At its eighth session in March 1973 the JOC (1973) responded to Recommendation (79d) from the UN Conference in Stockholm, in which the view was expressed that WMO in cooperation with ICSU should:
continue to carry out the GARP, and if necessary establish new programmes to better understand the general circulation of the atmosphere and the causes of climate change and whether the causes are natural or the result of man's activities.
The JOC formulated a set of guiding principles for such work by the committee:
The two GARP objectives are strongly related to each other. For consistency with the philosophy which has been inherent within GARP, GARP climatic studies should concentrate on those aspects which lend themselves to physical-mathematical (numerical and analytical) model studies.
The accomplishment of the second objective should not be considered as implying that it will be possible to predict climate changes. It does, however, imply that we will be able to understand the mechanisms that are responsible for the climate fluctuations and to determine the nature of the change in climate caused by given external or internal stimuli (man-made or natural) to the atmosphere-ocean-earth system.
It was further decided at the eighth JOC session that an international study conference on the physical basis of climate and climate modelling should be organised. I was given the responsibility of organising this conference, which took place near Stockholm in mid-1974. This was an opportunity to involve key scientists, who had not yet taken an active part in the work of GARP, and thereby to widen the scientific basis for dealing with the climate issue.10
The study conference represented a major step forward towards formulating a global research programme leading to a much deeper understanding of the general circulation of the atmosphere and the oceans and thus the climate system. The stage for planning a GARP climate programme was set. The presentations and discussions also provided an overview of our knowledge, three years after the SMIC. A few new findings deserve particular attention (see JOC (1975)).
As already mentioned, in 1967 Manabe and Wetherald had deduced the expected change of the surface temperature due to a doubling of the atmospheric carbon dioxide concentration, using a simple model of the heat balance in a vertical column through the atmosphere. Now Manabe (1975) presented the results obtained by employing for the first time a three-dimensional model (general circulation model, GCM) of the atmosphere, thus taking into consideration geographical differences and indirect effects, for example those due to changes of the distribution of snow and ice. Other assumptions were the same as those made before by Manabe and Wetherald (1967). Manabe was, however, now able to reproduce for the first time the spatial distribution of the mean temperature in winter and summer without enhanced greenhouse gas concentrations quite well, which of course is required in the validation of any climate model. While Arrhenius had estimated the warming due to doubling of the atmospheric carbon dioxide concentration to be 5-6 °C and the one-dimensional model used by Manabe and Wetharald in 1967 had yielded a warming by merely about 2 °C, the new three-dimensional model showed an average global warming of about 3 °C. The higher value as compared with the result obtained by Manabe and Wetherald was primarily due to the feedback of a reduced snow cover in a warmer world and to accounting for the distribution of land and sea on earth. It is interesting to note that Manabe and Wetherald's results for climate sensitivity still hold today, although the range of uncertainty has now been assessed: the best estimate is now 1.5-4.5 ° C. This rather wide range depends on the uncertainty about a number of factors that are of relevance, in particular the interplay between the atmosphere and the oceans, reduction of snow cover in winter and also the difficulties in accounting for changes of cloud cover and cloud amount.
Lorenz (1975) gave a thoughtful and very important analysis of the concept of predictability, emphasising the difference between a sensitivity analysis as carried out by Manabe and the prediction of the gradual change of the climate as a result of increasing greenhouse gas concentrations. Charney (1975) pointed out the importance of secondary changes in the climate system, such as the reflectivity of the earth's surface and the availability of water in the soil, implicitly emphasising the need for considering the biological responses to physical changes of climate. This presentation, as well as a few others, indicated the necessity of putting physics, chemistry and biology on an equal footing in the exploration of future changes of the global climate due to human activities on earth. It was, however, quite some time before it became possible to pursue such complex studies adequately.
Although the report from this conference was important as a starting point for the GARP efforts with regard to climate change, the preparations for the FGGE were given highest priority in the work by JOC during the following few years. A second GARP climate study conference was held in 1978.11 The aim of this conference was to assess the climate models available at the time with regard to performance and sensitivity. This was important basic work, but the likelihood of human-induced climate changes was not dealt with specifically. The conference did, however, provide a basis for the further planning of a climate research programme, which really was the key task for the JOC.
Scientists outside the community of climatologists had begun to notice the increasing amounts of carbon dioxide in the atmosphere. Ecologists and geologists entered the scene. The ICSU Scientific Committee on Problems of the Environment (SCOPE) began to bring together the available knowledge about the biogeochemical cycles, i.e. the circulation of carbon, nitrogen, phosphorus and sulphur in the environment, and their interactions. The carbon cycle, which traced the pathways of the basic element of life, was the subject of a week-long workshop in Germany in March 1977 (Bolin et al., 1979). The analysis of the climate issue was broadened to give ecological and geological perspectives, which later turned out to be very important in the analyses of the carbon cycle. Although the creation of SCOPE by ICSU was an attempt to be at the service of society on environmental matters, politics did not play a part at the workshop. The outreach from the scientific community to society and politicians was still hesitant and unsatisfactory, although I did not really fully realise this myself. I remember, however, the increasing interest from the German Research Council (Deutsche Forschungsgemeinschaft) in being informed about this new development of environmental research in order to set the right priorities in the future.
A first world climate conference was organised by WMO and United Nations Environment Program (UNEP) in 1979. The bulk of the presentations concerned the physical basis for understanding the characteristics of the climate and its changes in the past and possible human-induced changes in the future. The conference was largely technical, but an agreement was reached to appeal to the world to recognise the need for more resources for research in the field of climatology. I considered it important that the role of the biosphere was emphasised, not least in order to bring home the relevance of understanding the ongoing changes in the carbon cycle (Bolin, 1979; WMO, 1979). I was invited to give the WMO lecture at the WMO congress in 1979, which dealt with impacts of climate change on the biosphere (Bolin, 1980). It was, however, more than a decade before attempts began to consider the role of the biosphere in quantitative analyses of future changes of the global climate.
A systematic exchange of information between the scientific and political communities was thus still limited towards the end of the 1970s, except in the USA. There was little mutual understanding of the way to look at the global climate system and climate change on one hand, and the impacts on and response from society on the other. Global climate models provided the means for scientists to understand better the processes that determine the distribution of climatic zones around the world. They saw the possibility of projecting future changes induced by the varying composition of the atmosphere, but their results were still presented in terms of changes of the global mean temperature, which is a rather blunt tool for assessing the impacts of a global climate change on ecosystems and human activities. Available information did not yet stir public interest in the issue of a possible human-induced climate change.
The starting point for a politician to get to grips with the climate change issue is of course a different one. The questions are rather: Will there be more heat waves or more droughts? Will intense storms and hurricanes be more common? What about floods? And above all, will human activities on earth be threatened? The scientists were as yet giving few answers to such questions; those questions were not yet even formulated specifically.
There was, however, an increasing interest in raising public awareness. US scientists led scientific development. The US NAS initiated early assessments of what the future might bring. The climate issue had also increased the attention from ICSU and WMO, the two parent organisations of GARP in the sense that an agreement was reached in 1980 that GARP would be transformed into a committee for international cooperation in climate research. The World Climate Research Programme, WCRP, was born.
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