In the early 1980s, I presented my viewpoint on climate in an annual publication of Encyclopedia Britannica. I have decided to post on my early views to document how they have stood up over time. They are in
Pielke, R.A., 1984: Earth sciences: Atmospheric sciences – 1983, Encyclopedia Britannica Yearbook of Science and the Future, 279-281 where I wrote
“Concern regarding the impact of the steady increases of carbon dioxide on the Earth’s atmosphere continued in 1983. The U.S. Environmental Protection Agency released reports in the fall which suggested that by 2100 the average global temperature could increase by 5°C (9°F) with an associated rise in global sea level of between 144 cm (4.8 ft) and 217 cm (7 ft) as a result of the increased levels of carbon dioxide and other trace gases put into the atmosphere primarily through the burning of fossil fuels. These gases act to reduce the emission of long-wave radiation out into space yet still permit solar radiation to teach the Earth’s surface. This mechanism of heat increase is referred to as the “greenhouse effect.” At about the same time the U.S. National Research Council (NRC) issued a somewhat more conservative report on the same subject, which emphasized the remaining uncertainties in estimating the effect of carbon dioxide and other trace gases on climate. The report concluded, for instance, that if deforestation has contributed significantly to the increase in carbon dioxide during recent decades, then existing models that project future atmospheric concentrations based on man-made sources may overpredict the fraction of carbon dioxide remaining airborne. The NRC report concluded that existing evidence does not support a change away from fossil fuels but did suggest that some priority be given to the enhancement of long-term energy options that do not involve the combustion of such fuels.
Increased levels of aerosols in the upper atmosphere and lower stratosphere that are associated with high levels of industrial activity could counter the greenhouse effect of high levels of carbon dioxide. This possibility was not adequately examined in either of the studies. These aerosols appear to be ejected into the upper atmosphere and stratosphere via deep cumulus clouds, a process that is referred to as cloud venting.”
and in Pielke, R.A., 1985: Earth sciences: Atmospheric science – 1984. Encyclopedia Britannica Yearbook of Science and the Future, 284-287, where I wrote
“Concern continued with respect to the potential impact on climate of the increase of carbon dioxide in the atmosphere. Additions of carbon dioxide to the atmosphere as a result of the combustion of fossil fuel can retard radiational cooling to space, thereby causing a net warming at the Earth’s surface. Unless mitigated by other results of human activities, such as reduced sunlight at the ground due to additions of aerosols to the upper atmosphere, this warming could result in major changes in climate patterns. In 1984, as part of the continued study of this phenomenon, NOAA used aircraft to estimate how much carbon dioxide is transferred from the atmosphere into the North Atlantic during winter storms when the cold ocean waters are most efficient in absorbing carbon dioxide. “
What we know in 2009 is that the role of humans within the climate system includes the issues reported above. However, the effect of humans is even more diverse and significant than I reported in the 1980s. Aerosols are now recognized to have a large range of effects (e.g. see), while land use/land cover change has been demonstrated to be a first order climate forcing (e.g. see).
National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp
remains the best overview of the diversity of human climate forcings.
Climate Science: Roger Pielke Sr. 