United States senators are now on the record on the question of whether climate change is "a hoax." But a majority of the Senate, including 15 Republicans, are also on record stating that human activity contributes to climate change.

The Senate on Wednesday passed a measure stating that "climate change is real and is not a hoax" by a margin of 98-1.

The Senate also voted down two amendments to the bill approving the Keystone XL pipeline stating that human activity contributes to climate change. (Each amendment needed 60 votes to pass.)

The first amendment, which failed 59-40, was introduced by Sen John Hoeven (R-ND), and states: "Climate change is real; and human activity contributes to climate change." It also agrees with the State Department study which "suggest that significant impacts to most resources are not expected along the proposed Project route" for the Keystone pipeline.

The second amendment, which failed 50-49, went one step further and stated "climate change is real (and) human activity significantly contributes to climate change." The inclusion of "significantly," as well as the exclusion of the language reaffirming that the Keystone XL pipeline will not have a significant impact on the proposed route resulted in only five Republicans supporting it, instead of the 15 that supported the Hoeven amendment.

The "hoax" language, attached to a bill to authorize the Keystone XL pipeline, was a resolution introduced by Democrat Sen. Sheldon Whitehouse of Rhode Island.

The amendment was expected to fail, but Republicans parsed the words of the amendment, arguing they could vote for it but at the same time believe that climate change was not man-made.

The lone no vote was from Sen. Roger Wicker of Mississippi.

The amendment was designed in part as a jab at GOP Sen. James Inhofe of Oklahoma, who has questioned the science of climate change.

Inhofe voted for the measure, arguing that the true "hoax" is that climate change is the result of human activity.

"Climate is changing, and climate has always changed, and always will, there's archeological evidence of that, there's biblical evidence of that, there's historic evidence of that, it will always change," he said on the Senate floor. "The hoax is that there are some people that are so arrogant to think that they are so powerful that they can change climate. Man can't change climate."

Democrats, newly in the minority in the upper chamber, are split on whether the Keystone XL pipeline should be built, but they are using the ongoing debate in the Senate to push votes on largely symbolic amendments to the bill.

- Frank Thorp and Carrie Dann