Where did that “97% of all scientists agree” comment come from?

Where did that “97% of all scientists agree” comment come from? - Fusion4Freedom
Last week Secretary of State John Kerry warned graduating students at Boston College of the “crippling consequences” of climate change.
“Ninety-seven percent of the world’s scientists,” he added, “tell us this is urgent.”
Where did Mr. Kerry get the 97% figure? 
Perhaps from his boss, President Obama, who tweeted on May 16 that “Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous.”
Or maybe from NASA, which posted (in more measured language) on its website, “Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities.”
Yet the assertion that 97% of scientists believe that climate change is a man-made, urgent problem is a fiction. 
The so-called consensus comes from a handful of surveys and abstract-counting exercises that have been contradicted by more reliable research..."
Read it all!!