James E. Lovelock

Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate

The major source of cloud-condensation nuclei (CCN) over the oceans appears to be dimethylsulphide, which is produced by planktonic algae in sea water and oxidizes in the atmosphere to form a sulphate aerosol Because the reflectance (albedo) of clouds (and thus the Earths radiation budget) is sensitive to CCN density, biological regulation of the climate is possible through the effects of temperature and sunlight on phytoplankton population and dimethylsulphide production. To counteract the warming due to doubling of atmospheric CO2, an approximate doubling of CCN would be needed.

The haemolysis of human red blood-cells by freezing and thawing

Abstract The destructive processes which occur when red blood-cells are frozen and thawed have been observed. The results of these observations suggest that the principal damaging effect associated with freezing is the concentration of the electrolytes present within and without the cell. The destructive action of exposure to concentrated salt solutions is not instantaneous and the survival of rapidly frozen and thawed cells is attributed to this factor. The nature of the damage caused by exposure to strong salt solutions is complex. At moderate concentrations the blood-cell becomes sensitive to thermal and mechanical shock; at high concentrations the cell structure is dispersed by an apparently lyotropic effect.

Het mechanism of the protective action of glycerol against haemolysis by freezing and thawing

Abstract The effects of including glycerol in suspensions of human red blood-cells during freezing and thawing have been observed. The results of these observations confirm that damage on freezing results largely from the concentration of the electrolytes within the cell. In the presence of glycerol this concentration of electrolytes by freezing is greatly reduced, and is sufficient to explain its protective action. From this interpretation of the action of glycerol improvements are suggested in the technique of preserving red blood-cells at low temperatures.

Halogenated Hydrocarbons in and over the Atlantic

DURING the past few decades the production of the chlorofluorocarbons, the propellant solvents for aerosol dispensers, has grown exponentially. R. L. McCarthy (unpublished) estimates that the integrated production of CCl2F2 and of CCl3F, the two principal compounds of the class, was about one megaton of each in mid 1971; they are unusually stable chemically and only slightly soluble in water and might therefore persist and accumulate in the atmosphere. Preliminary tests in 1970 showed that CCl3F was present in the air over Ireland at concentrations exceeding 10−11 by volume1.

Gaia as Seen Through the Atmosphere

Life can flourish only within a narrowly circumscribed range of physical and chemical states and since life began the Earth has kept within this range. This is remarkable for there have been major perturbations such as a progressive increase in solar luminosity, extensive changes in the surface and atmospheric chemical composition and the impact of many planetesimals. The anomalous and chemically unstable composition of the Earth’s atmosphere when compared with those of the other terrestrial planets was the first indication of homeostasis by the biota to maintain conditions favourable for their continued survival. This paper will discuss recent evidence in support of the gaia hypothesis and present a simple model of a planetary ecosystem in which homeostasis is a direct and automatic result of the characteristic properties of life.

The Denaturation of Lipid-Protein Complexes as a Cause of Damage by Freezing

The practice of cold storage for preserving labile material of biological origin is widespread. The general utility of this method and the successful preservation of living cells and tissues in the frozen state has overshadowed the fact that freezing can be a harmful process to living cells (Wood 1956). It used to be thought that the crushing or spearing action of ice crystal growth was the principal source of damage by freezing; indeed so reasonable is this theory that it is difficult to believe that some at least of the harmful effects of freezing are not due to this cause. The development of the theories of damage by ice crystal growth have been described in detail by Luyet & Gehenio (1940), and by Meryman (1956). By contrast with damage on a macroscopic scale which might occur during the growth of ice crystals there is evidence to show that freezing can damage the molecular constituents of living cells, and this is most unlikely to be a direct consequence of the intrusion of ice crystals. This aspect of the problem of freezing damage forms the basis of this paper.

A Physical Basis for Life Detection Experiments

a fortunate circumstance that it has proved possible to accommodate the headquarters of both Councils in the same building. For the time being, the machinery of administration will be much the same as hitherto, with the Natural Environment Research Council taking over responsibility for the parts of the grants and awards programme that lie within its field. The emphasis on continuity should be particularly welcomed by universities and others concerned with this important aspect of the Governments policy for science.

Biological Modulation of the Earth's Atmosphere

Abstract We review the evidence that the Earths atmosphere is regulated by life on the surface so that the probability of growth of the entire biosphere is maximized. Acidity, gas composition including oxygen level, and ambient temperature are enormously important determinants for the distribution of life. We recognize that the earths atmosphere deviates greatly from that of the other terrestrial planets in particular with respect to acidity, composition, redox potential and temperature history as predicted from solar luminosity. These deviations from predicted steady state conditions have apparently persisted over millions of years. We explore the concept that these anomalies are evidence for a complex planet-wide homeostasis that is the product of natural selection. Possible homeostatic mechanisms that may be further investigated by both theoretical and experimental methods are suggested.

Methanogenesis, fires and the regulation of atmospheric oxygen.

Abstract The Gaia hypothesis states that the composition, oxidation-reduction potential and the temperature of the Earths lower atmosphere are modulated by and for the biota living on the surface (Lovelock, 1972; Margulis and Lovelock, 1974). A corollary is that atmospheric oxygen is presently regulated at about 21% for the dominant life forms today: vascular plants and metazoa. We suggest that the enormous annual production of methane (of the order of 10 14 mol) is directly related to the short term modulation of oxygen concentration. Atmospheric oxygen results from the burial of reduced carbon; methanogenesis and subsequent atmospheric oxidation of methane prevents that burial. We also present experimental work on the probability of ignition of vegetation as a function of increasing oxygen concentration (Watson, 1978). Both the experiments and consideration of the fossil record lead us to conclude that oxygen has been regulated by methane (and perhaps by N 2 O and others) at about 10–25% for very long periods relative to the atmospheric residence times of these reactive gases.

Thermodynamics and the recognition of alien biospheres

The presence of a mature biosphere is likely to change surface and atmospheric composition and the energy balance of a planet away from that of the abiotic state. Is it possible that such a change might be detected from afar by astronomical techniques and so form the basis of a test for the presence of a planetary biosphere? A distant view of the Earth in this context shows that certain of its thermodynamic properties are recognizably different from those of the other terrestrial planets, which presumably are lifeless. The general application of this test for the remote detection of other biospheres will be discussed, as will some implications of this way of viewing biospheres on the nature and organizations of life on Earth.