Scientific evidence can take many forms. For example, it can come in the form of a snowball.
In the screengrab below from the floor of the U.S. Senate, the chairman of the Senate Environment and Public Works Committee, James Inhofe of Oklahoma, holds a dripping, melting snowball in his hand as evidence of his contention that global warming is a liberal conspiracy concocted to undermine capitalism. (The Senate staffer looking on from the right seems a mite dubious, however.)
Inhofe's argument goes something like this: A snowball comes from snow; snow falls when it's cold; a lot of snow has fallen in the northeast United States this winter. Ergo, ipso facto, global warming is a fraud and is not occurring. Also, Noah.
On the other hand, there's contradictory evidence in this thermal map, released this week by the National Oceanic and Atmospheric Administration:
As you can see, there's a lot of red on the map, indicating higher than normal temperatures from December through February. It also contains rather large areas of bright red, indicating record high temperatures in those areas. But sure enough, if you look right along the eastern seaboard of the United States, you see a patch of blue, indicating that the small part of the globe inhabited by Inhofe experienced cooler-than-normal temperatures this winter.
Thus, the snowball. And thus the reason that it is referred to as global warming, not local warming.
According to NOAA, the December-February period depicted on the map is now the warmest December-February on record, coming after 2014, which was the warmest year on record. The weather for January and February is also the warmest January and February on record. "Nine of the past 12 months have been either warmest or second warmest on record for their respective months (March and July 2014 were each fourth warmest, while November was seventh warmest)," NOAA reports.
Such evidence itself constitutes a scientific experiment. It tests how receptive -- or how non-receptive -- human beings can be to evidence that contradicts what they wish to believe. How open are they to changing their minds as the evidence mounts? How passionately will they continue to defend beliefs discredited by facts on the ground, in the sea, in the air? How willing are they to suspend their own independent judgment in order to remain in good standing with others of their ideological tribe?
And most profoundly, how willing are they to avoid their own short-term and relatively minor inconvenience, even if it means courting major long-term ecological, economic, political and social conflict in generations still to come?
That particular experiment has yet to be completed, but early data are not encouraging.