A good deal of misinformation has appeared in recent months challenging the reality, causes and trajectory of human-induced climate change. A short paper published by the Climate Leadership Initiative at the Institute for a Sustainable Environment, University of Oregon, provides a highly readable and concise summary of scientifically credible responses to some of the most commonly heard challenges. It is well worth the read. 

It cites information from a variety of sources, including:

• The 2007 Fourth Assessment Report of the Intergovernmental Panel on Climate Change
• RealClimate, a blog on climate science written by some the nation’s top climate scientists that provides timely responses to misinformation about climate science;
• The Scientific Consensus Statement on the Likely Impacts of Climate Change on the Pacific Northwest, signed by 50 Northwest scientists in 2004; and
• The book Global Warming by Sir John Houghton, considered one of the most authoritative texts on climate change available today (Cambridge University Press, 2004).

 These are the questions the paper addresses: 

1. Despite what the computer models tell us, there is actually no evidence of significant global warming
2. There was some warming earlier in the last century but it stopped in 1998; there is now evidence that the globe is cooling
3. This winter is exceptionally cold and snowy which shows that average U.S. temperatures are going down, not up
4. U.S. annual mean temperature has fluctuated for decades and the primary cause is fluctuating solar activity levels and ocean temperatures, not CO2 
5. The current warming is just a natural cycle
6. There is no proof that rising CO2 causes global warming
7. CO2 traditionally follows warming, not the other way around
8. Global warming is happening on Mars and Pluto as well. Since there are no humans there driving vehicles, CO2 can’t be the cause of Global Warming
9. Over 30,000 scientists have signed the “Oregon petition” that states that human impacts on the climate can’t be reasonably proven
10. Global warming is a hoax committed by environmental extremists and liberals who want to regulate industry (or create more big government, establish a world government, undermine economic growth etc.)
11. Climate models can’t explain periods when it was even warmer than today, let along predict the weather next week, so why should we believe what they say about 50 or 100 years from now
12. There are many competing theories and unknowns about climate change. It is therefore impossible to claim that a consensus exists. Until a true consensus exists, no significant action should be taken

Hockey Stick graph, which is the basis of global warming theory, has been debunked many times.

Source: University of Oregon