This is a geological viewpoint of man’s impact on the climate and it is naturally very conservative.
The one event not recognized is the unusual temperature collapse coinciding with the end of the Bronze Age that has never been reversed. My conjecture is that this was caused directly by the deforesting of the whole Sahara resulting in the reflectance of incoming solar energy back out into space. This represents a huge chunk out of the global energy budget.
That is a man made climatic change event that puts current activities in the shade. We can and will reverse that event and in the process provide home and agriculture for billions of people.
Otherwise, the claims of significant human impact in the modern era are hard to substantiate or quantify and appear to be a distraction from real efforts aimed at the terraforming the earth.
As I have stated, it is becoming possible to convert all the deserts into productive farmland and woodland. It is also massively beneficial to do so.
Man's contribution to climate change is negligible in geologic time
http://www.examiner.com/x-2950-Denver-Energy-Industry-Examiner~y2009m3d21-Mans-contribution-to-climate-change-is-negligible-in-geologic-time
March 21, 11:49 AM
Most geologists, including those in the energy business, take a REALLY long view of the earth's history including global warming and cooling cycles. Within the framework of geologic time, i.e. the earth's history, man is a very late entry and relatively small contributor to climate changes.
The current debate concerning global warming is well publicized. It features histrionic presentations of data on both sides of the issue usually by writers or politicians, with no scientific background, "interpreting" volumes of data gathered by true scientists. The arguments, for and against, have been going on for about 40 years. The earth is about 4.6 billion (4,600,000,000) years old so the debate has been going on for about 0.000001% of geologic time. Man, or at least our earliest demonstrable "human" ancestors, arrived about 2.3 million (2,300,000) years ago so "man" has been an observer of climate change for about 0.05% of geologic time.
Climate change, as measured and recorded in the fossil and rock record, as "ice ages" (global cooling) and ocean expansion (global warming) have been occurring periodically but erratically throughout geologic time from about 3.3 billion (3,300,000000) years ago or approximately 1 billion years after the earth formed. The earth basically "cooled" from its nuclear, "Big Bang", inception for over 1 billion years. At least two, multi-million year length "ice ages" occurred before the first signs of organic, carbon based life in the form of algae or pond scum. At least four more ice ages occurred from the age of pond scum, through the age of creepy crawlers, fishes, amphibians, reptiles (dinosaurs) and early mammals. In the last 1 million (1,000,000) years, during the age of man, at least 10 well documented periods of cooling have occurred. The last "ice age", lasted about 60,000 years from approximately 70,000 years ago until about 10,000 years ago. In North America, the timing and duration are determined by measuring the advance and retreat of glaciers in the fossil plant and rock records. Within these overall "ice ages", there are also shorter cycles of warming and cooling. The warmer periods, in today's vernacular, would be called "global warming."
Without question, man's use of fire (wood), dating from 1.5 million years ago; coal, from about 3000 years ago; and petroleum for the last 150 years have contributed to the most recent cycle of warming. The significance of man's activity is a part of the ongoing debate. The CO2 emissions and ozone layer changes are measurable phenomena. The so called "greenhouse effect" is an unproven theory. At worst, however, man's contribution looks to have only "sped up" the earth's natural cycles by a few decades. Obviously, a "few decades" are significant to the earth's current human population but not in terms of impacting the earth's climate history. If this speeding up process began with the first burning of petroleum 150 years ago, man's activities have affected 0.000003% of the earth's history; 0.0065% of man's history; and 1.5% of the time since the end of the last ice age.
Some evidence exists suggesting that the current phase of warming MAY have peaked in the 1970s and the earth MAY be returning to a cooling phase. Regardless of the rhetoric on either side of the arguments, man's total contribution to global climate change is negligible and probably not measurable within the context of geologic time. Instantaneous events like the asteroid or meteor strike that ended the age of dinosaurs by creating a global wide "dust cloud" or continuous volcanic eruptions that have also shrouded the earth with ash and smoke clouds have had a far greater and long lasting effect on climates. If all of man's "contribution" were to cease immediately, the net effect, measured in geologic time, on the earth's natural warming and cooling cycles would not be measurable.
www.talkorigins.org/faqs/faq-age-of-earth.html
www.studyworld.com/newsite/ReportEssay/science/Earth%5CThe-Ice-Age-36240.html
http://icecap.us/index.php/go/joes-blog/global_cooling_is_here_evidence_for_predicting_global_cooling_for_the_next_
http://library.thinkquest.org/26157/fire_use.html
http://ecology.com/features/originsoflife/
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