I teach physical geography classes at the university level. I always make a point of telling my students that both the greenhouse effect and the global warming associated with the Holocene ARE natural effects. All climatic and physical scientists agree on this point. However, after telling them this, I then also point out the evidence that indicates that human activities since the beginning of the Industrial Revolution have added significant amounts of carbon dioxide and other gases such as nitrous oxides, chloroflourocarbons and methane. These gases are the main causes of the greenhouse effect, natural or otherwise, because they have a significantly higher capacity to absorb energy than do the other gases in the atmosphere. Even though they make up a tiny proportion of the total atmospheric volume, their impacts on the greenhouse effect are still significant. Now, when we keep in mind that measured levels of carbon dioxide alone have increased by 30-35% in the past century, that alone might indicate that this will have some impact on global warming. It can be argued that most of it is natural, but in my mind, and the mind of many climatic scientists, it is that extra amount that we contribute that we should be concerned about, since it might be something that we can correct, if we have the political will to do so.

Btw–the reason I teach my students this is to keep them from making the same assumption that many “global warming skeptics” make–that just because both global warming and the greenhouse effect are natural phenomena (they are), it does not mean that we have nothing to do with the rate and/or potential consequences.

Who says the universe is barren of life? Or for that matter, that someone hasn’t already beaten us to the panspermia thing by a few billion years.

The Anthropocene is the name proposed for our human-inundated era and not the Holocene, which began about 10,000 years ago and is an interstitial warmer period within a larger ice age. To be sure, the Holocene’s warmer weather has supported the explosion of human growth and technology to the present. But it is natural and not a result of human activity.

Here’s the wiki –
http://en.wikipedia.org/wiki/Holocene

‘The Holocene is a geological epoch which began at the end of the Pleistocene [1] (around 10,000 14C years ago) and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words ὅλος (holos, whole or entire) and καινός (kainos, new), meaning “entirely recent”. It has been identified with the current warm period, known as MIS 1 and based on that past evidence, can be considered an interglacial in the current ice age.

‘The Holocene also encompasses within it the growth and impacts of the human species world-wide, including all its written history and overall significant transition toward urban living in the present. Given these, a new synonym Anthropocene, is specifically proposed and used for the time period since approximately synchronous lithospheric evidence, or more recently atmospheric evidence, of human impacts have been found on the Earth and its ecosystems; these impacts may be considered of global significance for future evolution of living species….’

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A good book to read about the subject of overfishing is Kurlansky’s “Cod.” The boom and crash of an important species.

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But, hey, there’s nothing to worry about! All we need to do is cut the tuna’s marginal tax rates and they’ll be able to compete.