从全球变化看当前我国气候和环境问题

近100年来全球温度平均增长0.5℃这一数值可能偏大。一些气候模拟将其作为均由温室效应引起据此计算的未来增温值可能偏高。本世纪内自然因素对全球温度的影响是显而易见的。历史上多种时间尺度的温暖时代,都是自然灾害相对减少和人类文明大发展的时期。气候变冷时期才是全球性干旱沙漠化和各种严重自然灾害的群发时期。自然因子预示公元2020年前仍有变冷的可能。未来气候变暖,其后果可能是既有弊(导致海平面升高)又有利(利于农业发展等)。

THE PRESENT CLIMATIC AND ENVIRONMENTAL PROBLEMS SEEN FROM THE GLOBAL CHANGE

For the benefit of discriminating the influence of greenhouse effect to the global climateand their environmental problems,this paper discusses the characteristics of global climaticchanges during the historical period by many time scales from the view of the global changes,and also looks forward to the trend of future changes.(1) It is generally recognized that the global temperature has increased 0.5℃ on averageduring the past more than 100 years.This paper points out that this value may be higher thanthe actual.It is so because before 1900 the data were mainly from the middle latitudes whichmade the global temperature possibly lower;and in the last several decades of years,the heatisland effect in urban districts may be made the present temperature higher.This paper pointsout that the global temperature in the present century has about the same synchronous changeas the earth rotation speed,volcanic eruptions,global dryness and desertization,the frequencyof ElNi(?)o,global earthquakes of Ms.8 etc.,and it is quite clear that the nature factors have effect on global temperature.At present,in many numerical simulations,the temperature in-crease 0.5℃ during last 100 years is taken as the result of the greenhouse effect,and is usedto calculated the future climate change.This can bias the calculated result to the higher.(2) In the present 1000 years,the climate change in China and North Hemisphere hasquasi-periodic change every 140—180 years,which is related with the moment effect of PlanetarySynod.According to this,we may regard the period from 1960s to about 2020 A.D.as the pe-riod of temperature dropping and relatively frequent nature calamities.Up to now,a lot ofserious calamities have taken place frequently,and the dropping of temperature in 1960s-1970s was not yet enough.But,because this period doesn't end now,it is difficult to deter-mine the extent of the greenhouse effect at present.(3) Differing from other climatic model's result,this paper points out that there alwaysappeared global dryness and desertization and other kinds of synchronous phenomena of se-rious natural calamities during the cold climatic intervals in the historical periods and geologi-cal periods of various time scales.In the period of human civilization the climate always be-comes warmer and is accompanied by relatively fewer natural calamities.This has been shownboth in the “Climatic Optimum” at 6000 a B.P.and the “Little Climatic Optimum” in theMiddle Ages.(4) From the nature factors,we can see that the present climate is in the stage turningwarm on the time scale of thousand years and turning cold on that of hundred years.We ex-pect that there still has the possibility of turning cold before 2020 A.D.,and becoming com-paratively warm in the middle and the last of next century,during which it may be 1℃ higher.than today.If the greenhouse gasses is continually increasing,it will obviously effect the cli-mate.Its result may be both advantageous and disadvantageous.The warmer climate willcause the sea level rising,which will in turn imperil the coastal low-lying areas (especially inits economic developing areas) and will benefit the agriculture in arid and semi-arid regionson the edge of summer monsoon in China and other countries.