Cooling trend

From a thermal standpoint, cosmic history can be summed up as a generalised cooling trend induced by the dilatation of space. However, here and there, in certain regions, stars concentrate and bear matter to high temperatures, as balls of incandescent material floating in a cold ocean. 

One important issue raised recently which requires long term measurements of stratospheric composition is the coupling of climate change and ozone depletion chemistry (Shindell et al 1998). If these predictions are correct, which appears reasonable, it will result in a more efficient catalytic removal of ozone because of an expected cooling trend in the stratosphere. 

In Figure 8.1 Notz notes that the gas begins to warm (from mile 30 to mile 45) with shallower, warmer water conditions. From mile 45 to mile 50, however, a second cooling trend is observed due to Joule-Thomson expansion. The methanol exiting the pipeline in the vapor, aqueous, and condensate phases is usually not recovered, due to the expense of separation. 

Having analyzed the data of SST satellite observations since 1982, Strong et al. (2000) noted a warming over a large part of the tropics and in mid-latitudes of the Northern Hemisphere (with the global mean trend of +0.005°Cyr 1). Data on SAT in the Southern Hemisphere are less representative and reflect the existence of an opposite cooling trend (the problem of SST data variability needs a thorough study). 

In detail, we find that the Late Ordovician was a local peak in 5 0, presumably reflecting the cool conditions of the time and, for the Hirnantian, the growth of continental ice sheets. The Late Devonian ushered in a cooling trend. A similar trend in 5 0 was initiated in the Late Permian and continued through the Triassic and Jurassic, but interpreting this in terms of gradual cooling is inconsistent with other climate indicators (e.g., Frakes et al., 1992). 

The Cenozoic Era (c.65 million years BP to the present) encompasses the Tertiary and the Quaternary Periods. During the Tertiary the Earth s climate began an overall cooling trend of about 12 °C in the past 40 million years. Over the past two and a half million years the climate has varied from cool to warm periods, accompanied by massive expansions and contractions of the polar ice caps. This period of climate fluctuation is termed the Quaternary Period and spans the geologic time scale from the end of the Pliocene Epoch, roughly 1.8-2.6 million years ago, to the present. The Quaternary Period includes the Pleistocene and Holocene Epochs, with the Holocene... 

Proxy records indicate that the Earth s climate cooled gradually over the Cenozoic. This cooling trend was accompanied by a decrease of atmospheric Pcox- Other striking features of the Cenozoic are the sharp increase of the Sr/ Sr ratio of sea water and... 

Since the reliability of the Milankovich theory has been established from past records, it shotrld also provide some indication of future climate change, in the absence of complications produced by human activity. According to this theory, a cooling trend has already set in, will intensify several thousand years from now, and will produce peak glaciation in 20,000 years. 

Stratospheric O3 provides protection against UV-B radiation (wavelength range 1 = 280—320 nm) and it determines the temperature profile in the stratosphere by absorbing solar UV radiation. In the latter context, O3 is an important species that can affect climate warming/cooling trends (e.g. Roelofs et ai, 1997). In the troposphere, however, O3 is perceived as more of a pollutant, which has adverse effects on animals and plant life, especially above background levels of about 40 ppb. 

There are at least three important differences between past climate changes and what we are observing today. One difference is the accelerated rate at which the planet is getting warmer. In the past, warming (or cooling) trends have occurred at glacial speeds (pun intended) that have taken centuries. Life on Earth had time to adjust to the changing temperatures. 

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