from the letter:

"Before any precipitate action is taken, we must have solid observational data demonstrating that recent changes in climate differ substantially from changes observed in the past and are well in excess of normal variations caused by solar cycles, ocean currents, changes in the Earth's orbital parameters and other natural phenomena."

*sigh*... I see their concern, but they, being scientists, should know that some dangers can't wait to be addressed until they are all convinced of "solid observational data".

The situation IS complex, as the Earth undergoes 4-5 different cyclical changes on many different time scales... dozens of years (El Ninó), hundreds of years(the worlds currents), 43,000 years (axis tilts), 100,000 years(Earths orbit)...and even millions of years(continental drift). These all affect climate, and are operating semi-indepentently of humans. (I think I left out one)

but... No matter what else is happening, the HUGE amount of fossil fuel burning and deforestation, etc. that we contribute cannot be ignored!

I repeat....even IF human effects were not exacerbating the standard cycles, reducing our carbon footprint and living more in harmony with the Earth cannot help but be positive for everything...except those whose bank accounts are tied to short-term exploitation.

Concerned scientists need to show their concern by gathering the most data possible, not just by providing nay-sayers with fuel for continued denial.