Part two of a three-part series.
Five periods of mass extinction have been identified on our planet. Two were the result of asteroid collisions, with the more "recent" the massive impact zone centered on what is now the Yucatan Peninsula of Mexico sixty-six million years ago. The other three were caused by temperature changes, all from natural causes, primarily long periods of massive volcano eruptions over wide areas. Scientists have determined that a totally ice-free period of one such extinction resulted from high levels of residual carbon-dioxide concentrations in the atmosphere, levels of 1,000 parts per million, or ppm. At that time, the Earth was completely ice free, and tropical plants grew at or near the current polar regions. The lack of ice to contain liquid water in solid form resulted in much higher sea levels, around 240 feet higher than the present.
Carbon dioxide is produced from decaying organic matter (trees, animal poop, etc), and other natural phenomena such as volcano eruptions. In addition, automobile exhaust and burning of fossil fuels, mainly coal, produce this compound.
From a 2014 National Geographic article, a scientist at the Center for International Climate Research in Oslo, Norway, charted CO2 levels in the atmosphere from 1870 to the present. One-half of the rise is from human emissions in the past thirty years. It notes that at least 85% of the people in the world depend on burning fossil fuels for energy.
From the same magazine, climate change deniers often cite a 1990 paper by Dr. Richard Lindzen, the Alfred Sloan Professor of Meteorology at MIT. Dr. Lindzen's widely referenced paper states that the modern, yet pre-industrial concentration of CO2 is around 270-280 ppm, and has been "relatively stable." He called for a "decade or more of study to improve understanding" of the mechanisms.
Data referenced in Dr. Lindzen's paper indicate that between 1880 and 1980, the Earth's temperatures increased 0.5 degree Celsius over land and between 1900 and 1980, increased 0.25 C over sea. Lindzen went on to state that "Certainly the possibility of a significant greenhouse warming remains for the present. Since the more extreme forecasts predict warming in excess of the normal variances seen in this study, observations in the next decade of two (1980-2000) should begin to (narrow the conclusions). He went on to say "it is difficult to envision any practical actions that will make much difference to the final outcome," since "CO2 is peculiarly associated with population and the standard of living." This of course refers to the significant number of people entering into worldwide middle classes with higher aspirations and standards of living.
Ice core data from samples 120,000 years old indicate the sea level was 20-30 feet higher than it is today. The rise was based on ice melt from Greenland and Antarctica at a time the Earth's temperatures were 1 degree C (1.8 degree F) higher than today on average.
Other factors that have influenced the Earth's temperatures include a "wobble" in the Earth's rotation that exposed the Northern Hemisphere to more sunshine. This resulted in arboreal forests much farther west and north in North America all the way to Alaska, with animals including hippopotamuses and water buffaloes roaming the Rhine River Valley of present day Europe.
Three major reasons cause sea level rises: (1) Water expands at higher temperatures. Ocean water simply gets a little bigger when it is warmer; (2) The Earth's mountain glaciers, around 2,000 in number, occur everywhere from Argentina to Alaska and Greenland. These are melting rapidly and the melt water is flowing into the seas; (3) Ice sheets are shedding melt water and ice bergs at an accelerating rate. Greenland alone is losing 300 billion tons of ice a year!
One northeastern glacier in Greenland, the "Zachariac," holds ice equivalent to nearly 3.3 feet of sea level all by itself. It has become "destabilized" according to experts.
An increase of between 2 and 3 degrees Centigrade would result in no ice at all in Greenland. Greenland is three times the size of Texas, and its thickest ice now is two miles in depth.
Dr. Eric Rignot, professor of Earth Sciences at UC Irvine, has stated "What's going to happen by 2100 with the ice sheets melting is absolutely baked in ... it's going to happen!"
Cheers. Enjoy life, it's the only one we have.
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