A meteorologist who worked for the US weather bureau in the 1930s. In an essay in the September 1933 Monthly Weather Review entitled Is our climate changing, he became the first scientist to propose that trends in weather data suggested that an "apparent longer-term change" towards a warmer climate was occuring.
In the same essay, he also became the first to emphasize the distinction between globally and locally induced warming (i.e., between warming due to actual climate change vs. that caused by, for example, increased urbanization).
1. To read this seminal paper, click here.