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The article presents the second installment of a position paper about global climate change, issued by the Center for Inquiry's Office of Public Policy in Washington, D.C. Research scientists have agreed that the greenhouse effect is a real physical process that is contributing to global warming. The article explains the dominant role of carbon dioxide in the environment.

The article focuses on the Center for Inquiry's position paper about climate change and global warming. The paper offers evidence from a research that global climate change caused by global warming is already underway. The conclusion that there is significant warming of Earth's surface is not based primarily on theoretical models. Global warming is a fact confirmed by observations from many different sources.

We present observational evidence of the effect of small-scale ("microturbulent") velocities in enhancing the intensity of the He II l304 line with respect to other transition region emission lines, a process we call "velocity redistribution,". We first show results from the 1991 and 1993 flights of SERTS (Solar EUV Rocket Telescope and Spectrograph). The spectral resolution of the SERTS instrument was sufficient to infer that, at the spatial resolution of 5'', the line profile is nearly Gaussian both in the quiet Sun and in active regions. We were then able to determine, for the quiet Sun, a lower limit for the amplitude of nonthermal motions in the region of formation of the 304 A line of the order of 10 km s-1. We estimated that, in the presence of the steep temperature gradients of the solar transition region (TR), velocities of this magnitude can significantly enhance the intensity of that line, thus at least helping to bridge the gap between calculated and observed values. We also estimated the functional dependence of such an enhancement on the relevant parameters (nonthermal velocities, temperature gradient, and pressure). We then present results from a coordinated campaign, using SOHO/CDS and Ha spectroheliograms from Coimbra Observatory, aimed at determining the relationship between regions of enhanced helium emission and chromospheric velocity fields and transition region emission in the quiescent atmosphere. Using these data, we examined the behavior of the He II l304 line in the quiet-Sun supergranular network and compared it with other TR lines, in particular with O III l600. We also examined the association of 304 A emission with the so-called coarse dark mottle, chromospheric structures seen in Ha red-wing images and associated with spicules. We found that all these observations are consistent with the velocity redistribution picture.

Calculations performed with several models of the solar chromosphere support Ulmschneider's conclusion that relatively short period acoustic waves heat the low chromosphere in the region just above the temperature minimum. However, these same short period waves (10? period P?80 s) are not able to maintain chromospheric temperatures at heights where t5000Å(normal) < 10-6. The calculations also show that an earlier conjecture stating that the H2 population might influence the non-LTE chromospheric H- population is probably not correct, due to lower values of the ratio ne/nH inferred from more recent observations. Finally, the calculations support Athay's contention that the Cayrel mechanism alone cannot produce the observed temperature rise, because the magnitude of the radiative cooling in the lines is too great.

The Solar Optical Telescope (SOT), which NASA plans to operate on Spacelab, should provide resolution down to 0.1 arc sec, thus offering the capability for solving a number of fundamental problems in solar magnetism and in atmospheric heating and dynamics.

The low chromosphere now seems definitely to require mechanical heating, and dissipation of initially acoustic waves by shocking is one of the most promising possibilities. Results of recent calculations indicate that the weak shock theory may be applicable here, but discrepancies exist among various applications of this theory, and the explanations offered to date are not completely satisfactory. It is shown here that the different approximations used by different authors to evaluate the mechanical flux integral play an important role in producing these discrepancies, in addition to the already well known effects of the density scale heights and the wave periods. Arguments are presented favoring Ulmschneider's method for evaluation of this flux integral.

The author reflects on the issue of global warming and the role of science and scientists in democracy. He states that many working scientists would prefer to have little to do with the political process, yet there is no denying that most scientists today receive much of their support from governments. He adds that it is the duty of the scientist to inform the public and the political establishment of the best science available on the issue of climate change.