of the main observed features are also modelled satisfactorily. It is concluded that the major observed features concerning decadal scale variability and trends in precipitation at Spitsbergen are connected to variability in the atmospheric circulation pattern. The temperature model reproduces reasonably well the observed positive trend during the last 3 decades of the series. The very low temperature before 1920 and the high values in the 1930s and the 1950s, on the other hand, are not modelled satisfactorily. Thus, while the temperature increase of the later decades may mainly be explained as a result of changes in advection, the temperature increases in the Norwegian Arctic from the beginning of the measurements to the 1930s cannot be explained in this way.

TEMPERATURE VARIATIONS IN SPAIN SINCE 1901: A PRELIMINARY ANALYSIS

The long-term temperature trends since 1901 at ten meteorological stations on the Iberian Peninsula and one in the Canary Islands are analysed. These trends are identified by applying the Mann–Kendall trend test to the series of maximum and minimum temperatures, the variability of both, and the diurnal temperature range. A multidimensional scaling analysis is used to produce an automatic grouped systemization of all trends.The results appear to confirm the hypothesis of a local regionalization of the more global influences, yielding three types of regional trends in temperature variations since 1901: (i) less extreme in the north and north-west; (ii) more extreme conditions in the south-east and centre-east; and (iii) an overall increase in the south-west.

Long‐term temperature trends in the middle and upper atmosphere

We analyse data from weekly rocket temperature soundings up to 75 km carried out since mid‐1960s at polar (Heiss Island, 80.6°N and Molodezhnaya, 67.7°S), temperate (Volgograd, 48.7°N and Balkhash, 46.8°N) and tropical (Thumba, 8.5°N) latitudes. All records show significant cooling which is of the order of a few degrees K at 30–40 km, 10 K at 50 km and 20 K at 60–70 km. In the mesosphere the temperature trends are estimated from the hydroxyl rotational temperature records which start in 1957 at Zvenigorod (55.7°N) and Abastumani (41.8°N). These are related to the mesopause at 87 km and also show a cooling of about 30 K during the time. The cooling is qualitatively consistent with increasing concentration of greenhouse gases but may also reflect the changing chemistry of stratosphere and mesosphere, which is clearly seen in increasing emission intensities of hydroxyl during the last decades. Therefore the stratosphere and mesosphere may be regions with the strongest signals of global change.

Long-Term Winter Temperature Trends in the Southeastern United States

This study examines maximum and minimum temperatures in the southeastern United States during the winter months, 1910-1987. Our goal is to understand regional winter temperature trends in the context of global temperature and circulation patterns. To this end, we identify regional winter temperature patterns, relate them to continental-scale upper-air flow, and measure the relationship between mean temperature and interannual temperature variability at different spatial scales. At a regional level, we find a decrease in both maximum (1.06° C) and minimum (1.63° C) winter temperatures during the study period. All but 18 of the 156 stations investigated experienced a maximum winter temperature decrease, but these trends are significant (α = 0.01) at only 36 stations. Minimum winter temperature dropped at all except 14 stations, with decreases significant (α = 0.01) at 80 stations. While there is some correlation with anomalous upper-air circulation during individual months, no significant relationship was found between mean polar or hemispheric winter temperature and interannual variability in the region. This finding suggests that unusually cool southeastern winters frequently are caused by regional circulation anomalies that are not necessarily found at the hemispheric or global scale.

Temperature rising trends at Japanese cities during the last hundred years and their relationships with population, population increasing rates and daily temperature ranges.

Long-term temperature trends at 60 stations in Japan were evaluated by using monthly data during 1891-1992. The polynomial trends of minimum and maximum temperature were obtained with a least-squares method which included discontinuous changes due to site changes. The minimum temperature (Tmin) is found to show a rising trend with an average rate of about 2-5°C/(100 years) at large cities and about 1°C/(100 years) at medium-sized ones. The rising rate (T↑min) tends to be higher after World War II than before, but some cities in Hokkaido show exceptionally high rising trends of Tmin in the early part of the analysis period. Changes in maximum temperature (Tmax) are smaller, although a weak rising trend before World War II is found for many cities. The dependence of the temperature rising rate on the city size (population of cities or towns) was examined. It is found that T↑min is positively correlated with population parameters with only slight differences in correlation coefficients according to their functional forms (the logarithm and low powers). There is also a weak correlation between the rising rate of maximum temperature (T↑max) and the population parameters. A similar analysis was made for the increasing rate of the population parameters. There is a positive correlation between T↑min and the net increasing rate of the population adjusted to the present area of the city. On the other hand, there is little correlation between T↑min with the nominal increasing rate of population without adjustment for changes in the area of the city. Analysis was also made about the relationship between T↑min and the daily temperature range (R), which was regarded as a measure of the intensity of nighttime cooling. It is shown that T↑min has a positive correlation of 0.3-0.5 with R in old times, such as that in the 1910's, but is hardly correlated with R in recent years.

Long-Term Temperature Trends of the Hudson River: A Study of the Historical Data

Water temperature data from the Hudson River at Poughkeepsie from 1908 to the present were acquired. This long-term data set contains (with a few gaps) daily water temperatures at a constant location for the 82-yr period. We hypothesized that water temperatures, because of the dampened variability as compared to air temperatures, would provide a useful record of long-term temperature change. The data were analyzed for statistically significant trends, both annually and monthly for long-term and 10-yr blocks; both warming and cooling trends within all categories were found. The longest significant trend was a 0.12°C per decade increase from about 1920 to 1990. This increase, which was statistically significant for both simple regression and time-series analysis, is within the limits of the suggested rates of change on the global scale. On the other hand, there was no significant trend from the beginning of the record (1908) to the present, due to an apparent dramatic cooling from 1908 to about 1920.

Secular trends in high northern latitude temperature reconstructions based on tree rings

Boreal tree-ring records from high latitude North America, Scandinavia and Russia provide baseline data reflecting long-term trends in Arctic annual temperature. Reconstructions from 1682–1968 indicate the latter part and termination of the Little Ice Age and that the northern regions are now warmer by comparison. The resulting high-resolution, extended temperature time series allows examination of underlying causes of climatic change not possible using only the instrumental record. The recent recorded data for the Arctic show recovery from the cooling in the 1950's–1960's. The overall evaluation confirms that the high northern latitudes are now in an anomalously warm state relative to the past three centuries.

Reconstruction of Mass Balance Variations for Franz Josef Glacier, New Zealand, 1913 to 1989

A model of mass balance is constructed for the Franz Josef Glacier on the west coast of New Zealand. It uses daily data from a nearby, but short-record climate station. The model is extended back to 1913 by creating hybrid climate data from a long-record, but more distant, climate station. Its monthly data provide long-term temperature and precipitation trends, and daily fluctuations are simulated using a stochastic approach that is tuned to the characteristics of the short-record station. The glacier model provides estimates of equilibrium-line altitudes which are in reasonable agreement with those observed, and variations of cumulative mass balance that correspond with patterns of advance and retreat of the glacier terminus.

Urban bias influences on long-term California air temperature trends

An analysis of 80-year shelter level temperature records at 112 California sites has been carried out. Results show that sea surface temperature (SST) and urban heat island effects influence the magnitude of the observed warming trend in the overall data set. These effects, however, are masked by averaging all temperature records together. While a warming trend existed in the overall data set, areas with such trends generally corresponded to areas containing the state's major population centers. Warming trend magnitude also increased with county population size, and 20 small inland towns and rural areas actually showed cooling trends. SST trends over the last 40 years showed cooling in mid-ocean areas and an anomalous warming at coastal sites. The warming was associated with a decline in the normal frequency of cold water upwelling in the coastal area. SST warming was found to be highly correlated with the warming of shelter level temperatures at coastal land observation sites.

地球温暖化の実態

Observed long-term trends of the surface air temperature are treated, comparing with the results of numercal experiment for increase of greenhouse gases. Global mean of the marine surface air temperature, which is not suffered from the local effect of urbanization, is estimated from 1900 to 1986 using COADS . Linear regression of the annual mean temperature gives a trend of about + 0.32°C/86 years, that is consistent with the results of numerical experiment by upwelling-diffusion climate model. After the 1960s with remarkable increase of carbon dioxide, significant warming is seen in Southern Hemisphere while no appreciable warming for Northern Hemisphre. This interhemispherical asymmetry of the temperature trend is opposite to the results of numerical simulation by atmosphere-ocean coupled model . This discrepancy between observation and numerical simulation should be possibly dissolved by taking account of the effect of sulphate aerosols on albedo for insolation. In the northernmost zone of the Atlantic Ocean, significant cooling appears after the 1960s together with noticeable decrease of salinity and temperature of the water in the surface layer. These facts suggest some variation of the thermohaline circulation.

Past Temperature Record From The Analysis of Melt Features In The Dye 3, Greenland, Ice Core

The layered sequences of melt features preserved in inland polar ice sheets provide valuable proxy data on past variations in summer temperature. A continuous detailed light-table examination was made on the 2037 m-deep Dye 3 ice core immediately after core recovery. Melt features are products of high air temperatures or solar insolation which occur only at or near the snow surface during summer months. A correlation is made between these features and the extent and intensity of summer temperatures. Care must be exercised to identify and distinguish between all mm-thick radiation crusts and wind crusts contained in the record. The absence or presence of these discrete features serve respectively as indicators of total summer cloud cover and the extent of winter storm activity although they are difficult to differentiate from only light-table observations. In this analysis both thin radiation crusts and wind crusts are not in themselves significant indicators of long-term temperature trends, but may serve as incipient subsurface horizons or barrier crusts for the formation of thicker ice melt features caused by downward melt percolation during elevated surface temperature conditions.More than 10 000 individual melt features, including ice layers, ice lenses and ice wedges (but excluding ice glands) were measured down to a depth of 1278 m; below this depth transformation of air bubbles to transparent air hydrate inclusions occurs (Shoji and Langway, 1987) and the megascopic melt features become obscure. The melt-feature data extends back to 1883 B.c. or approximately 3900 years B.P., based on the accurate time scale of continuous δ18O measurements (Dansgaard and others, 1985) For the entire core profile investigated the annual melt percentage is 5.7. Individual melt features range in thickness from 1 mm to 100 mm. A mean value for melt-feature thickness was calculated for continuous 30-year time intervals to consider the general long-term summer temperature trends with corrections made for progressive annual accumulation layer thinning due to ice flow.Since the AMP parameter includes noise from radiation and wind crusts it appears that the simple average of melt-feature thickness per longer time-units is a better indication of air temperature paleodata. The average melt-feature thickness is 1.2 cm. The complete curve obtained shows a higher thickness value of about 1.5 cm for the period 1800 B.C. to 1300 B.C. A lower, almost constant thickness value of about 1cm is shown for the period 1000 B.c. to 1800 A.D., with a slight reduction in thickness recorded around 200 B.C., 400 A.D. and 1600 A.D. These long-term trends are coherent with those recorded in the δ18O profile for the same ice core.

Past Temperature Record From The Analysis of Melt Features In The Dye 3, Greenland, Ice Core

The layered sequences of melt features preserved in inland polar ice sheets provide valuable proxy data on past variations in summer temperature. A continuous detailed light-table examination was made on the 2037 m-deep Dye 3 ice core immediately after core recovery. Melt features are products of high air temperatures or solar insolation which occur only at or near the snow surface during summer months. A correlation is made between these features and the extent and intensity of summer temperatures. Care must be exercised to identify and distinguish between all mm-thick radiation crusts and wind crusts contained in the record. The absence or presence of these discrete features serve respectively as indicators of total summer cloud cover and the extent of winter storm activity although they are difficult to differentiate from only light-table observations. In this analysis both thin radiation crusts and wind crusts are not in themselves significant indicators of long-term temperature trends, but may serve as incipient subsurface horizons or barrier crusts for the formation of thicker ice melt features caused by downward melt percolation during elevated surface temperature conditions. More than 10 000 individual melt features, including ice layers, ice lenses and ice wedges (but excluding ice glands) were measured down to a depth of 1278 m; below this depth transformation of air bubbles to transparent air hydrate inclusions occurs (Shoji and Langway, 1987) and the megascopic melt features become obscure. The melt-feature data extends back to 1883 B.c. or approximately 3900 years B.P., based on the accurate time scale of continuous δ18O measurements (Dansgaard and others, 1985) For the entire core profile investigated the annual melt percentage is 5.7. Individual melt features range in thickness from 1 mm to 100 mm. A mean value for melt-feature thickness was calculated for continuous 30-year time intervals to consider the general long-term summer temperature trends with corrections made for progressive annual accumulation layer thinning due to ice flow. Since the AMP parameter includes noise from radiation and wind crusts it appears that the simple average of melt-feature thickness per longer time-units is a better indication of air temperature paleodata. The average melt-feature thickness is 1.2 cm. The complete curve obtained shows a higher thickness value of about 1.5 cm for the period 1800 B.C. to 1300 B.C. A lower, almost constant thickness value of about 1cm is shown for the period 1000 B.c. to 1800 A.D., with a slight reduction in thickness recorded around 200 B.C., 400 A.D. and 1600 A.D. These long-term trends are coherent with those recorded in the δ18O profile for the same ice core.

Antarctic and Southern Ocean Sea-Ice and Climate Trends

A computer-based climate monitoring project is described. Data sets include monthly and annual mean surface temperatures and pressures for occupied stations in Antarctica, the Southern Ocean and South Pacific Ocean; and monthly Antarctic sea-ice extent at each 10° of longitude.Simple statistical analyses of the data sets reveal a mean warming of ~0.15°C (10 a)−1 since the mid 1950s for Antarctic coastal stations and of ~0.04°C (10 a)−1 since the mid 1940s for the ocean stations. The sea-ice record from 1973 to 1988 reveals that the average northern ice limit has decreased at ~0.23°lat. (10 a)−1. Despite apparently compatible long-term trends of temperature and sea-ice extent, annual fluctuations of temperature and ice extent are highly variable and are not well correlated.

Antarctic and Southern Ocean Sea-Ice and Climate Trends

A computer-based climate monitoring project is described. Data sets include monthly and annual mean surface temperatures and pressures for occupied stations in Antarctica, the Southern Ocean and South Pacific Ocean; and monthly Antarctic sea-ice extent at each 10° of longitude. Simple statistical analyses of the data sets reveal a mean warming of ~0.15°C (10 a)−1 since the mid 1950s for Antarctic coastal stations and of ~0.04°C (10 a)−1 since the mid 1940s for the ocean stations. The sea-ice record from 1973 to 1988 reveals that the average northern ice limit has decreased at ~0.23°lat. (10 a)−1. Despite apparently compatible long-term trends of temperature and sea-ice extent, annual fluctuations of temperature and ice extent are highly variable and are not well correlated.

Greenhouse warming or Little Ice Age demise: A critical problem for climatology

A comparative analysis of long-term (several-hundred-year) temperature and carbon dioxide (CO2) trends suggests that the global warming of the past century is not due to the widely accepted CO2 greenhouse effect but rather to the natural recovery of the Earth from the global chill of the Little Ice Age, which was both initiated and ended by some unrelated phenomenon, the latter expression of which is the very warming generally attributed to the CO2 increase of the past century.

Characteristics and frequency of reversals in mean sea level pressure in the North Atlantic sector and their relationship to long-term temperature trends : Moses, T., G.N. Kiladis, H.F. Diaz and R.G. Barry, 1987. J. Climatol., 7(1):13–30

Characteristics and frequency of reversals in mean sea level pressure in the North Atlantic sector and their relationship to long-term temperature trends : Moses, T., G.N. Kiladis, H.F. Diaz and R.G. Barry, 1987. J. Climatol., 7(1):13–30