Other Answers (15)

• There are many credible Scientist saying that the warming that has occurred is within the normal cycle of warming and cooling . there was a report of one place where a glacier had retreated and man made artifacts were found indicating that there had been people living there in the past before the glacier covered it
  The claim that it is man made has turned out to be the most comprehensive ,most successful Global marketing campaign in history. Think of all the new products that have been developed or old products repackaged as green and sold at higher prices to combat %26quot;Global Warming%26quot;.
  Big Business is loving it. They will do whatever it takes to prolong the Hype.
  
  You may not have heard about it ,but an international conference on Climate Change was held in New York last week ,The media sent one reporter to cover it , it included some of the Scientist that were fighting to have their name removed from the IPCC report because they didn%26#039;t agree with the IPCC conclusions.
  you may check this link for more information
  http://www.heartland.org/NewYork08/newyo...
  
  We know it%26#039;s warming, and we%26#039;ve measured how much:
  
  http://www.epa.gov/climatechange/science...
  
  Scientists have a good idea how the Sun and the Earth%26#039;s natural cycles and volcanoes and all those natural effects change the global climate, so they%26#039;ve gone back and checked to see if they could be responsible for the current global warming. What they found is:
  
  Over the past 30 years, all solar effects on the global climate have been in the direction of (slight) cooling, not warming. This is during a very rapid period of global warming.
  
  http://news.bbc.co.uk/2/hi/uk_news/62902...
  http://www.pubs.royalsoc.ac.uk/media/pro...
  
  So the Sun certainly isn%26#039;t a large factor in the current warming. They%26#039;ve also looked at natural cycles, and found that we should be in the middle of a cooling period right now.
  
  %26quot;An often-cited 1980 study by Imbrie and Imbrie determined that %26#039;Ignoring anthropogenic and other possible sources of variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-term cooling trend which began some 6,000 years ago will continue for the next 23,000 years.%26#039;%26quot;
  
  http://en.wikipedia.org/wiki/Milankovitc...
  http://www.sciencemag.org/cgi/content/ab...
  
  So it%26#039;s definitely not the Earth%26#039;s natural cycles. They looked at volcanoes, and found that
  
  a) volcanoes cause more global cooling than warming, because the particles they emit block sunlight
  
  b) humans emit over 150 times more CO2 than volcanoes annually
  
  http://volcano.und.edu/vwdocs/Gases/man....
  
  So it%26#039;s certainly not due to volcanoes. Then they looked at human greenhouse gas emissions. We know how much atmospheric CO2 concentrations have increased over the past 50 years:
  
  http://en.wikipedia.org/wiki/Image:Mauna...
  
  And we know from isotope ratios that this increase is due entirely to human emissions from burning fossil fuels. We know how much of a greenhouse effect these gases like carbon dioxide have, and the increase we%26#039;ve seen is enough to have caused almost all of the warming we%26#039;ve seen over the past 30 years (about 80-90%). You can see a model of the various factors over the past century here:
  
  http://en.wikipedia.org/wiki/Image:Clima...
  
  This is enough evidence to convince almost all climate scientists that humans are the primary cause of the current global warming.