While the human contribution to change here remains unknown, many scientists say the potential risks are all too evident.

In the 1920s and early 1930s, Hine made a series of "work portraits," which emphasized the human contribution to modern industry.

He has also provided guidance for nuclear fuel waste disposal and reports on the human contribution to Global warming.

Perry has been a skeptic on human contributions to climate change.

The human contribution to global warming could range from highly significant to trivial.

But the human contribution is not to be discounted or down-played.

Hence there must be a human intellectual contribution to the work.

And about 50 percent of the human contribution comes from sewage-treatment plants.

He tried to separate the noise into parts, the human contribution first.

Individual public awareness of human contributions to climate change in the 1990s was limited.