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anthropogenically

K. Ya. Kondratyev. Key aspects of global climate change. ?

     In context of the results of the World Climate Change Conference which took place in Moscow during the time period September 29 October 3 (WCCC 2003) an analysis has been made of key issues

    of contemporary global climate change. The principal attention has been paid to the discussion of uncertainties of existing observation data and numerical modelling results. As fas as numerical modelling is concerned, a necessity has been emphasized of an analysis of present day models from the viewpoint of their ability to simulate real climate change which results from nonlinear interactions between numerous climatic system‟s components taking also into account potential contributions of cosmic factors such as

    solar activity.

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    K. Ya. KONDRATYEV

    KEY ASPECTS OF GLOBAL CLIMATE CHANGE

    INTRODUCTION

    An unprecedented increase of interest in the problems of climate observed during the last decades (this refers, in particular, to mass media) has stimulated the working out of both scientific and applied developments, which provided a considerable advance in understanding the causes of present climate changes, the laws of paleoclimate, and in substantiation of scenarios of possible changes of climate in future (the matter concerns with scenarios and not with predictions whose possibilities should be assessed as doubtful) [1-146]. Unfortunately, the growing interest in the problems of climate is partly explained by the important role of various speculative exaggerations and apocalyptic predictions (e.g., complete melting of the arctic sea ice in the first half of this century) due to which the problems of climate change formulated as a concept of anthropogenic global warming have become a focus of geopolicy. It is a paradox that Presidents and Prime Ministers of various countries discuss whether the Kyoto Protocol (KP) should be considered as a scientifically justified document. The confusion of the situation is determined, in particular, by lack of sufficiently clear and agreed-upon terminology. Leaving out of account a very complicated situation with the definition of the notion of climate (this subject needs a separate discussion), one should remember, for instance, that in the UN FCCC the notion of climate change was defined as being anthropogenically induced. One of the main unsolved problems consists in the absence of convincing quantitative estimates of the contribution of anthropogenic factors into the formation of global climate (there is no doubt, however, that anthropogenic forcings on climate do exist). Some international documents containing analyses of the present ideas of climate use the prevalent notion of consensus with respect to scientific conclusions drawn in these documents, as if the development of science was determined not by different views and respective discussions but by a general agreement (and even voting) on some concrete problems. Apart from definitions, of importance is the problem of uncertain conceptual estimates concerning various aspects of climate problems. This refers, in particular, to the main conclusion in the summary of the IPCC-2001 report [55]: “… An increasing body of observations gives a

    collective picture of a warming world and most of the observed warming over the last fifty years is likely to have been due to human activities”.

    It is a pity that in the recent (2003) paper in the British newspaper “The Guardian” the former Chairman of IPCC WG-1 Professor J. Houghton compared the threat of anthropogenic climate changes with weapons of mass destruction and accused the USA of their refusal to support the concept of global warming and KP, which, in his opinion, is the basic cause of this threat. No matter how paradoxical it may be, such a statement has been made against a background of an increasing understanding of imperfection of the present global climate models and the absence of their adequate verification, which makes the predictions on the basis of numerical modelling not more than conditional scenarios [61-63, 65-66, 68-69, 72-80, 82, 120, 122]. As for the USA, huge efforts of this country to support climate studies

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    should be backed. These efforts consist in special emphasis on the improvement of the observing systems [28] and on developments in the field of climate problems in general [126,128]. The US expenses on these problems planned for 2004 reach 4.5 billion dollars.

    The statement published on behalf of the intergovernmental group G-8 on 27 July 2003 [117] emphasizes that in the years to come, efforts will be undertaken in three directions: 1) coordination of strategies of global observations; 2) provision of the pure, stable and efficient use of energy; 3) provision of stable agricultural production and biodiversity.

    In the context of climate problems, uncertainty has become a key notion [84]. Of course, there is

    nothing new in that the present views of global climate and the causes of its changes are very uncertain. However, there are principal differences in estimates of the scales of such uncertainties. The basic conclusions of the IPCC-2001 Report are that these uncertainties are not critically important. This has been mentioned, in particular, in the summary of the report in the form of the following conclusion: “There is new and stronger evidence that most of the warming observed over the last fifty years is

    attributable to human activities”.

    The Earth‟s climate system has markedly changed during the time period from the industrial revolution, with some changes having been of anthropogenic origin. The climate change consequences determine a serious challenge to people responsible for the ecological policy, which determines an urgency of objective information on climate change, its impact and possible response to climate change. With this aim in view, the World Meteorological Organization (WMO) and the UN Environmental Programme organized in 1988 the Intergovernmental Panel on Climate Change. The IPCC incorporates three working groups (WG) whose spheres of responsibility include: 1) scientific aspects of climate and its change (WG-I), 2) effects on and adaptation to climate (WG-II), 3) analysis of possibilities to limit (restrain) climate changes (WG-III).

    During the last years the IPCC prepared three detailed reports (1990, 1996, 2001) as well as some special reports and technical papers. Griggs and Noguer [41] made a bried review of the first volume of the Third IPCC Report (TAR) prepared by WG-I for the period June 1998 January 2001 with the

    perticipation of 122 leading authors and 515 experts, each with their materials. Four hundred and twenty experts reviewed the first volume and 23 experts edited it. Besides, several hundred reviewers and representatives of many governments made additional remarks. With the participation of delegates from 99 countries and 50 scientists recommended by the leading authors, the final discussion of TAR was held in Shanghai on 17-20 January 2001. “Summary for decision-makers” was approved after a detailed

    discussion by 59 specialists.

    Analysis of the observation data contained in TAR has led to the conclusion about the presence of global climate change. In this connection, the Report [55] gives a detailed review of the data of observations of the spatial-temporal variability of concentrations of various GHGs and aerosol in the atmosphere. An adequacy of numerical models has been discussed from the viewpoint of consideration of the climate-forming factors and usefulness of models to predict climate change in the future. The main conclusion about anthropogenic impacts on climate is that “there is new and stronger evidence that most

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    of the warming observed during the last 50 years has been determined by human activity”. According to

    stall prognostic estimates considered in TAR, during the 21 century both SAT increase and sea level rise

    should take place.

    When characterizing the IPCC data on the empirical diagnostics of climate, Folland et al. [32] drew attention to the uncertainty of definitions of some basic notions. According to the IPCC therminology, climate changes are statistically substantial variations of an average state or its variability, whose stability is preserved for long time periods (decades and longer). Climate changes can be of natural origin (connected both with internal processes and exteernal impacts) and (or) they can be determined by anthropogenic factors (changes in the atmospheric composition or land use). This definition differs from that suggested in the Framework Climate Change Convention (FCCC) where climate changes are only of anthropogenic origin in contrast to natural climate changes. In accordance with the IPCC therminology, climatic variability means variations of the average state and other statistical characteristics (dispersion, repeatability of extreme events, etc.) of climate on every temporal and spatial scale, beyond individual weather phenomena. The climate variability can be both of natural (due to internal processes and external forcings) and anthropogenic origin. These are internal variability and external variability. As Folland et al. [32] noted, seven key questions are most important for diagnostics of the observed changes and variability of climate: 1) how much significat is climate warming? 2) is the present warming significant? 3) how rapidly had the climate changed in the distant past? 4) have precipitation and atmospheric water content changed? 5) do changes of general circulation of the atmosphere and ocean take place? 6) have the climate variability and climate extremes changed? 7) are the observed trends internally coordinated?

    The observation data reliability plays the fyndamental role for the adequate empirical diagnostics of climate. However, information about numerous meteorological parameters, which is very important for documentation, detection and attribution of climate changes, is inadequate for reliable conclusions. This especially concerns the global trends of parameters (e.g., precipitation) which are characterized by a great regional variability.

    Folland et al. [32] answered the questions above. A comparison of the secular change of average global avrtage annual sea surface temperature (SST), land surface air temperature (LSAT) and nocturnal air temperature over the ocean (NMAT) for the period 1861-2000 revealed on the whole some similarity though the warming in the 1980s from LSAT data turned out to be stronger, and the NMAT data showed

    tha moderate cooling in the end of the 19 century, not demonstrated by SST data. The global trend of

    temperature can be cautiously interpreted as an equivalently linear warming over 140 years constituting

    ooo0.61C at a 95% confidence level with an uncertainty ?0.16C. Later on, in 1901 a warming by 0.57C

    otook place with an uncertainty ?0.17C. These estimates suggested the conclusion that beginning from the

    thoend of the 19 century, an average global warming by 0.6C took place with the interval of estimates

    ocorresponding to a 95% confidence level equal to 0.4-0.8C.

    thThe spatial structure of the temperature field in the 20 century was characterized by a

    comparatively uniform warming in the tropics, but a considerable variability in the extratropical latitudes. The warming between 1910 and 1945 was initially concentrated in the Northern Atlantic and the adjacent

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    regions. The Northern Htmisphere was characterized by a cooling between 1946 and 1975, while in the Southern Hemisphere some warming was observed in this period. The temperature rise during several last decades (1976-2000) turned out, on the whole, to be globally synchronous and was clearly manifested on the Northern Hemisphere continents in winter and in spring. In some Southern Hemisphere regions and in the Antarctic there was a small all-year-round cooling. A temperature decrease in the Northern Atlantic between 1960 and 1985 was later followed by an opposite trend. On the whole, the climate warming over the period of measurements was more uniform in the Southern Hemisphere than in the Northern Hemisphere. In many continental regions in the period 1950-1993 the temperature increased more rapidly at night than in the day time (this does not refer, however, to the coastal regions). The rate of temperature

    oincrease varied from 0.1 to 0.2C/10 years.

    According to the data of aerological observations, the air temperature in the lower and middle

    otroposphere was increasing after 1958 at a rate of 0.1C/10 years, but in the upper troposphere (after 1960)

    it pracically remained constant. A combined analysis of the aerological and satellite information has shown that in the period 1979-2000 the temperature trend in the lower troposphere was weak, whereas

    onear the land surface it turned out to be statistically significant and reached 0.16?0.06C/10 years. The

    statistically substantial trend of the difference between the Earth‟s surface and the lower troposphere

    oconstituted 0.13?0.06C/10 years, which differs from the data for the period 1958-1978, when the average

    oglobal temperature in the lower troposphere increased more rapidly (by 0.03C/10 years) than near the

    surface. Considerable differences between the temperature trends in the lower troposphere and near the surface are most likely real. So far, these differences cannot be convincingly explained. The climate

    thwarming in the Northern Hemisphere observed in the 20 century was the most substantial over the last

    1000 years [94]. Due to [32], the observation data do not permit to confirm the global scales of the warming in the Minor Ice Age and Middle Age periods. However, both these conclusions remain contradictory [97].

    Special attention has been paid to the discussion in the IPCC-2001 Report of possibility to predict future climate changes. The chaotic character of the atmospheric dynamics limits the long-term weather forecasts by one-two weeks and hinders the prefiction of a detailed climate change (e.g., it is impossible to predict precipitation in Great Britain for the winter of 2050). However, it is possible to consider climate projections, that is, to develop scenarios of probable climate changes due to continuing growth of GHGs concentrations in the atmosphere. Such scenarios may be useful for decision-makers in the field of ecological policy. The basic means to substantiate such scenarios are numerical climate models that simulate interactive processes in the climatic system “atmosphere-ocean-land surface-cryosphere-

    biosphere”. As Collins and Senior [26] noted, there are many such models, and in this respect a serious difficulty is connected with an almost unsoluble problen of choosing the best model. There remain only a possibility to compare the climate scenarios obtained using various models.

    According to the IPCC recommendations, four levels of projections reliability are considered: 1) from reliable to very probable (in this case there is an agreement between the results for most of the models); 2) very probable (an agreement of new projections obtained with the latest models; 3) probable

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    (new projections with an agreement for a small number of models); 4) restrictedly probable (model results are not certain but changes are physically possible). A principal difficulty in substantiation of projections consists in impossibility to unanimously predict the evolution of GHGs in the future, which determines a necessity to take into account a totality of various scenarios. The huge thermal inertia of the World Ocean dictates a possibility of delayed climatic impact of the GHGs concentrations which had already increased.

    Calculations of average annual average global SAT using the energy-balance climate model with various scenarios of the temporal variations of CO concentrations have led to SAT intervals in 2020, 2

    o2050, and 2100 to be 0.3-0.9, 0.7-2.6, and 1.4-5.8C, respectively. Due to the ocean thermal inertia, a

    odelayed warming should manifest itself within 0.1-0.2C/10 years (such a delay can take place during

    several decades).

    The following conclusions can be attributed to the category of projections of the highest reliability [26]: 1) the surface air warming should be accompanied by a tropospheric warming and stratospheric cooling (the latter is due to a decrease of the upward longwave radiation flux from the troposphere); 2) a faster warming on land compared to oceanic regions (as a result of the great thermal inertia of the ocean); a faster warming in the high-mountain regions (due to albedo feedbacks); 3) the aerosol-induced atmospheric cooling holds a SAT increase (new estimates suggest the conclusion about a weaker manifestation of the aerosol impact); 4) the presence of the warming minima in the North Atlantic and in the circumpolar regions of the oceans in the Southern Hemisphere due to mixing in the oceanic thickness; 5) a decrease of the snow and sea ice cover extent in the Northern Hemisphere; 6) an increase of the average global content of water vapour in the atmosphere, enhancement of precipitation and evaporation, as well as intensification of the global water cycle; 7) intensification (on the average) of precipitation in the tropical and high latitudes, but its attenuation in the sub-tropical latitudes; 8) an increase of precipitation intensity (more substantial than expected as a result of precipitation enhancement, on the average); 9) a summertime decrease of soil moisture in the middle regions of the continents due to intensified evaporation; 10) an intensification of the El Niño regime in the tropical Pacific with a stronger warming in the eastern regions than in the western ones, which is accompanied by an eastward shift of the precipitation zones; 11) an intensification of the interannual variability of the summer monsoon in the Northern Hemisphere; 12) a more frequent appearance of high temperature extrema but infrequent occurrence of temperature minima (with an increasing amplitude of the diurnal temperature course in many regions and with a greater enhancement of nocturnal temperature minima compared to the daytime maxima); 13) a higher reliability of conclusions about temperature changes compared to those about precipitation; 14) an attenuation of the thermohaline circulation (THC) that causes a decrease of the warming in the North Atlantic (the effect of the THC dynamics cannot however compensate for the warming in West Europe due to the growing concentration of GHGs); 15) the most intensive penetration of the warming into the ocean depth in high latitudes where the vertical mixing is most intensive.

    As for the estimates characterized by a lower level of reliability, of special interest is the conclusion (level 4) about the absence of common opinion with regard to changing frequency of storms in middle latitudes as well as changing frequency of occurrence and rate of tropical cyclones in conditions

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    of global warming. An important task of future developments consists in improving climate models aimed at (eventually) reaching the level of reliability that would enable one to predict climate changes.

    Allen [4] discussed basic conclusions contained in the “Summary for policy-makers” (SPM) of

    the Third IPCC Report and, first of all, the main conclusion: “There is new and stronger evidence that most of the warming observed during the last 50 years should be attributed to human activity”. This

    conclusion supplements the statement according to which “as follows from the present climate models, it

    is very unlikely that the warming taking place during the last 100 years was determined only by the internal variability” (“very unlikely” means that there is less than one chance of ten for an opposite statement to be well-founded).

    Naturally, the reality of such a statement depends on an adequate modelling of the observed climatic variability. Analysis of calculation results using six different models has shown that three of six models reproduce the climate variability on time scales from 10 to 50 years which agrees with the observation data. One more conclusion contained in SPM consists in that “reconstruction of data on climate for the last 1000 years shows that the present warming is unusual and it is unlikely that it can be of only natural origin” („unlikely” means that there is less than one chance of three for an opposite conclusion).

    This conclusion is supplemented with the following: “Numerical modelling of the response to

    only natural disturbing forcings … does not explain the warming that took place in the second half of the th20 century”. This conclusion is based on analysis of results of the numerical modelling of changes in the

    average global SAT during the last 50 years, from which it follows that a consideration of natural forcings (solar activity, volcanic eruptions) has demonstrated a climate cooling (mainly due to large-scale eruptions in 1982 and 1991), which enabled one to conclude that the impact of only natural climatic factors is unlikely. However, there remains only one chance of three that it was in this way: such a carefulness is connected with insufficient reliability based on indirect information on natural forcings in the past.

    Results of numerical modelling suggested the conclusion that “Most of the models which consider both GHGs and sulphate aerosols, agree with the data of observations for the last 50 years”. Model calculations cannot explain the pre-1940 climate warming with only anthropogenic factors taken into account, but they are quite adequate considering both natural and anthropogenic impacts (due to GHGs and sulphate aerosol). It was mentioned in SPM TAR that “these results … do not exclude

    possibilities of contributions of other forcings”. Therefore it is possible that a good agreement of the

    calculated and observed secular trends of SAT is partly determined by a random mutual compensation of uncertainties. An important illustration of inadequacy of the numerical modelling results is their difference with observations regarding temperature changes near the Earth‟s surface and in the free troposphere. If, according to models, the tropospheric temperature increases more rapidly than near the surface, the analysis of observation data for the period 1979-2000 reveals another situation: the temperature increase in the free troposphere is slower and probably is absent at all.

    Assessing the content of the IPCC-2000 Report, Griggs and Noguer [41] believe that this report

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    1. contains a most complete description of the present ideas about the known and unknown aspects

    of the climate system and the associated factors;

    2. is based on the knowledge of an international group of experts;

    3. is prepared based on the open and professional reviewing;

    4. is based on scientific publications.

    It is a pity, however, that neither of these statements can be persuasively substantiated. Therefore the IPCC-2000 Report has been strongly criticized in scientific literature (see, in particular, [1, 13-15, 21, 30-31, 58-59, 62-63, 65-66, 68-69, 75, 83, 86, 90, 120, 122, 134]). Now we shall discuss the most important critical comments expressed in ten questions raised by Professor A. N. Illarionov, Economic Advisor to the President of Russia, in his two talks at the WCCC (Moscow, 29 September 3 October,

    2003).

    Detailed answers to these questions were given by Professor B. Bolin, Chair emeritus of the IPCC. The problem consists, however, in that these answers are rather disputable. In this situation, additional comments are needed.

    1. TEN QUESTIONS RAISED BY A. ILLARIONOV.

    Speaking about the level of the present understanding of the laws of the present global climate, A. Illarionov raised the following ten questions:

    1. What were real levels of CO concentrations in the atmosphere between 1980 and 2000? 2

    Of course, in this case the talk is not simply about the data of observations of CO and other 2

    GHGs concentrations, which are well known (between 1980 and 2000 the CO concentration increased 2

    from 338 to 368 ppm) and by themselves they are not that important. The problem is different: in official IPCC documents the SAT increase observed during the last 2-3 decades is mainly attributed to the effect of the growing GHGs concentration (an anthropogenically induced enhancement of the atmospheric greenhouse effect). As has been pointed out in the publications mentioned above, there are no grounds for this conclusion. Unfortunately, the IPCC-2001 Report does not contain even references to relevant lbterature.

    2. What are parameters of the models of temperature anomalies? How were they determined?

    How can strong differences of the estimates of anthropogenic impacts on climate be

    explained?

    These questions mainly concern an assessment of adequacy of the numerical climate modelling. Since this question has been widely discussed in literature [31, 61, 64, 107], one should pay attention to

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    only one of the important conclusions of the IPCC-2001 Report, which establishes an agreement of the observed and calculated secular trend of the average annual average global SAT, when two opposite factors were taken into account: the anthropogenically induced warming due to the CO concentration 2

    growth (an enhancement of the greenhouse effect) and the cooling caused by purely scattering sulphate aerosol (this conclusion was also emphasized by Bolin [18]). The apparent truth is, however, that an agreement of observations and calculations is the result of an adjustment and, in fact, reflects the difference but not an agreement, which definitely cannot take place. Even from the viewpoint of consideration of only one climate-forming factor atmospheric aerosol the real situation is much more

    complicated than that considered in the models. The fact that aerosol is not only a scattering but also absorbing component of the atmosphere has long been established [55, 73-74, 76, 81-82], but has only recently been properly acknowledged. The present climate models are also inadequate for some other reasons [31, 61, 63, 72, 75, 80], which prompts one to consider them as only an initial stage of development of the numerical climate modelling. In this connection, there appears a conceptual problem of the ultimate possibilities of numerical modelling from the viewpoint of simulating the actual global climate dynamics. Therefore it is difficult to share the optimism of B. Bolin and his colleagues [18] that

    stprojections of climate for the 21 century were obtained using the “sophisticated models and are based on a well-defined totality of socio-economic suppositions with respect to the development of technologies and society”. This assessment is far from being realistic. For instance, while according to TAR, a doubled

    oCO concentration should entail an increase of SAT within 1.4-5.8C, Lindzen and Giannitsis [90] 2

    oobtained estimates less than 1C. About the same estimates were demostrated in the talk by Dymnikov et al. [127] given at the WCCC.

    3. Can we explain the temperature changes by CO accumulated in the atmosphere during the 2

    last 1000 years?

    An actual content of this question concerns the problem of “ice-hockey stick” raised by Mann et

    al. [93, 94] (this is the form of description of a comparatively smooth course of SAT until recently and an anthropogenic elevation of SAT in this century determined by calculations). It follows from the “stick”

    concept supported in TAR that: 1) there will be an unprecedented anthropogenically induced SAT increase (global warming); 2) the SAT increase observed during the last decades is unprecedented from the viewpoint of both its rate and amplitude. Since some ideas regarding an inadequacy of the present climate models have been mentioned above, we shall only cite the work by McIntyre and McKitrick [97], which illustrated the unsoundness of the second statement of those mentioned above: the SAT increase during the last 20-30 years is not unprecedented compared to changes that took place during the last 1000 years. Not less important principal fact connected with the work [97] consists in that it testifies (like some other similar studies) to a necessity of critical attitude to the data of empirical diagnostics of climate. In this connection, one should mention very important results of McKitrick [98] and Pichugin [106].

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    4. Can we explain the temperature changes by CO accumulated in the atmosphere during the 2

    last 140 years?

    5. Can we explain the temperature changes by anthropogenic emissions of CO? 2

    As has been mentioned above, answers to these questions can be found in the IPCC-2001 Report. The essense of these answers is that climate changes in the second half of the last century were mainly of anthropogenic origin. Lack of grounds for this conclusion has been stated above. Besides, as Ellsaesser [30] long ago and recently Morgan [75] rightly noted, the SAT increase was observed only during last 2-

    th3 decades of the 20 century.

    6. What are other factors explaining temperature changes? For instance, volcanic activity?

    Maybe, it should be considered in the models?

    Really, the main reason of the climate models‟ inadequacy consists in that they do not take into

    account a number of substantial climate-forming factors. The problem of atmospheric aerosol has been mentioned above. Only first steps have been made to consider biospheric dynamics as an interactive component of the climate system (the IPCC-2001 Report has completely ignored the concept of biotic regulation of the environment [79]. The fact is neglected that the climate system is open with respect to external cosmic forcings (this far-from-being-solved problem has been focused in a number of recent publications [10,,44, 64, 96, 118].

    From the viewpoint of climatic implications of volcanic eruptions, of great interest are data on the 1783-1784 Laki volcano eruption that took place in Iceland followed by an emission of about 122 Mt SO 2

    into the atmosphere, which were then transformed into the HSO aerosol haze hanging over the Northern 24

    Hemisphere for more than five months [129]. The erupted products were concentrated mainly in the 9-13-km layer: the upper troposphere and lower stratosphere got about 95 Mt SO whose transformation into 2

    HSO aerosol during the eastward transfer has led to the formation of about 200 Mt of aerosol. At long 24

    distances from the volcano, the volcanic aerosol deposited onto the surface in the regions of downward air fluxes in anticyclones.

    Thordarson and Self [129] have shown that the process of sedimentation involved about 175 Mt of the HSO aerosol. This caused a strong pollution (including the formation of “dry fog”) in Europe and 24

    in other regions in 1783.. The remaining 25 Mt of aerosol resided at the tropopause level for more than a year. The 1783 summer was characterized by unusual and extreme weather conditions, including the abnormally hot July in West Europe, apparently, due to persistent southern winds. The subsequent winter was one of the most severe winters observed in Europe and North America for the whole period of

    oobservations. In these regions a decrease of the average annual surface temperature reached about -1.3C

    and continued during 2-3 years. It was supposed in [129] that the volcanic aerosol considered has caused considerable changes of heat balance in the Arctic regions during two summer seasons which were the main mechanism for climate changes caused by volcanic eruption.

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